ThEr3 is Magnesium-derived structured and crystallizes in the hexagonal P-6m2 space group. Th(1) is bonded to six equivalent Th(1) and six equivalent Er(2) atoms to form ThEr6Th6 cuboctahedra that share corners with six equivalent Th(1)Er6Th6 cuboctahedra, corners with twelve equivalent Er(1)Er12 cuboctahedra, edges with six equivalent Th(1)Er6Th6 cuboctahedra, edges with twelve equivalent Er(2)Er9Th3 cuboctahedra, faces with two equivalent Er(1)Er12 cuboctahedra, faces with six equivalent Th(1)Er6Th6 cuboctahedra, and faces with twelve equivalent Er(2)Er9Th3 cuboctahedra. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to six equivalent Er(1) and six equivalent Er(2) atoms to form ErEr12 cuboctahedra that share corners with six equivalent Er(1)Er12 cuboctahedra, corners with twelve equivalent Th(1)Er6Th6 cuboctahedra, edges with six equivalent Er(1)Er12 cuboctahedra, edges with twelve equivalent Er(2)Er9Th3 cuboctahedra, faces with two equivalent Th(1)Er6Th6 cuboctahedra, faces with six equivalent Er(1)Er12 cuboctahedra, and faces with twelve equivalent Er(2)Er9Th3 cuboctahedra. In the second Er site, Er(2) is bonded to three equivalent Th(1), three equivalent Er(1), and six equivalent Er(2) atoms to form ErEr9Th3 cuboctahedra that share corners with eighteen equivalent Er(2)Er9Th3 cuboctahedra, edges with six equivalent Th(1)Er6Th6 cuboctahedra, edges with six equivalent Er(1)Er12 cuboctahedra, edges with six equivalent Er(2)Er9Th3 cuboctahedra, faces with six equivalent Th(1)Er6Th6 cuboctahedra, faces with six equivalent Er(1)Er12 cuboctahedra, and faces with eight equivalent Er(2)Er9Th3 cuboctahedra.
ThEr3 is Magnesium-derived structured and crystallizes in the hexagonal P-6m2 space group. Th(1) is bonded to six equivalent Th(1) and six equivalent Er(2) atoms to form ThEr6Th6 cuboctahedra that share corners with six equivalent Th(1)Er6Th6 cuboctahedra, corners with twelve equivalent Er(1)Er12 cuboctahedra, edges with six equivalent Th(1)Er6Th6 cuboctahedra, edges with twelve equivalent Er(2)Er9Th3 cuboctahedra, faces with two equivalent Er(1)Er12 cuboctahedra, faces with six equivalent Th(1)Er6Th6 cuboctahedra, and faces with twelve equivalent Er(2)Er9Th3 cuboctahedra. All Th(1)-Th(1) bond lengths are 3.58 Å. All Th(1)-Er(2) bond lengths are 3.54 Å. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to six equivalent Er(1) and six equivalent Er(2) atoms to form ErEr12 cuboctahedra that share corners with six equivalent Er(1)Er12 cuboctahedra, corners with twelve equivalent Th(1)Er6Th6 cuboctahedra, edges with six equivalent Er(1)Er12 cuboctahedra, edges with twelve equivalent Er(2)Er9Th3 cuboctahedra, faces with two equivalent Th(1)Er6Th6 cuboctahedra, faces with six equivalent Er(1)Er12 cuboctahedra, and faces with twelve equivalent Er(2)Er9Th3 cuboctahedra. All Er(1)-Er(1) bond lengths are 3.58 Å. All Er(1)-Er(2) bond lengths are 3.48 Å. In the second Er site, Er(2) is bonded to three equivalent Th(1), three equivalent Er(1), and six equivalent Er(2) atoms to form ErEr9Th3 cuboctahedra that share corners with eighteen equivalent Er(2)Er9Th3 cuboctahedra, edges with six equivalent Th(1)Er6Th6 cuboctahedra, edges with six equivalent Er(1)Er12 cuboctahedra, edges with six equivalent Er(2)Er9Th3 cuboctahedra, faces with six equivalent Th(1)Er6Th6 cuboctahedra, faces with six equivalent Er(1)Er12 cuboctahedra, and faces with eight equivalent Er(2)Er9Th3 cuboctahedra. All Er(2)-Er(2) bond lengths are 3.58 Å.