Ab initio pseudopotential calculations of electronic structure of off-stoichiometric ZnO

We have investigated the electronic structure and valence electron density distribution of ideal-stoichiometric and off-stoichiometric ZnO. The ab initio pseudopotential calculation is carried out in the framework of the density function theory within the local density approximation. In calculating the Zn pseudopotential, the errors, particularly those of elements that have 3d electrons, introduced by the frozen-core approximation and linearizing the exchange-correlation potential, were corrected. The electronic structures of ideal-stoichiometric and off-stoichiometric ZnO shows a trend of increasing conductivity introduced by excess Zn, which is consistent with the experimental results. The calculated valence electron density distribution reveals the strong ionic characteristic Zn-O bond in ideal-stoichiometric and off-stoichiometric ZnO.