Torsional vibrations of two thiol groups in the HSOSH, DSOSH, and DSOSD molecules: 2D PES study in CBS limit

Abstract

2D surfaces of potential energy, dipole moment, and kinetic coefficients associated with internal rotation of the thiol groups in the HSOSH molecule were calculated and analyzed at MP2/CBS level of theory. Two stable conformers (trans- and cis-) with very close energies were found. Torsional vibrations of the HSOSH, DSOSH, and DSOSD molecules were calculated at harmonic and anharmonic approximations as well as by numerically solving of the 2D torsional Schrödinger equation using the Fourier method for the first time. The tunneling splitting of the first thirty torsional energy levels was found. The torsional IR spectra of the trans- and cis- conformers of the three analyzed molecules were calculated at different temperatures.