NaMg6Sb is beta Cu3Ti-derived structured and crystallizes in the orthorhombic Amm2 space group. Na(1) is bonded to two equivalent Mg(2); four Mg(1,1); four Mg(3,3); and two equivalent Sb(1) atoms to form NaMg10Sb2 cuboctahedra that share corners with four equivalent Mg(2)Na2Mg10 cuboctahedra; corners with six equivalent Na(1)Mg10Sb2 cuboctahedra; corners with eight Mg(1,1)Na2Mg8Sb2 cuboctahedra; edges with two equivalent Mg(2)Na2Mg10 cuboctahedra; edges with four Mg(1,1)Na2Mg8Sb2 cuboctahedra; edges with four equivalent Sb(1)Na2Mg10 cuboctahedra; edges with eight Mg(3,3,3)Na2Mg8Sb2 cuboctahedra; faces with two equivalent Na(1)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(2)Na2Mg10 cuboctahedra; faces with two equivalent Sb(1)Na2Mg10 cuboctahedra; faces with four Mg(1,1)Na2Mg8Sb2 cuboctahedra; faces with four Mg(3,3)Na2Mg8Sb2 cuboctahedra; and faces with six equivalent Mg(4)Mg10Sb2 cuboctahedra. There are seven inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Na(1), two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), and two equivalent Sb(1) atoms to form distorted MgNa2Mg8Sb2 cuboctahedra that share corners with four equivalent Na(1)Mg10Sb2 cuboctahedra; corners with four equivalent Mg(2)Na2Mg10 cuboctahedra; corners with ten Mg(1,1)Na2Mg8Sb2 cuboctahedra; edges with two equivalent Na(1)Mg10Sb2 cuboctahedra; edges with two equivalent Mg(2)Na2Mg10 cuboctahedra; edges with two equivalent Mg(1)Na2Mg8Sb2 cuboctahedra; edges with four equivalent Mg(4)Mg10Sb2 cuboctahedra; edges with four equivalent Mg(3)Na2Mg8Sb2 cuboctahedra; edges with four equivalent Sb(1)Na2Mg10 cuboctahedra; faces with two equivalent Na(1)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(4)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(2)Na2Mg10 cuboctahedra; faces with two equivalent Sb(1)Na2Mg10 cuboctahedra; faces with four Mg(1,1)Na2Mg8Sb2 cuboctahedra; and faces with eight Mg(3,3,3)Na2Mg8Sb2 cuboctahedra. In the second Mg site, Mg(1) is bonded to two equivalent Na(1), two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), and two equivalent Sb(1) atoms to form distorted MgNa2Mg8Sb2 cuboctahedra that share corners with four equivalent Na(1)Mg10Sb2 cuboctahedra; corners with four equivalent Mg(2)Na2Mg10 cuboctahedra; corners with ten Mg(1,1)Na2Mg8Sb2 cuboctahedra; edges with two equivalent Na(1)Mg10Sb2 cuboctahedra; edges with two equivalent Mg(2)Na2Mg10 cuboctahedra; edges with two equivalent Mg(1)Na2Mg8Sb2 cuboctahedra; edges with four equivalent Mg(4)Mg10Sb2 cuboctahedra; edges with four equivalent Mg(3)Na2Mg8Sb2 cuboctahedra; edges with four equivalent Sb(1)Na2Mg10 cuboctahedra; faces with two equivalent Na(1)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(4)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(2)Na2Mg10 cuboctahedra; faces with two equivalent Sb(1)Na2Mg10 cuboctahedra; faces with four Mg(1,1)Na2Mg8Sb2 cuboctahedra; and faces with eight Mg(3,3)Na2Mg8Sb2 cuboctahedra. In the third Mg site, Mg(2) is bonded to two equivalent Na(1); two equivalent Mg(4); four Mg(1,1); and four Mg(3,3) atoms to form distorted MgNa2Mg10 cuboctahedra that share corners with four equivalent Na(1)Mg10Sb2 cuboctahedra; corners with six equivalent Mg(2)Na2Mg10 cuboctahedra; corners with eight Mg(1,1)Na2Mg8Sb2 cuboctahedra; edges with two equivalent Na(1)Mg10Sb2 cuboctahedra; edges with four equivalent Mg(4)Mg10Sb2 cuboctahedra; edges with four Mg(1,1)Na2Mg8Sb2 cuboctahedra; edges with eight Mg(3,3,3)Na2Mg8Sb2 cuboctahedra; faces with two equivalent Na(1)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(4)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(2)Na2Mg10 cuboctahedra; faces with four Mg(1,1)Na2Mg8Sb2 cuboctahedra; faces with four Mg(3,3)Na2Mg8Sb2 cuboctahedra; and faces with six equivalent Sb(1)Na2Mg10 cuboctahedra. In the fourth Mg site, Mg(3) is bonded to two equivalent Na(1), two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), and two equivalent Sb(1) atoms to form distorted MgNa2Mg8Sb2 cuboctahedra that share corners with four equivalent Mg(4)Mg10Sb2 cuboctahedra; corners with four equivalent Sb(1)Na2Mg10 cuboctahedra; corners with ten Mg(3,3)Na2Mg8Sb2 cuboctahedra; edges with two equivalent Mg(4)Mg10Sb2 cuboctahedra; edges with two equivalent Mg(3)Na2Mg8Sb2 cuboctahedra; edges with two equivalent Sb(1)Na2Mg10 cuboctahedra; edges with four equivalent Na(1)Mg10Sb2 cuboctahedra; edges with four equivalent Mg(2)Na2Mg10 cuboctahedra; edges with four equivalent Mg(1)Na2Mg8Sb2 cuboctahedra; faces with two equivalent Na(1)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(4)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(2)Na2Mg10 cuboctahedra; faces with two equivalent Sb(1)Na2Mg10 cuboctahedra; faces with four Mg(3,3)Na2Mg8Sb2 cuboctahedra; and faces with eight Mg(1,1)Na2Mg8Sb2 cuboctahedra. In the fifth Mg site, Mg(3) is bonded to two equivalent Na(1), two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), and two equivalent Sb(1) atoms to form distorted MgNa2Mg8Sb2 cuboctahedra that share corners with four equivalent Mg(4)Mg10Sb2 cuboctahedra; corners with four equivalent Sb(1)Na2Mg10 cuboctahedra; corners with ten Mg(3,3,3)Na2Mg8Sb2 cuboctahedra; edges with two equivalent Mg(4)Mg10Sb2 cuboctahedra; edges with two equivalent Mg(3)Na2Mg8Sb2 cuboctahedra; edges with two equivalent Sb(1)Na2Mg10 cuboctahedra; edges with four equivalent Na(1)Mg10Sb2 cuboctahedra; edges with four equivalent Mg(2)Na2Mg10 cuboctahedra; edges with four equivalent Mg(1)Na2Mg8Sb2 cuboctahedra; faces with two equivalent Na(1)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(4)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(2)Na2Mg10 cuboctahedra; faces with two equivalent Sb(1)Na2Mg10 cuboctahedra; faces with four Mg(3,3)Na2Mg8Sb2 cuboctahedra; and faces with eight Mg(1,1)Na2Mg8Sb2 cuboctahedra. In the sixth Mg site, Mg(4) is bonded to two equivalent Mg(2); four equivalent Mg(1); four Mg(3,3,3); and two equivalent Sb(1) atoms to form distorted MgMg10Sb2 cuboctahedra that share corners with four equivalent Sb(1)Na2Mg10 cuboctahedra; corners with six equivalent Mg(4)Mg10Sb2 cuboctahedra; corners with eight Mg(3,3,3)Na2Mg8Sb2 cuboctahedra; edges with two equivalent Sb(1)Na2Mg10 cuboctahedra; edges with four equivalent Mg(2)Na2Mg10 cuboctahedra; edges with four Mg(3,3,3)Na2Mg8Sb2 cuboctahedra; edges with eight Mg(1,1)Na2Mg8Sb2 cuboctahedra; faces with two equivalent Mg(4)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(2)Na2Mg10 cuboctahedra; faces with two equivalent Sb(1)Na2Mg10 cuboctahedra; faces with four equivalent Mg(1)Na2Mg8Sb2 cuboctahedra; faces with four Mg(3,3,3)Na2Mg8Sb2 cuboctahedra; and faces with six equivalent Na(1)Mg10Sb2 cuboctahedra. In the seventh Mg site, Mg(3) is bonded to two equivalent Na(1), two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), and two equivalent Sb(1) atoms to form distorted MgNa2Mg8Sb2 cuboctahedra that share corners with four equivalent Mg(4)Mg10Sb2 cuboctahedra; corners with four equivalent Sb(1)Na2Mg10 cuboctahedra; corners with ten Mg(3,3,3)Na2Mg8Sb2 cuboctahedra; edges with two equivalent Mg(4)Mg10Sb2 cuboctahedra; edges with two equivalent Mg(3)Na2Mg8Sb2 cuboctahedra; edges with two equivalent Sb(1)Na2Mg10 cuboctahedra; edges with four equivalent Na(1)Mg10Sb2 cuboctahedra; edges with four equivalent Mg(2)Na2Mg10 cuboctahedra; edges with four equivalent Mg(1)Na2Mg8Sb2 cuboctahedra; faces with two equivalent Na(1)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(4)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(2)Na2Mg10 cuboctahedra; faces with two equivalent Sb(1)Na2Mg10 cuboctahedra; faces with four Mg(3,3)Na2Mg8Sb2 cuboctahedra; and faces with eight Mg(1,1)Na2Mg8Sb2 cuboctahedra. Sb(1) is bonded to two equivalent Na(1); two equivalent Mg(4); four Mg(1,1); and four Mg(3,3,3) atoms to form SbNa2Mg10 cuboctahedra that share corners with four equivalent Mg(4)Mg10Sb2 cuboctahedra; corners with six equivalent Sb(1)Na2Mg10 cuboctahedra; corners with eight Mg(3,3,3)Na2Mg8Sb2 cuboctahedra; edges with two equivalent Mg(4)Mg10Sb2 cuboctahedra; edges with four equivalent Na(1)Mg10Sb2 cuboctahedra; edges with four Mg(3,3,3)Na2Mg8Sb2 cuboctahedra; edges with eight Mg(1,1)Na2Mg8Sb2 cuboctahedra; faces with two equivalent Na(1)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(4)Mg10Sb2 cuboctahedra; faces with two equivalent Sb(1)Na2Mg10 cuboctahedra; faces with four Mg(1,1)Na2Mg8Sb2 cuboctahedra; faces with four Mg(3,3,3)Na2Mg8Sb2 cuboctahedra; and faces with six equivalent Mg(2)Na2Mg10 cuboctahedra.
NaMg6Sb is beta Cu3Ti-derived structured and crystallizes in the orthorhombic Amm2 space group. Na(1) is bonded to two equivalent Mg(2); four Mg(1,1); four Mg(3,3); and two equivalent Sb(1) atoms to form NaMg10Sb2 cuboctahedra that share corners with four equivalent Mg(2)Na2Mg10 cuboctahedra; corners with six equivalent Na(1)Mg10Sb2 cuboctahedra; corners with eight Mg(1,1)Na2Mg8Sb2 cuboctahedra; edges with two equivalent Mg(2)Na2Mg10 cuboctahedra; edges with four Mg(1,1)Na2Mg8Sb2 cuboctahedra; edges with four equivalent Sb(1)Na2Mg10 cuboctahedra; edges with eight Mg(3,3,3)Na2Mg8Sb2 cuboctahedra; faces with two equivalent Na(1)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(2)Na2Mg10 cuboctahedra; faces with two equivalent Sb(1)Na2Mg10 cuboctahedra; faces with four Mg(1,1)Na2Mg8Sb2 cuboctahedra; faces with four Mg(3,3)Na2Mg8Sb2 cuboctahedra; and faces with six equivalent Mg(4)Mg10Sb2 cuboctahedra. Both Na(1)-Mg(2) bond lengths are 3.29 Å. There are two shorter (3.23 Å) and two longer (3.29 Å) Na(1)-Mg(1,1) bond lengths. All Na(1)-Mg(3,3) bond lengths are 3.22 Å. Both Na(1)-Sb(1) bond lengths are 3.20 Å. There are seven inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Na(1), two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), and two equivalent Sb(1) atoms to form distorted MgNa2Mg8Sb2 cuboctahedra that share corners with four equivalent Na(1)Mg10Sb2 cuboctahedra; corners with four equivalent Mg(2)Na2Mg10 cuboctahedra; corners with ten Mg(1,1)Na2Mg8Sb2 cuboctahedra; edges with two equivalent Na(1)Mg10Sb2 cuboctahedra; edges with two equivalent Mg(2)Na2Mg10 cuboctahedra; edges with two equivalent Mg(1)Na2Mg8Sb2 cuboctahedra; edges with four equivalent Mg(4)Mg10Sb2 cuboctahedra; edges with four equivalent Mg(3)Na2Mg8Sb2 cuboctahedra; edges with four equivalent Sb(1)Na2Mg10 cuboctahedra; faces with two equivalent Na(1)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(4)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(2)Na2Mg10 cuboctahedra; faces with two equivalent Sb(1)Na2Mg10 cuboctahedra; faces with four Mg(1,1)Na2Mg8Sb2 cuboctahedra; and faces with eight Mg(3,3,3)Na2Mg8Sb2 cuboctahedra. There is one shorter (3.25 Å) and one longer (3.32 Å) Mg(1)-Mg(1) bond length. There is one shorter (3.23 Å) and one longer (3.29 Å) Mg(1)-Mg(2) bond length. Both Mg(1)-Mg(3) bond lengths are 3.18 Å. Both Mg(1)-Mg(4) bond lengths are 3.20 Å. Both Mg(1)-Sb(1) bond lengths are 3.22 Å. In the second Mg site, Mg(1) is bonded to two equivalent Na(1), two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), and two equivalent Sb(1) atoms to form distorted MgNa2Mg8Sb2 cuboctahedra that share corners with four equivalent Na(1)Mg10Sb2 cuboctahedra; corners with four equivalent Mg(2)Na2Mg10 cuboctahedra; corners with ten Mg(1,1)Na2Mg8Sb2 cuboctahedra; edges with two equivalent Na(1)Mg10Sb2 cuboctahedra; edges with two equivalent Mg(2)Na2Mg10 cuboctahedra; edges with two equivalent Mg(1)Na2Mg8Sb2 cuboctahedra; edges with four equivalent Mg(4)Mg10Sb2 cuboctahedra; edges with four equivalent Mg(3)Na2Mg8Sb2 cuboctahedra; edges with four equivalent Sb(1)Na2Mg10 cuboctahedra; faces with two equivalent Na(1)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(4)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(2)Na2Mg10 cuboctahedra; faces with two equivalent Sb(1)Na2Mg10 cuboctahedra; faces with four Mg(1,1)Na2Mg8Sb2 cuboctahedra; and faces with eight Mg(3,3)Na2Mg8Sb2 cuboctahedra. There is one shorter (3.23 Å) and one longer (3.29 Å) Mg(1)-Mg(2) bond length. Both Mg(1)-Mg(3) bond lengths are 3.18 Å. Both Mg(1)-Mg(4) bond lengths are 3.20 Å. Both Mg(1)-Sb(1) bond lengths are 3.22 Å. In the third Mg site, Mg(2) is bonded to two equivalent Na(1); two equivalent Mg(4); four Mg(1,1); and four Mg(3,3) atoms to form distorted MgNa2Mg10 cuboctahedra that share corners with four equivalent Na(1)Mg10Sb2 cuboctahedra; corners with six equivalent Mg(2)Na2Mg10 cuboctahedra; corners with eight Mg(1,1)Na2Mg8Sb2 cuboctahedra; edges with two equivalent Na(1)Mg10Sb2 cuboctahedra; edges with four equivalent Mg(4)Mg10Sb2 cuboctahedra; edges with four Mg(1,1)Na2Mg8Sb2 cuboctahedra; edges with eight Mg(3,3,3)Na2Mg8Sb2 cuboctahedra; faces with two equivalent Na(1)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(4)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(2)Na2Mg10 cuboctahedra; faces with four Mg(1,1)Na2Mg8Sb2 cuboctahedra; faces with four Mg(3,3)Na2Mg8Sb2 cuboctahedra; and faces with six equivalent Sb(1)Na2Mg10 cuboctahedra. Both Mg(2)-Mg(4) bond lengths are 3.21 Å. All Mg(2)-Mg(3,3) bond lengths are 3.19 Å. In the fourth Mg site, Mg(3) is bonded to two equivalent Na(1), two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), and two equivalent Sb(1) atoms to form distorted MgNa2Mg8Sb2 cuboctahedra that share corners with four equivalent Mg(4)Mg10Sb2 cuboctahedra; corners with four equivalent Sb(1)Na2Mg10 cuboctahedra; corners with ten Mg(3,3)Na2Mg8Sb2 cuboctahedra; edges with two equivalent Mg(4)Mg10Sb2 cuboctahedra; edges with two equivalent Mg(3)Na2Mg8Sb2 cuboctahedra; edges with two equivalent Sb(1)Na2Mg10 cuboctahedra; edges with four equivalent Na(1)Mg10Sb2 cuboctahedra; edges with four equivalent Mg(2)Na2Mg10 cuboctahedra; edges with four equivalent Mg(1)Na2Mg8Sb2 cuboctahedra; faces with two equivalent Na(1)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(4)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(2)Na2Mg10 cuboctahedra; faces with two equivalent Sb(1)Na2Mg10 cuboctahedra; faces with four Mg(3,3)Na2Mg8Sb2 cuboctahedra; and faces with eight Mg(1,1)Na2Mg8Sb2 cuboctahedra. There is one shorter (3.24 Å) and one longer (3.33 Å) Mg(3)-Mg(3) bond length. There is one shorter (3.25 Å) and one longer (3.27 Å) Mg(3)-Mg(4) bond length. There is one shorter (3.24 Å) and one longer (3.28 Å) Mg(3)-Sb(1) bond length. In the fifth Mg site, Mg(3) is bonded to two equivalent Na(1), two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), and two equivalent Sb(1) atoms to form distorted MgNa2Mg8Sb2 cuboctahedra that share corners with four equivalent Mg(4)Mg10Sb2 cuboctahedra; corners with four equivalent Sb(1)Na2Mg10 cuboctahedra; corners with ten Mg(3,3,3)Na2Mg8Sb2 cuboctahedra; edges with two equivalent Mg(4)Mg10Sb2 cuboctahedra; edges with two equivalent Mg(3)Na2Mg8Sb2 cuboctahedra; edges with two equivalent Sb(1)Na2Mg10 cuboctahedra; edges with four equivalent Na(1)Mg10Sb2 cuboctahedra; edges with four equivalent Mg(2)Na2Mg10 cuboctahedra; edges with four equivalent Mg(1)Na2Mg8Sb2 cuboctahedra; faces with two equivalent Na(1)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(4)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(2)Na2Mg10 cuboctahedra; faces with two equivalent Sb(1)Na2Mg10 cuboctahedra; faces with four Mg(3,3)Na2Mg8Sb2 cuboctahedra; and faces with eight Mg(1,1)Na2Mg8Sb2 cuboctahedra. Both Mg(3)-Na(1) bond lengths are 3.22 Å. There is one shorter (3.25 Å) and one longer (3.27 Å) Mg(3)-Mg(4) bond length. There is one shorter (3.24 Å) and one longer (3.28 Å) Mg(3)-Sb(1) bond length. In the sixth Mg site, Mg(4) is bonded to two equivalent Mg(2); four equivalent Mg(1); four Mg(3,3,3); and two equivalent Sb(1) atoms to form distorted MgMg10Sb2 cuboctahedra that share corners with four equivalent Sb(1)Na2Mg10 cuboctahedra; corners with six equivalent Mg(4)Mg10Sb2 cuboctahedra; corners with eight Mg(3,3,3)Na2Mg8Sb2 cuboctahedra; edges with two equivalent Sb(1)Na2Mg10 cuboctahedra; edges with four equivalent Mg(2)Na2Mg10 cuboctahedra; edges with four Mg(3,3,3)Na2Mg8Sb2 cuboctahedra; edges with eight Mg(1,1)Na2Mg8Sb2 cuboctahedra; faces with two equivalent Mg(4)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(2)Na2Mg10 cuboctahedra; faces with two equivalent Sb(1)Na2Mg10 cuboctahedra; faces with four equivalent Mg(1)Na2Mg8Sb2 cuboctahedra; faces with four Mg(3,3,3)Na2Mg8Sb2 cuboctahedra; and faces with six equivalent Na(1)Mg10Sb2 cuboctahedra. The Mg(4)-Mg(3) bond length is 3.27 Å. Both Mg(4)-Sb(1) bond lengths are 3.29 Å. In the seventh Mg site, Mg(3) is bonded to two equivalent Na(1), two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), and two equivalent Sb(1) atoms to form distorted MgNa2Mg8Sb2 cuboctahedra that share corners with four equivalent Mg(4)Mg10Sb2 cuboctahedra; corners with four equivalent Sb(1)Na2Mg10 cuboctahedra; corners with ten Mg(3,3,3)Na2Mg8Sb2 cuboctahedra; edges with two equivalent Mg(4)Mg10Sb2 cuboctahedra; edges with two equivalent Mg(3)Na2Mg8Sb2 cuboctahedra; edges with two equivalent Sb(1)Na2Mg10 cuboctahedra; edges with four equivalent Na(1)Mg10Sb2 cuboctahedra; edges with four equivalent Mg(2)Na2Mg10 cuboctahedra; edges with four equivalent Mg(1)Na2Mg8Sb2 cuboctahedra; faces with two equivalent Na(1)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(4)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(2)Na2Mg10 cuboctahedra; faces with two equivalent Sb(1)Na2Mg10 cuboctahedra; faces with four Mg(3,3)Na2Mg8Sb2 cuboctahedra; and faces with eight Mg(1,1)Na2Mg8Sb2 cuboctahedra. Both Mg(3)-Mg(1) bond lengths are 3.18 Å. Both Mg(3)-Mg(2) bond lengths are 3.19 Å. There is one shorter (3.24 Å) and one longer (3.33 Å) Mg(3)-Mg(3) bond length. There is one shorter (3.24 Å) and one longer (3.28 Å) Mg(3)-Sb(1) bond length. Sb(1) is bonded to two equivalent Na(1); two equivalent Mg(4); four Mg(1,1); and four Mg(3,3,3) atoms to form SbNa2Mg10 cuboctahedra that share corners with four equivalent Mg(4)Mg10Sb2 cuboctahedra; corners with six equivalent Sb(1)Na2Mg10 cuboctahedra; corners with eight Mg(3,3,3)Na2Mg8Sb2 cuboctahedra; edges with two equivalent Mg(4)Mg10Sb2 cuboctahedra; edges with four equivalent Na(1)Mg10Sb2 cuboctahedra; edges with four Mg(3,3,3)Na2Mg8Sb2 cuboctahedra; edges with eight Mg(1,1)Na2Mg8Sb2 cuboctahedra; faces with two equivalent Na(1)Mg10Sb2 cuboctahedra; faces with two equivalent Mg(4)Mg10Sb2 cuboctahedra; faces with two equivalent Sb(1)Na2Mg10 cuboctahedra; faces with four Mg(1,1)Na2Mg8Sb2 cuboctahedra; faces with four Mg(3,3,3)Na2Mg8Sb2 cuboctahedra; and faces with six equivalent Mg(2)Na2Mg10 cuboctahedra.