Input data format: { } = optional, [ ] = it depends, | = or All quantities whose dimensions are not explicitly specified are in RYDBERG ATOMIC UNITS BEWARE: TABS, DOS <CR><LF> CHARACTERS ARE POTENTIAL SOURCES OF TROUBLE neb.x DOES NOT READ FROM STANDARD INPUT ! There are two ways for running a calculation with neb.x: (1) specifying a file to parse with the ./neb.x -inp or ./neb.x -input command line option. (2) or specifying the number of copies of PWscf inputs with the ./neb.x -input_images For case (1) a file containing special KEYWORDS (aka SUPERCARDS) has to be written (see below). These KEYWORDS tell the parser which part of the file contains the neb specifics and which part contains the energy/force engine input (at the moment only PW). After the parsing, different files are generated: neb.dat, with the neb specific variables, and a set of pw_*.in PWscf input files, i.e., one for each input position. All options for a single SCF calculation apply. The general structure of the file to be parsed is: ================================================== BEGIN BEGIN_PATH_INPUT ... neb specific namelists and cards END_PATH_INPUT BEGIN_ENGINE_INPUT ...pw specific namelists and cards BEGIN_POSITIONS FIRST_IMAGE ...pw ATOMIC_POSITIONS card ...pw TOTAL_CHARGE card (only for FCP) INTERMEDIATE_IMAGE ...pw ATOMIC_POSITIONS card ...pw TOTAL_CHARGE card (only for FCP) LAST_IMAGE ...pw ATOMIC_POSITIONS card ...pw TOTAL_CHARGE card (only for FCP) END_POSITIONS ... other pw specific cards END_ENGINE_INPUT END For case (2) neb.dat and all pw_1.in, pw_2.in ... should be already present. Structure of the NEB-only input data (file neb.dat): ==================================================== &PATH ... / [ CLIMBING_IMAGES list of images, separated by a comma ] 'neb' A string describing the task to be performed. Options are: nudget-elastic-band string-method-dynamics 'from_scratch' Options are: from scratch from previous interrupted run number of ionic + electronic steps 1 0 Number of points used to discretize the path (it must be larger than 3). 'quick-min' Specify the type of optimization scheme: steepest descent quasi-Newton Broyden's second method (suggested) another variant of the quasi-Newton Broyden's second method to be tested and compared with the previous one. an optimisation algorithm based on the projected velocity Verlet scheme finite temperature langevin dynamics of the string (smd only). It is used to compute the average path and the free-energy profile. 'no-CI' Specify the type of Climbing Image scheme: climbing image is not used original CI scheme. The image highest in energy does not feel the effect of springs and is allowed to climb along the path images that have to climb are manually selected. See also CLIMBING_IMAGES card .FALSE. Also the first and the last configurations are optimized "on the fly" (these images do not feel the effect of the springs). .FALSE. Assume a "minimum image criterion" to build the path. If an atom moves by more than half the length of a crystal axis between one image and the next in the input (before interpolation), an appropriate periodic replica of that atom is chosen. Useful to avoid jumps in the initial reaction path. 0.D0 Kelvin Temperature used for the langevin dynamics of the string. 1.D0 Optimisation step length ( Hartree atomic units ). If opt_scheme=="broyden", ds is used as a guess for the diagonal part of the Jacobian matrix. 0.1D0 Hartree atomic units Set them to use a Variable Elastic Constants scheme elastic constants are in the range [ k_min, k_max ] this is useful to rise the resolution around the saddle point. 0.05D0 eV / Angstrom The simulation stops when the error ( the norm of the force orthogonal to the path in eV/A ) is less than path_thr. .FALSE. If. TRUE. the optimisation of the path is performed using mass-weighted coordinates. Useful together with quick-min optimization scheme, if some bonds are much stiffer than others. By assigning a larger (fictitious) mass to atoms with stiff bonds, one may use a longer time step "ds" .FALSE. If. TRUE. the images are optimised according to their error: only those images with an error larger than half of the largest are optimised. The other images are kept frozen. fcp_mu .FALSE. If .TRUE. perform a constant bias potential (constant-mu) calculation with - ESM method (assume_isolated = 'esm' and esm_bc = 'bc2' or 'bc3' must be set in SYSTEM namelist) or - ESM-RISM method (assume_isolated = 'esm' and esm_bc = 'bc1' must be set set in SYSTEM namelist, and trism = .TRUE. must be set set in CONTROL namelist). fcp_mu gives the target Fermi energy. See the header of PW/src/fcp_module.f90 for documentation lfcp 0.d0 If lfcp == .TRUE., gives the target Fermi energy [eV]. One can specify the total charge of the system for the first and last image by giving TOTAL_CHARGE cards so that the Fermi energy of these systems will be the target value, otherwise first_last_opt should be .TRUE. For the initial charge of intermediate images, the TOTAL_CHARGE is linearly interpolated between the initial and the final ones unless the TOTAL_CHARGE is given in the input file. lfcp 0.01D0 V The simulation stops when the error ( the maximum of the force acting on the FCP in V ) is less than fcp_thr. lfcp 'lm' Specify the type of optimization scheme for FCP: Line-Minimization method. Newton-Raphson method with diagonal hessian matrix. Also, coupling with DIIS. Coupled method with ionic positions. This is available only if opt_scheme == 'broyden', or 'broyden2'. Optional card, needed only if CI_scheme == 'manual', ignored otherwise ! index1, index2, ... indexN index1, index2, ..., indexN are indices of the images to which the Climbing-Image procedure apply. If more than one image is specified they must be separated by a comma. Here comes the pw.x specific namelists and cards (see file: INPUT_PW.html or INPUT_PW.txt) with the exception of ATOMIC_POSITIONS cards, which are specified separately within the BEGIN_POSITIONS/END_POSITIONS supercard as described below. So the input that follows here is of the following structure: &CONTROL ... / &SYSTEM ... / &ELECTRONS ... / ... NB: Atomic positions for all the images are specified within the BEGIN_POSITIONS / END_POSITIONS supercard, where each instance of ATOMIC_POSITIONS card is prefixed either by FIRST_IMAGE, INTERMEDIATE_IMAGE, or LAST_IMAGE keywords. IF lfcp == .TRUE., total charges for all images have to be specified with TOTAL_CHARGE cards. Note that intermediate images are optional, i.e., there can be none or any number of INTERMEDIATE_IMAGE images. For the description of ATOMIC_POSITIONS card see file: INPUT_PW.html or INPUT_PW.txt alat | bohr | angstrom | crystal | crystal_sg Optional card, needed only if lfcp == .TRUE. tot_charge tot_charge is the total charge of the system. For the description of ATOMIC_POSITIONS card see file: INPUT_PW.html or INPUT_PW.txt alat | bohr | angstrom | crystal | crystal_sg Optional card, needed only if lfcp == .TRUE. tot_charge tot_charge is the total charge of the system. For the description of ATOMIC_POSITIONS card see file: INPUT_PW.html or INPUT_PW.txt alat | bohr | angstrom | crystal | crystal_sg Optional card, needed only if lfcp == .TRUE. tot_charge tot_charge is the total charge of the system. Here can follow other pw specific cards ...