Lattice distortion in hcp rare gas solids

TL;DR

This paper investigates how lattice distortion varies with pressure in hcp phases of rare gases, using theoretical calculations to reveal different behaviors among helium, argon, krypton, and xenon.

Contribution

It provides the first comprehensive comparison of lattice distortion in hcp rare gases using both semi-empirical and density functional methods.

Findings

$ extdelta$ is negative for helium across all pressures.

$ extdelta$ changes sign from negative to positive for Ar, Kr, Xe with increasing pressure.

Lattice distortion magnitude increases rapidly at higher pressures for Ar, Kr, Xe.

Abstract

The lattice distortion parameter $\delta \equiv c/a-\sqrt{8/3}$ has been calculated as a function of molar volume for the hcp phases of He, Ar, Kr and Xe. Results from both semi-empirical potentials and density functional theory are presented. Our study shows that $\delta$ is negative for helium in the entire pressure range. For Ar, Kr and Xe, however, $\delta$ changes sign from negative to positive as the pressure increases, growing rapidly in magnitude at higher pressures.