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arXiv · 1912.09067

Self-diffusion in a quasi-two dimensional gas of hard spheres

J. Javier Brey·M. I. García de Soria·P. Maynar
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Abstract

A quasi-two-dimensional system of hard spheres strongly confined between two parallel plates is considered. The attention is focussed on the macroscopic self-diffusion process observed when the system is looked from above or from below. The transport equation, and the associated self-diffusion coefficient, are derived from a Boltzmann-Lorentz kinetic equation, valid in the dilute limit. Since the equilibrium state of the system is inhomogeneous, this requires the use of a modified Chapman-Enskog expansion that distinguishes between equilibrium and non-equilibrium gradients of the density of labelled particles. The self-diffusion coefficient is obtained as a function of the separation between the two confining plates. The theoretical predictions are compared with molecular dynamics simulation results and a good agreement is found.

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J. Javier Brey, M. I. García de Soria, P. Maynar. 2019-12-19. Self-diffusion in a quasi-two dimensional gas of hard spheres. https://doi.org/10.1103/physreve.101.012102

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