Microscopic mechanisms of proton diffusion in this Sc-doped protonic conductor were studied by using first-principles molecular dynamics simulations. It was shown that the proton formed an O-H bond with a neighboring O ion, and that the frequency of the stretching vibration of this bond was about 2800/cm. This agreed reasonably well with experimental data. Two types of diffusion path were observed. One of them involved diffusion around the O ion, while maintaining the O-H bond. The other involved diffusion between 2 neighboring O ions, while switching the O-H band. During the former process, the stretching vibration continued and the length of the O-H bond was almost unchanged. The latter type of diffusion was expected to occur frequently and quickly.

F.Shimojo, K.Hoshino, H.Okazaki: Journal of the Physical Society of Japan, 1997, 66[1], 8-10