Tolerance factor and phase stability of the garnet structure

Acta Cryst., 2019. C75, 1353-1358. https://scripts.iucr.org/cgi-bin/paper?qp3034

We introduce a structural descriptor, the tolerance factor, for the prediction and systematic description of the phase stability with the garnet structure. Like the tolerance factor widely adopted for the perovskite structure, it is a com­positional parameter derived from the geometrical relationship between multi-type polyhedra in the garnet structure, and the calculation only needs the information of the ionic radius. A survey of the tolerance factor over 130 garnet-type com­pounds reveals that the data points are scattered in a narrow range. The tolerance factor is helpful in understanding the crystal chemistry of some garnet-type com­pounds and could serve as a guide for predicting the stability of the garnet phase. The correlation between the tolerance factor and the garnet-phase stability could be utilized by machine learning or high-throughput screening methods in material design and discovery.

Tolerance factor, phase stability and order–disorder of the pyrochlore structure

Inorg. Chem. Front., 2020,7, 1583-1590. https://doi.org/10.1039/D0QI00016G

Graphical abstract: Tolerance factor, phase stability and order–disorder of the pyrochlore structure

The tolerance factor is a structural indicator that connects the crystal structure and chemical composition. In this work, we establish the tolerance factor for pyrochlore A2B2O7-type compounds, using ionic radii of the compositional species. It is derived following similar procedures to those of perovskite and garnet structures. More than 180 A2B2O7 type compounds are examined to test its validity in predicting the pyrochlore phase stability. It can also be used to understand the reverse and order–disorder cationic occupations. This structural descriptor could be used together with machine learning or high-throughput screening methods for new material design and discovery.

Tolerance Factor and Phase Stability of the Normal Spinel Structure

Cryst. Growth Des., 2020, 20, 3, 2014–2018 https://doi.org/10.1021/acs.cgd.9b01673

Tolerance factor for the normal-spinel structure is introduced as a structural descriptor to predict the phase stability. It is derived following similar principles as those of perovskite and garnet structures, i.e., the geometrical relationship between multitype polyhedra. The calculation of tolerance factor only requires the ionic radii of compositional components involved. A survey of the tolerance factor over 120 AB2X4-type compounds proves the reliability. The numerical values are distributed below 1, which originates from the compressed octahedra which support the framework of spinel. The tolerance factor will be helpful in machine learning and high-throughput screening methods for fast evaluation of phase stability and materials properties of spinel-type compounds.