Self-diffusion in multi-component glass-forming systems

Self-diffusion in multi-component glass-forming systems including fragile and strong glasses is studied from a unified viewpoint. A simple analytic form of long-time self-diffusion coefficient D(S)(L) is proposed. The equations for the mean-square displacements recently derived for two types of systems, (S) suspensions of colloids and (M) molecular systems, from a first principle by employing the Tokuyama-Mori projection-operator method are used to define D(S)(L) in each type formally, both of which are uniquely determined by the correlation function of the fluctuating forces. Analyses of the correlation functions in two types in terms of many-body interactions thus lead in type (M) to D(S)(L)(lambda) similar or equal to kappa(-1)(lambda(c)/lambda) (1 - lambda/lambda(c))(2), where a is a control parameter, such as an inverse temperature and a volume fraction. Here K is simply written in terms of the potential parameters and lambda(c) an adjustable parameter to be determined. The predictions for lambda dependence of D(S)(L) in multi-component glass-forming systems are in excellent agreement with available experimental data and simulation results in equilibrium states. (C) 2009 Elsevier B.V. All rights reserved.