ML-PET: PET machine-learning interatomic potentials (Point Edge Transformer,
the upet / PET-MAD family) through pet-kokkos, a C++/Kokkos implementation
with analytic forces and no libtorch.

  pair_style pet MODEL [mode images|exchange|ghosts] [gpu_aware auto|yes|no]
  pair_coeff * * ELEMENT...

pair_style pet/kk (KOKKOS package) keeps each step on the GPU.

This package lives in pet-kokkos (lammps/), which installs it into a LAMMPS
tree with lammps/patch_lammps.sh; lammps/README.md there has the build,
configuration and usage.
