Phase ordering in the mixed-valence oxide Sb2O4 has been examined by density functional theory (DFT) calculations. We find that the ground-state total energies of the two phases (α and β) are almost degenerate and are highly sensitive to the choice of the approximation to the exchange correlation (xc) functional used in our calculations. Interestingly, with the inclusion of the zero-point energy corrections, the α phase is predicted to be the ground state polymorph for most xc functionals used. We also illustrate the pronounced stereochemical activity of Sb in these polymorphs of Sb2O4, setting an exception to the Keve and Skapski rule. Here, we find that the actual bonding in the α phase is more asymmetric, while the anomalous stability of the β phase could be rationalized from kinetic considerations. We find a non-negligible activation barrier for this α-β phase transition, and the presence of a saddle point (β phase) supports the separation of Sb(III) over a continuous phase transition, as observed in experiments.
Bibliographical noteFunding Information:
We gratefully acknowledge support from the Samsung Research Funding Center of Samsung Electronics under Project Number SRFC-MA1501-03 and the Australian Research Council (ARC). Computational resources have been provided by the KISTI supercomputing center (KSC-2016-C3-0009) and the Australian National Computational Infrastructure (NCI).
© 2017 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Inorganic Chemistry