Is ReO3 a mixed ionic-electronic conductor? A DFT study of defect formation and migration in a BVIO3 perovskite-type oxideElectronic supplementary information (ESI) available. See DOI: 10.1039/c7cp08214b

Density-functional-theory (DFT) calculations within the generalised gradient approximation (GGA) were used to examine the behaviour of point defects in the cubic B VI O 3 perovskite-type oxide, ReO 3 . Energies of reduction and of hydration were calculated, and the results are compared with literature data for AB O 3 perovskite oxides. The activation energies of migration were determined for O 2− , H + , Li + , Na + , K + and H 3 O + . An occupied A site in ReO 3 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 3 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 2− , and especially Li + , are highly mobile ions in ReO 3 . Unexpected behaviour of the migration energetics of oxide ions, hydronium ions and lithium ions in perovskite-structured ReO 3 .