Displacive phase transitions in infinite-layer nickelates from first- and second-principles calculations

Abstract

Antiferrodistortive (AFD) motions in ABX 3 perovskites play an important role in determining, tuning, and creating functionalities. Here, through first-principles calculations, we predict that the AFD motions in RNiO 2 (where R denotes rare-earth ion), which recently gained significant interest as superconductor systems, show very similar behaviors with perovskites in various aspects, indicating an intrinsic property. The origin of AFD motions is rationalized by chemical bond valence theory, and we reveal that the undercoordination of the R cation is the driving force for the appearance of rotation, analogous to perovskites. Going further, the temperature dependence of local deformations is addressed by developing a second-principles model, and we suggest that the structural phase transitions should be classified as displacive. Eventually, a direct rotation-electron-spin connection is established, which opens a pathway to purposefully tune the Fermi surface, magnetic coupling strength, and magnetic dimensionality. Given that superconducting properties are associated with electronic and magnetic properties, our results provide the possibility and feasibility of the practical control of behaviors in nickelate superconductors through rotation engineering.