Mg2Sn crystallizes in the trigonal R32 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(2) and four equivalent Sn(1) atoms to form distorted MgMg2Sn4 cuboctahedra that share corners with four equivalent Mg(2)Mg6Sn6 cuboctahedra, corners with twelve equivalent Mg(1)Mg2Sn4 cuboctahedra, corners with twelve equivalent Sn(1)Mg9 cuboctahedra, edges with four equivalent Mg(2)Mg6Sn6 cuboctahedra, edges with six equivalent Mg(1)Mg2Sn4 cuboctahedra, and faces with two equivalent Mg(1)Mg2Sn4 cuboctahedra. In the second Mg site, Mg(2) is bonded to six equivalent Mg(1) and six equivalent Sn(1) atoms to form distorted MgMg6Sn6 cuboctahedra that share corners with six equivalent Mg(2)Mg6Sn6 cuboctahedra, corners with six equivalent Sn(1)Mg9 cuboctahedra, corners with twelve equivalent Mg(1)Mg2Sn4 cuboctahedra, edges with six equivalent Mg(2)Mg6Sn6 cuboctahedra, edges with six equivalent Sn(1)Mg9 cuboctahedra, edges with twelve equivalent Mg(1)Mg2Sn4 cuboctahedra, and faces with two equivalent Sn(1)Mg9 cuboctahedra. Sn(1) is bonded to three equivalent Mg(2) and six equivalent Mg(1) atoms to form distorted SnMg9 cuboctahedra that share corners with three equivalent Mg(2)Mg6Sn6 cuboctahedra, corners with eighteen equivalent Mg(1)Mg2Sn4 cuboctahedra, corners with eighteen equivalent Sn(1)Mg9 cuboctahedra, edges with three equivalent Mg(2)Mg6Sn6 cuboctahedra,  a faceface with one Mg(2)Mg6Sn6 cuboctahedra, and faces with four equivalent Sn(1)Mg9 cuboctahedra.
Mg2Sn crystallizes in the trigonal R32 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(2) and four equivalent Sn(1) atoms to form distorted MgMg2Sn4 cuboctahedra that share corners with four equivalent Mg(2)Mg6Sn6 cuboctahedra, corners with twelve equivalent Mg(1)Mg2Sn4 cuboctahedra, corners with twelve equivalent Sn(1)Mg9 cuboctahedra, edges with four equivalent Mg(2)Mg6Sn6 cuboctahedra, edges with six equivalent Mg(1)Mg2Sn4 cuboctahedra, and faces with two equivalent Mg(1)Mg2Sn4 cuboctahedra. Both Mg(1)-Mg(2) bond lengths are 3.16 Å. There are two shorter (3.14 Å) and two longer (3.18 Å) Mg(1)-Sn(1) bond lengths. In the second Mg site, Mg(2) is bonded to six equivalent Mg(1) and six equivalent Sn(1) atoms to form distorted MgMg6Sn6 cuboctahedra that share corners with six equivalent Mg(2)Mg6Sn6 cuboctahedra, corners with six equivalent Sn(1)Mg9 cuboctahedra, corners with twelve equivalent Mg(1)Mg2Sn4 cuboctahedra, edges with six equivalent Mg(2)Mg6Sn6 cuboctahedra, edges with six equivalent Sn(1)Mg9 cuboctahedra, edges with twelve equivalent Mg(1)Mg2Sn4 cuboctahedra, and faces with two equivalent Sn(1)Mg9 cuboctahedra. All Mg(2)-Sn(1) bond lengths are 3.25 Å. Sn(1) is bonded to three equivalent Mg(2) and six equivalent Mg(1) atoms to form distorted SnMg9 cuboctahedra that share corners with three equivalent Mg(2)Mg6Sn6 cuboctahedra, corners with eighteen equivalent Mg(1)Mg2Sn4 cuboctahedra, corners with eighteen equivalent Sn(1)Mg9 cuboctahedra, edges with three equivalent Mg(2)Mg6Sn6 cuboctahedra,  a faceface with one Mg(2)Mg6Sn6 cuboctahedra, and faces with four equivalent Sn(1)Mg9 cuboctahedra.