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Prediction of dispersive second virial coefficients of heavy alkali metals by using ab initio calculation
This paper presents the prediction of dispersive second virial coefficients B’2’s, of cesium and rubidium metals vapors using ab initio method by applying Gaussian 98W program at the B3LYP levels of theory in a wide temperature range. Prediction of B’2’s for both cesium and rubidium metal vapors is made possible by evaluation of equilibrium constants of dimerization of alkali metals. Based on equation Keq = – <B’2’s> [F. M. Mies, P. S. Julienne, J. chem. Phys. 77 (1982) 6162–6176], B’2’s for both cesium and rubidium metal vapors were obtained from evaluation of their thermodynamic equilibrium constants by obtaining standard Gibbs free energy differences of dimerization reactions, in a wide temperature range, covering from melting point up to hundreds degree of temperature above critical point. B’2’s of cesium metal vapor were obtained with reasonably good accuracies. In the case of rubidum metal vapor, excellent agreement with recently reported theoretical methods in all calculated range of temperature were obtained.
Keywords: Equilibrium constant; Standard Gibbs free energy; Dispersive Second virial coefficient; Alkali metals; Critical point.