Theoretical study of dynamical properties of binary metallic glasses in the harmonic approximation

Abstract

A theory is developed to calculate the vibrational frequency spectrum of binary amorphous solids in the harmonic approximation. It is shown that the spectrum of isotropically disordered material can be separated into longitudinal acoustic (LA), transverse acoustic (TA), longitudinal optical (LO) and transverse optical (TO) phonons in a strict sense. Calculations are performed both analytically and numerically for each mode of Mg 70Zn 30 metallic glass. It is clarified that the roton-like dispersion curve of the longitudinal vibrations, determined by an inelastic neutron-scattering experiment, is well described as consisting of LA and LO phonons.