Relationship between binding site and pressure dependence for defect-hydrogen complexes in ZnO

The effect of hydrostatic pressure on local vibrational modes of hydrogen defects in ZnO has been studied by first-principles methods. We find that the sign and magnitude of the frequency shift rate are strongly dependent on the local environment. In the case of isolated hydrogen, the bond centered (BC) and antibonding (AB) configurations lead to positive and negative pressure shifts, in agreement with previous work. However, this result cannot be extended to defect-hydrogen complexes. In general, the sign of the shift does not indicate whether the hydrogen atom is located at a BC or AB site.