Transport coefficients for dense hard-disk systems

TL;DR

This paper investigates the transport coefficients of dense hard-disk systems using Helfand-Einstein expressions, analyzing their dependence on density and size, and comparing results with Enskog's theory, especially near the fluid-solid transition.

Contribution

It introduces averaging techniques suitable for event-driven molecular dynamics to study transport coefficients in dense hard-disk systems and analyzes their behavior near phase transitions.

Findings

Viscosity diverges as a power law near the fluid-solid transition.

Self-diffusion and heat conductivity decrease in the same density range.

Comparison with Enskog's theory highlights deviations at high densities.

Abstract

A study of the transport coefficients of a system of elastic hard disks, based on the use of Helfand-Einstein expressions is reported. The self-diffusion, the viscosity, and the heat conductivity are examined with averaging techniques especially appropriate for the use in event-driven molecular dynamics algorithms with periodic boundary conditions. The density and size dependence of the results is analyzed, and comparison with the predictions from Enskog's theory is carried out. In particular, the behavior of the transport coefficients in the vicinity of the fluid-solid transition is investigated and a striking power law divergence of the viscosity in this region is obtained, while all other examined transport coefficients show a drop in that density range.