Calculation of intermolecular potentials for H2[sbnd]H2 and H2[sbnd]O2 dimers ab initio and prediction of second virial coefficients

Abstract

The intermolecular interaction potentials of the dimers H2H2 and H2O2 were calculated from quantum mechanics, using coupled-cluster theory CCSD(T) and correlation-consistent basis sets aug-cc-pVmZ (m=2,3); the results were extrapolated to the basis set limit aug-cc-pV23Z. The interaction energies were corrected for the basis set superposition error with the counterpoise scheme. For comparison also Møller–Plesset perturbation theory (at levels 2–4) with the basis sets aug-cc-pVTZ were considered, but the results proved inferior. The quantum mechanical results were used to construct analytical pair potential functions. From these functions the second virial coefficients of hydrogen and the cross virial coefficients of the hydrogen–oxygen system were obtained by integration; in both cases corrections for quantum effects were included. The results agree well with experimental data, if available, or with empirical correlations.