Protonic motion in these cubic perovskites was investigated by performing numerical simulations for high temperatures. The protons were found to form mainly transient H-bond complexes. Repulsive Ti-proton interactions caused a bending of the H bonds, and thus enhanced proton transfer. As the proton interaction also extended to next-next-nearest neighbour O sites, the formation of transient linear inter-octahedra H-bonds was also possible; between the tips of neighbouring octahedra, for instance. Although the time constants for proton reorientation were of similar magnitude in both materials, the time constant for proton transfer was larger, by an order of magnitude, in SrTiO3. The numerical simulations yielded an activation energy, for proton diffusion, of 0.50eV for SrTiO3 and 0.42eV for CaTiO3.

A Quantum Molecular Dynamics Study of Proton Diffusion in SrTiO3 and CaTiO3. W.Munch, K.D.Kreuer, G.Seifertli, J.Majer: Solid State Ionics, 1999, 125[1-4], 39-45