Computer Simulations of the Dynamic Properties of Methane in a Model Silica Gel

Abstract

Molecular dynamics (MD) simulations are reported for a Lennard-Jones fluid adsorbed into a model silica gel to study the dynamic properties of the adsorbed methane molecules. The mean-square displacement and velocity autocorrelation function of the adsorbed molecules are calculated for a set of supercritical temperatures at low (gas-like) and high (liquid-like) fluid densities and compared with the same data for a bulk fluid. The evaluated radial distribution functions illustrate the formation of a contact layer on the pore surface that is consistent with the decrease in the mobility of the adsorbed molecules in a porous environment. The calculated self-diffusion coefficient indicates a good quantitative agreement with the measured data for methane confined to the silica gel.

Computer Simulation Study of the Diffusion of Water Molecules Confined in Silica Gel

“…Although, for a high water density, this increase is slower ( figure 6). The same effect was observed in our previous study of the methane in silica gel [23], where the temperature dependency is getting weaker with the fluid density increase.…”

“…The main attention in the studies [17][18][19][20][21] based on the KM model has been paid so far to the structure and thermodynamic properties. However, there are some studies of dynamic properties as well [22,23].…”

Simple Fluid in an Attractive, Disordered Polydisperse Matrix

“…The strong fluid-matrix attractive potential (≈ 6ε F ) causes an adsorption of fluid molecules on the matrix particle surface that is treated as the surface of the silica gel pores. The KM model is widely used in various theoretical studies of structural [2][3][4][5], thermodynamic [6][7][8] and even dynamical [9] properties of the fluid confined in the silica gel. But this model is restricted to the monodisperse matrix particles as constituent parts of a model gel material.…”