An exhaustive symmetry approach to structure determination: phase transitions in Bi2Sn2O7

James W. Lewis, Julia L. Payne, Ivana Radosavljevic Evans, Harold T. Stokes, Branton J. Campbell, John S. O. Evans

Research output: Contribution to journalArticlepeer-review

24 Citations (Scopus)


The exploitable properties of many materials are intimately linked to symmetry-lowering structural phase transitions. We present an automated and exhaustive symmetry-mode method for systematically exploring and solving such structures which will be widely applicable to a range of functional materials. We exemplify the method with an investigation of the Bi2Sn2O7 pyrochlore, which has been shown to undergo transitions from a parent γ cubic phase to β and α structures on cooling. The results include the first reliable structural model for β-Bi2Sn2O7 (orthorhombic Aba2, a = 7.571833(8), b = 21.41262(2), and c = 15.132459(14) Å) and a much simpler description of α-Bi2Sn2O7 (monoclinic Cc, a = 13.15493(6), b = 7.54118(4), and c = 15.07672(7) Å, β = 125.0120(3)°) than has been presented previously. We use the symmetry-mode basis to describe the phase transition in terms of coupled rotations of the Bi2O′ anti-cristobalite framework, which allow Bi atoms to adopt low-symmetry coordination environments favored by lone-pair cations.

Original languageEnglish
Pages (from-to)8031-8042
Number of pages12
JournalJournal of the American Chemical Society
Issue number25
Early online date1 Jun 2016
Publication statusPublished - 29 Jun 2016


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