Interaction energies of the Na+·Rg complexes (Rg = He, Ne and Ar): Basis set considerations for Na+

Abstract

Calculation of the equilibrium bond lengths of the Na⁺·Rg complexes (Rg = He, Ne and Ar) is performed at the CCSD(T) level using a variety of basis sets. In addition, the binding energies are also calculated at a number of levels of theory. Contracted basis sets of a size equal to the aug-cc-pVXZ basis sets (X = T, Q and 5) are designed, using expansion coefficients optimized for Na⁺. These contracted basis sets are compared to their uncontracted counterparts, and to other readily available basis sets: aug-cc-pVXZ (X = T and Q) and a (19s11p) basis set, suitably augmented, where all three are optimized for Na; and a (16s11p) basis set, suitably augmented, which was optimized for Na⁺. Our best values for the internuclear separations for the Na⁺·Rg complexes are 2.31, 2.44 and 2.75 Å for Rg = He, Ne and Ar, respectively; the respective binding energies are 330, 510 and 1330 cm⁻¹. These results appear to be converged with the basis set, as adjudged by detailed consideration of the results for Na⁺·He, and are at one of the highest levels of theory readily available, and consequently should be very reliable.