The theory of H diffusion in this material was considered. In the case of low H concentrations, it was assumed that protonic H interacted with other positive and negative ions via screened Coulomb interactions. It was suggested that the stable configuration of H was not on symmetrical interstitial sites, but rather on a closed surface (in coordinate space) between positive and negative charged ions. The migration energy of H in Y sub-cells was also calculated and was found to be in good agreement with experimental data. Its value also depended upon an anisotropy factor.

S.Prakash, J.P.Burger: Zeitschrift für Physikalische Chemie, 1993, 181[1,2], 159-64