Mg14NbBi crystallizes in the orthorhombic Amm2 space group. 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 Bi(1)Mg10Nb2 cuboctahedra; corners with six equivalent Mg(1)Mg12 cuboctahedra; corners with eight Mg(3,3)Mg8Nb2Bi2 cuboctahedra; edges with two equivalent Mg(2)Mg12 cuboctahedra; edges with four equivalent Mg(6)Mg11Nb cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; edges with eight Mg(5,5)Mg10NbBi cuboctahedra; faces with two equivalent Mg(6)Mg11Nb cuboctahedra; faces with two equivalent Mg(2)Mg12 cuboctahedra; faces with two equivalent Nb(1)Mg10Bi2 cuboctahedra; faces with four Mg(5,5)Mg10NbBi cuboctahedra; faces with four equivalent Mg(4)Mg12 cuboctahedra; and faces with six equivalent Mg(7)Mg11Bi 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 Nb(1)Mg10Bi2 cuboctahedra; corners with six equivalent Mg(2)Mg12 cuboctahedra; corners with eight Mg(3,3)Mg8Nb2Bi2 cuboctahedra; edges with two equivalent Mg(1)Mg12 cuboctahedra; edges with four equivalent Mg(7)Mg11Bi cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; edges with eight Mg(5,5)Mg10NbBi cuboctahedra; faces with two equivalent Mg(7)Mg11Bi cuboctahedra; faces with two equivalent Mg(1)Mg12 cuboctahedra; faces with two equivalent Bi(1)Mg10Nb2 cuboctahedra; faces with four Mg(5,5)Mg10NbBi cuboctahedra; faces with four equivalent Mg(4)Mg12 cuboctahedra; and faces with six equivalent Mg(6)Mg11Nb cuboctahedra. In the third Mg site, Mg(3) is bonded to two equivalent Mg(3), two equivalent Mg(5), two equivalent Mg(6), two equivalent Mg(7), two equivalent Nb(1), and two equivalent Bi(1) atoms to form distorted MgMg8Nb2Bi2 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 equivalent Mg(3)Mg8Nb2Bi2 cuboctahedra; edges with two equivalent Mg(3)Mg8Nb2Bi2 cuboctahedra; edges with two equivalent Nb(1)Mg10Bi2 cuboctahedra; edges with two equivalent Bi(1)Mg10Nb2 cuboctahedra; edges with four Mg(5,5)Mg10NbBi cuboctahedra; edges with four equivalent Mg(7)Mg11Bi cuboctahedra; edges with four equivalent Mg(6)Mg11Nb cuboctahedra; faces with two equivalent Mg(7)Mg11Bi cuboctahedra; faces with two equivalent Mg(6)Mg11Nb cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Mg(3)Mg8Nb2Bi2 cuboctahedra; faces with two equivalent Nb(1)Mg10Bi2 cuboctahedra; faces with two equivalent Bi(1)Mg10Nb2 cuboctahedra; and faces with eight Mg(5,5)Mg10NbBi 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 Mg(3)Mg8Nb2Bi2 cuboctahedra; corners with four equivalent Nb(1)Mg10Bi2 cuboctahedra; corners with four equivalent Bi(1)Mg10Nb2 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 Mg(5,5)Mg10NbBi cuboctahedra; edges with four equivalent Mg(7)Mg11Bi cuboctahedra; edges with four equivalent Mg(6)Mg11Nb cuboctahedra; faces with two equivalent Mg(7)Mg11Bi cuboctahedra; faces with two equivalent Mg(6)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)Mg8Nb2Bi2 cuboctahedra; and faces with eight Mg(5,5)Mg10NbBi cuboctahedra. In the fifth Mg site, Mg(3) is bonded to two equivalent Mg(3); two Mg(5,5); two equivalent Mg(6); two equivalent Mg(7); two equivalent Nb(1); and two equivalent Bi(1) atoms to form distorted MgMg8Nb2Bi2 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)Mg8Nb2Bi2 cuboctahedra; edges with two equivalent Mg(3)Mg8Nb2Bi2 cuboctahedra; edges with two equivalent Nb(1)Mg10Bi2 cuboctahedra; edges with two equivalent Bi(1)Mg10Nb2 cuboctahedra; edges with four equivalent Mg(5)Mg10NbBi cuboctahedra; edges with four equivalent Mg(7)Mg11Bi cuboctahedra; edges with four equivalent Mg(6)Mg11Nb cuboctahedra; faces with two equivalent Mg(7)Mg11Bi cuboctahedra; faces with two equivalent Mg(6)Mg11Nb cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Mg(3)Mg8Nb2Bi2 cuboctahedra; faces with two equivalent Nb(1)Mg10Bi2 cuboctahedra; faces with two equivalent Bi(1)Mg10Nb2 cuboctahedra; and faces with eight Mg(5,5)Mg10NbBi cuboctahedra. In the sixth Mg site, Mg(5) is bonded to one Mg(1), one Mg(2), one Mg(3), one Mg(4), two equivalent Mg(5), two equivalent Mg(6), two equivalent Mg(7), one Nb(1), and one Bi(1) atom to form distorted MgMg10NbBi cuboctahedra that share corners with four equivalent Mg(7)Mg11Bi cuboctahedra; corners with four equivalent Mg(6)Mg11Nb cuboctahedra; corners with ten equivalent Mg(5)Mg10NbBi cuboctahedra; edges with two equivalent Mg(5)Mg10NbBi cuboctahedra; edges with two equivalent Mg(7)Mg11Bi cuboctahedra; edges with two equivalent Mg(6)Mg11Nb 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 two equivalent Mg(3)Mg8Nb2Bi2 cuboctahedra; edges with two equivalent Nb(1)Mg10Bi2 cuboctahedra; edges with two equivalent Bi(1)Mg10Nb2 cuboctahedra;  a faceface with one Mg(1)Mg12 cuboctahedra;  a faceface with one Mg(2)Mg12 cuboctahedra;  a faceface with one Nb(1)Mg10Bi2 cuboctahedra;  a faceface with one Bi(1)Mg10Nb2 cuboctahedra; faces with two equivalent Mg(7)Mg11Bi cuboctahedra; faces with two equivalent Mg(6)Mg11Nb cuboctahedra; faces with four Mg(5,5)Mg10NbBi cuboctahedra; faces with four equivalent Mg(4)Mg12 cuboctahedra; and faces with four Mg(3,3)Mg8Nb2Bi2 cuboctahedra. In the seventh Mg site, Mg(5) is bonded to one Mg(1), one Mg(2), one Mg(3), one Mg(4), two equivalent Mg(5), two equivalent Mg(6), two equivalent Mg(7), one Nb(1), and one Bi(1) atom to form distorted MgMg10NbBi cuboctahedra that share corners with four equivalent Mg(7)Mg11Bi cuboctahedra; corners with four equivalent Mg(6)Mg11Nb cuboctahedra; corners with ten Mg(5,5)Mg10NbBi cuboctahedra; edges with two equivalent Mg(5)Mg10NbBi cuboctahedra; edges with two equivalent Mg(7)Mg11Bi cuboctahedra; edges with two equivalent Mg(6)Mg11Nb 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 two equivalent Mg(3)Mg8Nb2Bi2 cuboctahedra; edges with two equivalent Nb(1)Mg10Bi2 cuboctahedra; edges with two equivalent Bi(1)Mg10Nb2 cuboctahedra;  a faceface with one Mg(1)Mg12 cuboctahedra;  a faceface with one Mg(2)Mg12 cuboctahedra;  a faceface with one Nb(1)Mg10Bi2 cuboctahedra;  a faceface with one Bi(1)Mg10Nb2 cuboctahedra; faces with two equivalent Mg(7)Mg11Bi cuboctahedra; faces with two equivalent Mg(6)Mg11Nb cuboctahedra; faces with four equivalent Mg(5)Mg10NbBi cuboctahedra; faces with four equivalent Mg(4)Mg12 cuboctahedra; and faces with four Mg(3,3)Mg8Nb2Bi2 cuboctahedra. In the eighth Mg site, Mg(6) is bonded to one Mg(1); two Mg(3,3); two equivalent Mg(4); two equivalent Mg(7); four Mg(5,5); and one Nb(1) atom to form distorted MgMg11Nb cuboctahedra that share corners with four equivalent Mg(7)Mg11Bi cuboctahedra; corners with six equivalent Mg(6)Mg11Nb cuboctahedra; corners with eight Mg(5,5)Mg10NbBi cuboctahedra; edges with two equivalent Mg(7)Mg11Bi cuboctahedra; edges with two equivalent Mg(1)Mg12 cuboctahedra; edges with two equivalent Nb(1)Mg10Bi2 cuboctahedra; edges with four Mg(5,5)Mg10NbBi cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; edges with four Mg(3,3)Mg8Nb2Bi2 cuboctahedra;  a faceface with one Mg(1)Mg12 cuboctahedra;  a faceface with one Nb(1)Mg10Bi2 cuboctahedra; faces with two equivalent Mg(7)Mg11Bi cuboctahedra; faces with two equivalent Mg(6)Mg11Nb cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two Mg(3,3)Mg8Nb2Bi2 cuboctahedra; faces with three equivalent Mg(2)Mg12 cuboctahedra; faces with three equivalent Bi(1)Mg10Nb2 cuboctahedra; and faces with four Mg(5,5)Mg10NbBi cuboctahedra. In the ninth Mg site, Mg(7) is bonded to one Mg(2); two Mg(3,3); two equivalent Mg(4); two equivalent Mg(6); four Mg(5,5); and one Bi(1) atom to form distorted MgMg11Bi cuboctahedra that share corners with four equivalent Mg(6)Mg11Nb cuboctahedra; corners with six equivalent Mg(7)Mg11Bi cuboctahedra; corners with eight Mg(5,5)Mg10NbBi cuboctahedra; edges with two equivalent Mg(6)Mg11Nb cuboctahedra; edges with two equivalent Mg(2)Mg12 cuboctahedra; edges with two equivalent Bi(1)Mg10Nb2 cuboctahedra; edges with four Mg(5,5)Mg10NbBi cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; edges with four Mg(3,3)Mg8Nb2Bi2 cuboctahedra;  a faceface with one Mg(2)Mg12 cuboctahedra;  a faceface with one Bi(1)Mg10Nb2 cuboctahedra; faces with two equivalent Mg(7)Mg11Bi cuboctahedra; faces with two equivalent Mg(6)Mg11Nb cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two Mg(3,3)Mg8Nb2Bi2 cuboctahedra; faces with three equivalent Mg(1)Mg12 cuboctahedra; faces with three equivalent Nb(1)Mg10Bi2 cuboctahedra; and faces with four Mg(5,5)Mg10NbBi cuboctahedra. Nb(1) is bonded to two equivalent Mg(6); four Mg(3,3); four Mg(5,5); and two equivalent Bi(1) atoms to form NbMg10Bi2 cuboctahedra that share corners with four equivalent Mg(2)Mg12 cuboctahedra; corners with six equivalent Nb(1)Mg10Bi2 cuboctahedra; corners with eight equivalent Mg(4)Mg12 cuboctahedra; edges with two equivalent Bi(1)Mg10Nb2 cuboctahedra; edges with four equivalent Mg(6)Mg11Nb cuboctahedra; edges with four Mg(3,3)Mg8Nb2Bi2 cuboctahedra; edges with eight Mg(5,5)Mg10NbBi cuboctahedra; faces with two equivalent Mg(6)Mg11Nb cuboctahedra; faces with two equivalent Mg(1)Mg12 cuboctahedra; faces with two equivalent Bi(1)Mg10Nb2 cuboctahedra; faces with four Mg(5,5)Mg10NbBi cuboctahedra; faces with four Mg(3,3)Mg8Nb2Bi2 cuboctahedra; and faces with six equivalent Mg(7)Mg11Bi cuboctahedra. Bi(1) is bonded to two equivalent Mg(7); four Mg(3,3); four Mg(5,5); and two equivalent Nb(1) atoms to form BiMg10Nb2 cuboctahedra that share corners with four equivalent Mg(1)Mg12 cuboctahedra; corners with six equivalent Bi(1)Mg10Nb2 cuboctahedra; corners with eight equivalent Mg(4)Mg12 cuboctahedra; edges with two equivalent Nb(1)Mg10Bi2 cuboctahedra; edges with four equivalent Mg(7)Mg11Bi cuboctahedra; edges with four Mg(3,3)Mg8Nb2Bi2 cuboctahedra; edges with eight Mg(5,5)Mg10NbBi cuboctahedra; faces with two equivalent Mg(7)Mg11Bi cuboctahedra; faces with two equivalent Mg(2)Mg12 cuboctahedra; faces with two equivalent Nb(1)Mg10Bi2 cuboctahedra; faces with four Mg(5,5)Mg10NbBi cuboctahedra; faces with four Mg(3,3)Mg8Nb2Bi2 cuboctahedra; and faces with six equivalent Mg(6)Mg11Nb cuboctahedra.
Mg14NbBi crystallizes in the orthorhombic Amm2 space group. 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 Bi(1)Mg10Nb2 cuboctahedra; corners with six equivalent Mg(1)Mg12 cuboctahedra; corners with eight Mg(3,3)Mg8Nb2Bi2 cuboctahedra; edges with two equivalent Mg(2)Mg12 cuboctahedra; edges with four equivalent Mg(6)Mg11Nb cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; edges with eight Mg(5,5)Mg10NbBi cuboctahedra; faces with two equivalent Mg(6)Mg11Nb cuboctahedra; faces with two equivalent Mg(2)Mg12 cuboctahedra; faces with two equivalent Nb(1)Mg10Bi2 cuboctahedra; faces with four Mg(5,5)Mg10NbBi cuboctahedra; faces with four equivalent Mg(4)Mg12 cuboctahedra; and faces with six equivalent Mg(7)Mg11Bi cuboctahedra. Both Mg(1)-Mg(2) bond lengths are 3.16 Å. Both Mg(1)-Mg(6) bond lengths are 3.17 Å. There are two shorter (3.18 Å) and two longer (3.19 Å) Mg(1)-Mg(4) bond lengths. All Mg(1)-Mg(5,5) bond lengths are 3.14 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 Nb(1)Mg10Bi2 cuboctahedra; corners with six equivalent Mg(2)Mg12 cuboctahedra; corners with eight Mg(3,3)Mg8Nb2Bi2 cuboctahedra; edges with two equivalent Mg(1)Mg12 cuboctahedra; edges with four equivalent Mg(7)Mg11Bi cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; edges with eight Mg(5,5)Mg10NbBi cuboctahedra; faces with two equivalent Mg(7)Mg11Bi cuboctahedra; faces with two equivalent Mg(1)Mg12 cuboctahedra; faces with two equivalent Bi(1)Mg10Nb2 cuboctahedra; faces with four Mg(5,5)Mg10NbBi cuboctahedra; faces with four equivalent Mg(4)Mg12 cuboctahedra; and faces with six equivalent Mg(6)Mg11Nb cuboctahedra. Both Mg(2)-Mg(7) bond lengths are 3.15 Å. There are two shorter (3.18 Å) and two longer (3.19 Å) Mg(2)-Mg(4) bond lengths. All Mg(2)-Mg(5,5) bond lengths are 3.18 Å. In the third Mg site, Mg(3) is bonded to two equivalent Mg(3), two equivalent Mg(5), two equivalent Mg(6), two equivalent Mg(7), two equivalent Nb(1), and two equivalent Bi(1) atoms to form distorted MgMg8Nb2Bi2 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 equivalent Mg(3)Mg8Nb2Bi2 cuboctahedra; edges with two equivalent Mg(3)Mg8Nb2Bi2 cuboctahedra; edges with two equivalent Nb(1)Mg10Bi2 cuboctahedra; edges with two equivalent Bi(1)Mg10Nb2 cuboctahedra; edges with four Mg(5,5)Mg10NbBi cuboctahedra; edges with four equivalent Mg(7)Mg11Bi cuboctahedra; edges with four equivalent Mg(6)Mg11Nb cuboctahedra; faces with two equivalent Mg(7)Mg11Bi cuboctahedra; faces with two equivalent Mg(6)Mg11Nb cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Mg(3)Mg8Nb2Bi2 cuboctahedra; faces with two equivalent Nb(1)Mg10Bi2 cuboctahedra; faces with two equivalent Bi(1)Mg10Nb2 cuboctahedra; and faces with eight Mg(5,5)Mg10NbBi cuboctahedra. There is one shorter (3.14 Å) and one longer (3.18 Å) Mg(3)-Mg(3) bond length. Both Mg(3)-Mg(5) bond lengths are 3.17 Å. Both Mg(3)-Mg(6) bond lengths are 3.14 Å. Both Mg(3)-Mg(7) bond lengths are 3.20 Å. There is one shorter (3.17 Å) and one longer (3.20 Å) Mg(3)-Nb(1) bond length. There is one shorter (3.15 Å) and one longer (3.22 Å) Mg(3)-Bi(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 Mg(3)Mg8Nb2Bi2 cuboctahedra; corners with four equivalent Nb(1)Mg10Bi2 cuboctahedra; corners with four equivalent Bi(1)Mg10Nb2 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 Mg(5,5)Mg10NbBi cuboctahedra; edges with four equivalent Mg(7)Mg11Bi cuboctahedra; edges with four equivalent Mg(6)Mg11Nb cuboctahedra; faces with two equivalent Mg(7)Mg11Bi cuboctahedra; faces with two equivalent Mg(6)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)Mg8Nb2Bi2 cuboctahedra; and faces with eight Mg(5,5)Mg10NbBi cuboctahedra. There is one shorter (3.15 Å) and one longer (3.17 Å) Mg(4)-Mg(4) bond length. Both Mg(4)-Mg(5) bond lengths are 3.17 Å. Both Mg(4)-Mg(6) bond lengths are 3.20 Å. Both Mg(4)-Mg(7) bond lengths are 3.11 Å. In the fifth Mg site, Mg(3) is bonded to two equivalent Mg(3); two Mg(5,5); two equivalent Mg(6); two equivalent Mg(7); two equivalent Nb(1); and two equivalent Bi(1) atoms to form distorted MgMg8Nb2Bi2 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)Mg8Nb2Bi2 cuboctahedra; edges with two equivalent Mg(3)Mg8Nb2Bi2 cuboctahedra; edges with two equivalent Nb(1)Mg10Bi2 cuboctahedra; edges with two equivalent Bi(1)Mg10Nb2 cuboctahedra; edges with four equivalent Mg(5)Mg10NbBi cuboctahedra; edges with four equivalent Mg(7)Mg11Bi cuboctahedra; edges with four equivalent Mg(6)Mg11Nb cuboctahedra; faces with two equivalent Mg(7)Mg11Bi cuboctahedra; faces with two equivalent Mg(6)Mg11Nb cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Mg(3)Mg8Nb2Bi2 cuboctahedra; faces with two equivalent Nb(1)Mg10Bi2 cuboctahedra; faces with two equivalent Bi(1)Mg10Nb2 cuboctahedra; and faces with eight Mg(5,5)Mg10NbBi cuboctahedra. Both Mg(3)-Mg(5,5) bond lengths are 3.17 Å. Both Mg(3)-Mg(6) bond lengths are 3.14 Å. Both Mg(3)-Mg(7) bond lengths are 3.20 Å. There is one shorter (3.17 Å) and one longer (3.20 Å) Mg(3)-Nb(1) bond length. There is one shorter (3.15 Å) and one longer (3.22 Å) Mg(3)-Bi(1) bond length. In the sixth Mg site, Mg(5) is bonded to one Mg(1), one Mg(2), one Mg(3), one Mg(4), two equivalent Mg(5), two equivalent Mg(6), two equivalent Mg(7), one Nb(1), and one Bi(1) atom to form distorted MgMg10NbBi cuboctahedra that share corners with four equivalent Mg(7)Mg11Bi cuboctahedra; corners with four equivalent Mg(6)Mg11Nb cuboctahedra; corners with ten equivalent Mg(5)Mg10NbBi cuboctahedra; edges with two equivalent Mg(5)Mg10NbBi cuboctahedra; edges with two equivalent Mg(7)Mg11Bi cuboctahedra; edges with two equivalent Mg(6)Mg11Nb 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 two equivalent Mg(3)Mg8Nb2Bi2 cuboctahedra; edges with two equivalent Nb(1)Mg10Bi2 cuboctahedra; edges with two equivalent Bi(1)Mg10Nb2 cuboctahedra;  a faceface with one Mg(1)Mg12 cuboctahedra;  a faceface with one Mg(2)Mg12 cuboctahedra;  a faceface with one Nb(1)Mg10Bi2 cuboctahedra;  a faceface with one Bi(1)Mg10Nb2 cuboctahedra; faces with two equivalent Mg(7)Mg11Bi cuboctahedra; faces with two equivalent Mg(6)Mg11Nb cuboctahedra; faces with four Mg(5,5)Mg10NbBi cuboctahedra; faces with four equivalent Mg(4)Mg12 cuboctahedra; and faces with four Mg(3,3)Mg8Nb2Bi2 cuboctahedra. There is one shorter (3.07 Å) and one longer (3.25 Å) Mg(5)-Mg(5) bond length. There is one shorter (3.13 Å) and one longer (3.24 Å) Mg(5)-Mg(6) bond length. There is one shorter (3.14 Å) and one longer (3.23 Å) Mg(5)-Mg(7) bond length. The Mg(5)-Nb(1) bond length is 3.13 Å. The Mg(5)-Bi(1) bond length is 3.19 Å. In the seventh Mg site, Mg(5) is bonded to one Mg(1), one Mg(2), one Mg(3), one Mg(4), two equivalent Mg(5), two equivalent Mg(6), two equivalent Mg(7), one Nb(1), and one Bi(1) atom to form distorted MgMg10NbBi cuboctahedra that share corners with four equivalent Mg(7)Mg11Bi cuboctahedra; corners with four equivalent Mg(6)Mg11Nb cuboctahedra; corners with ten Mg(5,5)Mg10NbBi cuboctahedra; edges with two equivalent Mg(5)Mg10NbBi cuboctahedra; edges with two equivalent Mg(7)Mg11Bi cuboctahedra; edges with two equivalent Mg(6)Mg11Nb 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 two equivalent Mg(3)Mg8Nb2Bi2 cuboctahedra; edges with two equivalent Nb(1)Mg10Bi2 cuboctahedra; edges with two equivalent Bi(1)Mg10Nb2 cuboctahedra;  a faceface with one Mg(1)Mg12 cuboctahedra;  a faceface with one Mg(2)Mg12 cuboctahedra;  a faceface with one Nb(1)Mg10Bi2 cuboctahedra;  a faceface with one Bi(1)Mg10Nb2 cuboctahedra; faces with two equivalent Mg(7)Mg11Bi cuboctahedra; faces with two equivalent Mg(6)Mg11Nb cuboctahedra; faces with four equivalent Mg(5)Mg10NbBi cuboctahedra; faces with four equivalent Mg(4)Mg12 cuboctahedra; and faces with four Mg(3,3)Mg8Nb2Bi2 cuboctahedra. The Mg(5)-Mg(4) bond length is 3.17 Å. There is one shorter (3.13 Å) and one longer (3.24 Å) Mg(5)-Mg(6) bond length. There is one shorter (3.14 Å) and one longer (3.23 Å) Mg(5)-Mg(7) bond length. The Mg(5)-Nb(1) bond length is 3.13 Å. The Mg(5)-Bi(1) bond length is 3.19 Å. In the eighth Mg site, Mg(6) is bonded to one Mg(1); two Mg(3,3); two equivalent Mg(4); two equivalent Mg(7); four Mg(5,5); and one Nb(1) atom to form distorted MgMg11Nb cuboctahedra that share corners with four equivalent Mg(7)Mg11Bi cuboctahedra; corners with six equivalent Mg(6)Mg11Nb cuboctahedra; corners with eight Mg(5,5)Mg10NbBi cuboctahedra; edges with two equivalent Mg(7)Mg11Bi cuboctahedra; edges with two equivalent Mg(1)Mg12 cuboctahedra; edges with two equivalent Nb(1)Mg10Bi2 cuboctahedra; edges with four Mg(5,5)Mg10NbBi cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; edges with four Mg(3,3)Mg8Nb2Bi2 cuboctahedra;  a faceface with one Mg(1)Mg12 cuboctahedra;  a faceface with one Nb(1)Mg10Bi2 cuboctahedra; faces with two equivalent Mg(7)Mg11Bi cuboctahedra; faces with two equivalent Mg(6)Mg11Nb cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two Mg(3,3)Mg8Nb2Bi2 cuboctahedra; faces with three equivalent Mg(2)Mg12 cuboctahedra; faces with three equivalent Bi(1)Mg10Nb2 cuboctahedra; and faces with four Mg(5,5)Mg10NbBi cuboctahedra. Both Mg(6)-Mg(7) bond lengths are 3.16 Å. The Mg(6)-Nb(1) bond length is 3.14 Å. In the ninth Mg site, Mg(7) is bonded to one Mg(2); two Mg(3,3); two equivalent Mg(4); two equivalent Mg(6); four Mg(5,5); and one Bi(1) atom to form distorted MgMg11Bi cuboctahedra that share corners with four equivalent Mg(6)Mg11Nb cuboctahedra; corners with six equivalent Mg(7)Mg11Bi cuboctahedra; corners with eight Mg(5,5)Mg10NbBi cuboctahedra; edges with two equivalent Mg(6)Mg11Nb cuboctahedra; edges with two equivalent Mg(2)Mg12 cuboctahedra; edges with two equivalent Bi(1)Mg10Nb2 cuboctahedra; edges with four Mg(5,5)Mg10NbBi cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; edges with four Mg(3,3)Mg8Nb2Bi2 cuboctahedra;  a faceface with one Mg(2)Mg12 cuboctahedra;  a faceface with one Bi(1)Mg10Nb2 cuboctahedra; faces with two equivalent Mg(7)Mg11Bi cuboctahedra; faces with two equivalent Mg(6)Mg11Nb cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two Mg(3,3)Mg8Nb2Bi2 cuboctahedra; faces with three equivalent Mg(1)Mg12 cuboctahedra; faces with three equivalent Nb(1)Mg10Bi2 cuboctahedra; and faces with four Mg(5,5)Mg10NbBi cuboctahedra. The Mg(7)-Bi(1) bond length is 3.21 Å. Nb(1) is bonded to two equivalent Mg(6); four Mg(3,3); four Mg(5,5); and two equivalent Bi(1) atoms to form NbMg10Bi2 cuboctahedra that share corners with four equivalent Mg(2)Mg12 cuboctahedra; corners with six equivalent Nb(1)Mg10Bi2 cuboctahedra; corners with eight equivalent Mg(4)Mg12 cuboctahedra; edges with two equivalent Bi(1)Mg10Nb2 cuboctahedra; edges with four equivalent Mg(6)Mg11Nb cuboctahedra; edges with four Mg(3,3)Mg8Nb2Bi2 cuboctahedra; edges with eight Mg(5,5)Mg10NbBi cuboctahedra; faces with two equivalent Mg(6)Mg11Nb cuboctahedra; faces with two equivalent Mg(1)Mg12 cuboctahedra; faces with two equivalent Bi(1)Mg10Nb2 cuboctahedra; faces with four Mg(5,5)Mg10NbBi cuboctahedra; faces with four Mg(3,3)Mg8Nb2Bi2 cuboctahedra; and faces with six equivalent Mg(7)Mg11Bi cuboctahedra. Both Nb(1)-Bi(1) bond lengths are 3.16 Å. Bi(1) is bonded to two equivalent Mg(7); four Mg(3,3); four Mg(5,5); and two equivalent Nb(1) atoms to form BiMg10Nb2 cuboctahedra that share corners with four equivalent Mg(1)Mg12 cuboctahedra; corners with six equivalent Bi(1)Mg10Nb2 cuboctahedra; corners with eight equivalent Mg(4)Mg12 cuboctahedra; edges with two equivalent Nb(1)Mg10Bi2 cuboctahedra; edges with four equivalent Mg(7)Mg11Bi cuboctahedra; edges with four Mg(3,3)Mg8Nb2Bi2 cuboctahedra; edges with eight Mg(5,5)Mg10NbBi cuboctahedra; faces with two equivalent Mg(7)Mg11Bi cuboctahedra; faces with two equivalent Mg(2)Mg12 cuboctahedra; faces with two equivalent Nb(1)Mg10Bi2 cuboctahedra; faces with four Mg(5,5)Mg10NbBi cuboctahedra; faces with four Mg(3,3)Mg8Nb2Bi2 cuboctahedra; and faces with six equivalent Mg(6)Mg11Nb cuboctahedra.