Linking quantum mechanical features to structural phase-transformation in inorganic solids

We present a new descriptor, i.e., local lattice distortion, to predict structural phase transformation in inorganic compounds containing lanthanides and transition metals. The descriptor utilizes local lattice and angular distortions obtained from structural optimization of experimentally known crystalline phases within state-of-the-art density-functional theory method. The predictive power of the descriptor was tested on lanthanide based RE2In (RE=rare-earth) compounds known for a variety of phase transformations. We show that the inclusion of quantum-mechanical effects through local-charge, bonding, symmetry, and electronic-structure enhances the robustness of the descriptor in predicting structural phase transformation. To gain further insights, we analyzed phononic and electronic behavior of Y2In, and show that experimentally observed phase transformation can only be predicted when atomic strains are included. The descriptor was used to predict structural phase change in couple of new compounds, i.e., (Yb1-xErx)2In and Gd2(In1-xAlx), which was validated by X-ray powder diffraction measurements. Finally, we demonstrated the generality of the proposed descriptor by predicting phase transformation behavior in different classes of compounds indicating the usefulness of our approach in mapping desired phase changes in novel functional materials.