Self-diffusion in single-component Yukawa fluids

TL;DR

This study evaluates a proposed approximation for self-diffusion in Yukawa fluids, using simulation data to confirm its effectiveness and exploring similarities with other soft matter systems near freezing.

Contribution

It tests and validates a simple approximation for self-diffusion coefficients in Yukawa fluids, extending understanding of diffusion near phase transitions.

Findings

Approximation provides a sensible normalization for self-diffusion.

Self-diffusion properties in Yukawa melts resemble those in plasma and liquid metals.

Results support a dynamical freezing indicator for soft matter systems.

Abstract

It was suggested in the literature that the self-diffusion coefficient of simple fluids can be approximated as a ratio of the squared thermal velocity of the atoms to the "fluid Einstein frequency," which can thus serve as a rough estimate of the friction (momentum transfer) rate in the dense fluid phase. In this article we test this suggestion using a single-component Yukawa fluid as a reference system. The available simulation data on self-diffusion in Yukawa fluids, complemented with new data for Yukawa melts (Yukawa fluids near the freezing phase transition), are carefully analyzed. It is shown that although not exact, this earlier suggestion nevertheless provides a very sensible way of normalization of the self-diffusion constant. Additionally, we demonstrate that certain quantitative properties of self-diffusion in Yukawa melts are also shared by systems like one-component plasma and liquid metals at freezing, providing support to an emerging dynamical freezing indicator for simple soft matter systems. The obtained results are also briefly discussed in the context of the theory of momentum transfer in complex (dusty) plasmas.