Self-Diffusion in Simple Liquids as a Random Walk Process.

Sergey A Khrapak

doi:10.3390/molecules26247499

Abstract

It is demonstrated that self-diffusion in dense liquids can be considered a random walk process; its characteristic length and time scales are identified. This represents an alternative to the often assumed hopping mechanism of diffusion in the liquid state. The approach is illustrated using the one-component plasma model.

Highlights

The purpose of the present paper is to demonstrate that the dynamical picture behind Zwanzig’s result is equivalent to a random walk process, with well defined length and time scales
6 τ where r is an actual length of the random walk, τ is the time scale, and we focus on sufficiently long times (t τ)
We have demonstrated that self-diffusion in dense liquids can be described as a random walk process with well defined time and length scales

Summary

Introduction

Self-Diffusion in Simple Liquids as a Random Walk Process. MoleculesAbout 40 years ago, Robert Zwanzig published an influential paper on the relation between self-diffusion and viscosity of liquids (Stokes–Einstein relation) [1]. Self-Diffusion in Simple Liquids as a Random Walk Process. About 40 years ago, Robert Zwanzig published an influential paper on the relation between self-diffusion and viscosity of liquids (Stokes–Einstein relation) [1]. The purpose of the present paper is to demonstrate that the dynamical picture behind Zwanzig’s result is equivalent to a random walk process, with well defined length and time scales. It is demonstrated that a theoretical prediction for the numerical factor relating the selfdiffusion and viscosity coefficients, in the form of the Stokes–Einstein relation, is quite sensitive to concrete assumptions about the liquid collective mode spectrum. The results provide a consistent picture of the diffusion mechanism in dense liquids with soft isotropic pairwise interactions

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Results

Conclusion