Lattice dynamics in light rare-gas crystals under pressure

Abstract

The lattice dynamics of compressed neon and argon crystals has been theoretically investigated within the ab initio approach in the framework of the Tolpygo model, which explicitly includes the deformation of electron shells. The energy of zero-point vibrations, mean-square displacements, and specific heat capacities of compressed neon and argon face-centered cubic crystals have been calculated in the harmonic approximation using the dynamic matrix constructed with the ab initio short-range repulsive potential and integration over the mean-value points in the Brillouin zone. The calculated temperature dependences of the specific heat capacity and the Debye temperature are in good agreement with the data available in the literature on the experiment at zero pressure. The role of zero-point vibrations in the thermodynamics of the entire series of rare-gas crystals and, in particular, in the validity of the Lindemann melting criterion has been analyzed.