Activation-relaxation technique study on β-relaxation in La55Ni20Al25 and Cu46Zr46Al8 metallic glasses

Activation-relaxation technique combined with molecular dynamics simulations was employed to investigate β-relaxation behavior in La55Ni20Al25 and Cu46Zr46Al8 model metallic glasses (MGs) for exploring the underlying mechanism. It is found that the activation energies are much smaller in La55Ni20Al25 MG, indicating that β-relaxation can be more easily activated in La55Ni20Al25 MG. It is also revealed that in both MGs, string-like diffusion dominates the atomic motions in β-relaxation. However, in different MGs, the string-like motions are found to involve atoms with different structure features, which could be the underlying structural basis of β-relaxation mechanism. In addition, because of very low activation energies, atomic hopping and cooperative rearrangements in La55Ni20Al25 MG also have significant impact on β-relaxation. However, such atomic motions are much weaker in Cu46Zr46Al8 MG, due to higher activation energies. These findings establish a physical link for activation energy and atomic motions in β-relaxation to atomic structures, and provide new understanding of β-relaxation mechanism in MGs.