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(fluorocarbony l) disulphide and bis(chlorocarbonyl) disulphide. The results show tha t FC(O)SSC(O)F has two stable conformers (I and II). Conformer I, whic h is the more stable in gas phase, possesses C-2 symmetry. Conformer I I belongs to the C-1 point. CIC(O)SSC(O)Cl has only one stable configu ration, which belongs to the C-2 point group. The potential energy dis tribution and isotope replacement methods were applied to determine th e vibrational assignment. The vibrational frequencies and correspondin g modes of these molecules were obtained. The numerical results of the vibrational frequencies are in good agreement with experiment.