Calculation of second virial coefficients using ab initio intermolecular pair potentials for F2-F2 and H2-F2 dimers

•We construct the angular orientations of dimers F2-F2 and H2-F2.•We calculate the ab initio intermolecular interaction energies for all built orientations.•Extrapolating the interaction energies to the complete basis set limit aug-cc-pV23Z.•We develop two 5-site ab initio intermolecular potentials of dimers F2-F2, H2-F2.•Calculating the virial coefficients of dimer F2-F2 and H2-F2.

The ab initio intermolecular pair potentials of dimers F2-F2 and H2-F2 were calculated from all constructed orientations, using the level of theory CCSD(T) and basis sets aug-cc-pVmZ (m = 2, 3, 23). The complete basis set limit aug-cc-pV23Z was extrapolated by ab initio interaction energies at the level of theory CCSD(T) with two basis sets aug-cc-pVmZ (m = 2, 3). Then the quantum mechanical results were used for constructing two new 5-site potential functions by fitting ab initio energies of dimers F2-F2 and H2-F2. The correlation between ab initio and the fitted ab initio energies of 5-site pair potentials for dimers F2-F2 and H2-F2 is appeared by fitness values R2 in range 0.99749-0.99997. The fitted potentials were used in standard thermodynamic relations to obtain the second virial coefficients and the results were compared to experimental data.

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