Tests of excess entropy scaling laws for diffusion of methane in silica nanopores

Molecular simulation was carried out to test the validity of two excess entropy scaling laws by Rosenfeld and Dzugutov, respectively, for their extended use in describing diffusion of CH4 molecules through silica nanopores of different sizes from 1.0 to 5.8 nm. The functional relationships between self-diffusivity and excess entropy formulated by the two laws are found to hold with the pre-exponential scaling parameters being peculiarly scale-dependent. Based on this, modified relations for the two scaling laws are proposed for predicting diffusivities of CH4 molecules in such pores over a wide range of concentration and temperature conditions.