Second virial coefficients, including quantum corrections, for nitrogen using model potentials

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Abstract
The second virial coefficient of nitrogen has been calculated in the temperature range 75–700 K, from the sum of the classical contribution B (0) and the quantum contribution B (1) of order ℏ2, using the intermolecular potential of Berns and van der Avoird (BV) and reasonable variants of it. In some cases results for the full potentials are compared with those obtained when only the isotropic components were retained. For the BV potential B (1) is significant compared with the experimental errors only for T < 130 K; the anisotropic parts of the potential contribute more than the isotropic parts for B (1) in this temperature range, and also for B (0) in the temperature range 170–350 K. The results for the complete BV potential differ significantly from experiment at all temperatures. The effect of varying the dispersion constants C 8 and C 10 in the BV potential within the ranges of their estimated uncertainties was studied. Increasing both isotropic and anisotropic components of C 8 and C 10 by 10 and 20 per cent respectively yields excellent agreement with experiment, whereas increasing the isotropic components alone by these amounts gives good agreement with experiment except at the lowest temperatures. If all the second order dispersion energies in the BV potential are replaced by those recently obtained by Visser, Wormer and Stam agreement with experiment is improved but significant deviations remain at most temperatures.