On the possibility of the existence of discrete breezers of various types in a long-range BCC lattice

Abstract

In this paper we investigate the possibility of existence of different types of localized excitations in a nonlinear body-centered cubic (BCC) lattice, called discrete breathers. The interactions between the lattice particles are described by the b-FPUT potential, and interactions up to the fourth neighbors are taken into account. The consideration of long-range forces is justified by the fact that they are realized, for example, for interatomic interactions in metals and ionic crystals. Recently it has been shown that a special class of exact solutions of the equations of motion of lattice particles having frequencies outside the phonon spectrum can serve to search for discrete breathers. Such exact solutions are found from lattice symmetry analysis and are called bushes of nonlinear normal modes or delocalized nonlinear vibrational modes (DNVMs). In this paper, three groups of DNVMs of the BCC lattice with wave vectors at the Brillouin zone boundary are found, which can have frequencies above the phonon spectrum over the whole range of vibrational amplitudes. Discrete breathers can be obtained by imposing localizing functions on such DNVMs. Some of the DNVMs can have frequencies above the phonon spectrum only if the long-range interactions are taken into account. The presented results are important in discussing the role of discrete breathers in the formation of macroscopic properties of crystals.