Ca2Mg crystallizes in the monoclinic Cm space group. There are four inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to two equivalent Ca(1), two equivalent Ca(2), two equivalent Ca(3), three equivalent Ca(4), one Mg(2), and two equivalent Mg(1) atoms to form distorted CaCa9Mg3 cuboctahedra that share corners with six equivalent Ca(2)Ca7Mg5 cuboctahedra, corners with six equivalent Ca(1)Ca9Mg3 cuboctahedra, edges with two equivalent Ca(4)Ca8Mg4 cuboctahedra, edges with three equivalent Ca(2)Ca7Mg5 cuboctahedra, faces with two equivalent Ca(1)Ca9Mg3 cuboctahedra, faces with three equivalent Ca(2)Ca7Mg5 cuboctahedra, and faces with five equivalent Ca(4)Ca8Mg4 cuboctahedra. In the second Ca site, Ca(2) is bonded to one Ca(4), two equivalent Ca(1), two equivalent Ca(2), two equivalent Ca(3), two equivalent Mg(2), and three equivalent Mg(1) atoms to form distorted CaCa7Mg5 cuboctahedra that share corners with six equivalent Ca(2)Ca7Mg5 cuboctahedra, corners with six equivalent Ca(1)Ca9Mg3 cuboctahedra, edges with three equivalent Ca(1)Ca9Mg3 cuboctahedra, edges with four equivalent Ca(4)Ca8Mg4 cuboctahedra, faces with two equivalent Ca(2)Ca7Mg5 cuboctahedra, faces with three equivalent Ca(1)Ca9Mg3 cuboctahedra, and faces with four equivalent Ca(4)Ca8Mg4 cuboctahedra. In the third Ca site, Ca(3) is bonded in a 3-coordinate geometry to two equivalent Ca(1), two equivalent Ca(2), two equivalent Ca(4), one Mg(1), and two equivalent Mg(2) atoms. In the fourth Ca site, Ca(4) is bonded to one Ca(2), two equivalent Ca(3), two equivalent Ca(4), three equivalent Ca(1), two equivalent Mg(1), and two equivalent Mg(2) atoms to form distorted CaCa8Mg4 cuboctahedra that share corners with six equivalent Ca(4)Ca8Mg4 cuboctahedra, edges with two equivalent Ca(1)Ca9Mg3 cuboctahedra, edges with four equivalent Ca(2)Ca7Mg5 cuboctahedra, faces with two equivalent Ca(4)Ca8Mg4 cuboctahedra, faces with four equivalent Ca(2)Ca7Mg5 cuboctahedra, and faces with five equivalent Ca(1)Ca9Mg3 cuboctahedra. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 8-coordinate geometry to one Ca(3), two equivalent Ca(1), two equivalent Ca(4), and three equivalent Ca(2) atoms. In the second Mg site, Mg(2) is bonded in a 7-coordinate geometry to one Ca(1), two equivalent Ca(2), two equivalent Ca(3), and two equivalent Ca(4) atoms.
Ca2Mg crystallizes in the monoclinic Cm space group. There are four inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to two equivalent Ca(1), two equivalent Ca(2), two equivalent Ca(3), three equivalent Ca(4), one Mg(2), and two equivalent Mg(1) atoms to form distorted CaCa9Mg3 cuboctahedra that share corners with six equivalent Ca(2)Ca7Mg5 cuboctahedra, corners with six equivalent Ca(1)Ca9Mg3 cuboctahedra, edges with two equivalent Ca(4)Ca8Mg4 cuboctahedra, edges with three equivalent Ca(2)Ca7Mg5 cuboctahedra, faces with two equivalent Ca(1)Ca9Mg3 cuboctahedra, faces with three equivalent Ca(2)Ca7Mg5 cuboctahedra, and faces with five equivalent Ca(4)Ca8Mg4 cuboctahedra. Both Ca(1)-Ca(1) bond lengths are 3.71 Å. Both Ca(1)-Ca(2) bond lengths are 3.76 Å. Both Ca(1)-Ca(3) bond lengths are 3.72 Å. There is one shorter (3.71 Å) and two longer (3.84 Å) Ca(1)-Ca(4) bond lengths. The Ca(1)-Mg(2) bond length is 3.71 Å. Both Ca(1)-Mg(1) bond lengths are 3.51 Å. In the second Ca site, Ca(2) is bonded to one Ca(4), two equivalent Ca(1), two equivalent Ca(2), two equivalent Ca(3), two equivalent Mg(2), and three equivalent Mg(1) atoms to form distorted CaCa7Mg5 cuboctahedra that share corners with six equivalent Ca(2)Ca7Mg5 cuboctahedra, corners with six equivalent Ca(1)Ca9Mg3 cuboctahedra, edges with three equivalent Ca(1)Ca9Mg3 cuboctahedra, edges with four equivalent Ca(4)Ca8Mg4 cuboctahedra, faces with two equivalent Ca(2)Ca7Mg5 cuboctahedra, faces with three equivalent Ca(1)Ca9Mg3 cuboctahedra, and faces with four equivalent Ca(4)Ca8Mg4 cuboctahedra. The Ca(2)-Ca(4) bond length is 3.71 Å. Both Ca(2)-Ca(2) bond lengths are 3.71 Å. Both Ca(2)-Ca(3) bond lengths are 3.70 Å. Both Ca(2)-Mg(2) bond lengths are 3.53 Å. There are two shorter (3.77 Å) and one longer (3.79 Å) Ca(2)-Mg(1) bond length. In the third Ca site, Ca(3) is bonded in a 3-coordinate geometry to two equivalent Ca(1), two equivalent Ca(2), two equivalent Ca(4), one Mg(1), and two equivalent Mg(2) atoms. Both Ca(3)-Ca(4) bond lengths are 3.81 Å. The Ca(3)-Mg(1) bond length is 3.40 Å. Both Ca(3)-Mg(2) bond lengths are 3.56 Å. In the fourth Ca site, Ca(4) is bonded to one Ca(2), two equivalent Ca(3), two equivalent Ca(4), three equivalent Ca(1), two equivalent Mg(1), and two equivalent Mg(2) atoms to form distorted CaCa8Mg4 cuboctahedra that share corners with six equivalent Ca(4)Ca8Mg4 cuboctahedra, edges with two equivalent Ca(1)Ca9Mg3 cuboctahedra, edges with four equivalent Ca(2)Ca7Mg5 cuboctahedra, faces with two equivalent Ca(4)Ca8Mg4 cuboctahedra, faces with four equivalent Ca(2)Ca7Mg5 cuboctahedra, and faces with five equivalent Ca(1)Ca9Mg3 cuboctahedra. Both Ca(4)-Ca(4) bond lengths are 3.71 Å. Both Ca(4)-Mg(1) bond lengths are 3.73 Å. Both Ca(4)-Mg(2) bond lengths are 3.66 Å. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 8-coordinate geometry to one Ca(3), two equivalent Ca(1), two equivalent Ca(4), and three equivalent Ca(2) atoms. In the second Mg site, Mg(2) is bonded in a 7-coordinate geometry to one Ca(1), two equivalent Ca(2), two equivalent Ca(3), and two equivalent Ca(4) atoms.