Issue Interfacing Calphy with MLIPs

[if3598]

Hello! I am trying to run calphy example 2 using the MLIP, mattersim-v1.0.0-5M, instead of the provided EAM model. I have adjusted the input script as follows:

calculations:

• element: Fe
  lattice: bcc
  lattice_constant: 2.884
  mass: 55.845
  md:
  barostat_damping: 0.1
  equilibration_control: nose_hoover
  thermostat_damping: 0.1
  timestep: 0.001
  mode: ts
  n_equilibration_steps: 10000
  n_iterations: 1
  n_switching_steps: 25000
  pair_coeff: '* * Fe'
  pair_style: mliap unified ../potentials/mattersim-v1.0.0-5M-mliap.pt
  pressure: 0.0
  queue:
  commands:
  • conda activate calphy
    cores: 4
    scheduler: local
    reference_phase: solid
    repeat:
  • 5
  • 5
  • 5
    temperature:
  • 100.0
  • 1400.0
• element: Fe
  lattice: FCC
  lattice_constant: 6.0
  mass: 55.845
  md:
  barostat_damping: 0.1
  equilibration_control: nose_hoover
  thermostat_damping: 0.1
  timestep: 0.001
  mode: ts
  n_equilibration_steps: 10000
  n_iterations: 1
  n_switching_steps: 25000
  pair_coeff: '* * Fe'
  pair_style: mliap unified ../potentials/mattersim-v1.0.0-5M-mliap.pt
  pressure: 0.0
  queue:
  commands:
  • conda activate $LAMMPS_PYENV
    cores: 4
    scheduler: local
    reference_phase: solid
    repeat:
  • 5
  • 5
  • 5
    temperature:
  • 100.0
  • 1400.0

I am getting the following error when attempting to run:
Exception: ERROR: Loading mliappy unified module failure. (src/lammps-patch_4Jul2026/src/ML-IAP/mliap_unified.cpp:208)
Last input line: pair_style mliap unified ../potentials/mattersim-v1.0.0-5M-mliap.pt

Based on this LAMMPS documentation on using pair_stlye mliap,

I believe I need to do the following to the lammps object:
from lammps import lammps
from lammps.mliap import activate_mliappy
lmp = lammps()
activate_mliappy(lmp)

But I'm not sure how best to implement this with calphy. Any advice on how to proceed would be greatly appreciated!

[Andrew-S-Rosen]

Thanks for reporting @if3598. Just a head's up --- it is helpful for developers if you paste code and tracebacks using code blocks with ``` like:

print("hello")

and if you upload files (e.g. YAML) as an attachment or (if sufficiently short, like this example) also in a formatted code block. Some details here. There is built-in syntax highlighting for python and YAML.

[Andrew-S-Rosen]

I am also linking this to pyiron/pylammpsmpi#475 where we raised a similar inquiry that is being addressed in pyiron/pylammpsmpi#476.

The following is where the update in calphy will likely need to live:

calphy/calphy/helpers.py

Line 117 in 820feec

lmp = LammpsLibrary(cores=cores, working_directory=directory, cmdargs=cmdargs)