Lattice distortion in hcp rare gas solids

Abstract

The lattice distortion parameter δ≡c/a – √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 δ is negative for helium in the entire pressure range. For Ar, Kr, and Xe, however, δ changes sign from negative to positive as the pressure increases, growing rapidly in magnitude at higher pressures.