First principles calculations showed that for both ZnO and BeZnO phases, H prefers the positive charge state and would bring about n-type conductivity as a donor, while H0 and H-are energetically unfavourable with positive heat of formation. Calculation also revealed that H+ would probably occupy both bond-centered and anti-bonding sites due to a big migration barrier of site diffusion, which could therefore give a reasonable explanation to the experimental controversy regarding the location of H+ in the literature. Interestingly, the addition of Be could increase the stability and migration barrier of H+ in ZnO, and such an effect would be attributed to a stronger chemical bonding around the H atom formed in BeZnO. In addition, it was found that all the H+, H0, and H - states would bring about a decrease of the band gap of ZnO and BeZnO due to the splitting of degenerate bands and leftward moving of energy bands.

Interstitial Hydrogen in ZnO and BeZnO. Kong, F.T., Tao, H.J., Gong, H.R.: International Journal of Hydrogen Energy, 2013, 38[14], 5974-82