CRYSTAL-STRUCTURES OF SEVERAL TERNARY LANTHANOID AND ACTINOID RUTHENIUM CARBIDES

The phase equilibria of the ternary system thorium-ruthenium-carbon we re reinvestigated and the crystal structures of the three carbides Th2 Ru6C5, Th11Ru12C18 and ThRu3C were refined from single-crystal diffrac tometer data. The compounds have the ideal compositions and the carbon atoms in the perovskite carbide ThRu3C occupy only those octahedral v oids formed by the ruthenium atoms. The previously reported carbide '' U2Fe2C3'' and the eta phase of the system plutonium-iron-carbon are is otypic with Th11Ru12C18. The six compounds LnRu(3)C (Ln=Dy-Lu) were pr epared from the elemental components by are melting and subsequent ann ealing. They have the cubic perovskite structure with lattice constant s varying between a=412.4(6) pm for DyRu3C and a=410.6(2) pm for LuRu3 C.