End Member of the Rhodium-Based Quaternary Borocarbides, ErRh₂B₂C

Erbium dirhodium diboron carbide, the end member of the rhodium-based quaternary borocarbides, was synthesized by the flux method. Structure analyses revealed that the compound crystallizes as a derivative structure of the ThCr₂Si₂ type, which can be viewed as a layered structure of tetrahedrally coordinated Rh₂B₂ thick layers and ErC NaCl-type layers. A comparison of the structural parameters of the RRh₂B₂C (R is a rare earth metal) compounds showed that the atomic distance between transition metal atoms contracts significantly with decreasing rare earth size, resulting in increasing instability of compounds with smaller R.

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