One‐Particle Distribution Functions and Thermodynamics of Crystals with Many‐Body Forces. III. Perturbation Theory

The theory of crystalline state described in preceding papers is considered as a zeroth‐order approximation. Statistical perturbation theory is used for the purpose of improving this approximation. The second‐order corrections to the Helmholtz free energy and thermodynamic properties of strongly anharmonic crystals are derived. The properties of solid Ar, Kr, and Xe are calculated using various pair‐potential functions in conjunction with the AXILROD‐TELLER‐MUTO three‐body potential. The first quantum corrections are taken into account in the quasi‐classical approximation. The result of computations are compared with the experimental data. Copyright © 1976 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim