Synthesis and crystal structure of La21Cr8−2aAlbGe7−bC12 [a = 0.22 (2) and b = 0.758 (19)]

• Main Authors: Jaskarun Pabla, Yuri Janssen, Jack W. Simonson
• Format: Article
• Language: English
• Published: International Union of Crystallography 2016-11-01
• Series: Acta Crystallographica Section E: Crystallographic Communications
• Subjects: crystal structure; geometric frustration; multinary chromium carbides
• Online Access: http://scripts.iucr.org/cgi-bin/paper?S2056989016015668
• ISSN: 2056-9890

Single crystals of a new multinary chromium carbide, La21Cr8−2aAlbGe7−bC12 (henicosalanthanum octachromium aluminium hexagermanium dodecacarbide), were grown from an La-rich self flux and were characterized by single-crystal X-ray diffraction. The face-centered cubic crystal structure is composed of isolated and geometrically frustrated regular Cr tetrahedra that are co-centered within regular C octahedra. These mutually separated Cr4−aC6 clusters are distributed throughout a three-dimensional framework of Al, Ge, and La. The title compound is isotypic with La21−δMn8X7C12 and R21Fe8X7C12 (R = La, Ce, Pr; X = Al, Bi, Ge, Sn, Sb, Te) and represents the first example of a Cr-based compound with this structure-type.