λ-RhO2, a prototype 4d transition metal oxide, has been prepared by oxidative delithiation of spinel LiRh2O4 using ceric ammonium nitrate. Average-structure studies of this RhO2 polytype, including synchrotron powder X-ray diffraction and electron diffraction, indicate the room temperature structure to be tetragonal, in the space group I41/amd, with a first-order structural transition to cubic Fd-3m at T = 345 K on warming. Synchrotron X-ray pair distribution function analysis and 7Li solid state nuclear magnetic resonance measurements suggest that the room temperature structure displays local Rh-Rh bonding. The formation of these local dimers appears to be associated with a metal-to insulator transition with a non-magnetic ground state, as also supported by density functional theory-based electronic structure calculations. This contribution demonstrates the power of soft chemistry to kinetically stabilize a surprisingly simple binary oxide compound.
@article{arxiv.2310.07053,
title = {Soft-Chemical Synthesis, Structure Evolution, and Insulator-to-Metal Transition in a Prototypical Metal Oxide, {\lambda}-RhO$_2$},
author = {Juan R. Chamorro and Julia L. Zuo and Euan N. Bassey and Aurland K. Watkins and Guomin Zhu and Arava Zohar and Kira E. Wyckoff and Tiffany L. Kinnibrugh and Saul H. Lapidus and Susanne Stemmer and Raphaële J. Clément and Stephen D. Wilson and Ram Seshadri},
journal= {arXiv preprint arXiv:2310.07053},
year = {2024}
}