DOE OSTI2020
Ca10Cu19Al2 is Bergman Structure: Mg32(Al,Zn)49 Bergman-like structured and crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. there are five inequivalent Ca sites. In the first Ca site, Ca is bonded to twelve Cu atoms to form distorted CaCu12 cuboctahedra that share corners with six equivalent CuCa5Cu7 cuboctahedra, a faceface with one CaCu12 cuboctahedra, and faces with six equivalent CuCa6Cu6 cuboctahedra. There are six shorter (3.09 Å) and six longer (3.36 Å) Ca–Cu bond lengths. In the second Ca site, Ca is bonded in a 10-coordinate geometry to ten Cu and two equivalent Al atoms. There are a spread of Ca–Cu bond distances ranging from 3.17–3.52 Å. Both Ca–Al bond lengths are 3.19 Å. In the third Ca site, Ca is bonded in a 11-coordinate geometry to nine Cu and two equivalent Al atoms. There are a spread of Ca–Cu bond distances ranging from 3.03–3.21 Å. Both Ca–Al bond lengths are 3.36 Å. In the fourth Ca site, Ca is bonded in a 12-coordinate geometry to nine Cu and three equivalent Al atoms. There are three shorter (3.02 Å) and six longer (3.06 Å) Ca–Cu bond lengths. All Ca–Al bond lengths are 3.28 Å. In the fifth Ca site, Ca is bonded in a 10-coordinate geometry to ten Cu atoms. There are a spread of Ca–Cu bond distances ranging from 3.08–3.17 Å. There are six inequivalent Cu sites. In the first Cu site, Cu is bonded to twelve Cu atoms to form CuCu12 cuboctahedra that share corners with four equivalent CuCa5Cu7 cuboctahedra, corners with four equivalent AlCa8Al2Cu2 cuboctahedra, and faces with twelve CuCa5Cu7 cuboctahedra. There are a spread of Cu–Cu bond distances ranging from 2.46–2.60 Å. In the second Cu site, Cu is bonded to five Ca and seven Cu atoms to form CuCa5Cu7 cuboctahedra that share corners with two equivalent AlCa8Al2Cu2 cuboctahedra, corners with six CuCu12 cuboctahedra, an edgeedge with one CuCa5Cu7 cuboctahedra, edges with two equivalent AlCa8Al2Cu2 cuboctahedra, faces with two equivalent AlCa8Al2Cu2 cuboctahedra, and faces with eighteen CuCu12 cuboctahedra. There are a spread of Cu–Cu bond distances ranging from 2.46–2.73 Å. In the third Cu site, Cu is bonded in a 9-coordinate geometry to six Ca and three Cu atoms. There are one shorter (2.48 Å) and two longer (2.49 Å) Cu–Cu bond lengths. In the fourth Cu site, Cu is bonded to six Ca and six Cu atoms to form CuCa6Cu6 cuboctahedra that share corners with two equivalent AlCa8Al2Cu2 cuboctahedra, corners with eight CuCa5Cu7 cuboctahedra, edges with five CuCa6Cu6 cuboctahedra, faces with two equivalent CaCu12 cuboctahedra, faces with two equivalent AlCa8Al2Cu2 cuboctahedra, and faces with eight CuCa6Cu6 cuboctahedra. Both Cu–Cu bond lengths are 2.72 Å. In the fifth Cu site, Cu is bonded to five Ca and seven Cu atoms to form CuCa5Cu7 cuboctahedra that share a cornercorner with one CaCu12 cuboctahedra, corners with two equivalent AlCa8Al2Cu2 cuboctahedra, corners with eight CuCa5Cu7 cuboctahedra, edges with two equivalent CuCa5Cu7 cuboctahedra, faces with two equivalent AlCa8Al2Cu2 cuboctahedra, and faces with fifteen CuCu12 cuboctahedra. There are two shorter (2.66 Å) and one longer (2.68 Å) Cu–Cu bond lengths. In the sixth Cu site, Cu is bonded to five Ca, six Cu, and one Al atom to form distorted CuCa5AlCu6 cuboctahedra that share corners with nine CuCa5Cu7 cuboctahedra, edges with five CuCa6Cu6 cuboctahedra, faces with four equivalent AlCa8Al2Cu2 cuboctahedra, and faces with fourteen CuCu12 cuboctahedra. The Cu–Cu bond length is 2.60 Å. The Cu–Al bond length is 2.65 Å. Al is bonded to eight Ca, two equivalent Cu, and two equivalent Al atoms to form distorted AlCa8Al2Cu2 cuboctahedra that share corners with twelve CuCu12 cuboctahedra, an edgeedge with one AlCa8Al2Cu2 cuboctahedra, edges with four equivalent CuCa5Cu7 cuboctahedra, faces with two equivalent AlCa8Al2Cu2 cuboctahedra, and faces with eighteen CuCa5Cu7 cuboctahedra. Both Al–Al bond lengths are 2.79 Å.