MOLECULAR GEOMETRIES, VIBRATIONAL FREQUENCIES, FORCE-FIELDS AND MEAN-SQUARE AMPLITUDES OF SILICON DIHALIDES DETERMINED FROM AB-INITIO CALCULATIONS

Ab initio studies and force field calculations are reported for the mo lecules SiF2, SiCl2 and SiBr2; Structural, vibrational and energetic f eatures of the dimers Si2F4 and Si2Cl4 are also determined. The molecu les have been optimized at the SCF level of theory employing split val ence basis sets; geometries and vibrational frequencies of the molecul es SiF2 and SiCl2 have been obtained at the MP2/DZP level. The compute d structural parameters and properties have been compared with the exp erimental ones. General valence force fields are used to calculate for ce constants. The mean square amplitudes are calculated and compared w ith the ps phase electron diffraction data. Theoretical calculations a re also reported for SiH2, SiHF, SiHCl and SiFCl.