Anharmonic Forces and the Vapor-Pressure Ratio of Monatomic Isotopic Solids. II

Abstract
The anharmonic contribution to the vapor‐pressure ratio of 36Ar and 40Ar has been calculated using a Mie—Lennard—Jones 6, n potential with n=10 and 12. The contribution of the vibrational anharmonicity was found to be large and tended to cancel the effect of thermal expansion. Numerical calculations for the 6, 10 potential were found to agree well with experimental measurements of the isotope separation factor. A brief discussion is given of vapor pressure ratio data for 20Ne and 22Ne.