It was recalled that the extraction rate of T from this material was controlled by its diffusion in the bulk, although the exact mechanism was unclear. First-principles density functional calculations were made here of the various diffusion pathways which had been suggested. These included the diffusion of T as an interstitial, and various vacancy-assisted mechanisms. The activation energy was calculated for each pathway, and a comparison with experimental data indicated that the most likely mechanism was the simple 2-stage swapping of a Li ion and a T ion.

R.Shah, A.De Vita, V.Heine, M.C.Payne: Physical Review B, 1996, 53[13], 8257-61