AB-INITIO CALCULATION OF STRUCTURES AND VIBRATIONAL-SPECTRA OF XC(O)SSC(O)X (X=F, CL)

LCAO-MO-SCF restricted Hartree-Fock calculations have been carried out to obtain the structures and vibrational spectra of bis(fluorocarbonyl) disulphide and bis(chlorocarbonyl) disulphide. The results show that FC(O)SSC(O)F has two stable conformers (I and II). Conformer I, which is the more stable in gas phase, possesses C-2 symmetry. Conformer II belongs to the C-1 point. CIC(O)SSC(O)Cl has only one stable configuration, which belongs to the C-2 point group. The potential energy distribution and isotope replacement methods were applied to determine the vibrational assignment. The vibrational frequencies and corresponding modes of these molecules were obtained. The numerical results of the vibrational frequencies are in good agreement with experiment.