Low Temperature Physics: 42, 411 (2016); https://doi.org/10.1063/1.4952644
Fizika Nizkikh Temperatur: Volume 42, Number 5 (May 2016), p. 526-537    ( to contents , go back )

Many-body interaction and deformation of the atomic electron shells in the lattice dynamics of compressed atomic cryocrystals

E.P. Troitskaya, Ie.Ie. Gorbenko, and E.A. Pilipenko

O.O. Galkin Donetsk Institute for Physics and Engineering NAS of Ukraine, Kyiv 03680, Ukraine
E-mail: pilipenko.katerina@mail.ru
pos Анотація:

Received November 24, 2016

Abstract

The lattice dynamics of compressed atomic cryocrystals is based on the ab initio version of the quantum-mechanical model of deformable and polarizable atoms (the Tolpygo model) taking into account the many-body interaction. Parameters of the three-body interaction and deformation of the atomic electron shells, calculated by the overlap integrals of atomic orbitals and their derivatives, have the same magnitude order and show the necessity of their mutual consideration. Accounting the deformation effects of the atomic electron shells in the dipole approximation in phonon frequencies calculations at high compressions lead to softening of longitudinal modes at L and X points for the entire series of Ne–Xe crystals and transverse modes in Σ and L directions for solid Xe. It was shown that the observed deviation from the Cauchy relation δ(p) for compressed atomic cryocrystals can-not be adequately reproduced without considering the deformation of the atomic electron shells in the quad-rupole approximation. Three-body and quadrupole interactions contributions in Ne, Kr and Xe crystals are mutually compensated, providing a weakly pressure-dependence of the δ(p) parameter. We have obtained a good agreement of the calculated phonon frequencies, the Birch and Fuchs elastic moduli, and the deviation from the Cauchy relation for the entire series of Ne–Xe crystals with the available experimental data over a wide range of pressure.

PACS: 62.50.–p High-pressure effects in solids and liquids;
PACS: 62.65.+k Acoustical properties of solids;
PACS: 64.10.+h General theory of equations of state and phase equilibria.

Key words: atomic cryocrystals, high pressure, many-body interaction, quadrupole deformation of the atomic electron shells.

Published online: March 23, 2016

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