Lattice dynamic theory of compressed rare-gases crystals in the deformed atom model

TL;DR

This paper develops a lattice dynamic theory for compressed rare-gas crystals using the deformed atom model, accounting for electron shell deformation, Van-der-Waals forces, and three-body interactions, with results matching experimental data.

Contribution

It introduces a novel lattice dynamic model incorporating electron shell deformation and three-body interactions for rare-gas crystals.

Findings

Calculated Birch elastic moduli for Xe agree with experiments.

The model explains deviations from the Cauchy relation under pressure.

Long-wave oscillation equations are derived and analyzed.

Abstract

Lattice dynamics of rare-gas crystals is built on the base of adiabatic approximation when the deformation of electron shells of atoms of dipole and quadrupole types depending on nucleus shift and simultaneously arising Van-der-Vaals forces. The dipole forces are the most long-range ones. The obtained oscillation equations are studied in long-wave approximation. The role of three-body interaction and quadrupole deformation in the violation of Cauchy relation is discussed. Birch elastic moduli calculated for Xe and deviations from Cauchy relation are in good agreement with the experiment in a wide pressure range.