Contrasting the theoretical properties of hydrogen in $SnO2$⁠, $In2O3$⁠, and $TiO2$

Stavola et al. have used IR spectroscopy to study H and D in single crystals of $SnO2$⁠, $In2O3$⁠, and $TiO2$⁠. Their work indicates that H acts as a shallow donor in $SnO2$ and $In2O3$⁠, while in $TiO2$⁠, the electron becomes self-trapped at a Ti site near H. We have undertaken extensive calculations on different H-related defect structures in these materials, using the DFT code CRYSTAL06 with a hybrid Hamiltonian. These calculations have involved not only intrinsic H-related defects, but also defects containing metal impurities. The results serve to narrow the possible choices of defects observed experimentally, and in the best cases, to strongly support particular defect models.