- Materials data are often fragmented across multiple PDFs or databases. Our group assembles useful data into machine-readable datasets for our use and for public dissemination.
- The group focuses on providing physical understanding of materials systems with complex interactions. We therefore prioritize tools from supervised and unsupervised machine learning that supply interpretable results when used.
- Linear models and tree-based methods have straightforward feature importances that highlight dominant distortions when searching for a structure-property relationship.
- Dimensionality reduction techniques like principal component analysis and uniform manifold approximation and projection can map multiple features into a latent space where clusters can be distinguished.
- The ultimate goal of the informatic system is to enhance the capabilities of the researcher, not replace them.
Crystal-Chemistry Guidelines for Noncentrosymmetric A2BO4 Ruddlesden−Popper Oxides
Noncentrosymmetric (NCS) phases are seldom seen in layered A2BO4 Ruddlesden−Popper (214 RP) oxides. In this work, we uncovered the underlying crystallographic symmetry restrictions that enforce the spatial parity operation of inversion and then subsequently showed how to lift them to achieve NCS structures. Simple octahedral distortions alone, while impacting the electronic and magnetic properties, are insufficient. We showed using group theory that the condensation of two distortion modes, which describe suitable symmetry unique octahedral distortions or a combination of a single octahedral distortion with a “compositional” A or B cation ordering mode, is able to transform the centrosymmetric aristotype into a NCS structure. With these symmetry guidelines, we formulated a data-driven model founded on Bayesian inference that allowed us to rationally search for combinations of A- and B-site elements satisfying the inversion symmetry lifting criterion. We described the general methodology and applied it to 214 iridates with A2+ cations, identifying RPstructured Ca2IrO4 as a potential NCS oxide, which we evaluated with density functional theory. We found a strong energetic competition between two closely related polar and nonpolar low-energy crystal structures in Ca2IrO4 and suggested pathways to stabilize the NCS structure.