Atomic cluster expansion interatomic potentials for lithium: Investigating the solid and liquid phases
We develop an atomic cluster expansion (ACE) interatomic potential for lithium that accurately models both
the solid and liquid phase and the corresponding melting point. The training data is obtained from 0 K density
functional theory (DFT) and finite temperature ab initio molecular dynamics simulations of both solid and
liquid Li. The ACE predicted properties for both phases obtained from molecular dynamics simulations are
in close agreement with DFT and experimental data from the literature. The potential is able to capture the
energy differences of the different competing phases of the solid at 0 K and finite temperature properties of the
experimentally observed bcc phase. The potential also accurately predicts the temperature dependence of liquid
density, viscosity, and the diffusion coefficient. The melting point is calculated using the two-phase coexistence
method and is remarkably close to the experimental value. The potential is used to predict stress-induced phase
transformations in solid Li and pressure-volume isotherms in liquid Li. We underline the necessity for a complete
training set that includes both solid and liquid configurations in order to obtain a potential that precisely models
both phases. By using the ACE formalism, we also systematically investigate the contributions of interactions
involving N bodies and the number of radial parameters needed to separately represent both phases since they
have a direct consequence on the computational cost of the potent