Structure and spectroscopy of graphite monofluoride

Abstract

The structure of graphite monofluoride, (CF)_n, has been debated since its discovery in 1934. In this work, we investigate a commercial graphite monofluoride by vibrational spectroscopy (infrared, Raman and the first inelastic neutron scattering spectra of this material). The spectroscopy shows that the material contains unreacted graphite and the partially fluorinated product dicarbon fluoride, (C₂F)_n, We evaluate the previously proposed $P\bar{6}m2$ and $P\bar{3}m1$ structures using computational methods and find F···F contacts render the $P\bar{6}m2$ structure dynamically unstable. We propose two alternative structures, $Cmc{2}_1$ and $P{6}_{3}mc$, generated by displacement of one layer relative to another and find that $Cmc{2}_1$ is also dynamically unstable. The calculations are validated by comparison of calculated and observed INS spectra