Elastic properties of compressed cryocrystals in a deformed atom model

A model with deformed atom shells is built to investigate the elastic properties of rare-gas crystals Ne and Kr under high pressure. It is shown that the observed deviation from the Cauchy relation δ cannot be adequately reproduced with taking into account of only the many-body interaction. The individual pressure dependence δ of is a result of competition of the many-body interaction and the quadrupole interaction associated with the quadrupole-type deformation of electron shells of the atoms during the displacements of the nuclei. Each kind of interaction makes a strongly pressure dependent contribution to δ . In the case of Ne and Kr, contributions of these interactions are compensated to the good precision, providing δ being almost constant against pressure.