Molecular orbital calculation for N-doped ZnO

The electronic structures of ZnO, Li-doped ZnO and N-doped ZnO are calculated using the discrete variational Xa: method on model clusters. For ZnO, it is found that the Zn-O bonding is not perfectly ionic but partially covalent because of the hybridization between Zn 3d and O 2p orbitals in the valence band. When a Zn atom of the cluster is replaced with a Li atom, the width of the valence band is expanded than that of the ZnO cluster, and at the same time the energy gap between HOMO and LUMO decreases. On the other hand, the new energy states originating from N 2p orbitals in the energy gap are formed for N-doped ZnO.