Accurately modelling polymorphism in crystalline solids remains a key challenge in computational chemistry. In this work, we apply a theoretically-rigorous phonon mode-mapping approach to understand the polymorphism in the ternary metal oxide Bi2Sn2O7. Starting from the high-temperature cubic pyrochlore aristotype, we systematically explore the structural potential-energy surface and recover the two known low-temperature phases alongside three new metastable phases, together with the transition pathways connecting them. This first-principles lattice-dynamics method is completely general and provides a practical means to identify and characterise the stable polymorphs and phase transitions in materials with complex crystal structures.
Bibliographical noteFunding Information:
Calculations were performed on the Archer HPC system, via the UK Materials Chemistry Consortium (EPSRC EP/L000202), and the UCL Legion and Grace facilities. We are also grateful for resources from UK Materials and Molecular Modelling Hub (EPSRC EP/P020194/1). WR is grateful to University College London for awarding the PhD scholarship. JMS is supported by a University of Manchester Presidential Fellowship.
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