SrMg14Nb crystallizes in the orthorhombic Amm2 space group. Sr(1) is bonded to two equivalent Mg(6); four Mg(3,3); four Mg(5,5); and two equivalent Nb(1) atoms to form SrMg10Nb2 cuboctahedra that share corners with four equivalent Mg(2)Mg12 cuboctahedra; corners with six equivalent Sr(1)Mg10Nb2 cuboctahedra; corners with eight equivalent Mg(4)Mg12 cuboctahedra; edges with two equivalent Nb(1)Sr2Mg10 cuboctahedra; edges with four Mg(3,3)Sr2Mg8Nb2 cuboctahedra; edges with four equivalent Mg(6)SrMg11 cuboctahedra; faces with two equivalent Mg(1)Mg12 cuboctahedra; faces with two equivalent Mg(6)SrMg11 cuboctahedra; faces with two equivalent Nb(1)Sr2Mg10 cuboctahedra; faces with four Mg(3,3)Sr2Mg8Nb2 cuboctahedra; and faces with six equivalent Mg(7)Mg11Nb cuboctahedra. There are nine inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(2); two equivalent Mg(6); four equivalent Mg(4); and four Mg(5,5) atoms to form MgMg12 cuboctahedra that share corners with four equivalent Nb(1)Sr2Mg10 cuboctahedra; corners with six equivalent Mg(1)Mg12 cuboctahedra; corners with eight Mg(3,3)Sr2Mg8Nb2 cuboctahedra; edges with two equivalent Mg(2)Mg12 cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; edges with four equivalent Mg(6)SrMg11 cuboctahedra; faces with two equivalent Sr(1)Mg10Nb2 cuboctahedra; faces with two equivalent Mg(2)Mg12 cuboctahedra; faces with two equivalent Mg(6)SrMg11 cuboctahedra; faces with four equivalent Mg(4)Mg12 cuboctahedra; and faces with six equivalent Mg(7)Mg11Nb cuboctahedra. In the second Mg site, Mg(2) is bonded to two equivalent Mg(1); two equivalent Mg(7); four equivalent Mg(4); and four Mg(5,5) atoms to form MgMg12 cuboctahedra that share corners with four equivalent Sr(1)Mg10Nb2 cuboctahedra; corners with six equivalent Mg(2)Mg12 cuboctahedra; corners with eight Mg(3,3)Sr2Mg8Nb2 cuboctahedra; edges with two equivalent Mg(1)Mg12 cuboctahedra; edges with four equivalent Mg(7)Mg11Nb cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Mg(7)Mg11Nb cuboctahedra; faces with two equivalent Mg(1)Mg12 cuboctahedra; faces with two equivalent Nb(1)Sr2Mg10 cuboctahedra; faces with four equivalent Mg(4)Mg12 cuboctahedra; and faces with six equivalent Mg(6)SrMg11 cuboctahedra. In the third Mg site, Mg(3) is bonded to two equivalent Sr(1), two equivalent Mg(3), two equivalent Mg(5), two equivalent Mg(6), two equivalent Mg(7), and two equivalent Nb(1) atoms to form distorted MgSr2Mg8Nb2 cuboctahedra that share corners with four equivalent Mg(1)Mg12 cuboctahedra; corners with four equivalent Mg(2)Mg12 cuboctahedra; corners with four equivalent Mg(4)Mg12 cuboctahedra; corners with six Mg(3,3)Sr2Mg8Nb2 cuboctahedra; edges with two equivalent Sr(1)Mg10Nb2 cuboctahedra; edges with two equivalent Mg(3)Sr2Mg8Nb2 cuboctahedra; edges with two equivalent Nb(1)Sr2Mg10 cuboctahedra; edges with four equivalent Mg(7)Mg11Nb cuboctahedra; edges with four equivalent Mg(6)SrMg11 cuboctahedra; faces with two equivalent Sr(1)Mg10Nb2 cuboctahedra; faces with two equivalent Mg(7)Mg11Nb cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Mg(3)Sr2Mg8Nb2 cuboctahedra; faces with two equivalent Mg(6)SrMg11 cuboctahedra; and faces with two equivalent Nb(1)Sr2Mg10 cuboctahedra. In the fourth Mg site, Mg(4) is bonded to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(4), two equivalent Mg(5), two equivalent Mg(6), and two equivalent Mg(7) atoms to form MgMg12 cuboctahedra that share corners with four equivalent Sr(1)Mg10Nb2 cuboctahedra, corners with four equivalent Mg(3)Sr2Mg8Nb2 cuboctahedra, corners with four equivalent Nb(1)Sr2Mg10 cuboctahedra, corners with six equivalent Mg(4)Mg12 cuboctahedra, edges with two equivalent Mg(1)Mg12 cuboctahedra, edges with two equivalent Mg(2)Mg12 cuboctahedra, edges with two equivalent Mg(4)Mg12 cuboctahedra, edges with four equivalent Mg(7)Mg11Nb cuboctahedra, edges with four equivalent Mg(6)SrMg11 cuboctahedra, faces with two equivalent Mg(7)Mg11Nb cuboctahedra, faces with two equivalent Mg(1)Mg12 cuboctahedra, faces with two equivalent Mg(2)Mg12 cuboctahedra, faces with two equivalent Mg(4)Mg12 cuboctahedra, faces with two equivalent Mg(3)Sr2Mg8Nb2 cuboctahedra, and faces with two equivalent Mg(6)SrMg11 cuboctahedra. In the fifth Mg site, Mg(3) is bonded to two equivalent Sr(1), two equivalent Mg(3), two equivalent Mg(5), two equivalent Mg(6), two equivalent Mg(7), and two equivalent Nb(1) atoms to form distorted MgSr2Mg8Nb2 cuboctahedra that share corners with four equivalent Mg(1)Mg12 cuboctahedra; corners with four equivalent Mg(2)Mg12 cuboctahedra; corners with four equivalent Mg(4)Mg12 cuboctahedra; corners with six Mg(3,3)Sr2Mg8Nb2 cuboctahedra; edges with two equivalent Sr(1)Mg10Nb2 cuboctahedra; edges with two equivalent Mg(3)Sr2Mg8Nb2 cuboctahedra; edges with two equivalent Nb(1)Sr2Mg10 cuboctahedra; edges with four equivalent Mg(7)Mg11Nb cuboctahedra; edges with four equivalent Mg(6)SrMg11 cuboctahedra; faces with two equivalent Sr(1)Mg10Nb2 cuboctahedra; faces with two equivalent Mg(7)Mg11Nb cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Mg(3)Sr2Mg8Nb2 cuboctahedra; faces with two equivalent Mg(6)SrMg11 cuboctahedra; and faces with two equivalent Nb(1)Sr2Mg10 cuboctahedra. In the sixth Mg site, Mg(5) is bonded in a 12-coordinate geometry to one Sr(1), one Mg(1), one Mg(2), one Mg(3), one Mg(4), two equivalent Mg(5), two equivalent Mg(6), two equivalent Mg(7), and one Nb(1) atom. In the seventh Mg site, Mg(5) is bonded in a 12-coordinate geometry to one Sr(1), one Mg(1), one Mg(2), one Mg(3), one Mg(4), two equivalent Mg(5), two equivalent Mg(6), two equivalent Mg(7), and one Nb(1) atom. In the eighth Mg site, Mg(6) is bonded to one Sr(1); one Mg(1); two equivalent Mg(3); two equivalent Mg(4); two equivalent Mg(7); and four Mg(5,5) atoms to form distorted MgSrMg11 cuboctahedra that share corners with four equivalent Mg(7)Mg11Nb cuboctahedra; corners with six equivalent Mg(6)SrMg11 cuboctahedra; edges with two equivalent Sr(1)Mg10Nb2 cuboctahedra; edges with two equivalent Mg(7)Mg11Nb cuboctahedra; edges with two equivalent Mg(1)Mg12 cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; edges with four Mg(3,3)Sr2Mg8Nb2 cuboctahedra;  a faceface with one Sr(1)Mg10Nb2 cuboctahedra;  a faceface with one Mg(1)Mg12 cuboctahedra; faces with two equivalent Mg(7)Mg11Nb cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Mg(3)Sr2Mg8Nb2 cuboctahedra; faces with two equivalent Mg(6)SrMg11 cuboctahedra; faces with three equivalent Mg(2)Mg12 cuboctahedra; and faces with three equivalent Nb(1)Sr2Mg10 cuboctahedra. In the ninth Mg site, Mg(7) is bonded to one Mg(2); two equivalent Mg(3); two equivalent Mg(4); two equivalent Mg(6); four Mg(5,5); and one Nb(1) atom to form distorted MgMg11Nb cuboctahedra that share corners with four equivalent Mg(6)SrMg11 cuboctahedra; corners with six equivalent Mg(7)Mg11Nb cuboctahedra; edges with two equivalent Mg(2)Mg12 cuboctahedra; edges with two equivalent Mg(6)SrMg11 cuboctahedra; edges with two equivalent Nb(1)Sr2Mg10 cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; edges with four Mg(3,3)Sr2Mg8Nb2 cuboctahedra;  a faceface with one Mg(2)Mg12 cuboctahedra;  a faceface with one Nb(1)Sr2Mg10 cuboctahedra; faces with two equivalent Mg(7)Mg11Nb cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Mg(3)Sr2Mg8Nb2 cuboctahedra; faces with two equivalent Mg(6)SrMg11 cuboctahedra; faces with three equivalent Sr(1)Mg10Nb2 cuboctahedra; and faces with three equivalent Mg(1)Mg12 cuboctahedra. Nb(1) is bonded to two equivalent Sr(1); two equivalent Mg(7); four Mg(3,3); and four Mg(5,5) atoms to form NbSr2Mg10 cuboctahedra that share corners with four equivalent Mg(1)Mg12 cuboctahedra; corners with six equivalent Nb(1)Sr2Mg10 cuboctahedra; corners with eight equivalent Mg(4)Mg12 cuboctahedra; edges with two equivalent Sr(1)Mg10Nb2 cuboctahedra; edges with four equivalent Mg(7)Mg11Nb cuboctahedra; edges with four Mg(3,3)Sr2Mg8Nb2 cuboctahedra; faces with two equivalent Sr(1)Mg10Nb2 cuboctahedra; faces with two equivalent Mg(7)Mg11Nb cuboctahedra; faces with two equivalent Mg(2)Mg12 cuboctahedra; faces with four Mg(3,3)Sr2Mg8Nb2 cuboctahedra; and faces with six equivalent Mg(6)SrMg11 cuboctahedra.
SrMg14Nb crystallizes in the orthorhombic Amm2 space group. Sr(1) is bonded to two equivalent Mg(6); four Mg(3,3); four Mg(5,5); and two equivalent Nb(1) atoms to form SrMg10Nb2 cuboctahedra that share corners with four equivalent Mg(2)Mg12 cuboctahedra; corners with six equivalent Sr(1)Mg10Nb2 cuboctahedra; corners with eight equivalent Mg(4)Mg12 cuboctahedra; edges with two equivalent Nb(1)Sr2Mg10 cuboctahedra; edges with four Mg(3,3)Sr2Mg8Nb2 cuboctahedra; edges with four equivalent Mg(6)SrMg11 cuboctahedra; faces with two equivalent Mg(1)Mg12 cuboctahedra; faces with two equivalent Mg(6)SrMg11 cuboctahedra; faces with two equivalent Nb(1)Sr2Mg10 cuboctahedra; faces with four Mg(3,3)Sr2Mg8Nb2 cuboctahedra; and faces with six equivalent Mg(7)Mg11Nb cuboctahedra. Both Sr(1)-Mg(6) bond lengths are 3.33 Å. There are two shorter (3.26 Å) and two longer (3.27 Å) Sr(1)-Mg(3,3) bond lengths. All Sr(1)-Mg(5,5) bond lengths are 3.30 Å. Both Sr(1)-Nb(1) bond lengths are 3.27 Å. There are nine inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(2); two equivalent Mg(6); four equivalent Mg(4); and four Mg(5,5) atoms to form MgMg12 cuboctahedra that share corners with four equivalent Nb(1)Sr2Mg10 cuboctahedra; corners with six equivalent Mg(1)Mg12 cuboctahedra; corners with eight Mg(3,3)Sr2Mg8Nb2 cuboctahedra; edges with two equivalent Mg(2)Mg12 cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; edges with four equivalent Mg(6)SrMg11 cuboctahedra; faces with two equivalent Sr(1)Mg10Nb2 cuboctahedra; faces with two equivalent Mg(2)Mg12 cuboctahedra; faces with two equivalent Mg(6)SrMg11 cuboctahedra; faces with four equivalent Mg(4)Mg12 cuboctahedra; and faces with six equivalent Mg(7)Mg11Nb cuboctahedra. Both Mg(1)-Mg(2) bond lengths are 3.27 Å. Both Mg(1)-Mg(6) bond lengths are 3.14 Å. There are two shorter (3.24 Å) and two longer (3.28 Å) Mg(1)-Mg(4) bond lengths. All Mg(1)-Mg(5,5) bond lengths are 3.21 Å. In the second Mg site, Mg(2) is bonded to two equivalent Mg(1); two equivalent Mg(7); four equivalent Mg(4); and four Mg(5,5) atoms to form MgMg12 cuboctahedra that share corners with four equivalent Sr(1)Mg10Nb2 cuboctahedra; corners with six equivalent Mg(2)Mg12 cuboctahedra; corners with eight Mg(3,3)Sr2Mg8Nb2 cuboctahedra; edges with two equivalent Mg(1)Mg12 cuboctahedra; edges with four equivalent Mg(7)Mg11Nb cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Mg(7)Mg11Nb cuboctahedra; faces with two equivalent Mg(1)Mg12 cuboctahedra; faces with two equivalent Nb(1)Sr2Mg10 cuboctahedra; faces with four equivalent Mg(4)Mg12 cuboctahedra; and faces with six equivalent Mg(6)SrMg11 cuboctahedra. Both Mg(2)-Mg(7) bond lengths are 3.24 Å. There are two shorter (3.25 Å) and two longer (3.28 Å) Mg(2)-Mg(4) bond lengths. All Mg(2)-Mg(5,5) bond lengths are 3.12 Å. In the third Mg site, Mg(3) is bonded to two equivalent Sr(1), two equivalent Mg(3), two equivalent Mg(5), two equivalent Mg(6), two equivalent Mg(7), and two equivalent Nb(1) atoms to form distorted MgSr2Mg8Nb2 cuboctahedra that share corners with four equivalent Mg(1)Mg12 cuboctahedra; corners with four equivalent Mg(2)Mg12 cuboctahedra; corners with four equivalent Mg(4)Mg12 cuboctahedra; corners with six Mg(3,3)Sr2Mg8Nb2 cuboctahedra; edges with two equivalent Sr(1)Mg10Nb2 cuboctahedra; edges with two equivalent Mg(3)Sr2Mg8Nb2 cuboctahedra; edges with two equivalent Nb(1)Sr2Mg10 cuboctahedra; edges with four equivalent Mg(7)Mg11Nb cuboctahedra; edges with four equivalent Mg(6)SrMg11 cuboctahedra; faces with two equivalent Sr(1)Mg10Nb2 cuboctahedra; faces with two equivalent Mg(7)Mg11Nb cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Mg(3)Sr2Mg8Nb2 cuboctahedra; faces with two equivalent Mg(6)SrMg11 cuboctahedra; and faces with two equivalent Nb(1)Sr2Mg10 cuboctahedra. There is one shorter (3.23 Å) and one longer (3.31 Å) Mg(3)-Mg(3) bond length. Both Mg(3)-Mg(5) bond lengths are 3.23 Å. Both Mg(3)-Mg(6) bond lengths are 3.28 Å. Both Mg(3)-Mg(7) bond lengths are 3.16 Å. There is one shorter (3.15 Å) and one longer (3.37 Å) Mg(3)-Nb(1) bond length. In the fourth Mg site, Mg(4) is bonded to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(4), two equivalent Mg(5), two equivalent Mg(6), and two equivalent Mg(7) atoms to form MgMg12 cuboctahedra that share corners with four equivalent Sr(1)Mg10Nb2 cuboctahedra, corners with four equivalent Mg(3)Sr2Mg8Nb2 cuboctahedra, corners with four equivalent Nb(1)Sr2Mg10 cuboctahedra, corners with six equivalent Mg(4)Mg12 cuboctahedra, edges with two equivalent Mg(1)Mg12 cuboctahedra, edges with two equivalent Mg(2)Mg12 cuboctahedra, edges with two equivalent Mg(4)Mg12 cuboctahedra, edges with four equivalent Mg(7)Mg11Nb cuboctahedra, edges with four equivalent Mg(6)SrMg11 cuboctahedra, faces with two equivalent Mg(7)Mg11Nb cuboctahedra, faces with two equivalent Mg(1)Mg12 cuboctahedra, faces with two equivalent Mg(2)Mg12 cuboctahedra, faces with two equivalent Mg(4)Mg12 cuboctahedra, faces with two equivalent Mg(3)Sr2Mg8Nb2 cuboctahedra, and faces with two equivalent Mg(6)SrMg11 cuboctahedra. There is one shorter (3.23 Å) and one longer (3.31 Å) Mg(4)-Mg(4) bond length. Both Mg(4)-Mg(5) bond lengths are 3.16 Å. Both Mg(4)-Mg(6) bond lengths are 3.10 Å. Both Mg(4)-Mg(7) bond lengths are 3.29 Å. In the fifth Mg site, Mg(3) is bonded to two equivalent Sr(1), two equivalent Mg(3), two equivalent Mg(5), two equivalent Mg(6), two equivalent Mg(7), and two equivalent Nb(1) atoms to form distorted MgSr2Mg8Nb2 cuboctahedra that share corners with four equivalent Mg(1)Mg12 cuboctahedra; corners with four equivalent Mg(2)Mg12 cuboctahedra; corners with four equivalent Mg(4)Mg12 cuboctahedra; corners with six Mg(3,3)Sr2Mg8Nb2 cuboctahedra; edges with two equivalent Sr(1)Mg10Nb2 cuboctahedra; edges with two equivalent Mg(3)Sr2Mg8Nb2 cuboctahedra; edges with two equivalent Nb(1)Sr2Mg10 cuboctahedra; edges with four equivalent Mg(7)Mg11Nb cuboctahedra; edges with four equivalent Mg(6)SrMg11 cuboctahedra; faces with two equivalent Sr(1)Mg10Nb2 cuboctahedra; faces with two equivalent Mg(7)Mg11Nb cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Mg(3)Sr2Mg8Nb2 cuboctahedra; faces with two equivalent Mg(6)SrMg11 cuboctahedra; and faces with two equivalent Nb(1)Sr2Mg10 cuboctahedra. There is one shorter (3.23 Å) and one longer (3.31 Å) Mg(3)-Mg(3) bond length. Both Mg(3)-Mg(5) bond lengths are 3.23 Å. Both Mg(3)-Mg(6) bond lengths are 3.28 Å. Both Mg(3)-Mg(7) bond lengths are 3.16 Å. There is one shorter (3.15 Å) and one longer (3.37 Å) Mg(3)-Nb(1) bond length. In the sixth Mg site, Mg(5) is bonded in a 12-coordinate geometry to one Sr(1), one Mg(1), one Mg(2), one Mg(3), one Mg(4), two equivalent Mg(5), two equivalent Mg(6), two equivalent Mg(7), and one Nb(1) atom. There is one shorter (3.08 Å) and one longer (3.46 Å) Mg(5)-Mg(5) bond length. There is one shorter (3.16 Å) and one longer (3.37 Å) Mg(5)-Mg(6) bond length. There is one shorter (3.18 Å) and one longer (3.36 Å) Mg(5)-Mg(7) bond length. The Mg(5)-Nb(1) bond length is 3.17 Å. In the seventh Mg site, Mg(5) is bonded in a 12-coordinate geometry to one Sr(1), one Mg(1), one Mg(2), one Mg(3), one Mg(4), two equivalent Mg(5), two equivalent Mg(6), two equivalent Mg(7), and one Nb(1) atom. The Mg(5)-Mg(4) bond length is 3.16 Å. There is one shorter (3.16 Å) and one longer (3.37 Å) Mg(5)-Mg(6) bond length. There is one shorter (3.18 Å) and one longer (3.36 Å) Mg(5)-Mg(7) bond length. The Mg(5)-Nb(1) bond length is 3.17 Å. In the eighth Mg site, Mg(6) is bonded to one Sr(1); one Mg(1); two equivalent Mg(3); two equivalent Mg(4); two equivalent Mg(7); and four Mg(5,5) atoms to form distorted MgSrMg11 cuboctahedra that share corners with four equivalent Mg(7)Mg11Nb cuboctahedra; corners with six equivalent Mg(6)SrMg11 cuboctahedra; edges with two equivalent Sr(1)Mg10Nb2 cuboctahedra; edges with two equivalent Mg(7)Mg11Nb cuboctahedra; edges with two equivalent Mg(1)Mg12 cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; edges with four Mg(3,3)Sr2Mg8Nb2 cuboctahedra;  a faceface with one Sr(1)Mg10Nb2 cuboctahedra;  a faceface with one Mg(1)Mg12 cuboctahedra; faces with two equivalent Mg(7)Mg11Nb cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Mg(3)Sr2Mg8Nb2 cuboctahedra; faces with two equivalent Mg(6)SrMg11 cuboctahedra; faces with three equivalent Mg(2)Mg12 cuboctahedra; and faces with three equivalent Nb(1)Sr2Mg10 cuboctahedra. Both Mg(6)-Mg(7) bond lengths are 3.28 Å. In the ninth Mg site, Mg(7) is bonded to one Mg(2); two equivalent Mg(3); two equivalent Mg(4); two equivalent Mg(6); four Mg(5,5); and one Nb(1) atom to form distorted MgMg11Nb cuboctahedra that share corners with four equivalent Mg(6)SrMg11 cuboctahedra; corners with six equivalent Mg(7)Mg11Nb cuboctahedra; edges with two equivalent Mg(2)Mg12 cuboctahedra; edges with two equivalent Mg(6)SrMg11 cuboctahedra; edges with two equivalent Nb(1)Sr2Mg10 cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; edges with four Mg(3,3)Sr2Mg8Nb2 cuboctahedra;  a faceface with one Mg(2)Mg12 cuboctahedra;  a faceface with one Nb(1)Sr2Mg10 cuboctahedra; faces with two equivalent Mg(7)Mg11Nb cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Mg(3)Sr2Mg8Nb2 cuboctahedra; faces with two equivalent Mg(6)SrMg11 cuboctahedra; faces with three equivalent Sr(1)Mg10Nb2 cuboctahedra; and faces with three equivalent Mg(1)Mg12 cuboctahedra. The Mg(7)-Nb(1) bond length is 3.14 Å. Nb(1) is bonded to two equivalent Sr(1); two equivalent Mg(7); four Mg(3,3); and four Mg(5,5) atoms to form NbSr2Mg10 cuboctahedra that share corners with four equivalent Mg(1)Mg12 cuboctahedra; corners with six equivalent Nb(1)Sr2Mg10 cuboctahedra; corners with eight equivalent Mg(4)Mg12 cuboctahedra; edges with two equivalent Sr(1)Mg10Nb2 cuboctahedra; edges with four equivalent Mg(7)Mg11Nb cuboctahedra; edges with four Mg(3,3)Sr2Mg8Nb2 cuboctahedra; faces with two equivalent Sr(1)Mg10Nb2 cuboctahedra; faces with two equivalent Mg(7)Mg11Nb cuboctahedra; faces with two equivalent Mg(2)Mg12 cuboctahedra; faces with four Mg(3,3)Sr2Mg8Nb2 cuboctahedra; and faces with six equivalent Mg(6)SrMg11 cuboctahedra.