ML-ALIGNN example: NVE stability of crystalline Si
==================================================

This example runs an NVE molecular-dynamics stability test on a Si supercell
using `pair_style alignn` with the default Materials-Project (`mps`) ALIGNN-FF
force field.

Files
-----

  in.alignn.si   LAMMPS input script

Two input files must be generated before running (they are not checked in
because the model is downloaded from figshare and the structure is relaxed by
the model itself):

  alignn_ff.pt   TorchScript-exported ALIGNN-FF model
  si.data        relaxed Si supercell in lammps-data format

Both are produced by helper scripts in the ALIGNN repository
(alignn/examples/lammps/):

  python get_model.py    # downloads the mps model, writes alignn_ff.pt
  python build_si.py     # relaxes a 3x3x3 Si supercell, writes si.data

Then run:

  lmp -in in.alignn.si

Open log.lammps and inspect the `etotal` column over the NVE production run; a
well-behaved model conserves total energy to within a few meV/atom. The run
also writes a trajectory (si.lammpstrj) viewable in OVITO.

Note: pair_style alignn requires the cutoff and max_neighbors arguments to
match the model's training configuration (top-level `cutoff` and
`max_neighbors` in config.json). For the mps model these are 5.0 and 12.
