First-principle study of C 1s core-level shifts in amorphous carbon
Using a first-principles approach, we compare calculated core-level shifts with experimental data for amorphous carbon at different densities. We used a molecular dynamics approach based on an environmental-dependent tight-binding (EDTB) Hamiltonian to generate model structures by quenching from the liquid phase. Further atomic relaxation and C Is core-level shift calculations were performed within density functional theory. Core-level shifts are obtained for seven different models of different atomic densities. Shifts associated with three- and fourfold coordinated C atoms show an average separation of I eV, in good agreement with the experimental value of 0.9 eV. These results support the interpretation which associates the two components in the spectra to graphite-like sp(2)- and diamond-like sp(3)-hybridized carbon atoms. (C) 2001 Elsevier Science B.V. All rights reserved.