Cu4.35Cd1.65As16: the first polyarsenic compound in the Cu–Cd–As system

• Main Authors: Oliver Osters, Tom Nilges
• Format: Article
• Language: English
• Published: International Union of Crystallography 2011-11-01
• Series: Acta Crystallographica Section E
• Online Access: http://scripts.iucr.org/cgi-bin/paper?S1600536811042127

The first polyarsenic compound in the Cu–Cd–As system was obtained by solid-state reaction of the elements and has a refined composition of Cu4.35 (2)Cd1.65 (2)As16 (tetracopper dicadmium hexadecaarsenide). It adopts the Cu5InP16 structure type. The asymmetric unit consists of one Cu site, a split Cu/Cd site and four As sites. The polyanionic structure can be described as being composed of As6 rings in chair conformations which are connected in the 1-, 2-, 4- and 5-positions. The resulting layers evolve along the c axis perpendicular to the ab plane. One Cu atom exhibits site symmetry 2 and is tetrahedrally coordinated by four As atoms. The other Cu atom, representing the split site, and the corresponding Cd atom have different coordination spheres. While the Cu atom is tetrahedrally coordinated by four As atoms, the Cd atom has a [3 + 1] coordination with a considerably longer Cd—As distance.