ErMg2 is Hexagonal Laves structured and crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Mg sites. In the first Mg site, Mg(2) is bonded to six equivalent Mg(1) and six equivalent Er(1) atoms to form a mixture of face, corner, and edge-sharing MgEr6Mg6 cuboctahedra. In the second Mg site, Mg(1) is bonded to two equivalent Mg(2), four equivalent Mg(1), and six equivalent Er(1) atoms to form a mixture of face, corner, and edge-sharing MgEr6Mg6 cuboctahedra. Er(1) is bonded in a 16-coordinate geometry to three equivalent Mg(2), nine equivalent Mg(1), and four equivalent Er(1) atoms.
ErMg2 is Hexagonal Laves structured and crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Mg sites. In the first Mg site, Mg(2) is bonded to six equivalent Mg(1) and six equivalent Er(1) atoms to form a mixture of face, corner, and edge-sharing MgEr6Mg6 cuboctahedra. All Mg(2)-Mg(1) bond lengths are 3.01 Å. All Mg(2)-Er(1) bond lengths are 3.51 Å. In the second Mg site, Mg(1) is bonded to two equivalent Mg(2), four equivalent Mg(1), and six equivalent Er(1) atoms to form a mixture of face, corner, and edge-sharing MgEr6Mg6 cuboctahedra. There are two shorter (2.91 Å) and two longer (3.07 Å) Mg(1)-Mg(1) bond lengths. There are four shorter (3.49 Å) and two longer (3.50 Å) Mg(1)-Er(1) bond lengths. Er(1) is bonded in a 16-coordinate geometry to three equivalent Mg(2), nine equivalent Mg(1), and four equivalent Er(1) atoms. There is one shorter (3.59 Å) and three longer (3.68 Å) Er(1)-Er(1) bond lengths.