Local Atomic Ordering in BaTaO₂N Studied by Neutron Pair Distribution Function Analysis and Density Functional Theory

The local structure and oxygen/nitrogen ordering of the high permittivity perovskite BaTaO 2 N has been studied using a combination of neutron total scattering and density functional electronic structure calculations. Although the average structure as revealed by neutron diffraction Rietveld analysis is cubic Pm 3̄ m with no evidence of O/N ordering, the local structure as revealed by pair distribution function analysis of the total neutron scattering appears to favor a cis configuration of the TaO 4 N 2 polyhedra with small Ta displacements toward the N atoms. Density functional calculations similarly suggest that the cis TaO 4 N 2 polyhedron is more stable than the corresponding trans variant.