Computational studies of the structure and vibrational spectra of hexachlorodisilane

Ab initio restricted Hartree-Fock (RHF) calculations and density functional theory calculations using B3' exchange and Lee-Yang-Parr's correlation fun ctionals (B3LYP) with 6 - 31G** basis set were carried out to study and opt imize equilibrium structure and to obtain energies of two rotational confor mers and fundamental vibrational frequencies in the equilibrium structure f or Si2Cl6. The optimized structural parameters are in good agreement with e xperimental results. The calculated potential barriers to internal rotation are 8.786 and 6.694kJ/mol determined from the calculations using HF/6 - 31 G** and B3LYP/6 - 31G** methods, respectively. The B3LYP/6 - 31G** value is in good agreement with the observed value of 4.1868kJ/mol. Infrared intens ities, Raman activities and vibrational frequencies are reported for Si2Cl6 under D-3d symmetry, A normal coordinate analysis employing scaled ab init io (HF/6 - 31G**) force field has been carried out. The average error betwe en the predicted fundamentals utilizing scaled HF/6 - 31G** force field wit h a scale factor of 0.9 pertinent to all vibrational modes and observed fun damental vibrational frequencies is 7.3cm(-1). Moreover, a mean absolute de viation between fundamentals obtained from B3LYP/6 - 31G** calculations usi ng unrefined SQM force field and the observed frequencies is 6.0cm(-1).