Two-Dimensional Second Virial Coefficients of Methane and Tetradeuteromethane on Graphitic Carbon

Publisher Website
Google Scholar
Abstract
Specific two‐dimensional second virial coefficients are obtained from low‐coverage adsorption isotherms for CH4 and CD4 on graphitic carbon between 220° and 290°K. These data are analyzed in terms of both classical and quantum‐statistical models employing a Lennard‐Jones potential, and corrections for non‐planarity of the adsorbed phase are also included. The sign of the quantity [ε(H)—ε(D)]/ε(D) cannot be unambiguously determined, but this quantity is somewhat smaller than in the corresponding three‐dimensional case. The measured nonadditivity of pair potentials amounts to about 15% of the gas‐phase energy, and is in good agreement with independent theoretical predictions.