The dynamic properties of bulk fluids remain a challenge to predict. Predicting the dynamic properties of confined fluids represents a greater scientific and engineering challenge. Developing simple heuristics or even robust correlations will be helpful in developing and understanding technologies that operate at increasingly smaller length scales.
To ascertain the effect of pore geometry (e.g., size, geometry, fluid-wall interactions) on correlations between dynamics and thermodynamics in bulk and confined fluids spanning vapor and dense liquid densities.
To understand the effect of pore geometry on correlations between dynamics and thermodynamics, we study a monodisperse hard-sphere fluid confined in neutral slit pores, square channels and cylindrical pores. We have also studied binary hard-sphere mixtures in bulk and under confinement. Eventually, we would like to extend this work to more real realistic fluids.
We have calculated the self-diffusion coefficient using molecular dynamics, and excess entropy and various measures of available volume transition-matrix Monte Carlo at approximately 1,000 state points, covering densities from the dilute gas to the freezing transition. The remarkably robust correlation between the available volume and diffusivity, can be used to provide an accurate, fast simulation-free approach to estimate the self-diffusivity coefficient of confined hard-sphere fluids.