Influence of interstitial beryllium on properties of ZnO: A first-principle research

First-principles calculation reveals that doping of Be atoms at interstitial positions of ZnO is energetically favorable with negative heats of formation and would be probably co-existed with substitution of Zn by Be in real situations, which was neglected by other theoretical studies in the literature. Calculation also shows that substitution of Zn atoms by Be could enhance the band gap of ZnBeO phases, while interstitial Be atoms would decrease the band gap, and that such changes of band gap are fundamentally due to the increase of covalent and metallic bonding as a result of Be doping, respectively. The calculated results agree well with experimental observations and could clarify the controversies of the ZnBeO phases in the literature.