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 View the MathML sourceFm3¯m to View the MathML sourceFm3¯. 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.