ANALYTICAL POTENTIAL MODELS AND PROPERTIES OF NOBLE GASES

Analytical expressions of the intermolecular potential function with two or more parameters are used to calculate the thermodynamic and transport properties of the heavy noble gases. Comparisons with data indicate that the Kihara potential is as good as any other model for predicting virial coefficients, viscosities, and diffusivities from a single set of parameters. However, the calculated coefficient for dispersion forces, the isotopic thermal diffusion factor, and the stable crystal structures of noble gases indicate that certain details of the potential may be inadequately described by all of the present expressions. In particular, over a wide temperature range, the thermal diffusion factor appears to be sensitive to the potential only in a narrow region of distance located somewhat to the right of the potential minimum; comparison with thermal diffusion data and analysis of crystal data suggest that in this region the slope of the potential should be greater than in present models.