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 stru cture of the ThCr3Si2 type, which can be viewed as a layered structure or tetrahedrally coordinated Rh2B2 thick layers and ErC NaCl-type lay ers. A comparison of the structural parameters of the RRh2B2C (R is a rare earth metal) compounds showed that the atomic distance between tr ansition metal atoms contracts significantly with decreasing rare eart h size, resulting in increasing instability of compounds with smaller R.