A theoretical investigation of the near-edge X-ray absorption spectrum of hexa-peri-hexabenzocoronene

The near-edge X-ray absorption spectrum of hexa-peri-hexabenzocoronene has been simulated by density functional theory techniques using transition sta te and full core hole potentials. The total spectrum is found to be a compo sition of multiple structure in the subspectra of the symmetry unique carbo ns, rather than by chemically shifted single pi* transitions. This quite 'f ullerene-like' behavior, with only minor reminiscence of either graphite or benzene spectral features, is used to argue that long-range effects must b e important to build up the dominating single excitonic pi* feature in grap hite. (C) 2001 Elsevier Science B.V. All rights reserved.