  Using the methods of computer modeling this scientific paper studies the
special features of diffusion of the particles subjected to the external
periodic force in the crystal lattice. The particle motion is described by a
Langevin equation. The systems with a low friction coefficient may experience
abnormal diffusion modes, in particular hyperdiffusion and subdiffusion. The
applied external time-periodic field causes limitation of time intervals of
abnormal diffusion making the diffusion coefficients dependent on frequency of
applied force. The temperature relationships of these values have been
calculated. It has been shown that the diffusion coefficients behave in
abnormal ways as the temperature changes. In some temperature intervals the
diffusion may increase as the temperature drops. Location and width of these
intervals depend on the frequency of the external field.
