Quantum-chemical study of structural, spectral, and electrooptical parameters of fluorosilanes SiH4− xFx(x=0–4)

The possibility of calculating the molecular structure, vibrational frequencies, and electrooptical parameters of the silane molecule SiH4 and the silicon tetrafluoride molecule SiF4 is analyzed by using the ab initio quantum-chemical method (the MP2 perturbation theory) and the density functional theory (the B3LYP functional) with a wide variation of basis sets up to the cc-pV5Z set. The results obtained are used as reference values for studing mixed fluorosilanes SiH4−xFx (x=1–3) and for refining their geometry, the vibrational frequencies, and the absolute intensities of absorption bands. Based on the results of high-level quantum-chemical calculation corrected against the experimental data for SiH4 and SiF4, the structural parameters of mixed flouro-silanes are estimated and their vibrational frequencies are calculated and assigned for the first time. The quantum-chemical estimates of the absolute intensities of IR spectra are for the first time presented for all mixed fluorosilanes.