Localisation and density of states in amorphous carbon-based alloys

The aim of this work was to thoroughly discuss all local effects affecting the nature and energy distribution of pi and pi* states. In particular, the role of overlap between atomic orbitals, disorder and localisation will be treated. It will be shown that, while the overlap of atomic p-orbitals lea ds to states asymmetric with respect to the non-bonding level, the disorder -induced fluctuations of the clusters non-bonding level lead to the broaden ing of Gaussian pi and pi* density-of-states (DOS) bands. The role of charg e transfer and its effect on the correlation energy will be discussed as we ll. On such basis, the optical and paramagnetic properties of (t)(a)-C(:H) will be successfully modelled. (C) 2001 Elsevicr Science B.V. All rights re served.