Theoretical study of spectroscopic constants and anharmonic force field of SiF2.

The equilibrium structure, spectroscopy constants, and anharmonic force field of SiF2 have been investigated at MP2, B3LYP, and B3PW91 levels of theory employing two basis sets cc-pVQZ and cc-pVTZ, respectively. The obtained equilibrium geometries, rotational constants, fundamental vibrational wave numbers, and centrifugal distortion constants are compared with the available experimental data or the previous theoretical values. The MP2/cc-pVQZ results of SiF2 are in excellent agreement with the available experimental data and afford a marked improvement over B3LYP/cc-pVQZ and B3PW91/cc-pVQZ in the calculation of spectroscopic constants and force constants of SiF2. The basis set enhancement beyond cc-pVQZ does not lead to a major improvement so that the cc-pVQZ basis set is sufficient for SiF2. The MP2/cc-pVQZ results may provide useful data for the spectroscopic experiment studies of SiF2. The used DFT method is also an advisable choice to study anharmonic force field of SiF2.