Benchmark CCSD-SAPT study of rare gas dimers with comparison to MP-SAPT and DFT-SAPT.

Abstract

Symmetry-adapted perturbation theory (SAPT) based on coupled cluster approach with single and double excitations (CCSD) treatment of intramonomer electron correlation effects was applied to study rare gas homodimers from He2 to Kr2. The obtained benchmark CCSD-SAPT energies, including cumulant contributions to first order exchange and second-order exchange-induction terms, were then compared to their counterparts found using other methods-Møller-Plesset-SAPT based on many-body Møller-Plesset perturbation theory and DFT-SAPT based on density functional theory. The SAPT terms up to the second-order were calculated with the basis sets close to the complete basis set at the large range of interatomic distances R. It was shown that overestimation of the binding energies De found with DFT-SAPT reported in the work of Shirkov and Makarewicz [J. Chem. Phys. 142, 064102 (2015)] for Ar2 and Kr2 is mostly due to underestimation of the exchange energy Eexch(1) when comparing to the CCSD-SAPT benchmark. The CCSD-SAPT potentials were found to give the following values of the dissociation energies D0: 0.0006 cm-1 for He2, 16.71 cm-1 for Ne2, 85.03 cm-1 for Ar2, and 129.81 cm-1 for Kr2, which agree well with the values found from previously reported highly accurate ab initio supermolecular potentials and experimental data. The long-range dispersion coefficients C2n up to n = 6 that give the dispersion energy asymptotically equivalent to its SAPT counterpart were calculated from dynamic multipole polarizabilities at different levels of theory.