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# HCP Ti example using LAMMPS interface
The `pair_style` of `polymlp` is a LAMMPS module of the polynomial machine
learning potentials provided at https://sekocha.github.io/lammps/index-e.html.
For the HCP Ti calculation found in the [example
directory](https://github.com/phonopy/phonopy/tree/develop/example), `mlp.lammp`
of gtinv-294 was obtained from [Polynomial Machine Learning Potential Repository
at Kyoto
University](http://cms.mtl.kyoto-u.ac.jp/seko/mlp-repository/index.html).
1. Read a lammps input structure file and create supercells with
```
% phonopy --lammps -c lammps_structure_Ti -d --dim 4 4 3
_
_ __ | |__ ___ _ __ ___ _ __ _ _
| '_ \| '_ \ / _ \| '_ \ / _ \ | '_ \| | | |
| |_) | | | | (_) | | | | (_) || |_) | |_| |
| .__/|_| |_|\___/|_| |_|\___(_) .__/ \__, |
|_| |_| |___/
2.18.0
Compiled with OpenMP support (max 10 threads).
Python version 3.10.8
Spglib version 2.0.2
Calculator interface: lammps
Crystal structure was read from "lammps_structure_Ti".
Unit of length: angstrom
Displacements creation mode
Settings:
Supercell: [4 4 3]
Spacegroup: P6_3/mmc (194)
Use -v option to watch primitive cell, unit cell, and supercell structures.
"phonopy_disp.yaml" and supercells have been created.
Summary of calculation was written in "phonopy_disp.yaml".
_
___ _ __ __| |
/ _ \ '_ \ / _` |
| __/ | | | (_| |
\___|_| |_|\__,_|
```
2. Run LAMMPS
```bash
% lmp_serial -in in.polymlp
```
Suppose that the LAMMPS output file name is removed to `lammps_forces_Ti.0`
after the LAMMPS calculation.
3. Make `FORCE_SETS`
```
% phonopy -f lammps_forces_Ti.0
_
_ __ | |__ ___ _ __ ___ _ __ _ _
| '_ \| '_ \ / _ \| '_ \ / _ \ | '_ \| | | |
| |_) | | | | (_) | | | | (_) || |_) | |_| |
| .__/|_| |_|\___/|_| |_|\___(_) .__/ \__, |
|_| |_| |___/
2.18.0
Compiled with OpenMP support (max 10 threads).
Python version 3.10.8
Spglib version 2.0.2
Calculator interface: lammps
Displacements were read from "phonopy_disp.yaml".
1. Drift force of "lammps_forces_Ti.0" to be subtracted
-0.00000000 -0.00000000 0.00000000
Forces parsed from LAMMPS output were rotated by F=R.F(lammps) with R:
1.00000 0.00000 0.00000
0.00000 0.00000 0.00000
0.00000 1.00000 1.00000
"FORCE_SETS" has been created.
_
___ _ __ __| |
/ _ \ '_ \ / _` |
| __/ | | | (_| |
\___|_| |_|\__,_|
```
|
