Molecular structure,atomization energy,ionization energy,electron affinity and vibrational spectrum of SiX 2 (X = F,Cl,Br,I) by theoretical methods

The molecular structure, atomization energy, ionization energy, electron affinity and vibrational spectra of silicon dihalides, SiX₂ (X = F, Cl, Br, I), have been obtained using theoretical methods in the gas phase. The neutral dihalides, their cations and anions have been studied in C_2v symmetry. The neutral species have been considered in both the ¹A₁ singlet and ³B₁ triplet states whereas the cations (SiX₂⁺) and anions (SiX₂⁻) have been considered in the ²A₁ and ²B₁ states, respectively. The methods used are Møller-Plesset perturbation theory (MP2), density functional theory (DFT), Gaussian-2 (G2) and complete basis set methods (CBS-4 and CBS-Q). The functional used for the DFT method is B3LYP. The basis sets used are 6-311++G(d,p) for all atoms except that 6-311G(d,p) has been used for iodine atom only. The silicon dihalides, their cations and anions have been fully optimized using MP2 and DFT methods. Single point energy computations (G2, CBS-4M and CBS-Q) have been performed except for silicon diiodide. The results obtained are in good agreement with literature although they are method dependent.