Coriolis coupling constants and inertial defect of B₂F₄ by ab initio calculations and the iterative method

Abstract

Structural parameters, harmonic frequencies, and force constants of B2F4 were obtained in internal coordinates from ab initio RHF calculations with the 6-311G* basis set. The results obtained are used to calculate the Coriolis coupling constants and the inertial defect for 10B2F4 and 11B2F4 and to compare these values with those obtained by using the autoconsistency method. Both the ab initio and the iterative force fields, despite some significant differences, reproduce the vibrational wave numbers equally well and yield nearly the same Coriolis coupling constants and inertial defects. The calculated inertial defects for 10B2F4 and 11B2F4 are -0.942 and -0.919 amu Å2, respectively.Key words: Coriolis coupling constants, inertial defect, B2F4, harmonic frequencies, force constants.

B2F4 Molecule: A Challenge for Theoretical Calculations

“…Recently, it was found that only with large basis sets at the HF level or including correlation effect can the planar structure of B 2 F 4 be a minimum and lower in energy than the staggered structure. 24, 26,32,33 To judge if a structure is a minimum or a transition state, vibrational frequency analysis is always necessary. However, few studies have performed vibrational frequency analysis on both conformations of B 2 F 4 .…”

“…Earlier ab initio calculations at the Hartree−Fock (HF) level with small basis sets indicate that the eclipsed structure of B 2 F 4 is higher in energy than the staggered structure, − while semiempirical calculations indicate a reverse energy order, − in accordance with experimental findings. Recently, it was found that only with large basis sets at the HF level or including correlation effect can the planar structure of B 2 F 4 be a minimum and lower in energy than the staggered structure. ,,, To judge if a structure is a minimum or a transition state, vibrational frequency analysis is always necessary. However, few studies have performed vibrational frequency analysis on both conformations of B 2 F 4 .…”