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arXiv · 1905.04930

Pressure-induced formation of rhodium zigzag chains in the honeycomb rhodate Li$_2$RhO$_3$

V. Hermann·S. Biswas·J. Ebad-Allah·F. Freund·A. Jesche·A. A. Tsirlin·M. Hanfland·D. Khomskii·P. Gegenwart·R. Valentí·C. A. Kuntscher
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Abstract

We use powder x-ray diffraction to study the effect of pressure on the crystal structure of the honeycomb rhodate Li$_2$RhO$_3$. We observe low-pressure ($P$$<$$P_{c1}$ = 6.5 GPa) and high-pressure ($P$$>$$P_{c2}$ = 14 GPa) regions corresponding to the monoclinic $C2/m$ symmetry, while a phase mixture is observed at intermediate pressures. At $P$$>$$P_{c2}$, the honeycomb structure becomes distorted and features short Rh--Rh bonds forming zigzag chains stretched along the crystallographic $a$ direction. This is in contrast to dimerized patterns observed in triclinic high-pressure polymorphs of $\alpha$-Li$_2$IrO$_3$ and $\alpha$-RuCl$_3$. Density-functional theory calculations at various pressure conditions reveal that the observed rhodium zigzag-chain pattern is not expected under hydrostatic pressure but can be reproduced by assuming anisotropic pressure conditions.

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V. Hermann, S. Biswas, J. Ebad-Allah, F. Freund, A. Jesche, A. A. Tsirlin, M. Hanfland, D. Khomskii, P. Gegenwart, R. Valentí, C. A. Kuntscher. 2019-05-13. Pressure-induced formation of rhodium zigzag chains in the honeycomb rhodate Li$_2$RhO$_3$. https://doi.org/10.1103/physrevb.100.064105

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