DOE OSTI2020
Cu7Te4 crystallizes in the trigonal P3m1 space group. The structure is three-dimensional. there are six inequivalent Cu+1.14+ sites. In the first Cu+1.14+ site, Cu+1.14+ is bonded in a distorted trigonal planar geometry to three equivalent Te2- atoms. All Cu–Te bond lengths are 2.49 Å. In the second Cu+1.14+ site, Cu+1.14+ is bonded in a 6-coordinate geometry to six Te2- atoms. There are three shorter (2.82 Å) and three longer (3.07 Å) Cu–Te bond lengths. In the third Cu+1.14+ site, Cu+1.14+ is bonded to five Te2- atoms to form distorted CuTe5 trigonal bipyramids that share corners with two equivalent CuTe5 trigonal bipyramids, corners with four equivalent CuTe4 trigonal pyramids, edges with two equivalent CuTe5 trigonal bipyramids, and a faceface with one CuTe4 trigonal pyramid. There are a spread of Cu–Te bond distances ranging from 2.73–2.80 Å. In the fourth Cu+1.14+ site, Cu+1.14+ is bonded in a 5-coordinate geometry to five Te2- atoms. There are a spread of Cu–Te bond distances ranging from 2.80–2.89 Å. In the fifth Cu+1.14+ site, Cu+1.14+ is bonded to four Te2- atoms to form distorted CuTe4 trigonal pyramids that share corners with four equivalent CuTe5 trigonal bipyramids, corners with two equivalent CuTe4 trigonal pyramids, edges with two equivalent CuTe4 trigonal pyramids, and a faceface with one CuTe5 trigonal bipyramid. There are a spread of Cu–Te bond distances ranging from 2.59–3.08 Å. In the sixth Cu+1.14+ site, Cu+1.14+ is bonded in a 5-coordinate geometry to five Te2- atoms. There are a spread of Cu–Te bond distances ranging from 2.76–3.02 Å. There are four inequivalent Te2- sites. In the first Te2- site, Te2- is bonded in a 6-coordinate geometry to six Cu+1.14+ atoms. In the second Te2- site, Te2- is bonded in a 9-coordinate geometry to nine Cu+1.14+ atoms. In the third Te2- site, Te2- is bonded in a 8-coordinate geometry to eight Cu+1.14+ atoms. In the fourth Te2- site, Te2- is bonded in a 9-coordinate geometry to nine Cu+1.14+ atoms.