Velocity Correlations Between Impinging and Reflecting Particles Using MD Simulations and Different Wall Models

Abstract

The replacement of the the explicit wall in Molecular Dynamics (MD) simulations of nanochannels with an appropriate wall model is important to model the behavior of the gas close to the channel wall correctly. In this paper a comparison of four different wall models with explicit wall MD simulations is reported in the case of a gas confined between two plates of different temperature. Accommodation coefficients are computed from the explicit wall MD simulations using different techniques. Examples are given that for the same system different methods may produce different accommodation coefficients. The computed accommodation coefficients are subsequently used as input to some of the wall models. From comparison of simulations with explicitly modelled walls or using wall models it is shown that not only is it important to look at the distribution of outgoing velocities, but also at the correlation of incoming and outgoing velocities.