Atomic caging in multicomponent glass-forming metallic liquids

¹ Department of Physics and Materials Science, City University of Hong Kong - Kowloon Tong, Hong Kong
² Institut Laue-Langevin - BP 156-38042 Grenoble Cedex, France
³ I. Physikalisches Institut, Georg-August-Universitat Goettingen - Goettingen, Germany

^(a) smavilac@cityu.edu.hk (corresponding author)

Received: 6 February 2015
Accepted: 7 May 2015

Abstract

We have examined the effect of density on atomic caging in highly dense glass-forming metallic liquids, Ni_59.5Nb_40.5 and Ni₆₀Nb_34.8Sn_5.2 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 Q², 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 . 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.