On the dynamical properties of a strongly anharmonic face-centered cubic crystal

We study the interatomic correlations and mean square relative displacement s (MSRD) in anharmonic crystals on the basis of the correlative method of u nsymmetrized self-consistent field (CUSF). Here we present general formulae for crystals with the anharmonicity, including the strong one, up to the f ourth anharmonic terms and perform calculations of tl le quadratic correlat ion moments (QCM) in a crystal with face centered cubic lattice, namely in solid Ar. The second order of CUSF allows one to investigate correlations i n this lattice between the nearest, second, third and fourth neighbors. The anharmonicity mas demonstrated to have strong effect on the interatomic co rrelations at temperatures above 0.4 of the melting temperature causing a d rastic rise near the spinodal point. The dependence of QCM on the distance between atoms and on the crystallographic direction is discussed.