Displacive Jahn-Teller transition in NaNiO2

Date:

This was a 4 day conference hosted at the Science Congress Centre and the MLZ in Garching, just outside of Munich in Germany, from the 20th to the 23rd March 2023. Each day there were plenary talks in the morning, followed by several sets of talks split into parallel sessions based on theme.

My talk was the third talk of the Energy Materials session on day 2 of the conference, chaired by Alois Kuhn of CEU San Pablo University in Madrid. I came after Professor Werner Paulus (Montpellier) who discussed La2CoO4+δ, a material with corner-sharing octahedra, and Ivana Pivarnikova (TUM Munich) who discussed the Na-ion battery cathode material NASICON; this was very convenient because it set the scene for my talk. I discussed the local structure of NaNiO2 according to neutron Pair Distribution Function data I obtained from the SNS at Oak Ridge National Laboratory, particularly our finding that the Jahn-Teller (JT) transition in NaNiO2 appears displacive rather than order-disorder like in similarly JT-distorted LaMnO$_3$. We attribute this in part to the edge-sharing octahedral interactions, as contrasted with the corner-sharing interactions in the perovskite-type LaMnO3.

Following the talk, I received questions from Pelayo Marin Villa, a PhD student at the University of the Basque Country (I paraphrase the question as “Would molecular dynamics help make sense of this?”), from the chair Alois Kuhn regarding comparison to battery material LiNiO2, and from others regarding the possibility for using inelastic neutron scattering to explore the transition and a query on the occurrence of stacking faults in the material.

More details here

Speaking photo

Presenting my talk

Photo credits to Dr Svemir Rudic (ISIS Neutron and Muon Source).

Conference photo

Conference photo