phonopy-load command

phonopy-load command#

The primary purpose of introducing this command is to ensure consistent usage across various force calculators (VASP, QE, …). Additionally, more optimized default settings are provided (see List of differences from phonopy command).

Example#

In the NaCl example for the VASP calculator,

% phonopy -d --dim 2 2 2 --pa auto -c POSCAR-unitcell
% phonopy --sp -f vasprun.xml-00{1,2}

In the NaCl-qe example for the QE calculator,

% phonopy --qe -d --dim 2 2 2 --pa auto -c NaCl.in
% phonopy --sp -f NaCl-00{1,2}.out

The first and second commands create phonopy_disp.yaml and phonopy_params.yaml, respectively.

Once having the phonopy_xxx.yaml file, it is unnecessary to specify the calculator name (e.g. --qe option). The phonon calculation as the post-process works:

% phonopy-load --band auto -p phonopy_params.yaml

phonopy-load can read files with the following extensions xz, lzma, gz, and bz2. Therefore when the file size of phonopy_params.yaml is large, it is recommended to compress it.

% xz phonopy_params.yaml
% phonopy-load --band auto -p phonopy_params.yaml.xz

List of differences from phonopy command#

The following default behaviours are different from that of those of phonopy command:

  • phonopy_xxx.yaml type file (phonopy-yaml format) is always necessary in either of two ways:

    1. phonopy_xxx.yaml type file is given as the first argument of the command.

    2. phonopy_disp.yaml or phonopy.yaml is put in the current directory. The searching preference order is phonopy_disp.yaml > phonopy.yaml.

  • -c option (read crystal structure) does not exist.

  • Use of command options is recommended, but a phonopy configuration file (Configuration file) can be read through --config option.

  • If parameters for non-analytical term correction (NAC) are found, NAC is automatically enabled. This can be disabled by --nonac option.

  • When force constants are calculated from displacements and forces dataset, force constants are automatically symmetrized. From phonopy v2.30.0, symfc is used for the symmetrization. From phonopy v2.41.0, symfc-projector is used to symmetrize force constants calculated by finite difference approach. The old behavior of the symmetrization can be performed by --fc-calculator traditional option. --no-sym-fc option can be used to calculate force constants in the traditional force constants calculator without symmetrization.

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