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 1s 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 1 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 sp2- and diamond-like sp3-hybridized carbon atoms.