Energy of phonons and zero-point vibrations in compressed rare-gas crystals

A dynamic matrix of rare-gas crystals is constructed on the basis of a nonempirical short-range repulsion potential taking into account the three-body interaction and dipole-type deformation of the electron shells of atoms in the two- and three-body approximations in the model of deformable and polorizable atoms. Ab initio calculations of the phonon energy for compressed rare-gas crystals were performed at the two and ten mean-value points of the Chadi–Cohen method in a wide pressure range. It is shown that the contribution of three-body forces associated with the overlap of the electron shells of nearest-neighbor atoms in the phonon frequencies is small against the background of pair interaction, even at high pressure and most noticeable in Xe. The contribution of the deformation of the electron shells in the two- and three-body approximations is different for the different mean-value points and increases with increasing pressure. Comparison of the zero-point energy calculated by the Chadi–Cohen method for compressed crystals of the Ne–Xe series was performed with the available experiment at $p$ = 0 and the results of other authors.