Explicitly correlated study of the torsional vibrations of HSOSH molecule. Comparison with MP2/CBS(T,Q) level of theory

Abstract

Geometric parameters of equilibrium configurations of trans- and cis-conformers of HSOSH molecule, their dipole moments, rotational constants in the ground electronic and vibrational states, and kinetic parameters corresponding to two torsional coordinates γ1 and γ2 were calculated at CCSD(T)-F12/cc-pVDZ-F12 level of theory. In the latter case, at each node of the two-dimensional grid γ1 and γ2 all other geometric parameters of the molecule were optimized. The obtained configurations were used for calculation of 2D potential energy surface at CCSD(T)-F12/cc-pVTZ-F12 level without additional optimization. The energies of a number of excited torsional states were determined by numerically solving the vibrational Schrödinger equation of bounded dimension using two-dimensional complex Fourier series. The obtained data on the frequencies of torsional vibrations of S-H groups in the two conformers and the frequencies of tunneling in the ground and excited torsional states are compared with the results obtained earlier at MP2/CBS(T,Q) level of theory.