Effect of pore wall model on prediction of diffusion coefficients for graphitic slit pores
Date
2008
Authors
Cai, Q.
Biggs, M.
Seaton, N.
Editors
Advisors
Journal Title
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Volume Title
Type:
Journal article
Citation
Physical Chemistry Chemical Physics, 2008; 10(18):2519-2527
Statement of Responsibility
Qiong Cai, Mark J. Biggs and Nigel A. Seaton
Conference Name
DOI
Abstract
The effect of the pore wall model on the self-diffusion coefficient and transport diffusivity predicted for methane in graphitic slit pores by equilibrium molecular dynamics (EMD) and non-equilibrium MD (NEMD) is investigated. Three pore wall models are compared—a structured wall and a smooth (specular) wall, both with a thermostat applied to the fluid to maintain the desired temperature, and a structured wall combined with the diffuse thermalizing scattering algorithm of MacElroy and Boyle (Chem. Eng. J., 1999, 74, 85). Pore sizes ranging between 7 and 35 and five pressures in the range of 1–40 bar are considered. The diffuse thermalizing wall yields incorrect self-diffusion coefficients and transport diffusivities for the graphitic slit pore model and should not be used. Surprisingly, the smooth specular wall gives self-diffusion coefficients inline with those obtained using the structured wall, indicating that this computationally much faster wall can be used for studying this phenomenon provided the fluid-wall interactions are somewhat weaker than the fluid–fluid interactions. The structured wall is required, however, if the transport diffusivity is of interest.