Multi-reference coupled pair approximation (MRCPA) calculations for the ground state of the ArI 2 complex

Abstract

We performed multi-reference coupled pair approximation (MRCPA) calculations as well as single-reference CPA (SRCPA) calculations for the ground state of the ArI 2 complex using relativistic model core potentials which included major relativistic effects. The localized natural orbital (LNO) set approach was used to calculate the correlation energy. The T-shaped and linear isomers had almost the same binding energies. MRCPA calculations gave a potential surface on which the T-shaped minimum was lower than the linear minimum by 9 cm −1, while SRCPA calculations predicted that the linear and the T-shaped isomers were almost degenerate within 2 cm −1. The MR approach preferred the T-shaped geometry. The vibrational frequencies for the van der Waals stretch mode in the T-shaped and linear isomers were calculated to be 64 and 46 cm −1, respectively.