The atomistic mechanism of fast relaxation processes in Cu65Zr35 glass

Molecular-dynamics simulations of the glass Cu65Zr35 show a rattling mode of atomic motion. While the frequency of the rattling mechanism is essentially independent of temperature and of the strain applied to the glass, the fraction of atoms undergoing rattling is dependent on temperature and strain. It is argued that the rattling motions constitute the ‘fast processes’ that lie between β relaxation and the boson peak in the characteristic spectrum of dynamic modes in glasses. It is concluded that the fast processes are a precursor to β relaxation and that their inhomogeneous distribution in the metallic glass is the origin of the shear transformation zones governing the onset of plastic flow.