Atomic caging in multicomponent glass-forming metallic liquids

We have examined the effect of density on atomic caging in highly dense glass-forming metallic liquids, Ni59.5Nb40.5 and Ni60Nb34.8Sn5.2 using quasielastic neutron scattering. The density of the liquids is unusually high and close to the mode-coupling dynamic transition. The self-correlation function obtained from the QENS data shows stretching and the temperature dependence of the diffusion coefficient shows non-Arrhenius behavior. The mean relaxation time exhibits a non-linear variation with Q(2), which is an indicative of a jump diffusion process in these highly dense liquids. We use a simple jump diffusion model to obtain the residence time of Ni atoms in these alloy liquids. The residence time of Ni atoms exhibits a linear dependence with density of these alloy liquids, but shows an abrupt change in the slope approximately at a density of 7.5 g cm(-3). The present observation indicates that the time at which the atoms are trapped in cages is not a monotonic function of density in hard-sphere-like metallic liquids. Our results indicate the existence of a hidden dynamic transition in glass-forming metallic liquids. Copyright (C) EPLA, 2015