The intermolecular interaction potentials of the dimer H2-O2 were calculated from quantum mechanics, using coupled-cluster theory CCSD(T) and correlation-consistent basis sets aug-ccpVmZ (m = 2, 3); the results were extrapolated to the basis set limit aug-cc-pV23Z. The quantum mechanical results were used to construct 5-site pair potential functions. The cross second virial coefficients of the dimer hydrogen-oxygen were obtained by integration; in these cases corrections for quantum effects were included. The results agree well with experimental data and empirical correlations. | Journal of Chemistry, Vol. 46 (1), P. 120 - 126, 2008 Prediction of cross second virial coefficients for dimer H2-O2 from ab initio calculations of intermolecular potentials Received May 23, 2007 Pham Van Tat1, U. K. Deiters2 1 Department of Chemistry, University of Dalat 2 Institute of Physical Chemistry, University of Cologne, Germany Summary The intermolecular interaction potentials of the dimer H2-O2 were calculated from quantum mechanics, using coupled-cluster theory CCSD(T) and correlation-consistent basis sets aug-ccpVmZ (m = 2, 3); the results were extrapolated to the basis set limit aug-cc-pV23Z. The quantum mechanical results were used to construct 5-site pair potential functions. The cross second virial coefficients of the dimer hydrogen-oxygen were obtained by integration; in these cases corrections for quantum effects were included. The results agree well with experimental data and empirical correlations. I - Introduction Computer simulation techniques, Monte Carlo as well as Molecular Dynamics, cannot work without some input, however: It is necessary to know the interaction potentials of the systems under study. The usual procedure is to assume a simple model potential. A system is the fluid mixture (H2-O2). Its thermodynamic properties are important for the design of efficient rocket engines [1], but there are remarkably few publications of experimental results only -for evident reasons. Recently an alternative approach has become feasible, for which the name “global simulation” has been coined [2]. One of the first attempts in such global simulations was that of Deiters, Hloucha and Leonhard [3] for neon to predict the vapour-liquid phase equilibria without recourse to experimental data. Further global simulation attempts for noble gases were published by the group of Huber [4]. Using a 120 functional form for the dispersion potentials of argon and krypton proposed by Korona et al. [5]. Leonhard and Deiters constructed a 5-site Morse potential
