Pressure Tensor of Fluids in Nanopores of Various Geometries: Molecular Simulation Studies By Mechanical Route and Thermodynamics Route

The pressure tensor components of LJ argon adsorbed in carbon pores of different simple geometries, i.e., ideal slit, sphere and cylinder, are studied and compared. We find that the pore geometry has large effects on the adsorption isotherm, the structure of the confined phase and the in-pore pressure of the adsorbate. Depending on the wall curvature, the attraction from the carbon wall acting on the contact layer of adsorbate is strengthened, and thus the confined phase is more compressed, which results in a more enhanced tangential pressure, especially at the contact layer. For the same reason, pore fillings occur at lower pressure in a spherical pore than in a slit or cylindrical pore of the same size. Moreover, our new framework to calculate pressure tensor components based on the thermodynamic route (or volume perturbation method) works well for calculating the pressure in pores of these three geometries.