An ab initio study of oxide ion dynamics in type-II Bi3NbO7

Abstract

Oxide ion dynamics in the type-II phase of Bi₃NbO₇ have been studied using a series of DFT molecular dynamics calculations. Coordination numbers and angular distribution functions for both bismuth and niobium cations were analysed. A strong preference for octahedral coordination of niobium cations was observed. This has the effect of reducing the overall number of mobile vacancies in the system. Energy landscapes for the system revealed low-energy barriers for oxide ion jumps in the 〈100〉 direction. Whilst oxide ion jumps were found to occur around both cations, only around bismuth cations do the jumps result in significant long-range movement of oxide ions, with those around niobium cations predominantly associated with dynamics of the niobate octahedra.