Interplay between Jahn–Teller Distortions and Structural Phase Transitions in Ruddlesden–Poppers

The interplay between crystallographic symmetry, structural distortions, and the tolerance factor derived from the isotropic ionic radii of the constituent cations and anions of inorganic perovskites and related materials is a ubiquitous concept in solid-state and materials chemistry. Here we demonstrate a model for the phase transition temperatures associated with these structural distortions in layered perovskites by considering the anisotropy associated with cations, which are susceptible to first-order Jahn–Teller distortions. These symmetry-lowering phase transitions are known to have a significant interplay with superconductivity in the high-T_C layered cuprates, and untangling the chemistry that can effectively control them is of the utmost relevance in the search for similar phenomena in the nickelates, the study of which has been greatly stimulated by recent reports of high-pressure superconductivity.