Ca2Mg crystallizes in the trigonal R32 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to two equivalent Ca(2), six equivalent Ca(1), and four equivalent Mg(1) atoms to form CaCa8Mg4 cuboctahedra that share corners with eighteen equivalent Ca(1)Ca8Mg4 cuboctahedra, edges with four equivalent Ca(2)Ca6Mg6 cuboctahedra, edges with six equivalent Ca(1)Ca8Mg4 cuboctahedra, faces with four equivalent Ca(2)Ca6Mg6 cuboctahedra, and faces with eight equivalent Ca(1)Ca8Mg4 cuboctahedra. In the second Ca site, Ca(2) is bonded to six equivalent Ca(1) and six equivalent Mg(1) atoms to form CaCa6Mg6 cuboctahedra that share corners with six equivalent Ca(2)Ca6Mg6 cuboctahedra, edges with six equivalent Ca(2)Ca6Mg6 cuboctahedra, edges with twelve equivalent Ca(1)Ca8Mg4 cuboctahedra, and faces with twelve equivalent Ca(1)Ca8Mg4 cuboctahedra. Mg(1) is bonded in a 9-coordinate geometry to three equivalent Ca(2) and six equivalent Ca(1) atoms.
Ca2Mg crystallizes in the trigonal R32 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to two equivalent Ca(2), six equivalent Ca(1), and four equivalent Mg(1) atoms to form CaCa8Mg4 cuboctahedra that share corners with eighteen equivalent Ca(1)Ca8Mg4 cuboctahedra, edges with four equivalent Ca(2)Ca6Mg6 cuboctahedra, edges with six equivalent Ca(1)Ca8Mg4 cuboctahedra, faces with four equivalent Ca(2)Ca6Mg6 cuboctahedra, and faces with eight equivalent Ca(1)Ca8Mg4 cuboctahedra. Both Ca(1)-Ca(2) bond lengths are 3.71 Å. There are two shorter (3.62 Å) and four longer (3.70 Å) Ca(1)-Ca(1) bond lengths. There are two shorter (3.68 Å) and two longer (3.71 Å) Ca(1)-Mg(1) bond lengths. In the second Ca site, Ca(2) is bonded to six equivalent Ca(1) and six equivalent Mg(1) atoms to form CaCa6Mg6 cuboctahedra that share corners with six equivalent Ca(2)Ca6Mg6 cuboctahedra, edges with six equivalent Ca(2)Ca6Mg6 cuboctahedra, edges with twelve equivalent Ca(1)Ca8Mg4 cuboctahedra, and faces with twelve equivalent Ca(1)Ca8Mg4 cuboctahedra. All Ca(2)-Mg(1) bond lengths are 3.68 Å. Mg(1) is bonded in a 9-coordinate geometry to three equivalent Ca(2) and six equivalent Ca(1) atoms.