The theoretical consistency of the experimental EELS of the fcc phase of carbon

Recently, Konyashin et al. [I. Konyashin, V. Khvostov, V. Babaev, M. Guseva, J. Mayer, A. Sirenko, A new hard allotropic form of carbon: dream or reality? International Journal of Refractory Metals and Hard Materials (article in press)] have reported electron energy loss spectra (EELS) of face centered cubic (fcc) carbon films that indicate unique electronic properties of this particular crystal phase of carbon.Motivated by that, we have investigated the optical properties of carbon in its fcc phase (Fm3¯m) by means of a first principles calculation. In this work we present the calculated dielectric tensor and EELS, which are in good agreement with the experimental spectra. In the EELS of fcc carbon there exists only one peak located at 22–23 eV, we have reproduced this by the density functional calculation at 22 eV. The electronic density of states and band structure is additionally shown to get a deeper understanding of the optical response.In order to check the accuracy of our calculations analogous results obtained for the diamond phase of carbon are included in this work.