Grown from lithium flux, the ErCo5Si3.17silicide is a combination of disordered derivatives of the UCo5Si3and Yb6Co30P19structure types

Abstract

A ternary hexaerbium triacontacobalt enneakaidecasilicide, ErCo5Si3.17, crystallizes as a combination of disordered variants of the hexagonal UCo5Si3(P63/m) and Yb6Co30P19(P-6) structure types and is closely related to the Sc6Co30Si19and Ce6Rh30Si19types. The Er, Co and three of the Si atoms occupy sites ofm.. symmetry and a fourth Si atom occupies a site of -6.. symmetry. The environment of the Er atom is a 21-vertex pseudo-Frank–Kasper polyhedron. Trigonal prismatic coordination is observed for the Si atoms. The Co atoms are enclosed in heavily deformed cuboctahedra and 11-vertex polyhedra. Crystallochemistry analysis and the data from electronic structure calculations (TB–LMTO–ASA) suggest that the Er atoms form positively charged cations which compensate the negative charge of the [Co12Si9]m−polyanions.