DISCRETE BREATHERS IN 3D MODEL BCC LATTICE OF Cr2Al WITH С11b SUPERSTRUCTURE BASED ON DELOCALIZED MODES

10.25712/ASTU.1811-1416.2023.03.007

Abstract

Nonlinear localized vibrational modes of large amplitude with a frequency of oscillation outside the phonon spectrum are called discrete breathers (DBs). A distinction is made between slot and so-called rigid-type EBs. The former are excited in two-atom crystals, for example, in ordered alloys where atoms of the components differ significantly in mass. Such crystals have a gap in the density of phonon states, within which the frequency of the gap DB can reside. Breathers of the second type usually occur in monatomic crystals. It is also known that they have been obtained in some two-atom crystals as well. In this work, the possibility of excitation of DB in Cr₂Al crystal is studied. Chromium-alumina alloys have great practical application in high power electric heating devices and industrial electric furnaces. The operating conditions of these devices create preconditions for excitation of DB in a crystal lattice of alloys from which heating elements are made. The interest in studying the possibility of the existence of DB in the said alloy is related to the fact that breathers affect the physical properties of materials, can reduce thermal conductivity due to phonon scattering, as well as contribute to the emergence and migration of defects. In this work 3D model of the BCC crystal lattice of Cr₂Al with C11_b superstructure was constructed. Coefficients of the Morse potential by which interaction between atoms was carried out were calculated. The possibility of excitation of DB in the specified model crystal was considered. The methodology developed by G.M. Chechin and      V.P. Sakhnenko et al. The cause of the instability of the hard type of excitation and its rapid attenuation, as well as one of the mechanisms of energy dissipation, are also considered.