SmMg3 is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to eight Mg(1,1) and four equivalent Sm(1) atoms to form distorted MgSm4Mg8 cuboctahedra that share corners with four equivalent Sm(1)Mg12 cuboctahedra; corners with fourteen Mg(1,1)Sm4Mg8 cuboctahedra; edges with six equivalent Sm(1)Mg12 cuboctahedra; edges with twelve Mg(1,1)Sm4Mg8 cuboctahedra; faces with four equivalent Sm(1)Mg12 cuboctahedra; and faces with sixteen Mg(1,1)Sm4Mg8 cuboctahedra. In the second Mg site, Mg(1) is bonded to eight Mg(1,1) and four equivalent Sm(1) atoms to form distorted MgSm4Mg8 cuboctahedra that share corners with four equivalent Sm(1)Mg12 cuboctahedra; corners with fourteen Mg(1,1)Sm4Mg8 cuboctahedra; edges with six equivalent Sm(1)Mg12 cuboctahedra; edges with twelve Mg(1,1)Sm4Mg8 cuboctahedra; faces with four equivalent Sm(1)Mg12 cuboctahedra; and faces with sixteen Mg(1,1)Sm4Mg8 cuboctahedra. Sm(1) is bonded to twelve Mg(1,1) atoms to form SmMg12 cuboctahedra that share corners with six equivalent Sm(1)Mg12 cuboctahedra; corners with twelve Mg(1,1)Sm4Mg8 cuboctahedra; edges with eighteen Mg(1,1)Sm4Mg8 cuboctahedra; faces with eight equivalent Sm(1)Mg12 cuboctahedra; and faces with twelve Mg(1,1)Sm4Mg8 cuboctahedra.
SmMg3 is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to eight Mg(1,1) and four equivalent Sm(1) atoms to form distorted MgSm4Mg8 cuboctahedra that share corners with four equivalent Sm(1)Mg12 cuboctahedra; corners with fourteen Mg(1,1)Sm4Mg8 cuboctahedra; edges with six equivalent Sm(1)Mg12 cuboctahedra; edges with twelve Mg(1,1)Sm4Mg8 cuboctahedra; faces with four equivalent Sm(1)Mg12 cuboctahedra; and faces with sixteen Mg(1,1)Sm4Mg8 cuboctahedra. There are a spread of Mg(1)-Mg(1,1) bond distances ranging from 3.21-3.49 Å. There are two shorter (3.28 Å) and two longer (3.38 Å) Mg(1)-Sm(1) bond lengths. In the second Mg site, Mg(1) is bonded to eight Mg(1,1) and four equivalent Sm(1) atoms to form distorted MgSm4Mg8 cuboctahedra that share corners with four equivalent Sm(1)Mg12 cuboctahedra; corners with fourteen Mg(1,1)Sm4Mg8 cuboctahedra; edges with six equivalent Sm(1)Mg12 cuboctahedra; edges with twelve Mg(1,1)Sm4Mg8 cuboctahedra; faces with four equivalent Sm(1)Mg12 cuboctahedra; and faces with sixteen Mg(1,1)Sm4Mg8 cuboctahedra. Both Mg(1)-Mg(1) bond lengths are 3.21 Å. There are two shorter (3.28 Å) and two longer (3.38 Å) Mg(1)-Sm(1) bond lengths. Sm(1) is bonded to twelve Mg(1,1) atoms to form SmMg12 cuboctahedra that share corners with six equivalent Sm(1)Mg12 cuboctahedra; corners with twelve Mg(1,1)Sm4Mg8 cuboctahedra; edges with eighteen Mg(1,1)Sm4Mg8 cuboctahedra; faces with eight equivalent Sm(1)Mg12 cuboctahedra; and faces with twelve Mg(1,1)Sm4Mg8 cuboctahedra.