Equilibrium Structure and Spectroscopic Constants of Difluorovinylidene: An ab Initio Study

Abstract

Highly correlated ab initio calculations with large basis sets are reported for difluorovinylidene, F₂CC. Based on CCSD(T)/aug-cc-pVQZ results and taking core correlation effects properly into account, a reliable theoretical equilibrium geometry is derived: r_e(CC) = 134.74(10) pm, r_e(CF) = 131.00(10) pm, and ∠_e(FCC) = 123.23(10)°. The error bars are estimated from analogous comparative calculations on the equilibrium structures of the CF₂, C₂, and C₃ species. Correlated harmonic [CCSD(T)/aug-cc-pVQZ] and anharmonic [CCSD(T)/TZ2Pf] force fields provide theoretical values for the fundamental vibrational wavenumbers which are in excellent agreement with those measured previously in an argon matrix. Many spectroscopic constants of F₂CC are predicted. In addition, the energy of F₂CC relative to difluoroethyne (FCCF) and the barrier to isomerization from F₂CC to FCCF have been reinvestigated by means of the present high-level ab initio calculations