Displacive Jahn–Teller Transition in NaNiO 2

Below its Jahn–Teller transition temperature, T JT, NaNiO2 has a monoclinic layered structure consisting of alternating layers of edge-sharing NaO6 and Jahn–Teller-distorted NiO6 octahedra. Above T JT where NaNiO2 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

Classical mechanics: a professor-student collaboration

Classical Mechanics: A professor-student collaboration is a textbook tailored for undergraduate physics students embarking on a first-year module in Newtonian mechanics. This book was written as a unique collaboration between Mario Campanelli and students that attended his course in classical mechanics at University College London. Taking his lecture notes as a starting point, and reflecting on their own experiences studying the material, the students worked together with Campanelli to produce a comprehensive course text that covers a familiar topic from a new perspective. All the fundamental topics are included, starting with an overview of the core mathematics and then moving on to statics, kinematics, dynamics and non-inertial frames, as well as fluid mechanics, which is often overlooked in standard university courses. Clear explanations and step-by-step examples are provided throughout to break down complicated ideas that can be taken for granted in other standard texts, giving students the expertise to confidently tackle their university tests and fully grasp important concepts that underpin all physics and engineering courses

Displacive Jahn--Teller transition in NaNiO₂

Below its Jahn--Teller transition temperature, $T_\mathrm{JT}$, NaNiO$_2$ has a monoclinic layered structure consisting of alternating layers of edge-sharing NaO$_6$ and Jahn--Teller-distorted NiO$_6$ octahedra. Above $T_\mathrm{JT}$ 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 $T_\mathrm{JT}$. This is supported by \textit{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.This work was supported by the Faraday Institution (FIRG001, FIRG017, FIRG024, FIRG060). L.A.V.N-C acknowledges a scholarship EP/R513180/1 to pursue doctoral research from the UK Engineering and Physical Sciences Research Council (EPSRC) and additional funding from the Cambridge Philosophical Society. J.M.A.S. acknowledges support from the EPSRC Cambridge NanoCDT, EP/L015978/1. A.L.G. acknowledges European Research Council (ERC) funding under grant 788144. The authors acknowledge Oak Ridge National Laboratory, a United States Department of Energy Office of Science User Facility, for use of the NOMAD instrument at the Spallation Neutron Source (experiment IPTS25164). We acknowledge the European Synchrotron Radiation Facility for provision of beam time on BM23 (experiment CH6437). We acknowledge I11 beamline at the Diamond Light Source, UK, for the synchrotron XRD measurement done under BAG proposal (the data presented in this work under CY34243; essential preliminary data from CY28349). Calculations were performed using the Sulis Tier 2 HPC platform hosted by the Scientific Computing Research Technology Platform at the University of Warwick (EP/T022108/1)

Data associated with "Displacive Jahn--Teller transition in NaNiO2"

This data repository contains the data associated with the paper "Displacive Jahn--Teller transitions in NaNiO2", published in the ACS Journal of the American Chemical Society in 2024. Authors: Nagle-Cocco, L. A. V.; Genreith-Schriever, A. R.; Steele, J. M. A.; Tacconis, C.; Bocarsly, J. D.; Mathon, O.; Neuefeind, J. C.; Liu, J.; O’Keefe, C. A.; Goodwin, A. L.; Grey, C. P.; Evans, J. S. O.; Dutton, S. E. For any queries, contact Liam Nagle-Cocco ([email protected]/[email protected]) or Sian E. Dutton ([email protected]). ### Contents This data repository contains a file called SI.pdf, which is the supporting information associated with the manuscript. It also contains several folders with additional data. This section lists the folders and their contents within this data repository. * Variable_temperature_synchrotron_diffraction. This folder contains the raw diffraction patterns used in this analysis. It also contains the Topas input file, along with files listing the angles of Bragg reflections, CIF files, and files containing the experimental data, calculated data, and difference patterns. * Raw_neutron_diffraction. This folder contains the neutron diffraction data in real and reciprocal space as used in this study. It also contains the standard Si data measured on 24th March 2021. * Small_box_PDF_analysis. This folder contains the Topas input files used for the small box PDF analysis which is presented in the SI. * Big_box_PDF_analysis. This folder contains the big box PDF analysis input files used for big box PDF analysis both with and without BVS restraints, associated CIF files, and files containing the real- and reciprocal-space fit plots (experimental, calculated, and difference data). This folder does NOT contain the big box PDF analysis at 500 K from a disordered Jahn--Teller-distorted starting structure. The folder contains two subfolders: * d+p: input and output files refined against data and penalties. * p: input and output files refined against penalties only. * Big_box_PDF_analysis_disordered_JT. This folder contains the big box PDF analysis input files used for big box PDF analysis both with and without BVS restraints, associated CIF files, and files containing the real- and reciprocal-space fit plots (experimental, calculated, and difference data). This folder contains only the data at 500 K from a JT-distorted randomly-generated starting structure. This folder also contains the code used to generate these input files. * XAS-data. This folder contains the XAS data and the Python code used to analyse it. Two samples of NaNiO2 were measured on heating and subsequent cooling. These are (1) Ramp_up followed by Ramp_Down, then (2) Ramp_up_2 followed by Ramp_Down_2. The second sample was used in the manuscript because the data was higher quality. Additional data can be found in doi:10.15151/ESRF-ES-962076745. * AIMD. This folder contains the POSCAR files at all studied timesteps from the ab initio molecular dynamics (AIMD) data, at all studied temperatures. AIMD was performed using VASP. The naming of the POSCAR is "POSCAR_ts.[time]" where [time] is the time in femtoseconds. Initial equilibriation timesteps are not included. POSCARs were obtained using OVITO. There are two sets of data: from a JT-distorted colinear start, and a JT-undistorted rhombohedral start. The folder also contains tabulated data for all octahedra at all timesteps. Note that in some of these tabulated data, the calculation of van Vleck parameters by VanVleckCalculator was unsuccessful, and in this case the data is written as "None". * Nuclear_magnetic_resonance. This folder contains the NMR data presented in the SI, in the format which can be opened using Topspin. These are split between two folders: static and magic angle spinning (MAS). Note that the MAS data is not calibrated by temperature and so the claimed temperatures are not accurate.This work was supported by the Faraday Institution (FIRG001, FIRG017, FIRG024, FIRG060). L.A.V.N-C acknowledges a scholarship EP/R513180/1 to pursue doctoral research from the UK Engineering and Physical Sciences Research Council (EPSRC) and additional funding from the Cambridge Philosophical Society. J.M.A.S. acknowledges support from the EPSRC Cambridge NanoCDT, EP/L015978/1. A.L.G. acknowledges European Research Council (ERC) funding under grant 788144

Displacive Jahn–Teller transition in NaNiO2

Below its Jahn–Teller transition temperature, TJT, NaNiO2 has a monoclinic layered structure consisting of alternating layers of edge-sharing NaO6 and Jahn–Teller-distorted NiO6 octahedra. Above TJT where NaNiO2 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 TJT. 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