Department of Mechanical Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
Phys Rev E. 2018 Jan;97(1-1):013101. doi: 10.1103/PhysRevE.97.013101.
We develop molecular transport simulation methods that simultaneously deal with gas- and surface-phase diffusions to determine the effect of surface diffusion on the overall diffusion coefficients. The phenomenon of surface diffusion is incorporated into the test particle method and the mean square displacement method, which are typically employed only for gas-phase transport. It is found that for a simple cylindrical pore, the diffusion coefficients in the presence of surface diffusion calculated by these two methods show good agreement. We also confirm that both methods reproduce the analytical solution. Then, the diffusion coefficients for ink-bottle-shaped pores are calculated using the developed method. Our results show that surface diffusion assists molecular transport in the gas phase. Moreover, the surface tortuosity factor, which is known to be uniquely determined by physical structure, is influenced by the presence of gas-phase diffusion. This mutual influence of gas-phase diffusion and surface diffusion indicates that their simultaneous calculation is necessary for an accurate evaluation of the diffusion coefficients.
我们开发了分子输运模拟方法，这些方法同时处理气相和表面相扩散，以确定表面扩散对整体扩散系数的影响。表面扩散现象被纳入测试粒子法和均方位移法中，这些方法通常仅用于气相输运。结果发现，对于简单的圆柱形孔，这两种方法计算的存在表面扩散时的扩散系数吻合较好。我们还确认这两种方法都再现了分析解。然后，使用开发的方法计算了墨水瓶形孔的扩散系数。我们的结果表明，表面扩散有助于气相中的分子输运。此外，表面迂曲因子通常由物理结构唯一确定，它受到气相扩散的影响。气相扩散和表面扩散的这种相互影响表明，为了准确评估扩散系数，需要同时计算它们。
