Abstract: The optimized geometries, infrared intensities, Raman activities and fundamental vibrational frequencies and PEDs are reported for D_3dsymmetry of Si₂Br₆utilizing HF/6-31G^*and B3LYP/6-31G^*method. The predicted value of Si-Si torsional vibrational frequency is given. Anormal coordinate analysis has been carried out and HF force field is scaled with scale factor of 0.9 pertinent to all vibrational modes. The average error between the predicted frequencies obtained from HF/6-31G^*SQM force field and the observed fundamental vibrational frequencies is 9.4cm^-1; the average error between the predicted value from unrefined DFTforce field and the observed result is 8. 6cm^-1. The fundamental vibrational frequencies obtained from DFT alculation with B3LYP/6-1G^*are in good agreement with the experimental results.

Key words: Ab initio calculation, Hexabrominedisilane, DFT method, Fundamental vibrational frequency, Normal coordinate analysis