Materials Data on Ca3Al7Cu2 by Materials Project

Abstract

Ca3Cu2Al7 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are two inequivalent Ca sites. In the first Ca site, Ca is bonded in a 6-coordinate geometry to six equivalent Cu and twelve equivalent Al atoms. All Ca–Cu bond lengths are 3.22 Å. All Ca–Al bond lengths are 3.43 Å. In the second Ca site, Ca is bonded in a 12-coordinate geometry to twelve Al atoms. There are a spread of Ca–Al bond distances ranging from 3.26–3.32 Å. Cu is bonded in a 9-coordinate geometry to three equivalent Ca and six equivalent Al atoms. There are three shorter (2.54 Å) and three longer (2.59 Å) Cu–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded to six equivalent Ca and six equivalent Al atoms to form AlCa6Al6 cuboctahedra that share corners with twelve equivalent AlCa5Al5Cu2 cuboctahedra, edges with six equivalent AlCa6Al6 cuboctahedra, and faces with eighteen equivalent AlCa5Al5Cu2 cuboctahedra. All Al–Al bond lengths are 2.82 Å. In the second Al site, Al is bonded to five Ca, two equivalent Cu, and five Al atoms to form distorted AlCa5Al5Cu2 cuboctahedra that share corners with seventeen AlCa6Al6 cuboctahedra, edges with eight equivalent AlCa5Al5Cu2 cuboctahedra, and faces with fourteen AlCa6Al6 cuboctahedra. There are two shorter (2.75 Å) and two longer (2.83 Å) Al–Al bond lengths.