Theoretical study of spectroscopic constants and anharmonic force field of SiF2

Abstract

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.

Ab Initio Studies on Spectroscopic Constants for the HAsO Molecule

“…The harmonic vibrational frequencies and the normal modes of the HAsO molecule were obtained from the quadratic force fields in the usual manner. , The remaining spectroscopic constants of the HAsO molecule were evaluated by obtaining quartic expansions of the potential energy surfaces in reduced normal coordinates from the theoretical Cartesian force constants by utilizing the standard vibrational–rotational Hamiltonian − expressed in normal coordinates for semirigid, asymmetric top molecules and the well-known formulas from perturbation theory. A systematic study − of the application of ab initio quartic force fields and perturbation theory to the prediction of the vibration–rotation spectra of asymmetric top molecules has been completed recently, and all of the procedures employed in the present article are described in detail therein.…”

The molecular structure and spectroscopic properties of formaldoxime (CH2NOH)

“…The quantum chemical calculations of DFT method in this paper were performed by Gaussian 16 quantum chemistry package [21]. The density functional theory methods (B3LYP and B2PLYP) [22][23][24][25] were selected for calculations of optimization, energy, and anharmonic force fields, in combination with different basis sets such as cc-pVTZ, aug-cc-pVTZ, 6-311+G ** , 6-311++G (3df,3pd) (contractions of basis sets were shown in table S1) [26,27]. Vibrational second-order perturbation theory (VPT2) was performed for calculations of anharmonic vibrational properties of formaldoxime [28].…”