(phonopy_yaml_format)=

# phonopy-yaml format

`phonopy_xxx.yaml` type file is a structure text format in YAML to store data
for phonopy. This file can contain the following information:

- Unit cell, primitive cell, and supercell crystal structures.
- Displacement in supercells
- Forces in supercells
- Energies of supercells
- Parameters used for non-analytical term correction

The `phonopy` command ({ref}`phonopy_command`) reads this type of file, e.g.,

```bash
% phonopy phonopy_params.yaml [OPTIONS]
```

## Compression support

`phonopy_xxx.yaml.gz`, `phonopy_xxx.yaml.bz2`, and `phonopy_xxx.yaml.xz` can be
read in the same way as shown above.

(phonopy_yaml_phonondb)=
## How to use PhononDB data

PhononDB data downloaded from <https://doi.org/10.48505/nims.4197> (its list of
crystals <https://github.com/atztogo/phonondb/blob/main/mdr/phonondb/README.md>)
are given in `phonopy_xxx.yaml.xz`. Therefore these are readily used with
the `phonopy` command. For example,

```bash
% wget https://mdr.nims.go.jp/download_all/9306t5111.zip
% unzip -d mp-661 9306t5111.zip
% cd mp-661
% phonopy phonopy_params.yaml.xz --band auto -p --pdos auto
```

```{image} phonondb-mp-661.png
:width: 50%
```