Structure of δ-Bi2O3 from density functional theory: A systematic crystallographic analysis

A systematic crystallographic analysis of the 〈110〉 and 〈111〉 vacancy-ordered structure of cubic δ-Bi2O3 obtained from electronic-structure calculations is presented. The ordering of vacancies leads to a doubling of the unit-cell that results in a 2×2×2 fluorite super-structure, with an associated reduction in its space group symmetry from Fm3¯m to Fm3¯. The Bi atoms present inside the 〈111〉 vacancy-ordered oxygen sublattice have equal Bi–O bond lengths, whereas, those present inside the 〈110〉 vacancy-ordered oxygen sublattice have three different pairs of Bi–O bond lengths. The specific ionic displacements and electronic charge configurations also depend on the nature of vacancy ordering in the oxygen sub-lattice.

Graphical abstract1/8 of a 2×2×2 δ-Bi2O3 superstructure having Fm3¯ space group. Every oxygen (black) has three possible positions, only one of which is filled either by O1 (red) or O2 (blue).Figure optionsDownload full-size imageDownload as PowerPoint slide