DOE OSTI2020
Cr4Cu3Te8 crystallizes in the orthorhombic Imm2 space group. The structure is three-dimensional. there are two inequivalent Cr3+ sites. In the first Cr3+ site, Cr3+ is bonded to six Te2- atoms to form distorted CrTe6 octahedra that share corners with six CuTe4 tetrahedra, edges with six CrTe6 octahedra, and a faceface with one CuTe4 tetrahedra. There are a spread of Cr–Te bond distances ranging from 2.70–2.88 Å. In the second Cr3+ site, Cr3+ is bonded to six Te2- atoms to form CrTe6 octahedra that share corners with nine CuTe4 tetrahedra and edges with six CrTe6 octahedra. There are a spread of Cr–Te bond distances ranging from 2.72–2.74 Å. There are three inequivalent Cu+1.33+ sites. In the first Cu+1.33+ site, Cu+1.33+ is bonded to four Te2- atoms to form CuTe4 tetrahedra that share corners with twelve CrTe6 octahedra and an edgeedge with one CuTe4 tetrahedra. The corner-sharing octahedra tilt angles range from 56–60°. There are two shorter (2.60 Å) and two longer (2.63 Å) Cu–Te bond lengths. In the second Cu+1.33+ site, Cu+1.33+ is bonded to four Te2- atoms to form distorted CuTe4 tetrahedra that share corners with six equivalent CrTe6 octahedra, corners with two equivalent CuTe4 tetrahedra, an edgeedge with one CuTe4 tetrahedra, and faces with two equivalent CrTe6 octahedra. The corner-sharing octahedra tilt angles range from 49–55°. There are two shorter (2.53 Å) and two longer (2.60 Å) Cu–Te bond lengths. In the third Cu+1.33+ site, Cu+1.33+ is bonded to four Te2- atoms to form CuTe4 tetrahedra that share corners with twelve CrTe6 octahedra and corners with two equivalent CuTe4 tetrahedra. The corner-sharing octahedra tilt angles range from 53–59°. There are two shorter (2.58 Å) and two longer (2.59 Å) Cu–Te bond lengths. There are four inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to three Cr3+ and one Cu+1.33+ atom to form a mixture of distorted corner and edge-sharing TeCr3Cu trigonal pyramids. In the second Te2- site, Te2- is bonded in a 5-coordinate geometry to three Cr3+ and two Cu+1.33+ atoms. In the third Te2- site, Te2- is bonded to three Cr3+ and one Cu+1.33+ atom to form a mixture of distorted corner and edge-sharing TeCr3Cu trigonal pyramids. In the fourth Te2- site, Te2- is bonded in a 5-coordinate geometry to three Cr3+ and two Cu+1.33+ atoms.