Molecular structure, atomization energy, ionization energy, electron affinity and vibrational spectrum of SiX₂(X = F, Cl, Br, I) by theoretical methods

Abstract

The molecular structure, atomization energy, ionization energy, electron affinity and vibrational spectra of silicon dihalides, SiX 2 (X ¼ 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 1 A 1 singlet and 3 B 1 triplet states whereas the cations (SiX 2 þ ) and anions (SiX 2 7) have been considered in the 2 A 1 and 2 B 1 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 6-311þþG(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.