## Contents

At phonopy v2.7.0, phonopy-load command is installed. This behaves similarly to phonopy.load (Shortcut to load input files (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


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 .

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