# Input File Description

## Program: ph.x / PWscf / Quantum Espresso (version: 6.2)

INTRODUCTION

&INPUTPH

amass | outdir | prefix | niter_ph | tr2_ph | alpha_mix(niter) | nmix_ph | verbosity | reduce_io | max_seconds | fildyn | fildrho | fildvscf | epsil | lrpa | lnoloc | trans | lraman | eth_rps | eth_ns | dek | recover | low_directory_check | only_init | qplot | q2d | q_in_band_form | electron_phonon | lshift_q | zeu | zue | elop | fpol | ldisp | nogg | asr | ldiag | lqdir | search_sym | nq1 | nq2 | nq3 | nk1 | nk2 | nk3 | k1 | k2 | k3 | start_irr | last_irr | nat_todo | modenum | start_q | last_q | dvscf_star | drho_star

qPointsSpecs

nqs | xq1 | xq2 | xq3 | nq

### INTRODUCTION

Input data format: { } = optional, [ ] = it depends, # = comment

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

title_line

&INPUTPH
...
/

[ xq(1) xq(2) xq(3) ]                        # if ldisp != .true.  and  qplot != .true.

[ nqs                                        # if qplot == .true.
xq(1,i)    xq(2,i)    xq(3,1)    nq(1)
...
xq(1,nqs)  xq(2,nqs)  xq(3,nqs)  nq(nqs) ]

[ atom(1)  atom(2)  ... atom(nat_todo) ]     # if nat_todo was specified

title_line

### Description of items:

title_line CHARACTER Title of the job, i.e., a line that is reprinted on output.

## Namelist: &INPUTPH

 amass(i), i=1,ntyp REAL Default: 0.0 Atomic mass [amu] of each atomic type. If not specified, masses are read from data file.
 outdir CHARACTER Default: value of the ESPRESSO_TMPDIR environment variable if set; current directory ('./') otherwise Directory containing input, output, and scratch files; must be the same as specified in the calculation of the unperturbed system.
 prefix CHARACTER Default: 'pwscf' Prepended to input/output filenames; must be the same used in the calculation of unperturbed system.
 niter_ph INTEGER Default: maxter=100 Maximum number of iterations in a scf step. If you want more than 100, edit variable "maxter" in PH/phcom.f90
 tr2_ph REAL Default: 1e-12 Threshold for self-consistency.
 alpha_mix(niter) REAL Default: alpha_mix(1)=0.7 Mixing factor (for each iteration) for updating the scf potential: vnew(in) = alpha_mix*vold(out) + (1-alpha_mix)*vold(in)
 nmix_ph INTEGER Default: 4 Number of iterations used in potential mixing.
 verbosity CHARACTER Default: 'default' Options are: 'debug', 'high', 'medium' : verbose output 'low', 'default', 'minimal' : short output
 reduce_io LOGICAL Default: .false. Reduce I/O to the strict minimum.
 max_seconds REAL Default: 1.d7 Maximum allowed run time before the job stops smoothly.
 fildyn CHARACTER Default: 'matdyn' File where the dynamical matrix is written.
 fildrho CHARACTER Default: ' ' File where the charge density responses are written. Note that the file will actually be saved as ${outdir}/_ph0/${prefix}.${fildrho}1 where${outdir}, ${prefix} and${fildrho} are the values of the corresponding input variables
 fildvscf CHARACTER Default: ' ' File where the the potential variation is written (for later use in electron-phonon calculation, see also fildrho).
 epsil LOGICAL Default: .false. If .true. in a q=0 calculation for a non metal the macroscopic dielectric constant of the system is computed. Do not set epsil to .true. if you have a metallic system or q/=0: the code will complain and stop.
 lrpa LOGICAL Default: .false. If .true. the dielectric constant is calculated at the RPA level with DV_xc=0.
 lnoloc LOGICAL Default: .false. If .true. the dielectric constant is calculated without local fields, i.e. by setting DV_H=0 and DV_xc=0.
 trans LOGICAL Default: .true. If .true. the phonons are computed. If trans .and. epsil are .true. effective charges are calculated.
 lraman LOGICAL Default: .false. If .true. calculate non-resonant Raman coefficients using second-order response as in: M. Lazzeri and F. Mauri, PRL 90, 036401 (2003).

Optional variables for Raman:

 eth_rps REAL Default: 1.0d-9 Threshold for calculation of Pc R |psi>.
 eth_ns REAL Default: 1.0e-12 Threshold for non-scf wavefunction calculation.
 dek REAL Default: 1.0e-3 Delta_xk used for wavefunction derivation wrt k.
 recover LOGICAL Default: .false. If .true. restart from an interrupted run.
 low_directory_check LOGICAL Default: .false. If .true. search in the phsave directory only the quantities requested in input.
 only_init LOGICAL Default: .false. If .true. only the bands and other initialization quantities are calculated. (used for GRID parallelization)
 qplot LOGICAL Default: .false. If .true. a list of q points is read from input.
 q2d LOGICAL Default: .false. If .true. three q points and relative weights are read from input. The three q points define the rectangle q(:,1) + l (q(:,2)-q(:,1)) + m (q(:,3)-q(:,1)) where 0< l,m < 1. The weights are integer and those of points two and three are the number of points in the two directions.
 q_in_band_form LOGICAL Default: .false. This flag is used only when qplot is .true. and q2d is .false.. When .true. each couple of q points q(:,i+1) and q(:,i) define the line from q(:,i) to q(:,i+1) and nq points are generated along that line. nq is the weigth of q(:,i). When .false. only the list of q points given as input is calculated. The weights are not used.
 electron_phonon CHARACTER Default: ' ' Options are: 'simple' : Electron-phonon lambda coefficients are computed for a given q and a grid of k-points specified by the variables nk1, nk2, nk3, k1, k2, k3. 'interpolated' : Electron-phonon is calculated by interpolation over the Brillouin Zone as in M. Wierzbowska, et al. arXiv:cond-mat/0504077 'lambda_tetra' : The electron-phonon coefficient \lambda_{q \nu} is calculated with the optimized tetrahedron method. 'gamma_tetra' : The phonon linewidth \gamma_{q \nu} is calculated from the electron-phonon interactions using the optimized tetrahedron method. For metals only, requires gaussian smearing. If trans=.true., the lambdas are calculated in the same run, using the same k-point grid for phonons and lambdas. If trans=.false., the lambdas are calculated using previously saved DeltaVscf in fildvscf, previously saved dynamical matrix, and the present punch file. This allows the use of a different (larger) k-point grid.
 lshift_q LOGICAL Default: .false. Use a wave-vector grid displaced by half a grid step in each direction - meaningful only when ldisp is .true. When this option is set, the q2r.x code cannot be used.
 zeu LOGICAL Default: zeu=epsil If .true. in a q=0 calculation for a non metal the effective charges are computed from the dielectric response. This is the default algorithm. If epsil=.true. and zeu=.false. only the dielectric tensor is calculated.
 zue LOGICAL Default: .false. If .true. in a q=0 calculation for a non metal the effective charges are computed from the phonon density responses. This is an alternative algorithm, different from the default one (if trans .and. epsil ) The results should be the same within numerical noise.
 elop LOGICAL Default: .false. If .true. calculate electro-optic tensor.
 fpol LOGICAL Default: .false. If .true. calculate dynamic polarizabilities Requires epsil=.true. ( experimental stage: see example09 for calculation of methane ).
 ldisp LOGICAL Default: .false. If .true. the run calculates phonons for a grid of q-points specified by nq1, nq2, nq3 - for direct calculation of the entire phonon dispersion.
 nogg LOGICAL Default: .false. If .true. disable the "gamma_gamma" trick used to speed up calculations at q=0 (phonon wavevector) if the sum over the Brillouin Zone includes k=0 only. The gamma_gamma trick exploits symmetry and acoustic sum rule to reduce the number of linear response calculations to the strict minimum, as it is done in code phcg.x.
 asr LOGICAL Default: .false. Apply Acoustic Sum Rule to dynamical matrix, effective charges Works only in conjunction with "gamma_gamma" tricks (see above)
 ldiag LOGICAL Default: .false. If .true. forces the diagonalization of the dynamical matrix also when only a part of the dynamical matrix has been calculated. It is used together with start_irr and last_irr. If all modes corresponding to a given irreducible representation have been calculated, the phonon frequencies of that representation are correct. The others are zero or wrong. Use with care.
 lqdir LOGICAL Default: .false. If .true. ph.x creates inside outdir a separate subdirectory for each q vector. The flag is set to .true. when ldisp=.true. and fildvscf /= ' ' or when an electron-phonon calculation is performed. The induced potential is saved separately for each q inside the subdirectories.
 search_sym LOGICAL Default: .true. Set it to .false. if you want to disable the mode symmetry analysis.
 nq1, nq2, nq3 INTEGER Default: 0,0,0 Parameters of the Monkhorst-Pack grid (no offset) used when ldisp=.true. Same meaning as for nk1, nk2, nk3 in the input of pw.x.
 nk1, nk2, nk3, k1, k2, k3 INTEGER Default: 0,0,0,0,0,0 When these parameters are specified the phonon program runs a pw non-self consistent calculation with a different k-point grid thant that used for the charge density. This occurs even in the Gamma case. nk1,nk2,nk3 are the parameters of the Monkhorst-Pack grid with offset determined by k1,k2,k3.

Specification of irreducible representation

 start_irr INTEGER Default: 1 See: last_irr Perform calculations only from start_irr to last_irr irreducible representations. IMPORTANT: * start_irr must be <= 3*nat * do not specify nat_todo together with start_irr, last_irr
 last_irr INTEGER Default: 3*nat See: start_irr Perform calculations only from start_irr to last_irr irreducible representations. IMPORTANT: * start_irr must be <= 3*nat * do not specify nat_todo together with start_irr, last_irr
 nat_todo INTEGER Default: 0, i.e. displace all atoms Choose the subset of atoms to be used in the linear response calculation: nat_todo atoms, specified in input (see below) are displaced. Can be used to estimate modes for a molecule adsorbed over a surface without performing a full fledged calculation. Use with care, at your own risk, and be aware that this is an approximation and may not work. IMPORTANT: * nat_todo <= nat * if linear-response is calculated for a given atom, it should also be done for all symmetry-equivalent atoms, or else you will get incorrect results
 modenum INTEGER Default: 0 For single-mode phonon calculation : modenum is the index of the irreducible representation (irrep) into which the reducible representation formed by the 3*nat atomic displacements are decomposed in order to perform the phonon calculation. Note that a single-mode calculation will not give you the frequency of a single phonon mode: in general, the selected "modenum" is not an eigenvector. What you get on output is a column of the dynamical matrix.

q-point specification

 start_q INTEGER Default: 1 See: last_q Used only when ldisp=.true.. Computes only the q points from start_q to last_q. IMPORTANT: * start_q must be <= nqs (number of q points found) * do not specify nat_todo together with start_q, last_q
 last_q INTEGER Default: number of q points See: start_q Used only when ldisp=.true.. Computes only the q points from start_q to last_q. IMPORTANT * last_q must be <= nqs (number of q points) * do not specify nat_todo together with start_q, last_q
 dvscf_star STRUCTURE Default: disabled It contains the following components: dvscf_star%open (logical, default: .false.) dvscf_star%dir (character, default: outdir//"Rotated_DVSCF" or the ESPRESSO_FILDVSCF_DIR environment variable) dvscf_star%ext (character, default: "dvscf") the extension to use for the name of the output files, see below dvscf_star%basis (character, default: "cartesian") the basis on which the rotated dvscf will be saved dvscf_star%pat (logical, default: false) save an optional file with the displacement patterns and q vector for each dvscf file IF dvscf_star%open is .true. use symmetry to compute and store the variation of the self-consistent potential on every q* in the star of the present q. The rotated dvscf will then be stored in directory dvscf_star%dir with name prefix.dvscf_star%ext.q_name//"1". Where q_name is derived from the coordinates of the q-point, expressed as fractions in crystalline coordinates (notice that ph.x reads q-points in cartesian coordinates). E.g. q_cryst= (0, 0.5, -0.25) -> q_name = "0_1o2_-1o4" The dvscf can be represented on a basis of cartesian 1-atom displacements (dvscf_star%basis='cartesian') or on the basis of the modes at the rotated q-point (dvscf_star%basis='modes'). Notice that the el-ph wannier code requires 'cartesian'. Each dvscf file comes with a corresponding pattern file with an additional ".pat" suffix; this file contains information about the basis and the q-point of the dvscf. Note: rotating dvscf can require a large amount of RAM memory and can be i/o intensive; in its current implementation all the operations are done on a single processor. Note2: this feature is currently untested with image parallelisation.
 drho_star STRUCTURE Default: disabled See: dvscf_star It contains the following components: drho_star%open (logical, default: .false.) drho_star%dir (character, default: outdir//"Rotated_DRHO" or the ESPRESSO_FILDRHO_DIR environment variable) drho_star%ext (character, default: "drho") the extension to use for the name of the output files, see below drho_star%basis (character, default: "modes") the basis on which the rotated drho will be saved drho_star%pat (logical, default: true) save an optional file with the displacement patterns and q vector for each drho file Like dvscf_star, but for the perturbation of the charge density. Notice that the defaults are different.
IF ldisp != .true. and qplot != .true. :

### Syntax:

xq(1) xq(2) xq(3)

### Description of items:

 xq(1) xq(2) xq(3) REAL The phonon wavevector, in units of 2pi/a0 (a0 = lattice parameter). Not used if ldisp=.true. or qplot=.true.
ELSEIF qplot == .true. :

Specification of q points when qplot == .true.

## Card: qPointsSpecs

### Syntax:

nqs
 xq1(1) xq2(1) xq3(1) nq(1) xq1(2) xq2(2) xq3(2) nq(2) . . . xq1(nqs) xq2(nqs) xq3(nqs) nq(nqs)

### Description of items:

nqs INTEGER Number of q points in the list. Used only if qplot=.true.
 xq1, xq2, xq3 REAL q-point coordinates; used only with ldisp=.true. and qplot=.true. The phonon wavevector, in units of 2pi/a0 (a0 = lattice parameter). The meaning of these q points and their weights nq depend on the flags q2d and q_in_band_form. (NB: nq is integer)
nq INTEGER The weight of the q-point; the meaning of nq depends on the flags q2d and q_in_band_form.
IF nat_todo was specified :

### Syntax:

atom(1) atom(2) ... atom(nat_todo)

### Description of items:

 atom(1) atom(2) ... atom(nat_todo) INTEGER Contains the list of indices of atoms used in the calculation if nat_todo is specified.

NB: The program ph.x writes on the tmp_dir/_ph0/{prefix}.phsave directory
a file for each representation of each q point. This file is called
dynmat.#iq.#irr.xml where #iq is the number of the q point and #irr
is the number of the representation. These files contain the
contribution to the dynamical matrix of the irr representation for the
iq point.

If recover=.true. ph.x does not recalculate the
representations already saved in the tmp_dir/_ph0/{prefix}.phsave
directory.  Moreover ph.x writes on the files patterns.#iq.xml in the
tmp_dir/_ph0/{prefix}.phsave directory the displacement patterns that it
is using. If recover=.true. ph.x does not recalculate the
displacement patterns found in the tmp_dir/_ph0/{prefix}.phsave directory.

This mechanism allows:

1) To recover part of the ph.x calculation even if the recover file
or files are corrupted. You just remove the _ph0/{prefix}.recover
files from the tmp_dir directory. You can also remove all the _ph0
files and keep only the _ph0/{prefix}.phsave directory.

2) To split a phonon calculation into several jobs for different
machines (or set of nodes). Each machine calculates a subset of
the representations and saves its dynmat.#iq.#irr.xml files on
its tmp_dir/_ph0/{prefix}.phsave directory. Then you collect all the
dynmat.#iq.#irr.xml files in one directory and run ph.x to
collect all the dynamical matrices and diagonalize them.

NB: To split the q points in different machines, use the input
variables start_q and last_q. To split the irreducible
representations, use the input variables start_irr, last_irr. Please
note that different machines will use, in general, different
displacement patterns and it is not possible to recollect partial
dynamical matrices generated with different displacement patterns.  A
calculation split into different machines will run as follows: A
preparatory run of ph.x with start_irr=0, last_irr=0 produces the sets
of displacement patterns and save them on the patterns.#iq.xml files.
These files are copied in all the tmp_dir/_ph0/{prefix}.phsave directories
of the machines where you plan to run ph.x. ph.x is run in different
machines with complementary sets of start_q, last_q, start_irr and
last_irr variables.  All the files dynmat.#iq.#irr.xml are
collected on a single tmp_dir/_ph0/{prefix}.phsave directory (remember to
collect also dynmat.#iq.0.xml).  A final run of ph.x in this
machine collects all the data contained in the files and diagonalizes
the dynamical matrices.  This is done requesting a complete dispersion
calculation without using start_q, last_q, start_irr, or last_irr.
See an example in examples/GRID_example.

On parallel machines the q point and the irreps calculations can be split
automatically using the -nimage flag. See the phonon user guide for further
information.

This file has been created by helpdoc utility on Mon Oct 23 19:37:10 CEST 2017.