ErY3 is Magnesium-derived structured and crystallizes in the hexagonal P6_3/mmc space group. Er(1) is bonded to twelve equivalent Y(1) atoms to form ErY12 cuboctahedra that share corners with six equivalent Er(1)Y12 cuboctahedra, corners with twelve equivalent Y(1)Y8Er4 cuboctahedra, edges with eighteen equivalent Y(1)Y8Er4 cuboctahedra, faces with eight equivalent Er(1)Y12 cuboctahedra, and faces with twelve equivalent Y(1)Y8Er4 cuboctahedra. Y(1) is bonded to four equivalent Er(1) and eight equivalent Y(1) atoms to form YY8Er4 cuboctahedra that share corners with four equivalent Er(1)Y12 cuboctahedra, corners with fourteen equivalent Y(1)Y8Er4 cuboctahedra, edges with six equivalent Er(1)Y12 cuboctahedra, edges with twelve equivalent Y(1)Y8Er4 cuboctahedra, faces with four equivalent Er(1)Y12 cuboctahedra, and faces with sixteen equivalent Y(1)Y8Er4 cuboctahedra.
ErY3 is Magnesium-derived structured and crystallizes in the hexagonal P6_3/mmc space group. Er(1) is bonded to twelve equivalent Y(1) atoms to form ErY12 cuboctahedra that share corners with six equivalent Er(1)Y12 cuboctahedra, corners with twelve equivalent Y(1)Y8Er4 cuboctahedra, edges with eighteen equivalent Y(1)Y8Er4 cuboctahedra, faces with eight equivalent Er(1)Y12 cuboctahedra, and faces with twelve equivalent Y(1)Y8Er4 cuboctahedra. There are six shorter (3.51 Å) and six longer (3.66 Å) Er(1)-Y(1) bond lengths. Y(1) is bonded to four equivalent Er(1) and eight equivalent Y(1) atoms to form YY8Er4 cuboctahedra that share corners with four equivalent Er(1)Y12 cuboctahedra, corners with fourteen equivalent Y(1)Y8Er4 cuboctahedra, edges with six equivalent Er(1)Y12 cuboctahedra, edges with twelve equivalent Y(1)Y8Er4 cuboctahedra, faces with four equivalent Er(1)Y12 cuboctahedra, and faces with sixteen equivalent Y(1)Y8Er4 cuboctahedra. There are a spread of Y(1)-Y(1) bond distances ranging from 3.53-3.68 Å.