The geometry and electronic structure of an interstitial H atom in the BaTiO3 crystal was investigated, considering both cubic and tetragonal crystallographic lattices. A quantum-chemical method based on the Hartree-Fock formalism was used throughout the study. Interstitial H was found to bind to one of the O atoms, forming the so-called OH group. At equilibrium, the O-H distances were found to be 0.089 and 0.091nm for cubic and tetragonal lattices respectively. The performed automated geometry optimization procedure of the defective region showed considerable outward movements of atoms closest to the impurity. The role of the H impurity in ferroelectric polarization in the BaTiO3 crystal was analyzed by using the results obtained in connection with the available experimental data on ferroelectric perovskites.

Effect of Interstitial Hydrogen on Structural and Electronic Properties of BaTiO3. A.Stashans, J.Chimborazo: Philosophical Magazine B, 2002, 82[10], 1145-54