Dynamics of cubic lattices with long-range interaction

Influence of long-range interaction upon phonon dispersion relations of sim ple cubic, body-centered cubic and face-centered cubic lattices is studied. It is shown that even the next-nearest neighbour interaction significantly affects the dynamic characteristics of the above lattices. In the long wav elength limit the dispersion relations for simple cubic and body-centered c ubic lattices correspond to a strongly anisotropic crystal: for certain dir ections of the wave vectors one of the transverse branches of the dispersio n curve is determined by weak next nearest neighbor interaction, while the remaining depend on the strong interaction of the nearest neighbors. (C) 19 99 Elsevier Science B.V. All rights reserved.