Atomistic simulation environment

The atomistic simulation environment, or ASE for short, is a popular Python package to simplify the process of setting up, running and analysing results from atomistic simulations across different simulation codes. By means of ASEconvert this python package is seamlessly integrated with the AtomsBase ecosystem and thus available to DFTK via our own AtomsBase integration and AtomsCalculators integration.

Most notably this integration is two-way, that is that DFTK can both be used as a calculator in ASE (to do computation on atomistic systems managed in python) and vice versa, i.e. atomistic systems set up in ASE can be used as starting points for calculations in a Julia-driven workflow. Both will be illustrated.

Using ASE to setup structures for DFTK calculations

An example of this workflow is given in Modelling a gallium arsenide surface.

Using DFTK as a calculator in ASE

The IPICalculator package contains an implementation of the i-PI protocol to pass energies, forces and virials between different atomistic calculators. This can be used, for example, to make julia-based calculators available in ASE.

The following example requests the computation of a silicon energy and force from DFTK.

import ase.build
from ase.calculators.socketio import SocketIOCalculator

atoms = ase.build.bulk("Si")
atoms.write("Si.cif")
atoms.calc = SocketIOCalculator(unixsocket="dftk")
atoms.get_forces()  # Stalls until you connect a driver

To supply this force request with an PBE force, we need to setup an initial system as a template as well as an PBE calculator with desired numerical parameters:

using AtomsIO
using DFTK
using IPICalculator
using PseudoPotentialData

# Setup DFTK calculator
calc = DFTKCalculator(
    model_kwargs=(; pseudopotentials=PseudoFamily("dojo.nc.sr.pbe.v0_4_1.standard.upf"),
                    functionals=PBE(), temperature=1e-3, smearing=Smearing.Gaussian()),
    basis_kwargs=(; Ecut=20, kgrid=(4, 4, 4)),
)

# Run IPI driver
run_driver(load_system("Si.cif"), calc; unixsocket="dftk")