Ab initio restricted Hartree-Fock (RHF) calculations and density functional theory calculations using B3^,exchange and Lee-Yang-Parr^, s correlation functionals (B3LYP) with 6-31G^*^*basis set were carried out to study and optimize equilibrium structure and to obtain energies of two rotational conformers and funamental vibrational frequencies in the equilibrium structure for Si~2Cl~6. The optimized structural parameters are in good agreement with experimental results. The calculated potential barriers to internal rotation are 8.786 and 6.694kJ/mol determined from the calculations using HF/6-31G^*^* and B3LYP/6--31G^*^* methods, respectively. The B3LYP/6--31G^*^* value is in good agreement with the observed value of 4.1868kJ/mol. Infrared intensities, Ruaman activities and vibrational frequencies are reported for Si~2Cl~6 under D~3~d symmetry. A normal coordinate analysis employing scaled ab initio (HF/6--31G^*^*) force field has been carried out.The average error between the predicted fundamentals utilizing scaled HF/6--31G^*^* force field with a scale factor of 0.9 pertinent to all vibrational modes and observed fundamental vibrational frequencies is 7.3cm^-^1. Moreover,a mean absolute deviation between fundamentals obtained from B3LYP/6--31G^*^* calculations using unrefined SQM force field and the observed frequencies is 6.0cm^-^1.

Key words: SILANE P, AB INITIO CALCULATION, NORMAL COORDINATE ANALYSIS, GEOMETRICAL ISOMERISM