Vibrational spectra of Fe3P and Fe2P metal-metalloid compound crystallites: Phonon and breather excitations

Abstract

The spectra of small-amplitude single-phonon vibrations and large-amplitude nonlinear multiphonon vibrations of Fe3P and Fe2P metal-metalloid compound crystallites are investigated. The vibrational spectra of 3D crystallites of gradually increasing volumes are calculated within a microscopic approach using previously tested interatomic interaction potentials. The calculated energy of the main low-frequency peak is closer to its experimental value in comparison with previous calculations, which reduces the significant discordance between the experimental and theoretical spectra. The fine structure of the high-frequency part of the vibrational spectrum is discussed. A study of large-amplitude nonlinear vibrations (which determine the diffusion of atoms and dispersive processes in materials) showed that a specific nonlinear breather mode of vibration can be generated in the crystallites in question, which is a genetic precursor of nonlinear self-localized vibrations.