# Input File Description

## Program: pw.x / PWscf / Quantum Espresso (version: 6.8)

INTRODUCTION

&CONTROL

calculation | title | verbosity | restart_mode | wf_collect | nstep | iprint | tstress | tprnfor | dt | outdir | wfcdir | prefix | lkpoint_dir | max_seconds | etot_conv_thr | forc_conv_thr | disk_io | pseudo_dir | tefield | dipfield | lelfield | nberrycyc | lorbm | lberry | gdir | nppstr | lfcp | gate

&SYSTEM

ibrav | celldm | A | B | C | cosAB | cosAC | cosBC | nat | ntyp | nbnd | tot_charge | starting_charge | tot_magnetization | starting_magnetization | ecutwfc | ecutrho | ecutfock | nr1 | nr2 | nr3 | nr1s | nr2s | nr3s | nosym | nosym_evc | noinv | no_t_rev | force_symmorphic | use_all_frac | occupations | one_atom_occupations | starting_spin_angle | degauss | smearing | nspin | noncolin | ecfixed | qcutz | q2sigma | input_dft | ace | exx_fraction | screening_parameter | exxdiv_treatment | x_gamma_extrapolation | ecutvcut | nqx1 | nqx2 | nqx3 | localization_thr | lda_plus_u | lda_plus_u_kind | Hubbard_U | Hubbard_J0 | Hubbard_V | Hubbard_alpha | Hubbard_beta | Hubbard_J | starting_ns_eigenvalue | U_projection_type | Hubbard_parameters | ensemble_energies | edir | emaxpos | eopreg | eamp | angle1 | angle2 | lforcet | constrained_magnetization | fixed_magnetization | lambda | report | lspinorb | assume_isolated | esm_bc | esm_w | esm_efield | esm_nfit | lgcscf | gcscf_mu | gcscf_conv_thr | gcscf_beta | vdw_corr | london | london_s6 | london_c6 | london_rvdw | london_rcut | dftd3_version | dftd3_threebody | ts_vdw_econv_thr | ts_vdw_isolated | xdm | xdm_a1 | xdm_a2 | space_group | uniqueb | origin_choice | rhombohedral | zgate | relaxz | block | block_1 | block_2 | block_height

&ELECTRONS

electron_maxstep | scf_must_converge | conv_thr | adaptive_thr | conv_thr_init | conv_thr_multi | mixing_mode | mixing_beta | mixing_ndim | mixing_fixed_ns | diagonalization | diago_thr_init | diago_cg_maxiter | diago_david_ndim | diago_full_acc | efield | efield_cart | efield_phase | startingpot | startingwfc | tqr | real_space

&IONS

ion_positions | ion_velocities | ion_dynamics | pot_extrapolation | wfc_extrapolation | remove_rigid_rot | ion_temperature | tempw | tolp | delta_t | nraise | refold_pos | upscale | bfgs_ndim | trust_radius_max | trust_radius_min | trust_radius_ini | w_1 | w_2

&CELL

cell_dynamics | press | wmass | cell_factor | press_conv_thr | cell_dofree

&FCP

fcp_mu | fcp_dynamics | fcp_conv_thr | fcp_ndiis | fcp_mass | fcp_velocity | fcp_temperature | fcp_tempw | fcp_tolp | fcp_delta_t | fcp_nraise | freeze_all_atoms

ATOMIC_SPECIES

X | Mass_X | PseudoPot_X

ATOMIC_POSITIONS

X | x | y | z | if_pos(1) | if_pos(2) | if_pos(3)

K_POINTS

nks | xk_x | xk_y | xk_z | wk | nk1 | nk2 | nk3 | sk1 | sk2 | sk3

nks_add | k_x | k_y | k_z | wk_

CELL_PARAMETERS

v1 | v2 | v3

CONSTRAINTS

nconstr | constr_tol | constr_type | constr(1) | constr(2) | constr(3) | constr(4) | constr_target

OCCUPATIONS

f_inp1 | f_inp2

ATOMIC_VELOCITIES

V | vx | vy | vz

ATOMIC_FORCES

X | fx | fy | fz

### INTRODUCTION

Input data format: { } = optional, [ ] = it depends, | = or

All quantities whose dimensions are not explicitly specified are in
RYDBERG ATOMIC UNITS. Charge is "number" charge (i.e. not multiplied
by e); potentials are in energy units (i.e. they are multiplied by e).

BEWARE: TABS, DOS <CR><LF> CHARACTERS ARE POTENTIAL SOURCES OF TROUBLE

Namelists must appear in the order given below.
Comment lines in namelists can be introduced by a "!", exactly as in
fortran code. Comments lines in cards can be introduced by
either a "!" or a "#" character in the first position of a line.
Do not start any line in cards with a "/" character.
Leave a space between card names and card options, e.g.
ATOMIC_POSITIONS (bohr), not ATOMIC_POSITIONS(bohr)
Do not start any line in cards with a "/" character.

Structure of the input data:
===============================================================================

&CONTROL
...
/

&SYSTEM
...
/

&ELECTRONS
...
/

[ &IONS
...
/ ]

[ &CELL
...
/ ]

[ &FCP
...
/ ]

ATOMIC_SPECIES
X  Mass_X  PseudoPot_X
Y  Mass_Y  PseudoPot_Y
Z  Mass_Z  PseudoPot_Z

ATOMIC_POSITIONS { alat | bohr | crystal | angstrom | crystal_sg }
X 0.0  0.0  0.0  {if_pos(1) if_pos(2) if_pos(3)}
Y 0.5  0.0  0.0
Z O.0  0.2  0.2

K_POINTS { tpiba | automatic | crystal | gamma | tpiba_b | crystal_b | tpiba_c | crystal_c }
if (gamma)
if (automatic)
nk1, nk2, nk3, k1, k2, k3
if (not automatic)
nks
xk_x, xk_y, xk_z,  wk
if (tpipa_b or crystal_b in a 'bands' calculation) see Doc/brillouin_zones.pdf

[ CELL_PARAMETERS { alat | bohr | angstrom }
v1(1) v1(2) v1(3)
v2(1) v2(2) v2(3)
v3(1) v3(2) v3(3) ]

[ OCCUPATIONS
f_inp1(1)  f_inp1(2)  f_inp1(3) ... f_inp1(10)
f_inp1(11) f_inp1(12) ... f_inp1(nbnd)
[ f_inp2(1)  f_inp2(2)  f_inp2(3) ... f_inp2(10)
f_inp2(11) f_inp2(12) ... f_inp2(nbnd) ] ]

[ CONSTRAINTS
nconstr  { constr_tol }
constr_type(.)   constr(1,.)   constr(2,.) [ constr(3,.)   constr(4,.) ] { constr_target(.) } ]

[ ATOMIC_FORCES
label_1 Fx(1) Fy(1) Fz(1)
.....
label_n Fx(n) Fy(n) Fz(n) ]

see: K_POINTS ]


## Namelist: &CONTROL

 calculation CHARACTER Default: 'scf' A string describing the task to be performed. Options are:  'scf'   'nscf'   'bands'   'relax'   'md'   'vc-relax'   'vc-md'   (vc = variable-cell). 
 title CHARACTER Default: ' ' reprinted on output. 
 verbosity CHARACTER Default: 'low' Currently two verbosity levels are implemented:  'high'   'low'   'debug' and 'medium' have the same effect as 'high'; 'default' and 'minimal' as 'low' 
 restart_mode CHARACTER Default: 'from_scratch'  Available options are:  'from_scratch' : From scratch. This is the normal way to perform a PWscf calculation  'restart' : From previous interrupted run. Use this switch only if you want to continue, using the same number of processors and parallelization, an interrupted calculation. Do not use to start a new one, or to perform a non-scf calculations. Works only if the calculation was cleanly stopped using variable max_seconds, or by user request with an "exit file" (i.e.: create a file "prefix".EXIT, in directory "outdir"; see variables prefix, outdir). The default for startingwfc and startingpot is set to 'file'. 
wf_collect LOGICAL  OBSOLETE - NO LONGER IMPLEMENTED 
 nstep INTEGER Default: 1 if calculation == 'scf', 'nscf', 'bands'; 50 for the other cases number of molecular-dynamics or structural optimization steps performed in this run. If set to 0, the code performs a quick "dry run", stopping just after initialization. This is useful to check for input correctness and to have the summary printed. NOTE: in MD calculations, the code will perform "nstep" steps even if restarting from a previously interrupted calculation. 
 iprint INTEGER Default: write only at convergence band energies are written every iprint iterations 
 tstress LOGICAL Default: .false. calculate stress. It is set to .TRUE. automatically if calculation == 'vc-md' or 'vc-relax' 
tprnfor LOGICAL calculate forces. It is set to .TRUE. automatically if calculation == 'relax','md','vc-md' 
 dt REAL Default: 20.D0 time step for molecular dynamics, in Rydberg atomic units (1 a.u.=4.8378 * 10^-17 s : beware, the CP code uses Hartree atomic units, half that much!!!) 
 outdir CHARACTER Default: value of the ESPRESSO_TMPDIR environment variable if set; current directory ('./') otherwise input, temporary, output files are found in this directory, see also wfcdir 
 wfcdir CHARACTER Default: same as outdir This directory specifies where to store files generated by each processor (*.wfc{N}, *.igk{N}, etc.). Useful for machines without a parallel file system: set wfcdir to a local file system, while outdir should be a parallel or network file system, visible to all processors. Beware: in order to restart from interrupted runs, or to perform further calculations using the produced data files, you may need to copy files to outdir. Works only for pw.x. 
 prefix CHARACTER Default: 'pwscf' prepended to input/output filenames: prefix.wfc, prefix.rho, etc. 
lkpoint_dir LOGICAL OBSOLETE - NO LONGER IMPLEMENTED 
 max_seconds REAL Default: 1.D+7, or 150 days, i.e. no time limit Jobs stops after max_seconds CPU time. Use this option in conjunction with option restart_mode if you need to split a job too long to complete into shorter jobs that fit into your batch queues. 
 etot_conv_thr REAL Default: 1.0D-4 Convergence threshold on total energy (a.u) for ionic minimization: the convergence criterion is satisfied when the total energy changes less than etot_conv_thr between two consecutive scf steps. Note that etot_conv_thr is extensive, like the total energy. See also forc_conv_thr - both criteria must be satisfied 
 forc_conv_thr REAL Default: 1.0D-3 Convergence threshold on forces (a.u) for ionic minimization: the convergence criterion is satisfied when all components of all forces are smaller than forc_conv_thr. See also etot_conv_thr - both criteria must be satisfied 
 disk_io CHARACTER Default: see below Specifies the amount of disk I/O activity: (only for binary files and xml data file in data directory; other files printed at each molecular dynamics / structural optimization step are not controlled by this option )  'high' : save charge to disk at each SCF step, keep wavefunctions on disk (in "distributed" format), save mixing data as well. Do not use this option unless you have a good reason! It is no longer needed to specify 'high' in order to be able to restart from an interrupted calculation (see restart_mode)  'medium' : save charge to disk at each SCF step, keep wavefunctions on disk only if more than one k-point, per process is present, otherwise keep them in memory; save them to disk only at the end (in "portable" format)  'low' : save charge to disk at each SCF step, keep wavefunctions in memory (for all k-points), save them to disk only at the end (in "portable" format). Reduces I/O but increases memory wrt the previous cases  'nowf' : save to disk only the xml data file, never save wavefunctions and charge density  'none' : do not save anything to disk  Default is 'low' for the scf case, 'medium' otherwise. Note that the needed RAM increases as disk I/O decreases 
 pseudo_dir CHARACTER Default: value of the $ESPRESSO_PSEUDO environment variable if set; '$HOME/espresso/pseudo/' otherwise directory containing pseudopotential files 
 tefield LOGICAL Default: .FALSE. If .TRUE. a saw-like potential simulating an electric field is added to the bare ionic potential. See variables edir, eamp, emaxpos, eopreg for the form and size of the added potential. 
 dipfield LOGICAL Default: .FALSE. If .TRUE. and tefield==.TRUE. a dipole correction is also added to the bare ionic potential - implements the recipe of L. Bengtsson, PRB 59, 12301 (1999). See variables edir, emaxpos, eopreg for the form of the correction. Must be used ONLY in a slab geometry, for surface calculations, with the discontinuity FALLING IN THE EMPTY SPACE. 
 lelfield LOGICAL Default: .FALSE. If .TRUE. a homogeneous finite electric field described through the modern theory of the polarization is applied. This is different from tefield == .true. ! 
 nberrycyc INTEGER Default: 1 In the case of a finite electric field ( lelfield == .TRUE. ) it defines the number of iterations for converging the wavefunctions in the electric field Hamiltonian, for each external iteration on the charge density 
 lorbm LOGICAL Default: .FALSE. If .TRUE. perform orbital magnetization calculation. If finite electric field is applied (lelfield==.true.) only Kubo terms are computed [for details see New J. Phys. 12, 053032 (2010), doi:10.1088/1367-2630/12/5/053032]. The type of calculation is 'nscf' and should be performed on an automatically generated uniform grid of k points. Works ONLY with norm-conserving pseudopotentials. 
 lberry LOGICAL Default: .FALSE. If .TRUE. perform a Berry phase calculation. See the header of PW/src/bp_c_phase.f90 for documentation. 
gdir INTEGER For Berry phase calculation: direction of the k-point strings in reciprocal space. Allowed values: 1, 2, 3 1=first, 2=second, 3=third reciprocal lattice vector For calculations with finite electric fields (lelfield==.true.) "gdir" is the direction of the field. 
nppstr INTEGER For Berry phase calculation: number of k-points to be calculated along each symmetry-reduced string. The same for calculation with finite electric fields (lelfield==.true.). 
 lfcp LOGICAL Default: .FALSE. See: fcp_mu If .TRUE. perform a constant bias potential (constant-mu) calculation for a system with ESM method. See the header of PW/src/fcp_module.f90 for documentation. To perform the calculation, you must set a namelist FCP. NB: - The total energy displayed in output includes the potentiostat contribution (-mu*N). - calculation must be 'relax' or 'md'. - assume_isolated = 'esm' and esm_bc = 'bc2' or 'bc3' must be set in SYSTEM namelist. 
 gate LOGICAL Default: .FALSE. See: zgate, relaxz, block, block_1, block_2, block_height In the case of charged cells (tot_charge .ne. 0) setting gate = .TRUE. represents the counter charge (i.e. -tot_charge) not by a homogeneous background charge but with a charged plate, which is placed at zgate (see below). Details of the gate potential can be found in T. Brumme, M. Calandra, F. Mauri; PRB 89, 245406 (2014). Note, that in systems which are not symmetric with respect to the plate, one needs to enable the dipole correction! (dipfield=.true.). Currently, symmetry can be used with gate=.true. but carefully check that no symmetry is included which maps z to -z even if in principle one could still use them for symmetric systems (i.e. no dipole correction). For nosym=.false. verbosity is set to 'high'. Note: this option was called "monopole" in v6.0 and 6.1 of pw.x 

## Namelist: &SYSTEM

 ibrav INTEGER Status: REQUIRED  Bravais-lattice index. Optional only if space_group is set. If ibrav /= 0, specify EITHER [ celldm(1)-celldm(6) ] OR [ A, B, C, cosAB, cosAC, cosBC ] but NOT both. The lattice parameter "alat" is set to alat = celldm(1) (in a.u.) or alat = A (in Angstrom); see below for the other parameters. For ibrav=0 specify the lattice vectors in CELL_PARAMETERS, optionally the lattice parameter alat = celldm(1) (in a.u.) or = A (in Angstrom). If not specified, the lattice parameter is taken from CELL_PARAMETERS IMPORTANT NOTICE 1: with ibrav=0 lattice vectors must be given with a sufficiently large number of digits and with the correct symmetry, or else symmetry detection may fail and strange problems may arise in symmetrization. IMPORTANT NOTICE 2: do not use celldm(1) or A as a.u. to Ang conversion factor, use the true lattice parameters or nothing, specify units in CELL_PARAMETERS and ATOMIC_POSITIONS ibrav structure celldm(2)-celldm(6) or: b,c,cosbc,cosac,cosab 0 free crystal axis provided in input: see card CELL_PARAMETERS 1 cubic P (sc) v1 = a(1,0,0), v2 = a(0,1,0), v3 = a(0,0,1) 2 cubic F (fcc) v1 = (a/2)(-1,0,1), v2 = (a/2)(0,1,1), v3 = (a/2)(-1,1,0) 3 cubic I (bcc) v1 = (a/2)(1,1,1), v2 = (a/2)(-1,1,1), v3 = (a/2)(-1,-1,1) -3 cubic I (bcc), more symmetric axis: v1 = (a/2)(-1,1,1), v2 = (a/2)(1,-1,1), v3 = (a/2)(1,1,-1) 4 Hexagonal and Trigonal P celldm(3)=c/a v1 = a(1,0,0), v2 = a(-1/2,sqrt(3)/2,0), v3 = a(0,0,c/a) 5 Trigonal R, 3fold axis c celldm(4)=cos(gamma) The crystallographic vectors form a three-fold star around the z-axis, the primitive cell is a simple rhombohedron: v1 = a(tx,-ty,tz), v2 = a(0,2ty,tz), v3 = a(-tx,-ty,tz) where c=cos(gamma) is the cosine of the angle gamma between any pair of crystallographic vectors, tx, ty, tz are: tx=sqrt((1-c)/2), ty=sqrt((1-c)/6), tz=sqrt((1+2c)/3) -5 Trigonal R, 3fold axis <111> celldm(4)=cos(gamma) The crystallographic vectors form a three-fold star around <111>. Defining a' = a/sqrt(3) : v1 = a' (u,v,v), v2 = a' (v,u,v), v3 = a' (v,v,u) where u and v are defined as u = tz - 2*sqrt(2)*ty, v = tz + sqrt(2)*ty and tx, ty, tz as for case ibrav=5 Note: if you prefer x,y,z as axis in the cubic limit, set u = tz + 2*sqrt(2)*ty, v = tz - sqrt(2)*ty See also the note in Modules/latgen.f90 6 Tetragonal P (st) celldm(3)=c/a v1 = a(1,0,0), v2 = a(0,1,0), v3 = a(0,0,c/a) 7 Tetragonal I (bct) celldm(3)=c/a v1=(a/2)(1,-1,c/a), v2=(a/2)(1,1,c/a), v3=(a/2)(-1,-1,c/a) 8 Orthorhombic P celldm(2)=b/a celldm(3)=c/a v1 = (a,0,0), v2 = (0,b,0), v3 = (0,0,c) 9 Orthorhombic base-centered(bco) celldm(2)=b/a celldm(3)=c/a v1 = (a/2, b/2,0), v2 = (-a/2,b/2,0), v3 = (0,0,c) -9 as 9, alternate description v1 = (a/2,-b/2,0), v2 = (a/2, b/2,0), v3 = (0,0,c) 91 Orthorhombic one-face base-centered A-type celldm(2)=b/a celldm(3)=c/a v1 = (a, 0, 0), v2 = (0,b/2,-c/2), v3 = (0,b/2,c/2) 10 Orthorhombic face-centered celldm(2)=b/a celldm(3)=c/a v1 = (a/2,0,c/2), v2 = (a/2,b/2,0), v3 = (0,b/2,c/2) 11 Orthorhombic body-centered celldm(2)=b/a celldm(3)=c/a v1=(a/2,b/2,c/2), v2=(-a/2,b/2,c/2), v3=(-a/2,-b/2,c/2) 12 Monoclinic P, unique axis c celldm(2)=b/a celldm(3)=c/a, celldm(4)=cos(ab) v1=(a,0,0), v2=(b*cos(gamma),b*sin(gamma),0), v3 = (0,0,c) where gamma is the angle between axis a and b. -12 Monoclinic P, unique axis b celldm(2)=b/a celldm(3)=c/a, celldm(5)=cos(ac) v1 = (a,0,0), v2 = (0,b,0), v3 = (c*cos(beta),0,c*sin(beta)) where beta is the angle between axis a and c 13 Monoclinic base-centered celldm(2)=b/a (unique axis c) celldm(3)=c/a, celldm(4)=cos(gamma) v1 = ( a/2, 0, -c/2), v2 = (b*cos(gamma), b*sin(gamma), 0 ), v3 = ( a/2, 0, c/2), where gamma=angle between axis a and b projected on xy plane -13 Monoclinic base-centered celldm(2)=b/a (unique axis b) celldm(3)=c/a, celldm(5)=cos(beta) v1 = ( a/2, b/2, 0), v2 = ( -a/2, b/2, 0), v3 = (c*cos(beta), 0, c*sin(beta)), where beta=angle between axis a and c projected on xz plane IMPORTANT NOTICE: until QE v.6.4.1, axis for ibrav=-13 had a different definition: v1(old) =-v2(now), v2(old) = v1(now) 14 Triclinic celldm(2)= b/a, celldm(3)= c/a, celldm(4)= cos(bc), celldm(5)= cos(ac), celldm(6)= cos(ab) v1 = (a, 0, 0), v2 = (b*cos(gamma), b*sin(gamma), 0) v3 = (c*cos(beta), c*(cos(alpha)-cos(beta)cos(gamma))/sin(gamma), c*sqrt( 1 + 2*cos(alpha)cos(beta)cos(gamma) - cos(alpha)^2-cos(beta)^2-cos(gamma)^2 )/sin(gamma) ) where alpha is the angle between axis b and c beta is the angle between axis a and c gamma is the angle between axis a and b 

Either:

 celldm(i), i=1,6 REAL See: ibrav Crystallographic constants - see the ibrav variable. Specify either these OR A,B,C,cosAB,cosBC,cosAC NOT both. Only needed values (depending on "ibrav") must be specified alat = celldm(1) is the lattice parameter "a" (in BOHR) If ibrav==0, only celldm(1) is used if present; cell vectors are read from card CELL_PARAMETERS 

Or:

 A, B, C, cosAB, cosAC, cosBC REAL See: ibrav Traditional crystallographic constants: a,b,c in ANGSTROM cosAB = cosine of the angle between axis a and b (gamma) cosAC = cosine of the angle between axis a and c (beta) cosBC = cosine of the angle between axis b and c (alpha) The axis are chosen according to the value of ibrav. Specify either these OR celldm but NOT both. Only needed values (depending on ibrav) must be specified. The lattice parameter alat = A (in ANGSTROM ). If ibrav == 0, only A is used if present, and cell vectors are read from card CELL_PARAMETERS. 
 nat INTEGER Status: REQUIRED number of atoms in the unit cell (ALL atoms, except if space_group is set, in which case, INEQUIVALENT atoms) 
 ntyp INTEGER Status: REQUIRED number of types of atoms in the unit cell 
 nbnd INTEGER Default: for an insulator, nbnd = number of valence bands (nbnd = # of electrons /2); for a metal, 20% more (minimum 4 more) Number of electronic states (bands) to be calculated. Note that in spin-polarized calculations the number of k-point, not the number of bands per k-point, is doubled 
 tot_charge REAL Default: 0.0 Total charge of the system. Useful for simulations with charged cells. By default the unit cell is assumed to be neutral (tot_charge=0). tot_charge=+1 means one electron missing from the system, tot_charge=-1 means one additional electron, and so on. In a periodic calculation a compensating jellium background is inserted to remove divergences if the cell is not neutral. 
 starting_charge(i), i=1,ntyp REAL Default: 0.0 starting charge on atomic type 'i', to create starting potential with startingpot = 'atomic'. 
 tot_magnetization REAL Default: -1 [unspecified] Total majority spin charge - minority spin charge. Used to impose a specific total electronic magnetization. If unspecified then tot_magnetization variable is ignored and the amount of electronic magnetization is determined during the self-consistent cycle. 
 starting_magnetization(i), i=1,ntyp REAL Default: 0 Starting spin polarization on atomic type 'i' in a spin polarized (LSDA or noncollinear/spin-orbit) calculation. Allowed values range between -1 (all spins down for the valence electrons of atom type 'i') to 1 (all spins up). If you expect a nonzero magnetization in your ground state, you MUST either specify a nonzero value for at least one atomic type, or constrain the magnetization using variable tot_magnetization for LSDA, constrained_magnetization for noncollinear/spin-orbit calculations. If you don't, you will get a nonmagnetic (zero magnetization) state. In order to perform LSDA calculations for an antiferromagnetic state, define two different atomic species corresponding to sublattices of the same atomic type. NOTE 1: starting_magnetization is ignored in most BUT NOT ALL cases in non-scf calculations: it is safe to keep the same values for the scf and subsequent non-scf calculation. NOTE 2: If you fix the magnetization with tot_magnetization, do not specify starting_magnetization. NOTE 3: In the noncollinear/spin-orbit case, starting with zero starting_magnetization on all atoms imposes time reversal symmetry. The magnetization is never calculated and is set to zero (the internal variable domag is set to .FALSE.). 
 ecutwfc REAL Status: REQUIRED kinetic energy cutoff (Ry) for wavefunctions 
 ecutrho REAL Default: 4 * ecutwfc Kinetic energy cutoff (Ry) for charge density and potential For norm-conserving pseudopotential you should stick to the default value, you can reduce it by a little but it will introduce noise especially on forces and stress. If there are ultrasoft PP, a larger value than the default is often desirable (ecutrho = 8 to 12 times ecutwfc, typically). PAW datasets can often be used at 4*ecutwfc, but it depends on the shape of augmentation charge: testing is mandatory. The use of gradient-corrected functional, especially in cells with vacuum, or for pseudopotential without non-linear core correction, usually requires an higher values of ecutrho to be accurately converged. 
 ecutfock REAL Default: ecutrho Kinetic energy cutoff (Ry) for the exact exchange operator in EXX type calculations. By default this is the same as ecutrho but in some EXX calculations, a significant speed-up can be obtained by reducing ecutfock, at the expense of some loss in accuracy. Must be .gt. ecutwfc. Not implemented for stress calculation and for US-PP and PAW pseudopotentials. Use with care, especially in metals where it may give raise to instabilities. 
 nr1, nr2, nr3 INTEGER Three-dimensional FFT mesh (hard grid) for charge density (and scf potential). If not specified the grid is calculated based on the cutoff for charge density (see also ecutrho) Note: you must specify all three dimensions for this setting to be used. 
 nr1s, nr2s, nr3s INTEGER Three-dimensional mesh for wavefunction FFT and for the smooth part of charge density ( smooth grid ). Coincides with nr1, nr2, nr3 if ecutrho = 4 * ecutwfc ( default ) Note: you must specify all three dimensions for this setting to be used. 
 nosym LOGICAL Default: .FALSE. if (.TRUE.) symmetry is not used. Consequences: - if a list of k points is provided in input, it is used "as is": symmetry-inequivalent k-points are not generated, and the charge density is not symmetrized; - if a uniform (Monkhorst-Pack) k-point grid is provided in input, it is expanded to cover the entire Brillouin Zone, irrespective of the crystal symmetry. Time reversal symmetry is assumed so k and -k are considered as equivalent unless noinv=.true. is specified. Do not use this option unless you know exactly what you want and what you get. May be useful in the following cases: - in low-symmetry large cells, if you cannot afford a k-point grid with the correct symmetry - in MD simulations - in calculations for isolated atoms 
 nosym_evc LOGICAL Default: .FALSE. if (.TRUE.) symmetry is not used, and k points are forced to have the symmetry of the Bravais lattice; an automatically generated Monkhorst-Pack grid will contain all points of the grid over the entire Brillouin Zone, plus the points rotated by the symmetries of the Bravais lattice which were not in the original grid. The same applies if a k-point list is provided in input instead of a Monkhorst-Pack grid. Time reversal symmetry is assumed so k and -k are equivalent unless noinv=.true. is specified. This option differs from nosym because it forces k-points in all cases to have the full symmetry of the Bravais lattice (not all uniform grids have such property!) 
 noinv LOGICAL Default: .FALSE. if (.TRUE.) disable the usage of k => -k symmetry (time reversal) in k-point generation 
 no_t_rev LOGICAL Default: .FALSE. if (.TRUE.) disable the usage of magnetic symmetry operations that consist in a rotation + time reversal. 
 force_symmorphic LOGICAL Default: .FALSE. if (.TRUE.) force the symmetry group to be symmorphic by disabling symmetry operations having an associated fractionary translation 
 use_all_frac LOGICAL Default: .FALSE. if (.FALSE.) force real-space FFT grids to be commensurate with fractionary translations of non-symmorphic symmetry operations, if present (e.g.: if a fractional translation (0,0,c/4) exists, the FFT dimension along the c axis must be multiple of 4). if (.TRUE.) do not impose any constraints to FFT grids, even in the presence of non-symmorphic symmetry operations. BEWARE: use_all_frac=.TRUE. may lead to wrong results for hybrid functionals and phonon calculations. Both cases use symmetrization in real space that works for non-symmorphic operations only if the real-space FFT grids are commensurate. 
occupations CHARACTER  Available options are:  'smearing' : gaussian smearing for metals; see variables smearing and degauss  'tetrahedra' : Tetrahedron method, Bloechl's version: P.E. Bloechl, PRB 49, 16223 (1994) Requires uniform grid of k-points, to be automatically generated (see card K_POINTS). Well suited for calculation of DOS, less so (because not variational) for force/optimization/dynamics calculations.  'tetrahedra_lin' : Original linear tetrahedron method. To be used only as a reference; the optimized tetrahedron method is more efficient.  'tetrahedra_opt' : Optimized tetrahedron method: see M. Kawamura, PRB 89, 094515 (2014). Can be used for phonon calculations as well.  'fixed' : for insulators with a gap  'from_input' : The occupation are read from input file, card OCCUPATIONS. Option valid only for a single k-point, requires nbnd to be set in input. Occupations should be consistent with the value of tot_charge. 
 one_atom_occupations LOGICAL Default: .FALSE. This flag is used for isolated atoms (nat=1) together with occupations='from_input'. If it is .TRUE., the wavefunctions are ordered as the atomic starting wavefunctions, independently from their eigenvalue. The occupations indicate which atomic states are filled. The order of the states is written inside the UPF pseudopotential file. In the scalar relativistic case: S -> l=0, m=0 P -> l=1, z, x, y D -> l=2, r^2-3z^2, xz, yz, xy, x^2-y^2 In the noncollinear magnetic case (with or without spin-orbit), each group of states is doubled. For instance: P -> l=1, z, x, y for spin up, l=1, z, x, y for spin down. Up and down is relative to the direction of the starting magnetization. In the case with spin-orbit and time-reversal (starting_magnetization=0.0) the atomic wavefunctions are radial functions multiplied by spin-angle functions. For instance: P -> l=1, j=1/2, m_j=-1/2,1/2. l=1, j=3/2, m_j=-3/2, -1/2, 1/2, 3/2. In the magnetic case with spin-orbit the atomic wavefunctions can be forced to be spin-angle functions by setting starting_spin_angle to .TRUE.. 
 starting_spin_angle LOGICAL Default: .FALSE. In the spin-orbit case when domag=.TRUE., by default, the starting wavefunctions are initialized as in scalar relativistic noncollinear case without spin-orbit. By setting starting_spin_angle=.TRUE. this behaviour can be changed and the initial wavefunctions are radial functions multiplied by spin-angle functions. When domag=.FALSE. the initial wavefunctions are always radial functions multiplied by spin-angle functions independently from this flag. When lspinorb is .FALSE. this flag is not used. 
 degauss REAL Default: 0.D0 Ry value of the gaussian spreading (Ry) for brillouin-zone integration in metals. 
 smearing CHARACTER Default: 'gaussian' Available options are:  'gaussian', 'gauss' : ordinary Gaussian spreading (Default)  'methfessel-paxton', 'm-p', 'mp' : Methfessel-Paxton first-order spreading (see PRB 40, 3616 (1989)).  'marzari-vanderbilt', 'cold', 'm-v', 'mv' : Marzari-Vanderbilt-DeVita-Payne cold smearing (see PRL 82, 3296 (1999))  'fermi-dirac', 'f-d', 'fd' : smearing with Fermi-Dirac function 
 nspin INTEGER Default: 1 nspin = 1 : non-polarized calculation (default) nspin = 2 : spin-polarized calculation, LSDA (magnetization along z axis) nspin = 4 : spin-polarized calculation, noncollinear (magnetization in generic direction) DO NOT specify nspin in this case; specify noncolin=.TRUE. instead 
 noncolin LOGICAL Default: .false. if .true. the program will perform a noncollinear calculation. 
 ecfixed REAL Default: 0.0 See: q2sigma
 qcutz REAL Default: 0.0 See: q2sigma
 q2sigma REAL Default: 0.1 ecfixed, qcutz, q2sigma: parameters for modified functional to be used in variable-cell molecular dynamics (or in stress calculation). "ecfixed" is the value (in Rydberg) of the constant-cutoff; "qcutz" and "q2sigma" are the height and the width (in Rydberg) of the energy step for reciprocal vectors whose square modulus is greater than "ecfixed". In the kinetic energy, G^2 is replaced by G^2 + qcutz * (1 + erf ( (G^2 - ecfixed)/q2sigma) ) See: M. Bernasconi et al, J. Phys. Chem. Solids 56, 501 (1995), doi:10.1016/0022-3697(94)00228-2 
 input_dft CHARACTER Default: read from pseudopotential files Exchange-correlation functional: eg 'PBE', 'BLYP' etc See Modules/funct.f90 for allowed values. Overrides the value read from pseudopotential files. Use with care and if you know what you are doing! 
 ace LOGICAL Default: true Use Adaptively Compressed Exchange operator as in Lin Lin, J. Chem. Theory Comput. 2016, 12, 2242--2249, doi:10.1021/acs.jctc.6b00092 Set to false to use standard Exchange (much slower) 
 exx_fraction REAL Default: it depends on the specified functional Fraction of EXX for hybrid functional calculations. In the case of input_dft='PBE0', the default value is 0.25, while for input_dft='B3LYP' the exx_fraction default value is 0.20. 
 screening_parameter REAL Default: 0.106 screening_parameter for HSE like hybrid functionals. For more information, see: J. Chem. Phys. 118, 8207 (2003), doi:10.1063/1.1564060 J. Chem. Phys. 124, 219906 (2006), doi:10.1063/1.2204597 
 exxdiv_treatment CHARACTER Default: 'gygi-baldereschi' Specific for EXX. It selects the kind of approach to be used for treating the Coulomb potential divergencies at small q vectors.  'gygi-baldereschi' :  appropriate for cubic and quasi-cubic supercells  'vcut_spherical' :  appropriate for cubic and quasi-cubic supercells  'vcut_ws' :  appropriate for strongly anisotropic supercells, see also ecutvcut.  'none' :  sets Coulomb potential at G,q=0 to 0.0 (required for GAU-PBE) 
 x_gamma_extrapolation LOGICAL Default: .true. Specific for EXX. If .true., extrapolate the G=0 term of the potential (see README in examples/EXX_example for more) Set this to .false. for GAU-PBE. 
 ecutvcut REAL Default: 0.0 Ry See: exxdiv_treatment Reciprocal space cutoff for correcting Coulomb potential divergencies at small q vectors. 
 nqx1, nqx2, nqx3 INTEGER Three-dimensional mesh for q (k1-k2) sampling of the Fock operator (EXX). Can be smaller than the number of k-points. Currently this defaults to the size of the k-point mesh used. In QE =< 5.0.2 it defaulted to nqx1=nqx2=nqx3=1. 
 localization_thr REAL Default: 0.0 Overlap threshold over which the exchange integral over a pair of localized orbitals is included in the evaluation of EXX operator. Any value greater than 0.0 triggers the SCDM localization and the evaluation on EXX using the localized orbitals. Very small value of the threshold should yield the same result as the default EXX evaluation 
 lda_plus_u LOGICAL Default: .FALSE. Status: DFT+U (formerly known as LDA+U) currently works only for a few selected elements. Modify Modules/set_hubbard_l.f90 and PW/src/tabd.f90 if you plan to use DFT+U with an element that is not configured there. Specify lda_plus_u = .TRUE. to enable DFT+U, DFT+U+V, or DFT+U+J calculations. See: Anisimov, Zaanen, and Andersen, PRB 44, 943 (1991); Anisimov et al., PRB 48, 16929 (1993); Liechtenstein, Anisimov, and Zaanen, PRB 52, R5467 (1994). You must specify, for each Hubbard atom, the value of U and (optionally) V, J, alpha of the Hubbard model (all in eV): see lda_plus_u_kind, Hubbard_U, Hubbard_V, Hubbard_J, Hubbard_alpha 
 lda_plus_u_kind INTEGER Default: 0  Specifies the type of calculation:  lda_plus_u_kind = 0 : DFT+U simplified version of Cococcioni and de Gironcoli, PRB 71, 035105 (2005), using Hubbard_U  lda_plus_u_kind = 1 : DFT+U rotationally invariant scheme of Liechtenstein et al., using Hubbard_U and Hubbard_J  lda_plus_u_kind = 2 : DFT+U+V simplified version of Campo Jr and Cococcioni, J. Phys.: Condens. Matter 22, 055602 (2010), doi:10.1088/0953-8984/22/5/055602, using Hubbard_V 
 Hubbard_U(i), i=1,ntyp REAL Default: 0.D0 for all species Hubbard_U(i): U parameter (eV) for species i, DFT+U calculation 
 Hubbard_J0(i), i=1,ntype REAL Default: 0.D0 for all species Hubbard_J0(i): J0 parameter (eV) for species i, DFT+U+J calculation, see PRB 84, 115108 (2011) for details. 
 Hubbard_V(na,nb,k), (na,nb,k) = (1,1,1) ... (natx,27*natx,4) REAL Default: 0.D0 for all elements Hubbard_V(na,nb,k): V parameters (eV) between atoms na and nb, used in DFT+U+V calculations (only for lda_plus_u_kind=2). The atomic indices na and nb correspond to the atomic positions in the ATOMIC_POSITIONS card (this is not the same as Hubbard_U which is specified for ATOMIC_SPECIES). When na=nb, then Hubbard_V(na,na,k) is the on-site Hubbard_U for the atom na. natx=50 (if needed it can be changed in /Modules/parameters.f90) The index k controls the "interaction type" (k=1 is used for the simplest DFT+U+V calculation): k=1 - interaction between standard orbitals (both on na and nb); k=2 - interaction between standard (on na) and background (on nb) orbitals; k=3 - interaction between background orbitals (both on na and nb); k=4 - interaction between background (on na) and standard (on nb) orbitals. Standard orbitals correspond to the main Hubbard channel (e.g. d electrons in transition metals) and background orbitals correspond to the secondary Hubbard channel (e.g. p electrons in transition metals). 
 Hubbard_alpha(i), i=1,ntyp REAL Default: 0.D0 for all species Hubbard_alpha(i) is the perturbation (on atom i, in eV) used to compute U (and V) with the linear-response method of Cococcioni and de Gironcoli, PRB 71, 035105 (2005) (only for lda_plus_u_kind=0 and 2). Note: Hubbard U and V can be computed using the HP code which is based on density-functional perturbation theory, and it gives exactly the same result as the method of Cococcioni and de Gironcoli. 
 Hubbard_beta(i), i=1,ntyp REAL Default: 0.D0 for all species Hubbard_beta(i) is the perturbation (on atom i, in eV) used to compute J0 with the linear-response method of Cococcioni and de Gironcoli, PRB 71, 035105 (2005) (only for lda_plus_u_kind=0 and 2). See also PRB 84, 115108 (2011). 
 Hubbard_J(i,ityp), (i,ityp) = (1,1) ... (3,ntyp) REAL Default: 0.D0 for all species Hubbard_J(i,ityp): J parameters (eV) for species ityp, used in DFT+U calculations (only for lda_plus_u_kind=1) For p orbitals: J = Hubbard_J(1,ityp); For d orbitals: J = Hubbard_J(1,ityp), B = Hubbard_J(2,ityp); For f orbitals: J = Hubbard_J(1,ityp), E2 = Hubbard_J(2,ityp), E3= Hubbard_J(3,ityp). If B or E2 or E3 are not specified or set to 0 they will be calculated from J using atomic ratios. 
 starting_ns_eigenvalue(m,ispin,ityp), (m,ispin,ityp) = (1,1,1) ... (2*lmax+1,nspin or npol,ntyp) REAL Default: -1.d0 that means NOT SET In the first iteration of an DFT+U run it overwrites the m-th eigenvalue of the ns occupation matrix for the ispin component of atomic species ityp. For the noncollinear case, the ispin index runs up to npol=2 The value lmax is given by the maximum angular momentum number to which the Hubbard U is applied. Leave unchanged eigenvalues that are not set. This is useful to suggest the desired orbital occupations when the default choice takes another path. 
 U_projection_type CHARACTER Default: 'atomic' Only active when lda_plus_U is .true., specifies the type of projector on localized orbital to be used in the DFT+U scheme. Currently available choices:  'atomic' :  use atomic wfc's (as they are) to build the projector  'ortho-atomic' :  use Lowdin orthogonalized atomic wfc's  'norm-atomic' : Lowdin normalization of atomic wfc. Keep in mind: atomic wfc are not orthogonalized in this case. This is a "quick and dirty" trick to be used when atomic wfc from the pseudopotential are not normalized (and thus produce occupation whose value exceeds unity). If orthogonalized wfc are not needed always try 'atomic' first.  'file' : use the information from file "prefix".atwfc that must have been generated previously, for instance by pmw.x (see PP/src/poormanwannier.f90 for details).  'pseudo' : use the pseudopotential projectors. The charge density outside the atomic core radii is excluded. N.B.: for atoms with +U, a pseudopotential with the all-electron atomic wavefunctions is required (i.e., as generated by ld1.x with lsave_wfc flag).  NB: forces and stress currently implemented only for the 'atomic' and 'pseudo' choice. 
 Hubbard_parameters CHARACTER Default: 'input' Available choices:  'input' : read the Hubbard_U (or Hubbard_V) parameters from the PW input file  'file' : read the Hubbard_V parameters from the file "parameters.in" which can be generated after the linear-response calculation (using the HP code). This option has a higher priority over the Hubbard_V if they are specified in the input. This option can be used only when lda_plus_u_kind = 2. 
 ensemble_energies LOGICAL Default: .false. If ensemble_energies = .true., an ensemble of xc energies is calculated non-selfconsistently for perturbed exchange-enhancement factors and LDA vs. PBE correlation ratios after each converged electronic ground state calculation. Ensemble energies can be analyzed with the 'bee' utility included with libbeef. Requires linking against libbeef. input_dft must be set to a BEEF-type functional (e.g. input_dft = 'BEEF-vdW') 
edir INTEGER The direction of the electric field or dipole correction is parallel to the bg(:,edir) reciprocal lattice vector, so the potential is constant in planes defined by FFT grid points; edir = 1, 2 or 3. Used only if tefield is .TRUE. 
 emaxpos REAL Default: 0.5D0 Position of the maximum of the saw-like potential along crystal axis edir, within the unit cell (see below), 0 < emaxpos < 1 Used only if tefield is .TRUE. 
 eopreg REAL Default: 0.1D0 Zone in the unit cell where the saw-like potential decreases. ( see below, 0 < eopreg < 1 ). Used only if tefield is .TRUE. 
 eamp REAL Default: 0.001 a.u. Amplitude of the electric field, in ***Hartree*** a.u.; 1 a.u. = 51.4220632*10^10 V/m. Used only if tefield==.TRUE. The saw-like potential increases with slope eamp in the region from (emaxpos+eopreg-1) to (emaxpos), then decreases to 0 until (emaxpos+eopreg), in units of the crystal vector edir. Important: the change of slope of this potential must be located in the empty region, or else unphysical forces will result. 
angle1(i), i=1,ntyp REAL The angle expressed in degrees between the initial magnetization and the z-axis. For noncollinear calculations only; index i runs over the atom types. 
angle2(i), i=1,ntyp REAL The angle expressed in degrees between the projection of the initial magnetization on x-y plane and the x-axis. For noncollinear calculations only. 
lforcet LOGICAL When starting a non collinear calculation using an existing density file from a collinear lsda calculation assumes previous density points in z direction and rotates it in the direction described by angle1 and angle2 variables for atomic type 1 
 constrained_magnetization CHARACTER Default: 'none' See: lambda, fixed_magnetization Used to perform constrained calculations in magnetic systems. Currently available choices:  'none' : no constraint  'total' : total magnetization is constrained by adding a penalty functional to the total energy: LAMBDA * SUM_{i} ( magnetization(i) - fixed_magnetization(i) )**2 where the sum over i runs over the three components of the magnetization. Lambda is a real number (see below). Noncolinear case only. Use tot_magnetization for LSDA  'atomic' : atomic magnetization are constrained to the defined starting magnetization adding a penalty: LAMBDA * SUM_{i,itype} ( magnetic_moment(i,itype) - mcons(i,itype) )**2 where i runs over the cartesian components (or just z in the collinear case) and itype over the types (1-ntype). mcons(:,:) array is defined from starting_magnetization, (also from angle1, angle2 in the noncollinear case). lambda is a real number  'total direction' : the angle theta of the total magnetization with the z axis (theta = fixed_magnetization(3)) is constrained: LAMBDA * ( arccos(magnetization(3)/mag_tot) - theta )**2 where mag_tot is the modulus of the total magnetization.  'atomic direction' : not all the components of the atomic magnetic moment are constrained but only the cosine of angle1, and the penalty functional is: LAMBDA * SUM_{itype} ( mag_mom(3,itype)/mag_mom_tot - cos(angle1(ityp)) )**2  N.B.: symmetrization may prevent to reach the desired orientation of the magnetization. Try not to start with very highly symmetric configurations or use the nosym flag (only as a last remedy) 
 fixed_magnetization(i), i=1,3 REAL Default: 0.d0 See: constrained_magnetization total magnetization vector (x,y,z components) to be kept fixed when constrained_magnetization=='total' 
 lambda REAL Default: 1.d0 See: constrained_magnetization parameter used for constrained_magnetization calculations N.B.: if the scf calculation does not converge, try to reduce lambda to obtain convergence, then restart the run with a larger lambda 
 report INTEGER Default: -1 determines when atomic magnetic moments are printed on output: report = 0 never report =-1 at the beginning of the scf and at convergence report = N as -1, plus every N scf iterations 
lspinorb LOGICAL if .TRUE. the noncollinear code can use a pseudopotential with spin-orbit. 
 assume_isolated CHARACTER Default: 'none' Used to perform calculation assuming the system to be isolated (a molecule or a cluster in a 3D supercell). Currently available choices:  'none' : (default): regular periodic calculation w/o any correction.  'makov-payne', 'm-p', 'mp' : the Makov-Payne correction to the total energy is computed. An estimate of the vacuum level is also calculated so that eigenvalues can be properly aligned. ONLY FOR CUBIC SYSTEMS (ibrav=1,2,3). Theory: G.Makov, and M.C.Payne, "Periodic boundary conditions in ab initio calculations" , PRB 51, 4014 (1995).  'martyna-tuckerman', 'm-t', 'mt' : Martyna-Tuckerman correction to both total energy and scf potential. Adapted from: G.J. Martyna, and M.E. Tuckerman, "A reciprocal space based method for treating long range interactions in ab-initio and force-field-based calculation in clusters", J. Chem. Phys. 110, 2810 (1999), doi:10.1063/1.477923.  'esm' : Effective Screening Medium Method. For polarized or charged slab calculation, embeds the simulation cell within an effective semi- infinite medium in the perpendicular direction (along z). Embedding regions can be vacuum or semi-infinite metal electrodes (use esm_bc to choose boundary conditions). If between two electrodes, an optional electric field ('esm_efield') may be applied. Method described in M. Otani and O. Sugino, "First-principles calculations of charged surfaces and interfaces: A plane-wave nonrepeated slab approach", PRB 73, 115407 (2006). NB: - Two dimensional (xy plane) average charge density and electrostatic potentials are printed out to 'prefix.esm1'. - Requires cell with a_3 lattice vector along z, normal to the xy plane, with the slab centered around z=0. - For bc2 with an electric field and bc3 boundary conditions, the inversion symmetry along z-direction is automatically eliminated. - In case of calculation='vc-relax', use cell_dofree='2Dxy' or other parameters so that c-vector along z-axis should not be moved. See esm_bc, esm_efield, esm_w, esm_nfit.  '2D' : Truncation of the Coulomb interaction in the z direction for structures periodic in the x-y plane. Total energy, forces and stresses are computed in a two-dimensional framework. Linear-response calculations () done on top of a self-consistent calculation with this flag will automatically be performed in the 2D framework as well. Please refer to: Sohier, T., Calandra, M., & Mauri, F. (2017), Density functional perturbation theory for gated two-dimensional heterostructures: Theoretical developments and application to flexural phonons in graphene. Physical Review B, 96(7), 75448. https://doi.org/10.1103/PhysRevB.96.075448 NB: - The length of the unit-cell along the z direction should be larger than twice the thickness of the 2D material (including electrons). A reasonable estimate for a layer's thickness could be the interlayer distance in the corresponding layered bulk material. Otherwise, the atomic thickness + 10 bohr should be a safe estimate. There is also a lower limit of 20 bohr imposed by the cutoff radius used to read pseudopotentials (see read_pseudo.f90 in Modules). - As for ESM above, only in-plane stresses make sense and one should use cell_dofree='2Dxy' in a vc-relax calculation. 
 esm_bc CHARACTER Default: 'pbc' See: assume_isolated If assume_isolated = 'esm', determines the boundary conditions used for either side of the slab. Currently available choices:  'pbc' :  (default): regular periodic calculation (no ESM).  'bc1' :  Vacuum-slab-vacuum (open boundary conditions).  'bc2' : Metal-slab-metal (dual electrode configuration). See also esm_efield.  'bc3' :  Vacuum-slab-metal 
 esm_w REAL Default: 0.d0 See: assume_isolated If assume_isolated = 'esm', determines the position offset [in a.u.] of the start of the effective screening region, measured relative to the cell edge. (ESM region begins at z = +/- [L_z/2 + esm_w] ). 
 esm_efield REAL Default: 0.d0 See: assume_isolated If assume_isolated = 'esm' and esm_bc = 'bc2', gives the magnitude of the electric field [Ry/a.u.] to be applied between semi-infinite ESM electrodes. 
 esm_nfit INTEGER Default: 4 See: assume_isolated If assume_isolated = 'esm', gives the number of z-grid points for the polynomial fit along the cell edge. 
 lgcscf LOGICAL Default: .FALSE. If .TRUE. perform a constant bias potential (constant-mu) calculation with Grand-Canonical SCF. (JCP 146, 114104 (2017), R.Sundararaman, et al.) NB: - The total energy displayed in output includes the potentiostat contribution (-mu*N). - assume_isolated = 'esm' and esm_bc = 'bc2' or 'bc3' must be set in SYSTEM namelist. - ESM-RISM is also supported (assume_isolated = 'esm' and esm_bc = 'bc1' and trism = .TRUE.). - mixing_mode has to be 'TF' or 'local-TF', also its default is 'TF.' - The default of mixing_beta is 0.1 with ESM-RISM, 0.2 without ESM-RISM. - The default of diago_thr_init is 1.D-5. - diago_full_acc is always .TRUE. . - diago_rmm_conv is always .TRUE. . 
 gcscf_mu REAL Status: REQUIRED The target Fermi energy (eV) of GC-SCF. One can start with appropriate total charge of the system by giving tot_charge . 
 gcscf_conv_thr REAL Default: 1.D-2 Convergence threshold of Fermi energy (eV) for GC-SCF. 
 gcscf_beta REAL Default: 0.05D0 Mixing factor for GC-SCF. Larger values are recommended, if systems with small DOS on Fermi surface as graphite. 
 vdw_corr CHARACTER Default: 'none' See: london_s6, london_rcut, london_c6, london_rvdw, dftd3_version, dftd3_threebody, ts_vdw_econv_thr, ts_vdw_isolated, xdm_a1, xdm_a2, mbd_vdw Type of Van der Waals correction. Allowed values:  'grimme-d2', 'Grimme-D2', 'DFT-D', 'dft-d' : Semiempirical Grimme's DFT-D2. Optional variables: london_s6, london_rcut, london_c6, london_rvdw S. Grimme, J. Comp. Chem. 27, 1787 (2006), doi:10.1002/jcc.20495 V. Barone et al., J. Comp. Chem. 30, 934 (2009), doi:10.1002/jcc.21112  'grimme-d3', 'Grimme-D3', 'DFT-D3', 'dft-d3' : Semiempirical Grimme's DFT-D3. Optional variables: dftd3_version, dftd3_threebody S. Grimme et al, J. Chem. Phys 132, 154104 (2010), doi:10.1063/1.3382344  'TS', 'ts', 'ts-vdw', 'ts-vdW', 'tkatchenko-scheffler' : Tkatchenko-Scheffler dispersion corrections with first-principle derived C6 coefficients. Optional variables: ts_vdw_econv_thr, ts_vdw_isolated See A. Tkatchenko and M. Scheffler, PRL 102, 073005 (2009).  'mbd_vdw', 'many-body dispersion' : Many-body dipersion (MBD) correction to long-range interactions. Optional variables: ts_vdw_isolated A. Ambrosetti, A. M. Reilly, R. A. DiStasio, A. Tkatchenko, J. Chem. Phys. 140 18A508 (2014).  'XDM', 'xdm' : Exchange-hole dipole-moment model. Optional variables: xdm_a1, xdm_a2 A. D. Becke et al., J. Chem. Phys. 127, 154108 (2007), doi:10.1063/1.2795701 A. Otero de la Roza et al., J. Chem. Phys. 136, 174109 (2012), doi:10.1063/1.4705760   Note that non-local functionals (eg vdw-DF) are NOT specified here but in input_dft 
 london LOGICAL Default: .FALSE. Status: OBSOLESCENT, same as vdw_corr='DFT-D'
 london_s6 REAL Default: 0.75 global scaling parameter for DFT-D. Default is good for PBE. 
 london_c6(i), i=1,ntyp REAL Default: standard Grimme-D2 values atomic C6 coefficient of each atom type ( if not specified default values from S. Grimme, J. Comp. Chem. 27, 1787 (2006), doi:10.1002/jcc.20495 are used; see file Modules/mm_dispersion.f90 ) 
 london_rvdw(i), i=1,ntyp REAL Default: standard Grimme-D2 values atomic vdw radii of each atom type ( if not specified default values from S. Grimme, J. Comp. Chem. 27, 1787 (2006), doi:10.1002/jcc.20495 are used; see file Modules/mm_dispersion.f90 ) 
 london_rcut REAL Default: 200 cutoff radius (a.u.) for dispersion interactions 
 dftd3_version integer Default: 3 Version of Grimme implementation of Grimme-D3:  dftd3_version = 2 : Original Grimme-D2 parametrization  dftd3_version = 3 : Grimme-D3 (zero damping)  dftd3_version = 4 : Grimme-D3 (BJ damping)  dftd3_version = 5 : Grimme-D3M (zero damping)  dftd3_version = 6 : Grimme-D3M (BJ damping)  NOTE: not all functionals are parametrized. 
 dftd3_threebody LOGICAL Default: TRUE Turn three-body terms in Grimme-D3 on. If .false. two-body contributions only are computed, using two-body parameters of Grimme-D3. If dftd3_version=2, three-body contribution is always disabled. 
 ts_vdw_econv_thr REAL Default: 1.D-6 Optional: controls the convergence of the vdW energy (and forces). The default value is a safe choice, likely too safe, but you do not gain much in increasing it 
 ts_vdw_isolated LOGICAL Default: .FALSE. Optional: set it to .TRUE. when computing the Tkatchenko-Scheffler vdW energy or the Many-Body dispersion (MBD) energy for an isolated (non-periodic) system. 
 xdm LOGICAL Default: .FALSE. Status: OBSOLESCENT, same as vdw_corr='xdm'
 xdm_a1 REAL Default: 0.6836 Damping function parameter a1 (adimensional). It is NOT necessary to give a value if the functional is one of B86bPBE, PW86PBE, PBE, BLYP. For functionals in this list, the coefficients are given in: http://schooner.chem.dal.ca/wiki/XDM A. Otero de la Roza, E. R. Johnson, J. Chem. Phys. 138, 204109 (2013), doi:10.1063/1.4705760 
 xdm_a2 REAL Default: 1.5045 Damping function parameter a2 (angstrom). It is NOT necessary to give a value if the functional is one of B86bPBE, PW86PBE, PBE, BLYP. For functionals in this list, the coefficients are given in: http://schooner.chem.dal.ca/wiki/XDM A. Otero de la Roza, E. R. Johnson, J. Chem. Phys. 138, 204109 (2013), doi:10.1063/1.4705760 
 space_group INTEGER Default: 0 The number of the space group of the crystal, as given in the International Tables of Crystallography A (ITA). This allows to give in input only the inequivalent atomic positions. The positions of all the symmetry equivalent atoms are calculated by the code. Used only when the atomic positions are of type crystal_sg. See also uniqueb, origin_choice, rhombohedral 
 uniqueb LOGICAL Default: .FALSE. Used only for monoclinic lattices. If .TRUE. the b unique ibrav (-12 or -13) are used, and symmetry equivalent positions are chosen assuming that the twofold axis or the mirror normal is parallel to the b axis. If .FALSE. it is parallel to the c axis. 
 origin_choice INTEGER Default: 1 Used only for space groups that in the ITA allow the use of two different origins. origin_choice=1, means the first origin, while origin_choice=2 is the second origin. 
 rhombohedral LOGICAL Default: .TRUE. Used only for rhombohedral space groups. When .TRUE. the coordinates of the inequivalent atoms are given with respect to the rhombohedral axes, when .FALSE. the coordinates of the inequivalent atoms are given with respect to the hexagonal axes. They are converted internally to the rhombohedral axes and ibrav=5 is used in both cases. 

variables used only if gate = .TRUE.

 zgate REAL Default: 0.5 used only if gate = .TRUE. Specifies the position of the charged plate which represents the counter charge in doped systems (tot_charge .ne. 0). In units of the unit cell length in z direction, zgate in ]0,1[ Details of the gate potential can be found in T. Brumme, M. Calandra, F. Mauri; PRB 89, 245406 (2014). 
 relaxz LOGICAL Default: .FALSE. used only if gate = .TRUE. Allows the relaxation of the system towards the charged plate. Use carefully and utilize either a layer of fixed atoms or a potential barrier (block=.TRUE.) to avoid the atoms moving to the position of the plate or the dipole of the dipole correction (dipfield=.TRUE.). 
 block LOGICAL Default: .FALSE. used only if gate = .TRUE. Adds a potential barrier to the total potential seen by the electrons to mimic a dielectric in field effect configuration and/or to avoid electrons spilling into the vacuum region for electron doping. Potential barrier is from block_1 to block_2 and has a height of block_height. If dipfield = .TRUE. then eopreg is used for a smooth increase and decrease of the potential barrier. 
 block_1 REAL Default: 0.45 used only if gate = .TRUE. and block = .TRUE. lower beginning of the potential barrier, in units of the unit cell size along z, block_1 in ]0,1[ 
 block_2 REAL Default: 0.55 used only if gate = .TRUE. and block = .TRUE. upper beginning of the potential barrier, in units of the unit cell size along z, block_2 in ]0,1[ 
 block_height REAL Default: 0.1 used only if gate = .TRUE. and block = .TRUE. Height of the potential barrier in Rydberg. 

## Namelist: &ELECTRONS

 electron_maxstep INTEGER Default: 100 maximum number of iterations in a scf step 
 scf_must_converge LOGICAL Default: .TRUE. If .false. do not stop molecular dynamics or ionic relaxation when electron_maxstep is reached. Use with care. 
 conv_thr REAL Default: 1.D-6 Convergence threshold for selfconsistency: estimated energy error < conv_thr (note that conv_thr is extensive, like the total energy). For non-self-consistent calculations, conv_thr is used to set the default value of the threshold (ethr) for iterative diagonalizazion: see diago_thr_init 
 adaptive_thr LOGICAL Default: .FALSE If .TRUE. this turns on the use of an adaptive conv_thr for the inner scf loops when using EXX. 
 conv_thr_init REAL Default: 1.D-3 When adaptive_thr = .TRUE. this is the convergence threshold used for the first scf cycle. 
 conv_thr_multi REAL Default: 1.D-1 When adaptive_thr = .TRUE. the convergence threshold for each scf cycle is given by: max( conv_thr, conv_thr_multi * dexx ) 
 mixing_mode CHARACTER Default: 'plain'  Available options are:  'plain' :  charge density Broyden mixing  'TF' : as above, with simple Thomas-Fermi screening (for highly homogeneous systems)  'local-TF' : as above, with local-density-dependent TF screening (for highly inhomogeneous systems) 
 mixing_beta REAL Default: 0.7D0 mixing factor for self-consistency 
 mixing_ndim INTEGER Default: 8 number of iterations used in mixing scheme. If you are tight with memory, you may reduce it to 4 or so. 
 mixing_fixed_ns INTEGER Default: 0 For DFT+U : number of iterations with fixed ns ( ns is the atomic density appearing in the Hubbard term ). 
 diagonalization CHARACTER Default: 'david'  Available options are:  'david' : Davidson iterative diagonalization with overlap matrix (default). Fast, may in some rare cases fail.  'cg' : Conjugate-gradient-like band-by-band diagonalization. MUCH slower than 'david' but uses less memory and is (a little bit) more robust.  'ppcg' : PPCG iterative diagonalization  'paro', 'ParO' : ParO iterative diagonalization 
diago_thr_init REAL Convergence threshold (ethr) for iterative diagonalization (the check is on eigenvalue convergence). For scf calculations: default is 1.D-2 if starting from a superposition of atomic orbitals; 1.D-5 if starting from a charge density. During self consistency the threshold is automatically reduced (but never below 1.D-13) when approaching convergence. For non-scf calculations: default is (conv_thr/N elec)/10. 
diago_cg_maxiter INTEGER For conjugate gradient diagonalization: max number of iterations 
 diago_david_ndim INTEGER Default: 2 For Davidson diagonalization: dimension of workspace (number of wavefunction packets, at least 2 needed). A larger value may yield a smaller number of iterations in the algorithm but uses more memory and more CPU time in subspace diagonalization (cdiaghg/rdiaghg). You may try diago_david_ndim=4 if you are not tight on memory and if the time spent in subspace diagonalization is small compared to the time spent in h_psi 
 diago_full_acc LOGICAL Default: .FALSE. If .TRUE. all the empty states are diagonalized at the same level of accuracy of the occupied ones. Otherwise the empty states are diagonalized using a larger threshold (this should not affect total energy, forces, and other ground-state properties). 
 efield REAL Default: 0.D0 Amplitude of the finite electric field (in Ry a.u.; 1 a.u. = 36.3609*10^10 V/m). Used only if lelfield==.TRUE. and if k-points (K_POINTS card) are not automatic. 
 efield_cart(i), i=1,3 REAL Default: (0.D0, 0.D0, 0.D0) Finite electric field (in Ry a.u.=36.3609*10^10 V/m) in cartesian axis. Used only if lelfield==.TRUE. and if k-points (K_POINTS card) are automatic. 
 efield_phase CHARACTER Default: 'none'  Available options are:  'read' : set the zero of the electronic polarization (with lelfield==.true..) to the result of a previous calculation  'write' : write on disk data on electronic polarization to be read in another calculation  'none' : none of the above points 
startingpot CHARACTER  Available options are:  'atomic' : starting potential from atomic charge superposition (default for scf, *relax, *md)  'file' : start from existing "charge-density.xml" file in the directory specified by variables prefix and outdir For nscf and bands calculation this is the default and the only sensible possibility. 
 startingwfc CHARACTER Default: 'atomic+random'  Available options are:  'atomic' : Start from superposition of atomic orbitals. If not enough atomic orbitals are available, fill with random numbers the remaining wfcs The scf typically starts better with this option, but in some high-symmetry cases one can "loose" valence states, ending up in the wrong ground state.  'atomic+random' : As above, plus a superimposed "randomization" of atomic orbitals. Prevents the "loss" of states mentioned above.  'random' : Start from random wfcs. Slower start of scf but safe. It may also reduce memory usage in conjunction with diagonalization='cg'.  'file' : Start from an existing wavefunction file in the directory specified by variables prefix and outdir. 
 tqr LOGICAL Default: .FALSE. If .true., use a real-space algorithm for augmentation charges of ultrasoft pseudopotentials and PAWsets. Faster but numerically less accurate than the default G-space algorithm. Use with care and after testing! 
 real_space LOGICAL Default: .FALSE. If .true., exploit real-space localization to compute matrix elements for nonlocal projectors. Faster and in principle better scaling than the default G-space algorithm, but numerically less accurate, may lead to some loss of translational invariance. Use with care and after testing! 

## Namelist: &IONS

REQUIRED if calculation == 'relax', 'md', 'vc-relax', or 'vc-md' OPTIONAL for calculation == 'scf' (only ion_positions is used)

 ion_positions CHARACTER Default: 'default'  Available options are:  'default' : if restarting, use atomic positions read from the restart file; in all other cases, use atomic positions from standard input.  'from_input' : read atomic positions from standard input, even if restarting. 
 ion_velocities CHARACTER Default: 'default' Initial ionic velocities. Available options are:  'default' : start a new simulation from random thermalized distribution of velocities if tempw is set, with zero velocities otherwise; restart from atomic velocities read from the restart file  'from_input' : start or continue the simulation with atomic velocities read from standard input - see card ATOMIC_VELOCITIES 
ion_dynamics CHARACTER Specify the type of ionic dynamics. For different type of calculation different possibilities are allowed and different default values apply: CASE ( calculation == 'relax' )  'bfgs' : (default) use BFGS quasi-newton algorithm, based on the trust radius procedure, for structural relaxation  'damp' : use damped (quick-min Verlet) dynamics for structural relaxation Can be used for constrained optimisation: see CONSTRAINTS card  CASE ( calculation == 'md' )  'verlet' : (default) use Verlet algorithm to integrate Newton's equation. For constrained dynamics, see CONSTRAINTS card  'langevin' : ion dynamics is over-damped Langevin  'langevin-smc' : over-damped Langevin with Smart Monte Carlo: see R.J. Rossky, JCP, 69, 4628 (1978), doi:10.1063/1.436415  CASE ( calculation == 'vc-relax' )  'bfgs' : (default) use BFGS quasi-newton algorithm; cell_dynamics must be 'bfgs' too  'damp' : use damped (Beeman) dynamics for structural relaxation  CASE ( calculation == 'vc-md' )  'beeman' : (default) use Beeman algorithm to integrate Newton's equation 
 pot_extrapolation CHARACTER Default: 'atomic' Used to extrapolate the potential from preceding ionic steps.  'none' :  no extrapolation  'atomic' : extrapolate the potential as if it was a sum of atomic-like orbitals  'first_order' : extrapolate the potential with first-order formula  'second_order' : as above, with second order formula  Note: 'first_order' and 'second-order' extrapolation make sense only for molecular dynamics calculations 
 wfc_extrapolation CHARACTER Default: 'none' Used to extrapolate the wavefunctions from preceding ionic steps.  'none' :  no extrapolation  'first_order' : extrapolate the wave-functions with first-order formula.  'second_order' : as above, with second order formula.  Note: 'first_order' and 'second-order' extrapolation make sense only for molecular dynamics calculations 
 remove_rigid_rot LOGICAL Default: .FALSE. This keyword is useful when simulating the dynamics and/or the thermodynamics of an isolated system. If set to true the total torque of the internal forces is set to zero by adding new forces that compensate the spurious interaction with the periodic images. This allows for the use of smaller supercells. BEWARE: since the potential energy is no longer consistent with the forces (it still contains the spurious interaction with the repeated images), the total energy is not conserved anymore. However the dynamical and thermodynamical properties should be in closer agreement with those of an isolated system. Also the final energy of a structural relaxation will be higher, but the relaxation itself should be faster. 

variables used for molecular dynamics

 ion_temperature CHARACTER Default: 'not_controlled'  Available options are:  'rescaling' : control ionic temperature via velocity rescaling (first method) see parameters tempw, tolp, and nraise (for VC-MD only). This rescaling method is the only one currently implemented in VC-MD  'rescale-v' : control ionic temperature via velocity rescaling (second method) see parameters tempw and nraise  'rescale-T' : scale temperature of the thermostat every nraise steps by delta_t, starting from tempw. The temperature is controlled via velocitiy rescaling.  'reduce-T' : reduce temperature of the thermostat every nraise steps by the (negative) value delta_t, starting from tempw. If delta_t is positive, the target temperature is augmented. The temperature is controlled via velocitiy rescaling.  'berendsen' : control ionic temperature using "soft" velocity rescaling - see parameters tempw and nraise  'andersen' : control ionic temperature using Andersen thermostat see parameters tempw and nraise  'svr' : control ionic temperature using stochastic-velocity rescaling (Donadio, Bussi, Parrinello, J. Chem. Phys. 126, 014101, 2007), with parameters tempw and nraise.  'initial' : initialize ion velocities to temperature tempw and leave uncontrolled further on  'not_controlled' : (default) ionic temperature is not controlled 
 tempw REAL Default: 300.D0 Starting temperature (Kelvin) in MD runs target temperature for most thermostats. 
 tolp REAL Default: 100.D0 Tolerance for velocity rescaling. Velocities are rescaled if the run-averaged and target temperature differ more than tolp. 
 delta_t REAL Default: 1.D0 if ion_temperature == 'rescale-T' : at each step the instantaneous temperature is multiplied by delta_t; this is done rescaling all the velocities. if ion_temperature == 'reduce-T' : every 'nraise' steps the instantaneous temperature is reduced by -delta_t (i.e. delta_t < 0 is added to T) The instantaneous temperature is calculated at the end of every ionic move and BEFORE rescaling. This is the temperature reported in the main output. For delta_t < 0, the actual average rate of heating or cooling should be roughly C*delta_t/(nraise*dt) (C=1 for an ideal gas, C=0.5 for a harmonic solid, theorem of energy equipartition between all quadratic degrees of freedom). 
 nraise INTEGER Default: 1 if ion_temperature == 'reduce-T' : every nraise steps the instantaneous temperature is reduced by -delta_t (i.e. delta_t is added to the temperature) if ion_temperature == 'rescale-v' : every nraise steps the average temperature, computed from the last nraise steps, is rescaled to tempw if ion_temperature == 'rescaling' and calculation == 'vc-md' : every nraise steps the instantaneous temperature is rescaled to tempw if ion_temperature == 'berendsen' : the "rise time" parameter is given in units of the time step: tau = nraise*dt, so dt/tau = 1/nraise if ion_temperature == 'andersen' : the "collision frequency" parameter is given as nu=1/tau defined above, so nu*dt = 1/nraise if ion_temperature == 'svr' : the "characteristic time" of the thermostat is set to tau = nraise*dt 
 refold_pos LOGICAL Default: .FALSE. This keyword applies only in the case of molecular dynamics or damped dynamics. If true the ions are refolded at each step into the supercell. 

keywords used only in BFGS calculations

 upscale REAL Default: 100.D0 Max reduction factor for conv_thr during structural optimization conv_thr is automatically reduced when the relaxation approaches convergence so that forces are still accurate, but conv_thr will not be reduced to less that conv_thr / upscale. 
 bfgs_ndim INTEGER Default: 1 Number of old forces and displacements vectors used in the PULAY mixing of the residual vectors obtained on the basis of the inverse hessian matrix given by the BFGS algorithm. When bfgs_ndim = 1, the standard quasi-Newton BFGS method is used. (bfgs only) 
 trust_radius_max REAL Default: 0.8D0 Maximum ionic displacement in the structural relaxation. (bfgs only) 
 trust_radius_min REAL Default: 1.D-3 Minimum ionic displacement in the structural relaxation BFGS is reset when trust_radius < trust_radius_min. (bfgs only) 
 trust_radius_ini REAL Default: 0.5D0 Initial ionic displacement in the structural relaxation. (bfgs only) 
 w_1 REAL Default: 0.01D0 See: w_2
 w_2 REAL Default: 0.5D0 Parameters used in line search based on the Wolfe conditions. (bfgs only) 

## Namelist: &CELL

input this namelist only if calculation == 'vc-relax' or 'vc-md'

cell_dynamics CHARACTER Specify the type of dynamics for the cell. For different type of calculation different possibilities are allowed and different default values apply: CASE ( calculation == 'vc-relax' )  'none' :  no dynamics  'sd' :  steepest descent ( not implemented )  'damp-pr' : damped (Beeman) dynamics of the Parrinello-Rahman extended lagrangian  'damp-w' : damped (Beeman) dynamics of the new Wentzcovitch extended lagrangian  'bfgs' : BFGS quasi-newton algorithm (default) ion_dynamics must be 'bfgs' too  CASE ( calculation == 'vc-md' )  'none' :  no dynamics  'pr' : (Beeman) molecular dynamics of the Parrinello-Rahman extended lagrangian  'w' : (Beeman) molecular dynamics of the new Wentzcovitch extended lagrangian 
 press REAL Default: 0.D0 Target pressure [KBar] in a variable-cell md or relaxation run. 
 wmass REAL Default: 0.75*Tot_Mass/pi**2 for Parrinello-Rahman MD; 0.75*Tot_Mass/pi**2/Omega**(2/3) for Wentzcovitch MD Fictitious cell mass [amu] for variable-cell simulations (both 'vc-md' and 'vc-relax') 
 cell_factor REAL Default: 2.0 for variable-cell calculations, 1.0 otherwise Used in the construction of the pseudopotential tables. It should exceed the maximum linear contraction of the cell during a simulation. 
 press_conv_thr REAL Default: 0.5D0 Kbar Convergence threshold on the pressure for variable cell relaxation ('vc-relax' : note that the other convergence thresholds for ionic relaxation apply as well). 
 cell_dofree CHARACTER Default: 'all' Select which of the cell parameters should be moved:  'all' :  all axis and angles are moved  'ibrav' :  all axis and angles are moved, but the lattice remains consistent with the initial ibrav choice. You can use this option in combination with any other one by specifying "ibrav+option". Please note that some combinations do not make sense for some crystals and will guarantee that the relax will never converge. E.g. 'ibrav+2Dxy' is not a problem for hexagonal cells, but will never converge for cubic ones.  'x' :  only the x component of axis 1 (v1_x) is moved  'y' :  only the y component of axis 2 (v2_y) is moved  'z' :  only the z component of axis 3 (v3_z) is moved  'xy' :  only v1_x and v2_y are moved  'xz' :  only v1_x and v3_z are moved  'yz' :  only v2_y and v3_z are moved  'xyz' :  only v1_x, v2_y, v3_z are moved  'shape' :  all axis and angles, keeping the volume fixed  'volume' :  the volume changes, keeping all angles fixed (i.e. only celldm(1) changes)  '2Dxy' :  only x and y components are allowed to change  '2Dshape' :  as above, keeping the area in xy plane fixed  'epitaxial_ab' :  fix axis 1 and 2 while allowing axis 3 to move  'epitaxial_ac' :  fix axis 1 and 3 while allowing axis 2 to move  'epitaxial_bc' :  fix axis 2 and 3 while allowing axis 1 to move  BEWARE: if axis are not orthogonal, some of these options do not work (symmetry is broken). If you are not happy with them, edit subroutine init_dofree in file Modules/cell_base.f90 

## Namelist: &FCP

Input this namelist only if lfcp = .TRUE.

 fcp_mu REAL Status: REQUIRED The target Fermi energy (eV). One can start with appropriate total charge of the system by giving tot_charge . 
fcp_dynamics CHARACTER Specify the type of dynamics for the Fictitious Charge Particle (FCP). For different type of calculation different possibilities are allowed and different default values apply: CASE ( calculation == 'relax' )  'bfgs' : (default) BFGS quasi-newton algorithm, coupling with ions relaxation ion_dynamics must be 'bfgs' too  'newton' : Newton-Raphson algorithm with DIIS ion_dynamics must be 'damp' too  'damp' : damped (quick-min Verlet) dynamics for FCP relaxation ion_dynamics must be 'damp' too  'lm' : Line-Minimization algorithm for FCP relaxation ion_dynamics must be 'damp' too  CASE ( calculation == 'md' )  'velocity-verlet' : (default) Velocity-Verlet algorithm to integrate Newton's equation. ion_dynamics must be 'verlet' too  'verlet' : Verlet algorithm to integrate Newton's equation. ion_dynamics must be 'verlet' too 
 fcp_conv_thr REAL Default: 1.D-2 Convergence threshold on force (eV) for FCP relaxation. 
 fcp_ndiis INTEGER Default: 4 Size of DIIS for FCP relaxation, used only if fcp_dynamics = 'newton'. 

Variables used for FCP dynamics.

 fcp_mass REAL Default: 5.D+6 / (xy area) for ESM only; Mass of the FCP. 
 fcp_velocity REAL Default: determined by fcp_temperature Initial velocity of the FCP. 
 fcp_temperature CHARACTER Default: ion_temperature  Available options are:  'rescaling' : control FCP's temperature via velocity rescaling (first method) see parameters fpc_tempw and fcp_tolp.  'rescale-v' : control FCP's temperature via velocity rescaling (second method) see parameters fcp_tempw and fcp_nraise  'rescale-T' : control FCP's temperature via velocity rescaling (third method) see parameter fcp_delta_t  'reduce-T' : reduce FCP's temperature every fcp_nraise steps by the (negative) value fcp_delta_t  'berendsen' : control FCP's temperature using "soft" velocity rescaling - see parameters fcp_tempw and fcp_nraise  'andersen' : control FCP's temperature using Andersen thermostat see parameters fcp_tempw and fcp_nraise  'initial' : initialize FCP's velocities to temperature fcp_tempw and leave uncontrolled further on  'not_controlled' : (default) FCP's temperature is not controlled 
 fcp_tempw REAL Default: tempw Starting temperature (Kelvin) in FCP dynamics runs target temperature for most thermostats. 
 fcp_tolp REAL Default: tolp Tolerance for velocity rescaling. Velocities are rescaled if the run-averaged and target temperature differ more than tolp. 
 fcp_delta_t REAL Default: delta_t if fcp_temperature == 'rescale-T' : at each step the instantaneous temperature is multiplied by fcp_delta_t; this is done rescaling all the velocities. if fcp_temperature == 'reduce-T' : every fcp_nraise steps the instantaneous temperature is reduced by -fcp_delta_t (i.e. fcp_delta_t < 0 is added to T) The instantaneous temperature is calculated at the end of FCP's move and BEFORE rescaling. This is the temperature reported in the main output. For fcp_delta_t < 0, the actual average rate of heating or cooling should be roughly C*fcp_delta_t/(fcp_nraise*dt) (C=1 for an ideal gas, C=0.5 for a harmonic solid, theorem of energy equipartition between all quadratic degrees of freedom). 
 fcp_nraise INTEGER Default: nraise if fcp_temperature == 'reduce-T' : every fcp_nraise steps the instantaneous temperature is reduced by -fcp_delta_t (i.e. fcp_delta_t is added to the temperature) if fcp_temperature == 'rescale-v' : every fcp_nraise steps the average temperature, computed from the last fcp_nraise steps, is rescaled to fcp_tempw if fcp_temperature == 'berendsen' : the "rise time" parameter is given in units of the time step: tau = fcp_nraise*dt, so dt/tau = 1/fcp_nraise if fcp_temperature == 'andersen' : the "collision frequency" parameter is given as nu=1/tau defined above, so nu*dt = 1/fcp_nraise 
 freeze_all_atoms LOGICAL Default: .FALSE. If .TRUE., freeze all atoms to perform relaxation or dynamics only with FCP. 

## Card: ATOMIC_SPECIES

### Syntax:

ATOMIC_SPECIES
 X(1) Mass_X(1) PseudoPot_X(1) X(2) Mass_X(2) PseudoPot_X(2) . . . X(ntyp) Mass_X(ntyp) PseudoPot_X(ntyp)

### Description of items:

X CHARACTER label of the atom. Acceptable syntax: chemical symbol X (1 or 2 characters, case-insensitive) or chemical symbol plus a number or a letter, as in "Xn" (e.g. Fe1) or "X_*" or "X-*" (e.g. C1, C_h; max total length cannot exceed 3 characters) 
Mass_X REAL mass of the atomic species [amu: mass of C = 12] Used only when performing Molecular Dynamics run or structural optimization runs using Damped MD. Not actually used in all other cases (but stored in data files, so phonon calculations will use these values unless other values are provided) 
PseudoPot_X CHARACTER File containing PP for this species. The pseudopotential file is assumed to be in the new UPF format. If it doesn't work, the pseudopotential format is determined by the file name: *.vdb or *.van Vanderbilt US pseudopotential code *.RRKJ3 Andrea Dal Corso's code (old format) none of the above old PWscf norm-conserving format 

## Card: ATOMIC_POSITIONS { alat | bohr | angstrom | crystal | crystal_sg }

IF calculation == 'bands' OR calculation == 'nscf' :
 Specified atomic positions will be IGNORED and those from the previous scf calculation will be used instead !!! 
ELSE

### Syntax:

ATOMIC_POSITIONS { alat | bohr | angstrom | crystal | crystal_sg }
 X(1) x(1) y(1) z(1) { if_pos(1)(1) if_pos(2)(1) if_pos(3)(1) } X(2) x(2) y(2) z(2) { if_pos(1)(2) if_pos(2)(2) if_pos(3)(2) } . . . X(nat) x(nat) y(nat) z(nat) { if_pos(1)(nat) if_pos(2)(nat) if_pos(3)(nat) }

### Description of items:

Card's options: alat | bohr | angstrom | crystal | crystal_sg
Default: (DEPRECATED) alat
Units for ATOMIC_POSITIONS:

alat :
atomic positions are in cartesian coordinates, in
units of the lattice parameter (either celldm(1)
or A). If no option is specified, 'alat' is assumed;
not specifying units is DEPRECATED and will no
longer be allowed in the future

bohr :
atomic positions are in cartesian coordinate,
in atomic units (i.e. Bohr radii)

angstrom :
atomic positions are in cartesian coordinates, in Angstrom

crystal :
atomic positions are in crystal coordinates, i.e.
in relative coordinates of the primitive lattice
vectors as defined either in card CELL_PARAMETERS
or via the ibrav + celldm / a,b,c... variables

crystal_sg :
atomic positions are in crystal coordinates, i.e.
in relative coordinates of the primitive lattice.
This option differs from the previous one because
in this case only the symmetry inequivalent atoms
are given. The variable space_group must indicate
the space group number used to find the symmetry
equivalent atoms. The other variables that control
this option are uniqueb, origin_choice, and
rhombohedral.

X CHARACTER  label of the atom as specified in ATOMIC_SPECIES 
 x, y, z REAL atomic positions NOTE: each atomic coordinate can also be specified as a simple algebraic expression. To be interpreted correctly expression must NOT contain any blank space and must NOT start with a "+" sign. The available expressions are: + (plus), - (minus), / (division), * (multiplication), ^ (power) All numerical constants included are considered as double-precision numbers; i.e. 1/2 is 0.5, not zero. Other functions, such as sin, sqrt or exp are not available, although sqrt can be replaced with ^(1/2). Example: C 1/3 1/2*3^(-1/2) 0 is equivalent to C 0.333333 0.288675 0.000000 Please note that this feature is NOT supported by XCrysDen (which will display a wrong structure, or nothing at all). When atomic positions are of type crystal_sg coordinates can be given in the following four forms (Wyckoff positions): C 1a C 8g x C 24m x y C 48n x y z The first form must be used when the Wyckoff letter determines uniquely all three coordinates, forms 2,3,4 when the Wyckoff letter and 1,2,3 coordinates respectively are needed. The forms: C 8g x x x C 24m x x y are not allowed, but C x x x C x x y C x y z are correct. 
 if_pos(1), if_pos(2), if_pos(3) INTEGER Default: 1 component i of the force for this atom is multiplied by if_pos(i), which must be either 0 or 1. Used to keep selected atoms and/or selected components fixed in MD dynamics or structural optimization run. With crystal_sg atomic coordinates the constraints are copied in all equivalent atoms. 

## Card: K_POINTS { tpiba | automatic | crystal | gamma | tpiba_b | crystal_b | tpiba_c | crystal_c }

IF tpiba OR crystal OR tpiba_b OR crystal_b OR tpiba_c OR crystal_c :

### Syntax:

K_POINTS tpiba | crystal | tpiba_b | crystal_b | tpiba_c | crystal_c
nks
 xk_x(1) xk_y(1) xk_z(1) wk(1) xk_x(2) xk_y(2) xk_z(2) wk(2) . . . xk_x(nks) xk_y(nks) xk_z(nks) wk(nks)
ELSEIF automatic :

### Syntax:

K_POINTS automatic
ELSEIF gamma :

K_POINTS gamma

### Description of items:

Card's options: tpiba | automatic | crystal | gamma | tpiba_b | crystal_b | tpiba_c | crystal_c
Default: tbipa
K_POINTS options are:

tpiba :
read k-points in cartesian coordinates,
in units of 2 pi/a (default)

automatic :
automatically generated uniform grid of k-points, i.e,
generates ( nk1, nk2, nk3 ) grid with ( sk1, sk2, sk3 ) offset.
nk1, nk2, nk3 as in Monkhorst-Pack grids
k1, k2, k3 must be 0 ( no offset ) or 1 ( grid displaced
by half a grid step in the corresponding direction )
BEWARE: only grids having the full symmetry of the crystal
work with tetrahedra. Some grids with offset may not work.

crystal :
read k-points in crystal coordinates, i.e. in relative
coordinates of the reciprocal lattice vectors

gamma :
use k = 0 (no need to list k-point specifications after card)
In this case wavefunctions can be chosen as real,
and specialized subroutines optimized for calculations
at the gamma point are used (memory and cpu requirements
are reduced by approximately one half).

tpiba_b :
Used for band-structure plots.
See Doc/brillouin_zones.pdf for usage of BZ labels;
otherwise, k-points are in units of  2 pi/a.
nks points specify nks-1 lines in reciprocal space.
Every couple of points identifies the initial and
final point of a line. pw.x generates N intermediate
points of the line where N is the weight of the first point.

crystal_b :
As tpiba_b, but k-points are in crystal coordinates.
See Doc/brillouin_zones.pdf for usage of BZ labels.

tpiba_c :
Used for band-structure contour plots.
k-points are in units of  2 pi/a. nks must be 3.
3 k-points k_0, k_1, and k_2 specify a rectangle
in reciprocal space of vertices k_0, k_1, k_2,
k_1 + k_2 - k_0: k_0 + \alpha (k_1-k_0)+
\beta (k_2-k_0) with 0 <\alpha,\beta < 1.
The code produces a uniform mesh n1 x n2
k points in this rectangle. n1 and n2 are
the weights of k_1 and k_2. The weight of k_0
is not used.

crystal_c :
As tpiba_c, but k-points are in crystal coordinates.

nks INTEGER  Number of supplied special k-points. 
 xk_x, xk_y, xk_z, wk REAL Special k-points (xk_x/y/z) in the irreducible Brillouin Zone (IBZ) of the lattice (with all symmetries) and weights (wk) See the literature for lists of special points and the corresponding weights. If the symmetry is lower than the full symmetry of the lattice, additional points with appropriate weights are generated. Notice that such procedure assumes that ONLY k-points in the IBZ are provided in input In a non-scf calculation, weights do not affect the results. If you just need eigenvalues and eigenvectors (for instance, for a band-structure plot), weights can be set to any value (for instance all equal to 1). 
 nk1, nk2, nk3 INTEGER These parameters specify the k-point grid (nk1 x nk2 x nk3) as in Monkhorst-Pack grids. 
 sk1, sk2, sk3 INTEGER The grid offsets; sk1, sk2, sk3 must be 0 ( no offset ) or 1 ( grid displaced by half a grid step in the corresponding direction ). 

## Card: ADDITIONAL_K_POINTS { tpiba | crystal | gamma | tpiba_b | crystal_b | tpiba_c | crystal_c }

Optional card. Adds a list of k-points with zero weight, after those used for
the scf calculation. When doing an EXX calculation and nq1x, nq2x or nq3x are
different from one, also include the required k+q points. The main use of this
card is to do band plots with EXX.


### Syntax:

ADDITIONAL_K_POINTS tpiba | crystal | tpiba_b | crystal_b | tpiba_c | crystal_c

### Description of items:

Card's options: tpiba | crystal | gamma | tpiba_b | crystal_b | tpiba_c | crystal_c
Default: tbipa
for the explanation of the K_POINTS' options, see K_POINTS

nks_add INTEGER  Number of supplied "additional" k-points. 
 k_x, k_y, k_z, wk_ REAL for the respective explanation, see the xk_x, xk_y, xk_z, wk 

## Card: CELL_PARAMETERS { alat | bohr | angstrom }

Optional card, needed only if ibrav == 0 is specified, ignored otherwise !

### Syntax:

CELL_PARAMETERS { alat | bohr | angstrom }
 v1(1) v1(2) v1(3) v2(1) v2(2) v2(3) v3(1) v3(2) v3(3)

### Description of items:

Card's options: alat | bohr | angstrom
Unit for lattice vectors; options are:

'bohr' / 'angstrom':
lattice vectors in bohr-radii / angstrom.
In this case the lattice parameter alat = sqrt(v1*v1).

'alat' / nothing specified:
lattice vectors in units of the lattice parameter (either
celldm(1) or A). Not specifying units is DEPRECATED
and will not be allowed in the future.

If neither unit nor lattice parameter are specified,
'bohr' is assumed - DEPRECATED, will no longer be allowed

 v1, v2, v3 REAL Crystal lattice vectors (in cartesian axis): v1(1) v1(2) v1(3) ... 1st lattice vector v2(1) v2(2) v2(3) ... 2nd lattice vector v3(1) v3(2) v3(3) ... 3rd lattice vector 

## Card: CONSTRAINTS

Optional card, used for constrained dynamics or constrained optimisations (only if ion_dynamics=='damp' or 'verlet', variable-cell excepted)

When this card is present the SHAKE algorithm is automatically used.


### Syntax:

CONSTRAINTS
nconstr   { constr_tol   }
 constr_type(1) constr(1)(1) constr(2)(1) [ constr(3)(1) constr(4)(1) ] { constr_target(1) } constr_type(2) constr(1)(2) constr(2)(2) [ constr(3)(2) constr(4)(2) ] { constr_target(2) } . . . constr_type(nconstr) constr(1)(nconstr) constr(2)(nconstr) [ constr(3)(nconstr) constr(4)(nconstr) ] { constr_target(nconstr) }

### Description of items:

nconstr INTEGER  Number of constraints. 
constr_tol REAL  Tolerance for keeping the constraints satisfied. 
constr_type CHARACTER Type of constraint :  'type_coord' : constraint on global coordination-number, i.e. the average number of atoms of type B surrounding the atoms of type A. The coordination is defined by using a Fermi-Dirac. (four indexes must be specified).  'atom_coord' : constraint on local coordination-number, i.e. the average number of atoms of type A surrounding a specific atom. The coordination is defined by using a Fermi-Dirac. (four indexes must be specified).  'distance' : constraint on interatomic distance (two atom indexes must be specified).  'planar_angle' : constraint on planar angle (three atom indexes must be specified).  'torsional_angle' : constraint on torsional angle (four atom indexes must be specified).  'bennett_proj' : constraint on the projection onto a given direction of the vector defined by the position of one atom minus the center of mass of the others. G. Roma, J.P. Crocombette: J. Nucl. Mater. 403, 32 (2010), doi:10.1016/j.jnucmat.2010.06.001 
 constr(1), constr(2), constr(3), constr(4) These variables have different meanings for different constraint types: 'type_coord' : constr(1) is the first index of the atomic type involved constr(2) is the second index of the atomic type involved constr(3) is the cut-off radius for estimating the coordination constr(4) is a smoothing parameter 'atom_coord' : constr(1) is the atom index of the atom with constrained coordination constr(2) is the index of the atomic type involved in the coordination constr(3) is the cut-off radius for estimating the coordination constr(4) is a smoothing parameter 'distance' : atoms indices object of the constraint, as they appear in the ATOMIC_POSITIONS card 'planar_angle', 'torsional_angle' : atoms indices object of the constraint, as they appear in the ATOMIC_POSITIONS card (beware the order) 'bennett_proj' : constr(1) is the index of the atom whose position is constrained. constr(2:4) are the three coordinates of the vector that specifies the constraint direction. 
constr_target REAL Target for the constrain ( angles are specified in degrees ). This variable is optional. 

## Card: OCCUPATIONS

Optional card, used only if occupations == 'from_input', ignored otherwise !

### Syntax:

OCCUPATIONS
 f_inp1(1) f_inp1(2) . . . f_inp1(nbnd) [ f_inp2(1) f_inp2(2) . . . f_inp2(nbnd) ]

### Description of items:

f_inp1 REAL Occupations of individual states (MAX 10 PER ROW). For spin-polarized calculations, these are majority spin states. 
f_inp2 REAL Occupations of minority spin states (MAX 10 PER ROW) To be specified only for spin-polarized calculations. 

## Card: ATOMIC_VELOCITIES { a.u }

Optional card, reads velocities from standard input

### Syntax:

ATOMIC_VELOCITIES { a.u }
 V(1) vx(1) vy(1) vz(1) V(2) vx(2) vy(2) vz(2) . . . V(nat) vx(nat) vy(nat) vz(nat)

### Description of items:

V CHARACTER  label of the atom as specified in ATOMIC_SPECIES 
 vx, vy, vz REAL  atomic velocities along x y and z direction 

## Card: ATOMIC_FORCES

Optional card used to specify external forces acting on atoms.

BEWARE: if the sum of external forces is not zero, the center of mass of
the system will move


### Syntax:

ATOMIC_FORCES
 X(1) fx(1) fy(1) fz(1) X(2) fx(2) fy(2) fz(2) . . . X(nat) fx(nat) fy(nat) fz(nat)

### Description of items:

X CHARACTER  label of the atom as specified in ATOMIC_SPECIES 
 fx, fy, fz REAL external force on atom X (cartesian components, Ry/a.u. units) 
This file has been created by helpdoc utility on Fri Jul 16 11:28:04 CEST 2021.