DOE OSTI2020
Cu4PbBi5S11 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are four inequivalent Cu+1.25+ sites. In the first Cu+1.25+ site, Cu+1.25+ is bonded in a 3-coordinate geometry to five S2- atoms. There are a spread of Cu–S bond distances ranging from 2.24–3.26 Å. In the second Cu+1.25+ site, Cu+1.25+ is bonded in a 5-coordinate geometry to four S2- atoms. There are a spread of Cu–S bond distances ranging from 2.28–2.44 Å. In the third Cu+1.25+ site, Cu+1.25+ is bonded to four S2- atoms to form CuS4 tetrahedra that share corners with three equivalent PbS6 octahedra, corners with two equivalent CuS4 tetrahedra, and edges with two equivalent CuS4 tetrahedra. The corner-sharing octahedra tilt angles range from 3–76°. There are a spread of Cu–S bond distances ranging from 2.28–2.47 Å. In the fourth Cu+1.25+ site, Cu+1.25+ is bonded to four S2- atoms to form CuS4 tetrahedra that share corners with two equivalent BiS5 square pyramids and corners with two equivalent CuS4 tetrahedra. There are a spread of Cu–S bond distances ranging from 2.32–2.37 Å. There are two inequivalent Pb2+ sites. In the first Pb2+ site, Pb2+ is bonded to six S2- atoms to form PbS6 octahedra that share corners with six equivalent CuS4 tetrahedra and edges with two equivalent PbS6 octahedra. There are four shorter (2.88 Å) and two longer (2.89 Å) Pb–S bond lengths. In the second Pb2+ site, Pb2+ is bonded to six S2- atoms to form PbS6 octahedra that share corners with two equivalent BiS6 octahedra, edges with two equivalent PbS6 octahedra, and edges with four equivalent BiS6 octahedra. The corner-sharing octahedral tilt angles are 9°. There are four shorter (2.89 Å) and two longer (2.91 Å) Pb–S bond lengths. There are five inequivalent Bi3+ sites. In the first Bi3+ site, Bi3+ is bonded to six S2- atoms to form BiS6 octahedra that share a cornercorner with one PbS6 octahedra, edges with two equivalent PbS6 octahedra, and edges with four equivalent BiS6 octahedra. The corner-sharing octahedral tilt angles are 9°. There are a spread of Bi–S bond distances ranging from 2.70–3.10 Å. In the second Bi3+ site, Bi3+ is bonded in a 7-coordinate geometry to seven S2- atoms. There are a spread of Bi–S bond distances ranging from 2.69–3.39 Å. In the third Bi3+ site, Bi3+ is bonded to five S2- atoms to form distorted BiS5 square pyramids that share corners with two equivalent CuS4 tetrahedra and edges with two equivalent BiS5 square pyramids. There are a spread of Bi–S bond distances ranging from 2.62–3.05 Å. In the fourth Bi3+ site, Bi3+ is bonded in a 7-coordinate geometry to seven S2- atoms. There are a spread of Bi–S bond distances ranging from 2.68–3.43 Å. In the fifth Bi3+ site, Bi3+ is bonded in a 5-coordinate geometry to seven S2- atoms. There are a spread of Bi–S bond distances ranging from 2.58–3.50 Å. There are eleven inequivalent S2- sites. In the first S2- site, S2- is bonded to two equivalent Cu+1.25+, one Pb2+, and three equivalent Bi3+ atoms to form a mixture of distorted edge and corner-sharing SCu2Bi3Pb octahedra. The corner-sharing octahedra tilt angles range from 0–3°. In the second S2- site, S2- is bonded in a 5-coordinate geometry to two equivalent Pb2+ and three Bi3+ atoms. In the third S2- site, S2- is bonded in a 3-coordinate geometry to two equivalent Cu+1.25+ and three Bi3+ atoms. In the fourth S2- site, S2- is bonded in a 5-coordinate geometry to two equivalent Cu+1.25+ and three Bi3+ atoms. In the fifth S2- site, S2- is bonded in a 3-coordinate geometry to one Cu+1.25+ and four Bi3+ atoms. In the sixth S2- site, S2- is bonded to one Cu+1.25+, two equivalent Pb2+, and three Bi3+ atoms to form distorted SCuBi3Pb2 octahedra that share corners with three SCu2Bi3Pb octahedra, corners with two equivalent SCu2Bi2 trigonal pyramids, edges with seven SCu2Bi3Pb octahedra, and an edgeedge with one SCu2Bi2 trigonal pyramid. The corner-sharing octahedra tilt angles range from 0–3°. In the seventh S2- site, S2- is bonded in a 3-coordinate geometry to one Cu+1.25+ and four Bi3+ atoms. In the eighth S2- site, S2- is bonded in a 6-coordinate geometry to three equivalent Cu+1.25+, one Pb2+, and two equivalent Bi3+ atoms. In the ninth S2- site, S2- is bonded to two Cu+1.25+ and two equivalent Bi3+ atoms to form a mixture of distorted edge and corner-sharing SCu2Bi2 trigonal pyramids. In the tenth S2- site, S2- is bonded to two Cu+1.25+ and two equivalent Bi3+ atoms to form SCu2Bi2 trigonal pyramids that share corners with two equivalent SCuBi3Pb2 octahedra, corners with two equivalent SCu2Bi2 trigonal pyramids, an edgeedge with one SCuBi3Pb2 octahedra, and an edgeedge with one SCu2Bi2 trigonal pyramid. The corner-sharing octahedral tilt angles are 15°. In the eleventh S2- site, S2- is bonded in a 4-coordinate geometry to one Cu+1.25+ and three Bi3+ atoms.