Intermolecular forces in globular molecules VI: octopole moments of tetrahedral molecules

The octopole moments for methane and carbon tetrafluoride have been estimated from the temperature dependence of second virial coefficients. The central potential employed was the spherical shell model for which the force constants were derived from the temperature dependence of gas viscosity on the assumption that the octopole moment had no measurable effect on the viscosity. The values obtained for the moments, defined as Ω= (5/2) Σieixiyizi, were: methane, ± 3.7 × 10–34 esu·cm3 and carbon tetrafluoride, ± 13.7 × 10–34 esu·cm3.