The HSO-SOH isomers revisited: The effect of tight d functions

The tight d-augmented correlation consistent basis sets, cc-pV(n+d)Z, and standard correlation consistent basis sets, cc-pVnZ, where n = D(2), (3), Q(4), and 5, for the second-row atoms have been used to reexamine the relative energy of the HSO and SOH isomers using Hartree-Fock, coupled cluster with single and double excitation, and coupled cluster with single, double, and perturbative triple excitation levels of theory. Geometries, dissociation energies, and vibrational frequencies have also been determined for each species. The relative energies of the two isomers converge more rapidly and smoothly for the new tight d-augmented sets than for the standard sets. The impact of the tight d function is most significant upon dissociation energies at the double-zeta and triple-zeta levels for HSO, with differences of 5.46 and 2.57 kcal/mol, respectively, and less significant for SOH, with differences of 1.90 and 1.20 kcal/mol. The impact of the additional d functions in the basis set upon vibrational frequencies and zero-point energies is minor.