DOE OSTI2020
Ca2AgGa7 crystallizes in the tetragonal P-4m2 space group. The structure is three-dimensional. Ca is bonded in a 8-coordinate geometry to two equivalent Ag and fourteen Ga atoms. Both Ca–Ag bond lengths are 3.51 Å. There are eight shorter (3.29 Å) and six longer (3.51 Å) Ca–Ga bond lengths. Ag is bonded to four equivalent Ca and eight Ga atoms to form distorted AgCa4Ga8 cuboctahedra that share corners with four equivalent AgCa4Ga8 cuboctahedra, corners with twelve GaCa4Ga8 cuboctahedra, edges with two equivalent GaCa4Ga8 cuboctahedra, faces with four equivalent AgCa4Ga8 cuboctahedra, and faces with four equivalent GaCa4Ga4Ag4 cuboctahedra. There are four shorter (2.65 Å) and four longer (3.05 Å) Ag–Ga bond lengths. There are five inequivalent Ga sites. In the first Ga site, Ga is bonded in a 9-coordinate geometry to four equivalent Ca, two equivalent Ag, and three Ga atoms. There are one shorter (2.48 Å) and two longer (2.65 Å) Ga–Ga bond lengths. In the second Ga site, Ga is bonded in a 9-coordinate geometry to four equivalent Ca and five Ga atoms. All Ga–Ga bond lengths are 2.64 Å. In the third Ga site, Ga is bonded to four equivalent Ca and eight Ga atoms to form distorted GaCa4Ga8 cuboctahedra that share corners with eight equivalent AgCa4Ga8 cuboctahedra, corners with eight GaCa4Ga8 cuboctahedra, edges with two equivalent GaCa4Ga4Ag4 cuboctahedra, and faces with eight GaCa4Ga8 cuboctahedra. All Ga–Ga bond lengths are 3.05 Å. In the fourth Ga site, Ga is bonded to four equivalent Ca, four equivalent Ag, and four equivalent Ga atoms to form GaCa4Ga4Ag4 cuboctahedra that share corners with sixteen GaCa4Ga8 cuboctahedra, edges with two equivalent GaCa4Ga8 cuboctahedra, faces with four equivalent AgCa4Ga8 cuboctahedra, and faces with four equivalent GaCa4Ga4Ag4 cuboctahedra. In the fifth Ga site, Ga is bonded to four equivalent Ca and eight Ga atoms to form distorted GaCa4Ga8 cuboctahedra that share corners with four equivalent AgCa4Ga8 cuboctahedra, corners with twelve GaCa4Ga8 cuboctahedra, edges with two equivalent AgCa4Ga8 cuboctahedra, and faces with eight GaCa4Ga8 cuboctahedra.