Molecular geometries, vibrational frequencies, force fields and mean-square amplitudes of silicon dihalides determined from ab initio calculations

Abstract

Ab initio studies and force field calculations are reported for the molecules SiF 2, SiCl 2 and SiBr 2; structural, vibrational and energetic features of the dimers Si 2F 4 and Si 2Cl 4 are also determined. The molecules have been optimized at the SCF level of theory employing split valence basis sets; geometries and vibrational frequencies of the molecules SiF 2 and SiCl 2 have been obtained at the MP2/DZP level. The computed structural parameters and properties have been compared with the experimental ones. General valence force fields are used to calculate force constants. The mean square amplitudes are calculated and compared with the gas phase electron diffraction data. Theoretical calculations are also reported for SiH 2, SiHF, SiHCl and SiFCl.