DOE OSTI2020
Er2CoGa8 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Er is bonded to twelve Ga atoms to form ErGa12 cuboctahedra that share corners with eight equivalent ErGa12 cuboctahedra, edges with twelve GaEr4Ga8 cuboctahedra, faces with five equivalent ErGa12 cuboctahedra, and faces with eight GaEr4Ga8 cuboctahedra. There are a spread of Er–Ga bond distances ranging from 2.97–3.02 Å. Co is bonded in a body-centered cubic geometry to eight Ga atoms. All Co–Ga bond lengths are 2.48 Å. There are six inequivalent Ga sites. In the first Ga site, Ga is bonded to four equivalent Er and eight Ga atoms to form distorted GaEr4Ga8 cuboctahedra that share corners with four equivalent GaEr4Ga8 cuboctahedra, edges with eight equivalent ErGa12 cuboctahedra, edges with eight equivalent GaEr4Ga8 cuboctahedra, faces with four equivalent ErGa12 cuboctahedra, and faces with twelve GaEr4Ga8 cuboctahedra. There are four shorter (3.00 Å) and four longer (3.05 Å) Ga–Ga bond lengths. In the second Ga site, Ga is bonded to four equivalent Er and eight Ga atoms to form distorted GaEr4Ga8 cuboctahedra that share corners with eight equivalent GaEr4Ga8 cuboctahedra, edges with four equivalent ErGa12 cuboctahedra, edges with eight equivalent GaEr4Ga8 cuboctahedra, faces with four equivalent ErGa12 cuboctahedra, and faces with nine GaEr4Ga8 cuboctahedra. All Ga–Ga bond lengths are 2.95 Å. In the third Ga site, Ga is bonded in a 4-coordinate geometry to two equivalent Er, two equivalent Co, and seven Ga atoms. There are one shorter (2.57 Å) and four longer (3.00 Å) Ga–Ga bond lengths. In the fourth Ga site, Ga is bonded in a 4-coordinate geometry to two equivalent Er, two equivalent Co, and seven Ga atoms. The Ga–Ga bond length is 2.57 Å. In the fifth Ga site, Ga is bonded in a 4-coordinate geometry to two equivalent Er, two equivalent Co, and seven Ga atoms. Both Ga–Er bond lengths are 2.97 Å. There are two shorter (2.95 Å) and four longer (3.00 Å) Ga–Ga bond lengths. In the sixth Ga site, Ga is bonded in a 4-coordinate geometry to two equivalent Er, two equivalent Co, and seven Ga atoms. Both Ga–Er bond lengths are 2.97 Å. Both Ga–Ga bond lengths are 2.95 Å.