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(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 {ref}`phonopy_load_command_differences`).
## Example
In the NaCl example for the VASP calculator,
```bash
% 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,
```bash
% 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:
```bash
% 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.
```bash
% xz phonopy_params.yaml
% phonopy-load --band auto -p phonopy_params.yaml.xz
```
(phonopy_load_command_differences)=
## List of differences from phonopy command
The following default behaviours are different from that of those of `phonopy`
command:
- `phonopy_xxx.yaml` type file ({ref}`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
({ref}`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.
|
