Anomalous supercooled liquid structure of Ga on β-relaxation dynamics

We study the {β}-relaxation dynamics for liquid metal gallium using computer-simulated liquid structures in conjunction with idealized mode-coupling theory. At the dynamical transition point, our calculated mode-coupling parameter {λ} is numerically more consistent with the increasing trend of the magnitude of the experimentally fitted {λ} (~0.8) observed in several glass-forming materials. The implication is that the empirically fitted {λ} inherently must contain contributions arising from other subtle mechanisms to the {β}-relaxation dynamics in addition to the usual cage-diffused mechanism. Of particular interest in our calculations is the behavior of the tagged particle distribution function, which shows a distinct double-peaked structure and, within the {β}-relaxation time regime, exhibits a much slower retarded motion compared with other simple monatomic systems. This curious behavior is interpreted here as due to the influences of temporally fluctuating atomic bonded-pair clusters that have been observed recently in molecular dynamics simulations.