Nagle-Cocco Liam A V, Genreith-Schriever Annalena R, Steele James M A, Tacconis Camilla, Bocarsly Joshua D, Mathon Olivier, Neuefeind Joerg C, Liu Jue, O'Keefe Christopher A, Goodwin Andrew L, Grey Clare P, Evans John S O, Dutton Siân E
Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge CB2 1EW United Kingdom.
J Am Chem Soc. 2024 Oct 30;146(43):29560-29574. doi: 10.1021/jacs.4c09922. Epub 2024 Oct 14.
Below its Jahn-Teller transition temperature, , NaNiO has a monoclinic layered structure consisting of alternating layers of edge-sharing NaO and Jahn-Teller-distorted NiO octahedra. Above where NaNiO 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 . This is supported by 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.
在其 Jahn-Teller 转变温度以下，NaNiO 具有单斜层状结构，由交替的边共享 NaO 层和 Jahn-Teller 畸变的 NiO 八面体层组成。在高于此温度时，NaNiO 为菱面体结构，衍射测量表明不存在协同 Jahn-Teller 畸变，同时伴随着晶胞体积的增加。使用中子全散射、固态核磁共振（NMR）和扩展 X 射线吸收精细结构（EXAFS）实验作为结构的局部探针，我们发现了在该温度下发生位移型（而非有序-无序型）Jahn-Teller 转变的直接证据。这得到了分子动力学（AIMD）模拟的支持。据我们所知，本研究是首次使用局部探针技术的直接观测在任何材料中展示位移型 Jahn-Teller 转变。
