CARBON K-SHELL NEAR-EDGE STRUCTURE CALCULATIONS FOR GRAPHITE USING THE MULTIPLE-SCATTERING APPROACH

The near-edge absorption fine structure of carbon in graphite has been calculated using the multiple-scattering approach. The effects of bot h a neutral carbon absorber and taking into account the effect of the core hole by using a nitrogen (Z + 1) absorber atom are considered. Th e best agreement with experiment, was obtained for the case of the nit rogen absorber and a cluster of 145 atoms, with the calculated near-ed ge structure (NES) containing the main features observed experimentall y. A splitting near the onset of the sigma-peak, similar to that seen experimentally, was found to occur in the calculated NES for one of t he two inequivalent carbon atoms in the graphite structure. This split ting was not observed in the calculated NES for a single sheet of grap hite, supporting the proposition that it only occurs in well ordered g raphite. This result supports the proposition that the splitting origi nates from a sharp sigma-peak and a dipole-allowed bandlike contribut ion associated to the Gamma(2)(-) branch of the free-electron-like int erlayer states.