Local order of orthorhombic weberite-type Y3TaO7 as determined by neutron total scattering and density functional theory calculations✰

Weberite-type oxides are a family of oxides with A3BO7 stoichiometry that can adopt different space groups depending on chemical composition. There is a discrepancy in previous studies as to whether Y3TaO7 is the orthorhombic C2221 or the Ccmm space group. Here, we describe the short- and long-range structural properties of weberite-type Y3TaO7 using neutron total scattering data, which has a high sensitivity to the oxygen sublattice. Simultaneous analysis of both short- and long-range structural data via conventional Rietveld and small box modeling demonstrates that Y3TaO7 is best modeled as C2221. While the Ccmm describes equally well the long-range structure, pair distribution function analysis revealed that the local atomic configuration can be best modelled as C2221. This is corroborated by first-principles calculations that confirm the energetic preference of the C2221 over Ccmm. Neutron total scattering data are reported for the first time for the Y3TaO7 weberite-type ceramics.