Crossover behaviour and critical amplitude of the viscosity of binary liquid mixtures of critical composition

Abstract

Bhattacharjee et al.(Phys. Rev. A, 1981, 24, 1469) have proposed a function based on the mode-coupling theory of critical dynamics to describe the temperature dependence of shear viscosity of binary liquid mixtures of critical composition in the temperature range in which the shear viscosity is determined by ‘critical’ contributions as well as by ‘background’ contributions. This function is used to analyse the temperature dependence of the shear viscosity of seven binary liquid mixtures of critical composition in the intermediate temperature range just mentioned. The experimental data are taken from the literature. In all mixtures studied the crossover behaviour belongs to the case for which the ratio of the parameters q_d and q_c of the crossover function approaches the value zero [i.e.(q_d/q_c)→ 0]. These parameters characterize the coupling between viscous and diffusive modes in a mixture of critical composition. Under the condition (q_d/q_c)→ 0 non-critical background contributions to the mutual diffusion coefficient (i.e. deviations from the asymptotic from of the universal dynamic scaling function for lim T→T_c) can be neglected.