Pore Width-Sensitive Filling Mechanism for CCl₄ in a Graphitic Micropore by Computer Simulation

The effect of the pore width on the adsorption isotherm and radial distribution of CCl 4 in a graphitic slit micropore was examined by Grand Canonical Monte Carlo simulation over the pore width range 0.7−1.8 nm at 303 K. The simulated adsorption isotherms were divided into three pore groups of 0.7−0.9, 1.0−1.5, and 1.6−1.8 nm in width. The low-pressure uptake below P / P 0 = 10 - 3 was predominant in the narrowest pore system of 0.7−0.9 nm, while a marked uptake in the range of P / P 0 = 10 - 3 to 10 - 2 was observed for the medium-range pores of 1.0−1.5 nm. The adsorption isotherms for the pores 1.6−1.8 nm in width had no plateau above P / P 0 = 10 - 1 . The difference in the adsorption isotherms was associated with the different packing structure of CCl 4 molecules. Although the brief feature of the basic radial distribution of CCl 4 molecules confined in the graphitic slit micropore at 303 K was similar to that of bulk liquid CCl 4, the fine structure of the radial distribution varied sensitively with the change of the pore width. In particular the radial distribution for the pore 0.98−1.04 nm in width showed the unusual ordered feature which is close to that of the plastic crystalline form of the bulk CCl 4 observed at 253 K in the literature.