Transport coefficients in hard-sphere fluids: thermodynamic versus kinetic descriptions

Abstract

A thermodynamic theory for transport coefficients in hard-sphere fluids is developed from a general expression for the Onsager matrix. The theory predicts the ratio $σ/σ_{\rm id}$, where $σ$ is a transport coefficient and $σ_{\rm id}$ denotes its dilute-gas value. This ratio depends exclusively on equilibrium thermodynamic properties and can therefore be computed directly from the equation of state. Compact expressions are obtained for the thermal conductivity, viscosity, and self-diffusion coefficient. These expressions quantitatively reproduce simulation data over almost the entire fluid range and, in the case of self-diffusion, significantly improve upon the predictions of Enskog kinetic theory. The results demonstrate that transport coefficients can be accurately described within a purely thermodynamic framework.