Interactions of ThO(X) with He, Ne and Ar from the ab initio coupled cluster and symmetry adapted perturbation theory calculations

Two-dimensional interaction potential energy surfaces for the ground-state ThO complexes with RG atoms from He to Ar are calculated ab initio at the coupled cluster CCSD(T) level of theory. The global minimum for all complexes is related to a bent geometry, with the RG atom closer to the oxygen end. Parallel symmetry adapted perturbation theory (SAPT) calculations for the ThO-He complex showed that this configuration is favored by the exchange interaction that slightly prevails over the dispersion and induction contributions which prefer the collinear arrangement. Variational calculations of rovibrational energy levels provided the dissociation energies of 9, 15 and 184 cm ^-1, for the ³He, Ne and Ar complexes, respectively. The He and Ne complexes in the ground state resemble linear molecules as their zero-point energies exceed the barrier at the linear RG-OTh arrangement. Vibrationally-averaged structure of the Ar-ThO complex better reflects the bent geometry of the equilibrium point.