The ionic diffusion mechanism of mobile ions within an underlying body-centred cubic sub-lattice of immobile counter-ions was considered. In particular, the case of equal numbers of 2 ionic species forming long-range ordered and disordered body- centered cubic arrays was considered, since these formed the basis of the cubic perovskite and α-AgI-type crystal structures, respectively. Their structural behaviour, and its influence on the dynamic ionic disorder which characterized superionic conduction, was illustrated for the case of Ag+ diffusion within the β and α* phases of Ag3SI. The calculated behaviour obtained by molecular dynamics computer simulations was validated with reference to published neutron diffraction and ionic conductivity measurements of Ag3SI, and used to examine the preferred diffusion pathways. The relevance of these findings for the anion conduction mechanisms within perovskite structured compounds was briefly considered.

Ionic Diffusion within the α* and β Phases of Ag3SI. S.Hull, D.A.Keen, P.A.Madden, M.Wilson: Journal of Physics - Condensed Matter, 2007, 19[40], 406214 (16pp)