We present an overview of a method developed for the calculation of dynamic interatomic correlations in anharmonic crystals based on the correlative method of unsymmetrized self-consistent field (CUSF). The quadratic correlation momenta and the mean square relative displacements have been calculated for one-, two- and three-dimensional classical models.

The correlative method of unsymmetrized self-consistent field (CUSF) is used to study dynamical characteristics of a strongly anharmonic crystal with body-centered cubic lattice, namely, the inter-atomic and mean square relative displacements. We present the general formulae for crystals with anharmonicity, including the strong one, up to fourth anharmonic terms. Taking into account the second order of the method we calculate correlations in this lattice between the nearest, second, third, fourth and fifth neighbors. The influence of more distant interactions is discussed. The results are compared with those obtained previously for an weakly anharmonic BCC crystal. We use the Schiff potencial for Na and also Lennard-Jones potentials for comparison.

Using the correlative method of unsymmetrized self-consistent field we study equilibrium atomic properties of anharmonic crystals. Here we calculate dynamical characteristics of a weakly anharmonic crystal with the body-centered cubic lattice, namely, the quadratic correlation moments between atomic displacements and the mean square relative atomic displacements. Taking into account the nearest neighbour interactions in this lattice, the second order of the method enables one to calculate the correlations between the nearest, second, third and fifth neighbours. An influence of more distant interactions is discussed. Results are also correlated with those calculated early for the simple and face-centered cubic lattices.