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phonopy/doc/phonopy-load.md

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(phonopy_load_command)=

phonopy-load command

At phonopy v2.7.0, phonopy-load command is installed. This behaves similarly to phonopy.load ({ref}phonopy_load) in the phonopy python module. The main aim of introducing this command is to provide uniform usage over many different force calculators. Once phonopy_disp.yaml is created, the following operations will be the same using this command.

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

  1. phonopy_xxx.yaml type file is always necessary in either of two ways:

    • phonopy_xxx.yaml type file is given as the first argument of the command.
    • phonopy_xxx.yaml type file is put in the current directory with one of the default filenames of phonopy_params.yaml, phonopy_disp.yaml, phonopy.yaml. The searching preference order is phonopy_params.yaml > phonopy_disp.yaml > phonopy.yaml.

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

  3. Use of command options is recommended, but phonopy configuration file can be read through --config option.

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

  5. When force constants are calculated from displacements and forces dataset, force constants are automatically symmetrized. To disable this, --no-sym-fc option is used.

  6. --save-params option is added. With this option, phonopy_params.yaml that contains most of the information to run phonopy, i.e., crystal structure, displacement-force dataset, and non-analytical term correction parameters. When displacement-force dataset didn't exist, force constants are written.

Examples

In the NaCl-qe example,

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

With these commands, phonopy_disp.yaml and FORCE_SETS are created. After this step, it is unnecessary to specify --qe option to run with phonopy-load. The following command works to draw band structure.

% phonopy-load --band auto -p

Data in FORCE_SETS and BORN can be saved in phonopy_params.yaml using --save-params option. Then phonons can be calculated only with this file as fillows:

% phonopy-load --save-params
% mkdir test && cd test
% mv ../phonopy_params.yaml .
% phonopy-load --band auto -p

In the last line, phonopy_params.yaml is read without specifying because this filename is reserved name to be searched.