Sound velocities of hexagonal close-packed H2 and He under pressure

TL;DR

This paper calculates the sound velocities of hexagonal close-packed hydrogen and helium under pressure using both semi-empirical and density-functional approaches, providing insights into intermolecular interactions at high pressures.

Contribution

It offers a comparative analysis of semi-empirical and first-principles methods for sound velocity calculations in H2 and He under pressure, constraining intermolecular interactions.

Findings

Good agreement between calculations and experiments

Pressure dependence of Debye temperature characterized

Constraints on intermolecular potentials established

Abstract

Bulk, shear, and compressional aggregate sound velocities of hydrogen and helium in the close- packed hexagonal structure are calculated over a wide pressure range using two complementary approaches: semi-empirical lattice dynamics based on the many-body intermolecular potentials and density-functional theory in the generalized gradient approximation. The sound velocities are used to calculate pressure dependence of the Debye temperature. The comparison between experiment and first-principle and semi-empirical calculations provide constraints on the density dependence of intermolecular interactions in the zero-temperature limit.