The structure and dynamics of the fast-ionic conductor, Na+-β-alumina, were studied by means of classical molecular dynamics simulations. Four different compounds were simulated: stoichiometric-, non-stoichiometric- and 2 Mg-stabilized β-aluminas. The Beevers-Ross site was the most stable position for stoichiometric Na+ ions in the conduction plane. Excess Na+ ions were found to occupy positions that were slightly off-center from the a-Beevers-Ross lattice site. This shifted a-Beevers-Ross, or A-site, occupation was associated with a reconstruction of 3 ions and a neighbouring Beevers-Ross vacancy. Interstitial O atoms in the conduction plane stabilized the A-site by creating permanent Beevers-Ross vacancies. The diffusion coefficients and conductivities exhibited a behaviour, which was close to Arrhenius, as a function of temperature. The results were in agreement with experiments performed at 300 to 900K. There was a tendency to increasing apparent activation energy at higher temperatures.

Ionic Conduction in Na+-β-Alumina Studied by Molecular Dynamics Simulation. J.V.L.Beckers, K.J.Van der Bent, S.W.De Leeuw: Solid State Ionics, 2000, 133[3-4], 217-31