Ionic transport was analyzed microscopically for the case of Cu3Ba2RO7 high-temperature superconductors, where R was a rare earth. It was considered that electronic correlation effects were responsible for the formation of a local double-well potential for apical O. This, in turn, led to a decrease in the activation energy for interstitial chain O defects.

A.Rakitin, M.Kobayashi, A.P.Litvinchuk: Physical Review B, 1997, 55[1], 89-92