Is ReO 3 a mixed ionic-electronic conductor? A DFT study of defect formation and migration in a B VI O 3 perovskite-type oxide

Density-functional-theory (DFT) calculations within the generalised gradient approximation (GGA) were used to examine the behaviour of point defects in the cubic B O perovskite-type oxide, ReO . Energies of reduction and of hydration were calculated, and the results are compared with literature data for ABO perovskite oxides. The activation energies of migration were determined for O , H , Li , Na , K and H O . An occupied A site in ReO is found to be beneficial to oxide-ion migration by a vacancy mechanism as well as to proton migration by a Grotthuss mechanism. Na , K and H O exhibit activation energies of migration higher than 2 eV, whereas Li is characterised by a very low migration barrier of 0.1 eV. Reasons for this behaviour are discussed. Our results suggest that H , O , and especially Li , are highly mobile ions in ReO .