ACE calculator

ACEpotentials is an atomic cluster expansion (ACE)-based linear MLIP.

Below are the instructions on how to initialize the ACEpotentials calculator, to run dynamics simulations within NQCDynamics.jl using ASE interface.

The following instructions will include Julia-based code.

We start with importing NQCDynamics.jl packages and PyCall which allows importing Python-based packages.

using NQCDynamics
using PyCall
using NQCModels

# Importing Python modules with PyCall
io = pyimport("ase.io")
pyjulip = pyimport("pyjulip")

Now, we specify the cutoff distance, paths to the model, and Atoms objects. Then we read the ASE atoms object and we convert it to NQCDynamics object.

pes_model_path = "path/to/ace/model/h2cu_ace.json"
atoms_path = "path/to/atoms.xyz"
ase_atoms = io.read(atoms_path)
atoms, positions, cell = NQCDynamics.convert_from_ase_atoms(ase_atoms)

We then set up our ACEpotentials calculator and create NQCModels AdiabaticASEModel object that includes the model.

calculator = pyjulip.ACE1(pes_model_path)
ase_atoms.set_calculator(calculator)
pes_model = AdiabaticASEModel(ase_atoms)

The model can be loaded also directly within julia:

using ASE
using JuLIP
using ACE1

IP = ACE1.read_dict(load_dict(model_path)["IP"])
JuLIP.set_calculator!(ase_atoms, IP)
pes_model = AdiabaticModels.JuLIPModel(ase_atoms)

Finally, we can use the model to e.g. initialize Simulation object that is employed to run MD simulations.

sim = Simulation{Classical}(atoms, pes_model, cell=cell)

References

R. Drautz, Atomic cluster expansion for accurate and transferable interatomic potentials, Phys. Rev. B Condens. Matter. 99, 014104, 2019 G. Dusson, M. Bachmayr, G. Csanyi, S. Etter, C. van der Oord, and C. Ortner, ACEpotentials.jl: A Julia implementation of the atomic cluster expansion, J. Chem. Phys. 159, 164101, 2023