DOE OSTI2020
Er8CoGa3 crystallizes in the hexagonal P6_3mc space group. The structure is three-dimensional. there are four inequivalent Er sites. In the first Er site, Er is bonded to six equivalent Ga atoms to form distorted ErGa6 octahedra that share corners with six equivalent ErGa3Co tetrahedra, corners with six equivalent ErGa4Co trigonal pyramids, faces with two equivalent ErGa6 octahedra, and faces with six equivalent ErGa4Co trigonal pyramids. There are three shorter (3.23 Å) and three longer (3.37 Å) Er–Ga bond lengths. In the second Er site, Er is bonded to one Co and four equivalent Ga atoms to form distorted ErGa4Co trigonal pyramids that share corners with two equivalent ErGa6 octahedra, corners with three equivalent ErGa3Co tetrahedra, corners with six equivalent ErGa4Co trigonal pyramids, an edgeedge with one ErGa3Co tetrahedra, edges with four equivalent ErGa4Co trigonal pyramids, and faces with two equivalent ErGa6 octahedra. The corner-sharing octahedra tilt angles range from 54–58°. The Er–Co bond length is 2.80 Å. There are a spread of Er–Ga bond distances ranging from 2.92–3.75 Å. In the third Er site, Er is bonded to one Co and three equivalent Ga atoms to form distorted ErGa3Co tetrahedra that share corners with six equivalent ErGa6 octahedra, corners with nine equivalent ErGa4Co trigonal pyramids, and edges with three equivalent ErGa4Co trigonal pyramids. The corner-sharing octahedra tilt angles range from 16–47°. The Er–Co bond length is 2.65 Å. All Er–Ga bond lengths are 3.06 Å. In the fourth Er site, Er is bonded in a 3-coordinate geometry to one Co and four equivalent Ga atoms. The Er–Co bond length is 2.77 Å. There are two shorter (3.15 Å) and two longer (3.67 Å) Er–Ga bond lengths. Co is bonded in a 7-coordinate geometry to seven Er atoms. Ga is bonded in a 11-coordinate geometry to eleven Er atoms.