Ab Initio Prediction of the Equilibrium Structure and Vibrational−Rotational Energy Levels of Fluorofulminate

Abstract

The molecular parameters of fluorofulminate, FCNO, have been predicted in ab initio calculations using the coupled-cluster method, CCSD(T), and basis sets of double- through quadruple-< quality. In contrast to other halofulminates (ClCNO and BrCNO), the equilibrium structure of the FCNO molecule was found to be well bent, with the parameters r e (FC) = 1.301 A, r e (CN) = 1.200 A, r e (NO) = 1.199 A, e (FCN) = 135.1°, and e (CNO) = 162.0°. The height of a barrier to linearity of the FCNO chain was predicted to be 1870 cm - 1 . The harmonic frequencies and, in particular, FCN bending-rotation energy levels were calculated. To assist in a future analysis of the high-resolution spectra of fluorofulminate, the effective rotational constant B, was predicted for various states of the FCN bending mode. The determined regular pattern of low-lying energy levels is consistent with that characteristic of a semirigid bent molecule with a moderately anharmonic bending potential energy function.