Displacive Jahn–Teller Transition in NaNiO<sub>2</sub>
Liam A. V. Nagle‐Cocco, Annalena R. Genreith‐Schriever, J. Steele, Camilla Tacconis, Joshua D. Bocarsly, Olivier Mathon, Jöerg C. Neuefeind, Jue Liu, Christopher A. O’Keefe, Andrew L. Goodwin, Clare P. Grey, John S. O. Evans, Siân E. Dutton
Abstract
High Resolution Image Download MS PowerPoint Slide Below its Jahn–Teller transition temperature, T JT, NaNiO 2 has a monoclinic layered structure consisting of alternating layers of edge-sharing NaO 6 and Jahn–Teller-distorted NiO 6 octahedra. Above T JT where NaNiO 2 is rhombohedral, diffraction measurements show the absence of a cooperative Jahn–Teller distortion, accompanied by an increase in the unit cell volume. Using neutron total scattering, solid-state Nuclear Magnetic Resonance (NMR), and extended X-ray absorption fine structure (EXAFS) experiments as local probes of the structure we find direct evidence for a displacive, as opposed to order–disorder, Jahn–Teller transition at T JT . This is supported by ab initio molecular dynamics (AIMD) simulations. To our knowledge this study is the first to show a displacive Jahn–Teller transition in any material using direct observations with local probe techniques.