Intermolecular Potential Functions for Nonpolar Molecules

Abstract

The Morse potential function is used to represent the intermolecular potential for several nonpolar substances. The potential constants are determined from a combination of crystal structure and second virial coefficient data for Ne, Ar, Kr, Xe, CH₄, and N₂. Over a wide temperature range the theoretical second virial coefficients determined from the Morse potential for these substances agree very well with experimental data and are quite comparable with calculations using the Buckingham (exp−‐6) or the Lennard‐Jones (12–6) potentials. For Kr, it is found that the agreement with the experimental second virial coefficients is greatly improved by dividing the intermolecular potential into two separate Morse functions, one applicable where the potential is negative and the other applicable where the potential is positive.