Abstract
The microscopic mechanism of proton diffusion in the protonic conductor Sc-doped SrTiO3is studied by a first-principles molecular-dynamics simulation.It is shown that the proton forms an O-H bond with a neighboring O ion, and the frequency of the stretching vibration of the O-H bondis about 2800 cm-1, which agrees reasonably well with the result of experiment.Two types of diffusion paths are observed:one is diffusion around the O ion while retaining the O-H bond, and the other is diffusion between the two neighboring O ionswhile switching the O-H bond.During the former type of diffusion, the stretching vibration proceeds and the length of the O-H bond is almost unchanged.The latter type of diffusion occurs frequently and quickly.
