The mechanism and energetics of proton migration in perovskite oxides were investigated by means of  ab initio  quantum mechanical cluster calculations. The energy barrier to proton transfer between 2 adjacent O ions was calculated. Charge distribution and relaxation effects were also considered. The results indicated the existence of very low energy barriers to such transfer. This supported the suggestion that proton migration occurred by tunnelling.

M.Cherry, M.S.Islam, J.D.Gale, C.R.A.Catlow: Solid State Ionics, 1995, 77, 207-9