The pressure second virial coefficient for vibrating homonuclear diatomic molecules

Abstract

The contribution of molecular vibrational flexibility to the pressure second virial coefficient, B, has been evaluated for nitrogen and chlorine molecules, including an estimate of the effect of quantization of the vibrations. The change in B is very small, at most 3·8 and often as small as 0·01 cm³/mol. Consequently this correction is expected to be totally negligible in the deduction of intermolecular potentials from experimental data on B for diatomic molecules. This result is very different from the case of water where contributions of up to 100 cm³/mole have recently been reported (Refson et al., 1987, J. chem. Phys., 87, 3634).