Er2Mg crystallizes in the monoclinic Pm space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a distorted body-centered cubic geometry to two equivalent Er(1), two equivalent Er(2), and four equivalent Er(3) atoms. In the second Mg site, Mg(2) is bonded in a distorted body-centered cubic geometry to two equivalent Er(3), two equivalent Er(4), and four equivalent Er(1) atoms. There are four inequivalent Er sites. In the first Er site, Er(1) is bonded in a 6-coordinate geometry to two equivalent Mg(1), four equivalent Mg(2), two equivalent Er(2), and two equivalent Er(4) atoms. In the second Er site, Er(2) is bonded to two equivalent Mg(1), two equivalent Er(1), two equivalent Er(2), two equivalent Er(3), and four equivalent Er(4) atoms to form a mixture of distorted face, corner, and edge-sharing ErEr10Mg2 cuboctahedra. In the third Er site, Er(3) is bonded in a 6-coordinate geometry to two equivalent Mg(2), four equivalent Mg(1), two equivalent Er(2), and two equivalent Er(4) atoms. In the fourth Er site, Er(4) is bonded to two equivalent Mg(2), two equivalent Er(1), two equivalent Er(3), two equivalent Er(4), and four equivalent Er(2) atoms to form a mixture of distorted face, corner, and edge-sharing ErEr10Mg2 cuboctahedra.
Er2Mg crystallizes in the monoclinic Pm space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a distorted body-centered cubic geometry to two equivalent Er(1), two equivalent Er(2), and four equivalent Er(3) atoms. Both Mg(1)-Er(1) bond lengths are 3.26 Å. Both Mg(1)-Er(2) bond lengths are 3.29 Å. There are two shorter (3.28 Å) and two longer (3.29 Å) Mg(1)-Er(3) bond lengths. In the second Mg site, Mg(2) is bonded in a distorted body-centered cubic geometry to two equivalent Er(3), two equivalent Er(4), and four equivalent Er(1) atoms. There is one shorter (3.25 Å) and one longer (3.26 Å) Mg(2)-Er(3) bond length. There is one shorter (3.28 Å) and one longer (3.30 Å) Mg(2)-Er(4) bond length. There are two shorter (3.28 Å) and two longer (3.29 Å) Mg(2)-Er(1) bond lengths. There are four inequivalent Er sites. In the first Er site, Er(1) is bonded in a 6-coordinate geometry to two equivalent Mg(1), four equivalent Mg(2), two equivalent Er(2), and two equivalent Er(4) atoms. There is one shorter (3.56 Å) and one longer (3.57 Å) Er(1)-Er(2) bond length. Both Er(1)-Er(4) bond lengths are 3.54 Å. In the second Er site, Er(2) is bonded to two equivalent Mg(1), two equivalent Er(1), two equivalent Er(2), two equivalent Er(3), and four equivalent Er(4) atoms to form a mixture of distorted face, corner, and edge-sharing ErEr10Mg2 cuboctahedra. Both Er(2)-Er(2) bond lengths are 3.65 Å. Both Er(2)-Er(3) bond lengths are 3.54 Å. All Er(2)-Er(4) bond lengths are 3.34 Å. In the third Er site, Er(3) is bonded in a 6-coordinate geometry to two equivalent Mg(2), four equivalent Mg(1), two equivalent Er(2), and two equivalent Er(4) atoms. Both Er(3)-Er(4) bond lengths are 3.56 Å. In the fourth Er site, Er(4) is bonded to two equivalent Mg(2), two equivalent Er(1), two equivalent Er(3), two equivalent Er(4), and four equivalent Er(2) atoms to form a mixture of distorted face, corner, and edge-sharing ErEr10Mg2 cuboctahedra. Both Er(4)-Er(4) bond lengths are 3.65 Å.