Anharmonic free energy of lattice vibrations in fcc crystals from a mean-field bond

Swinburne, T.D. and Janssen, J. and Todorova, M. and Simpson, G. and Plechac, P. and Luskin, M. and Neugebauer, J.

Volume: 102 Pages:
DOI: 10.1103/PhysRevB.102.100101
Published: 2020

It has recently been shown that the ab initio anharmonic free energy of fcc crystals can be approximated to meV/atom accuracy by a lattice of anharmonic nearest-neighbor bonds, where the bonding potential can be efficiently parametrized from the target system. We develop a mean-field approach for the free energy of a general bond lattice, analytically accounting for strong bond-bond correlations while enforcing material compatibility and thermodynamic self-consistency. Applying our fundamentally anharmonic model to fcc crystals yields free energies within meV/atom of brute force thermodynamic integration for core seconds of computational effort. Potential applications of this approach in computational materials science are discussed. © 2020 American Physical Society.

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