DFT calculations of XPS/NEXAFS and IR spectra to elucidate the reaction products of acetonitrile with Si(0 0 1)-2 × 1

NEXAFS data [S. Rangan et al., Phys. Rev. B 71 (2005) 165319] and FTIR data [M.P. Schwartz, R.J. Hamers, Surf. Sci. 601 (2007) 945] apparently do not converge in the identification of the reaction products of acetonitrile (CH₃CN) with Si(0 0 1)-2 × 1 at room temperature. Using DFT calculations of core-excited/core-ionized spectra and of IR vibrational frequencies and intensities, we show the consistency of the body of experimental data. Three species are present on the surface in equivalent amounts, a CN moiety, a pendent CN and a CCN ketenimine submitted to a strong twist imposed by the Si bond directionality. More generally, the paper shows the usefulness of spectroscopic data simulations in the elucidation of complex surface chemistry problems.