Mg14ZrNb crystallizes in the orthorhombic Amm2 space group. There are seven 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 equivalent Mg(5) atoms to form MgMg12 cuboctahedra that share corners with four equivalent Nb(1)Mg10Zr2 cuboctahedra, corners with six equivalent Mg(1)Mg12 cuboctahedra, corners with eight equivalent Mg(3)Mg8Zr2Nb2 cuboctahedra, edges with two equivalent Mg(2)Mg12 cuboctahedra, edges with four equivalent Mg(6)Mg11Zr cuboctahedra, edges with four equivalent Mg(4)Mg12 cuboctahedra, edges with eight equivalent Mg(5)Mg10ZrNb cuboctahedra, faces with two equivalent Mg(6)Mg11Zr cuboctahedra, faces with two equivalent Mg(2)Mg12 cuboctahedra, faces with two equivalent Zr(1)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(5)Mg10ZrNb 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 equivalent Mg(5) atoms to form MgMg12 cuboctahedra that share corners with four equivalent Zr(1)Mg10Nb2 cuboctahedra, corners with six equivalent Mg(2)Mg12 cuboctahedra, corners with eight equivalent Mg(3)Mg8Zr2Nb2 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, edges with eight equivalent Mg(5)Mg10ZrNb cuboctahedra, faces with two equivalent Mg(7)Mg11Nb cuboctahedra, faces with two equivalent Mg(1)Mg12 cuboctahedra, faces with two equivalent Nb(1)Mg10Zr2 cuboctahedra, faces with four equivalent Mg(5)Mg10ZrNb cuboctahedra, faces with four equivalent Mg(4)Mg12 cuboctahedra, and faces with six equivalent Mg(6)Mg11Zr 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 Zr(1), and two equivalent Nb(1) atoms to form MgMg8Zr2Nb2 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)Mg8Zr2Nb2 cuboctahedra, edges with two equivalent Mg(3)Mg8Zr2Nb2 cuboctahedra, edges with two equivalent Zr(1)Mg10Nb2 cuboctahedra, edges with two equivalent Nb(1)Mg10Zr2 cuboctahedra, edges with four equivalent Mg(5)Mg10ZrNb cuboctahedra, edges with four equivalent Mg(7)Mg11Nb cuboctahedra, edges with four equivalent Mg(6)Mg11Zr cuboctahedra, faces with two equivalent Mg(7)Mg11Nb cuboctahedra, faces with two equivalent Mg(6)Mg11Zr cuboctahedra, faces with two equivalent Mg(4)Mg12 cuboctahedra, faces with two equivalent Mg(3)Mg8Zr2Nb2 cuboctahedra, faces with two equivalent Zr(1)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Zr2 cuboctahedra, and faces with eight equivalent Mg(5)Mg10ZrNb 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)Mg8Zr2Nb2 cuboctahedra, corners with four equivalent Zr(1)Mg10Nb2 cuboctahedra, corners with four equivalent Nb(1)Mg10Zr2 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(5)Mg10ZrNb cuboctahedra, edges with four equivalent Mg(7)Mg11Nb cuboctahedra, edges with four equivalent Mg(6)Mg11Zr cuboctahedra, faces with two equivalent Mg(7)Mg11Nb cuboctahedra, faces with two equivalent Mg(6)Mg11Zr 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)Mg8Zr2Nb2 cuboctahedra, and faces with eight equivalent Mg(5)Mg10ZrNb cuboctahedra. In the fifth 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 Zr(1), and one Nb(1) atom to form distorted MgMg10ZrNb cuboctahedra that share corners with four equivalent Mg(7)Mg11Nb cuboctahedra, corners with four equivalent Mg(6)Mg11Zr cuboctahedra, corners with ten equivalent Mg(5)Mg10ZrNb cuboctahedra, edges with two equivalent Mg(5)Mg10ZrNb cuboctahedra, edges with two equivalent Mg(7)Mg11Nb cuboctahedra, edges with two equivalent Mg(6)Mg11Zr 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)Mg8Zr2Nb2 cuboctahedra, edges with two equivalent Zr(1)Mg10Nb2 cuboctahedra, edges with two equivalent Nb(1)Mg10Zr2 cuboctahedra,  a faceface with one Mg(1)Mg12 cuboctahedra,  a faceface with one Mg(2)Mg12 cuboctahedra,  a faceface with one Zr(1)Mg10Nb2 cuboctahedra,  a faceface with one Nb(1)Mg10Zr2 cuboctahedra, faces with two equivalent Mg(7)Mg11Nb cuboctahedra, faces with two equivalent Mg(6)Mg11Zr cuboctahedra, faces with four equivalent Mg(5)Mg10ZrNb cuboctahedra, faces with four equivalent Mg(4)Mg12 cuboctahedra, and faces with four equivalent Mg(3)Mg8Zr2Nb2 cuboctahedra. In the sixth Mg site, Mg(6) is bonded to one Mg(1), two equivalent Mg(3), two equivalent Mg(4), two equivalent Mg(7), four equivalent Mg(5), and one Zr(1) atom to form MgMg11Zr cuboctahedra that share corners with four equivalent Mg(7)Mg11Nb cuboctahedra, corners with six equivalent Mg(6)Mg11Zr cuboctahedra, corners with eight equivalent Mg(5)Mg10ZrNb cuboctahedra, edges with two equivalent Mg(7)Mg11Nb cuboctahedra, edges with two equivalent Mg(1)Mg12 cuboctahedra, edges with two equivalent Zr(1)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(5)Mg10ZrNb cuboctahedra, edges with four equivalent Mg(4)Mg12 cuboctahedra, edges with four equivalent Mg(3)Mg8Zr2Nb2 cuboctahedra,  a faceface with one Mg(1)Mg12 cuboctahedra,  a faceface with one Zr(1)Mg10Nb2 cuboctahedra, faces with two equivalent Mg(7)Mg11Nb cuboctahedra, faces with two equivalent Mg(6)Mg11Zr cuboctahedra, faces with two equivalent Mg(4)Mg12 cuboctahedra, faces with two equivalent Mg(3)Mg8Zr2Nb2 cuboctahedra, faces with three equivalent Mg(2)Mg12 cuboctahedra, faces with three equivalent Nb(1)Mg10Zr2 cuboctahedra, and faces with four equivalent Mg(5)Mg10ZrNb cuboctahedra. In the seventh Mg site, Mg(7) is bonded to one Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Mg(6), four equivalent Mg(5), and one Nb(1) atom to form distorted MgMg11Nb cuboctahedra that share corners with four equivalent Mg(6)Mg11Zr cuboctahedra, corners with six equivalent Mg(7)Mg11Nb cuboctahedra, corners with eight equivalent Mg(5)Mg10ZrNb cuboctahedra, edges with two equivalent Mg(6)Mg11Zr cuboctahedra, edges with two equivalent Mg(2)Mg12 cuboctahedra, edges with two equivalent Nb(1)Mg10Zr2 cuboctahedra, edges with four equivalent Mg(5)Mg10ZrNb cuboctahedra, edges with four equivalent Mg(4)Mg12 cuboctahedra, edges with four equivalent Mg(3)Mg8Zr2Nb2 cuboctahedra,  a faceface with one Mg(2)Mg12 cuboctahedra,  a faceface with one Nb(1)Mg10Zr2 cuboctahedra, faces with two equivalent Mg(7)Mg11Nb cuboctahedra, faces with two equivalent Mg(6)Mg11Zr cuboctahedra, faces with two equivalent Mg(4)Mg12 cuboctahedra, faces with two equivalent Mg(3)Mg8Zr2Nb2 cuboctahedra, faces with three equivalent Mg(1)Mg12 cuboctahedra, faces with three equivalent Zr(1)Mg10Nb2 cuboctahedra, and faces with four equivalent Mg(5)Mg10ZrNb cuboctahedra. Zr(1) is bonded to two equivalent Mg(6), four equivalent Mg(3), four equivalent Mg(5), and two equivalent Nb(1) atoms to form ZrMg10Nb2 cuboctahedra that share corners with four equivalent Mg(2)Mg12 cuboctahedra, corners with six equivalent Zr(1)Mg10Nb2 cuboctahedra, corners with eight equivalent Mg(4)Mg12 cuboctahedra, edges with two equivalent Nb(1)Mg10Zr2 cuboctahedra, edges with four equivalent Mg(6)Mg11Zr cuboctahedra, edges with four equivalent Mg(3)Mg8Zr2Nb2 cuboctahedra, edges with eight equivalent Mg(5)Mg10ZrNb cuboctahedra, faces with two equivalent Mg(6)Mg11Zr cuboctahedra, faces with two equivalent Mg(1)Mg12 cuboctahedra, faces with two equivalent Nb(1)Mg10Zr2 cuboctahedra, faces with four equivalent Mg(5)Mg10ZrNb cuboctahedra, faces with four equivalent Mg(3)Mg8Zr2Nb2 cuboctahedra, and faces with six equivalent Mg(7)Mg11Nb cuboctahedra. Nb(1) is bonded to two equivalent Mg(7), four equivalent Mg(3), four equivalent Mg(5), and two equivalent Zr(1) atoms to form NbMg10Zr2 cuboctahedra that share corners with four equivalent Mg(1)Mg12 cuboctahedra, corners with six equivalent Nb(1)Mg10Zr2 cuboctahedra, corners with eight equivalent Mg(4)Mg12 cuboctahedra, edges with two equivalent Zr(1)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(7)Mg11Nb cuboctahedra, edges with four equivalent Mg(3)Mg8Zr2Nb2 cuboctahedra, edges with eight equivalent Mg(5)Mg10ZrNb cuboctahedra, faces with two equivalent Mg(7)Mg11Nb cuboctahedra, faces with two equivalent Mg(2)Mg12 cuboctahedra, faces with two equivalent Zr(1)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(5)Mg10ZrNb cuboctahedra, faces with four equivalent Mg(3)Mg8Zr2Nb2 cuboctahedra, and faces with six equivalent Mg(6)Mg11Zr cuboctahedra.
Mg14ZrNb crystallizes in the orthorhombic Amm2 space group. There are seven 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 equivalent Mg(5) atoms to form MgMg12 cuboctahedra that share corners with four equivalent Nb(1)Mg10Zr2 cuboctahedra, corners with six equivalent Mg(1)Mg12 cuboctahedra, corners with eight equivalent Mg(3)Mg8Zr2Nb2 cuboctahedra, edges with two equivalent Mg(2)Mg12 cuboctahedra, edges with four equivalent Mg(6)Mg11Zr cuboctahedra, edges with four equivalent Mg(4)Mg12 cuboctahedra, edges with eight equivalent Mg(5)Mg10ZrNb cuboctahedra, faces with two equivalent Mg(6)Mg11Zr cuboctahedra, faces with two equivalent Mg(2)Mg12 cuboctahedra, faces with two equivalent Zr(1)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(5)Mg10ZrNb 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 3.07 Å. Both Mg(1)-Mg(6) bond lengths are 3.14 Å. There are two shorter (3.21 Å) and two longer (3.23 Å) Mg(1)-Mg(4) bond lengths. All Mg(1)-Mg(5) bond lengths are 3.17 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 equivalent Mg(5) atoms to form MgMg12 cuboctahedra that share corners with four equivalent Zr(1)Mg10Nb2 cuboctahedra, corners with six equivalent Mg(2)Mg12 cuboctahedra, corners with eight equivalent Mg(3)Mg8Zr2Nb2 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, edges with eight equivalent Mg(5)Mg10ZrNb cuboctahedra, faces with two equivalent Mg(7)Mg11Nb cuboctahedra, faces with two equivalent Mg(1)Mg12 cuboctahedra, faces with two equivalent Nb(1)Mg10Zr2 cuboctahedra, faces with four equivalent Mg(5)Mg10ZrNb cuboctahedra, faces with four equivalent Mg(4)Mg12 cuboctahedra, and faces with six equivalent Mg(6)Mg11Zr cuboctahedra. Both Mg(2)-Mg(7) bond lengths are 3.18 Å. There are two shorter (3.21 Å) and two longer (3.22 Å) Mg(2)-Mg(4) bond lengths. All Mg(2)-Mg(5) bond lengths are 3.15 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 Zr(1), and two equivalent Nb(1) atoms to form MgMg8Zr2Nb2 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)Mg8Zr2Nb2 cuboctahedra, edges with two equivalent Mg(3)Mg8Zr2Nb2 cuboctahedra, edges with two equivalent Zr(1)Mg10Nb2 cuboctahedra, edges with two equivalent Nb(1)Mg10Zr2 cuboctahedra, edges with four equivalent Mg(5)Mg10ZrNb cuboctahedra, edges with four equivalent Mg(7)Mg11Nb cuboctahedra, edges with four equivalent Mg(6)Mg11Zr cuboctahedra, faces with two equivalent Mg(7)Mg11Nb cuboctahedra, faces with two equivalent Mg(6)Mg11Zr cuboctahedra, faces with two equivalent Mg(4)Mg12 cuboctahedra, faces with two equivalent Mg(3)Mg8Zr2Nb2 cuboctahedra, faces with two equivalent Zr(1)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Zr2 cuboctahedra, and faces with eight equivalent Mg(5)Mg10ZrNb cuboctahedra. There is one shorter (3.05 Å) and one longer (3.10 Å) Mg(3)-Mg(3) bond length. Both Mg(3)-Mg(5) bond lengths are 3.09 Å. Both Mg(3)-Mg(6) bond lengths are 3.14 Å. Both Mg(3)-Mg(7) bond lengths are 3.10 Å. There is one shorter (3.21 Å) and one longer (3.22 Å) Mg(3)-Zr(1) bond length. There is one shorter (3.19 Å) and one longer (3.24 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 Mg(3)Mg8Zr2Nb2 cuboctahedra, corners with four equivalent Zr(1)Mg10Nb2 cuboctahedra, corners with four equivalent Nb(1)Mg10Zr2 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(5)Mg10ZrNb cuboctahedra, edges with four equivalent Mg(7)Mg11Nb cuboctahedra, edges with four equivalent Mg(6)Mg11Zr cuboctahedra, faces with two equivalent Mg(7)Mg11Nb cuboctahedra, faces with two equivalent Mg(6)Mg11Zr 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)Mg8Zr2Nb2 cuboctahedra, and faces with eight equivalent Mg(5)Mg10ZrNb cuboctahedra. There is one shorter (3.06 Å) and one longer (3.09 Å) Mg(4)-Mg(4) bond length. Both Mg(4)-Mg(5) bond lengths are 3.19 Å. Both Mg(4)-Mg(6) bond lengths are 3.14 Å. Both Mg(4)-Mg(7) bond lengths are 3.20 Å. In the fifth 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 Zr(1), and one Nb(1) atom to form distorted MgMg10ZrNb cuboctahedra that share corners with four equivalent Mg(7)Mg11Nb cuboctahedra, corners with four equivalent Mg(6)Mg11Zr cuboctahedra, corners with ten equivalent Mg(5)Mg10ZrNb cuboctahedra, edges with two equivalent Mg(5)Mg10ZrNb cuboctahedra, edges with two equivalent Mg(7)Mg11Nb cuboctahedra, edges with two equivalent Mg(6)Mg11Zr 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)Mg8Zr2Nb2 cuboctahedra, edges with two equivalent Zr(1)Mg10Nb2 cuboctahedra, edges with two equivalent Nb(1)Mg10Zr2 cuboctahedra,  a faceface with one Mg(1)Mg12 cuboctahedra,  a faceface with one Mg(2)Mg12 cuboctahedra,  a faceface with one Zr(1)Mg10Nb2 cuboctahedra,  a faceface with one Nb(1)Mg10Zr2 cuboctahedra, faces with two equivalent Mg(7)Mg11Nb cuboctahedra, faces with two equivalent Mg(6)Mg11Zr cuboctahedra, faces with four equivalent Mg(5)Mg10ZrNb cuboctahedra, faces with four equivalent Mg(4)Mg12 cuboctahedra, and faces with four equivalent Mg(3)Mg8Zr2Nb2 cuboctahedra. There is one shorter (3.03 Å) and one longer (3.12 Å) Mg(5)-Mg(5) bond length. There is one shorter (3.20 Å) and one longer (3.23 Å) Mg(5)-Mg(6) bond length. There is one shorter (3.15 Å) and one longer (3.28 Å) Mg(5)-Mg(7) bond length. The Mg(5)-Zr(1) bond length is 3.11 Å. The Mg(5)-Nb(1) bond length is 3.08 Å. In the sixth Mg site, Mg(6) is bonded to one Mg(1), two equivalent Mg(3), two equivalent Mg(4), two equivalent Mg(7), four equivalent Mg(5), and one Zr(1) atom to form MgMg11Zr cuboctahedra that share corners with four equivalent Mg(7)Mg11Nb cuboctahedra, corners with six equivalent Mg(6)Mg11Zr cuboctahedra, corners with eight equivalent Mg(5)Mg10ZrNb cuboctahedra, edges with two equivalent Mg(7)Mg11Nb cuboctahedra, edges with two equivalent Mg(1)Mg12 cuboctahedra, edges with two equivalent Zr(1)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(5)Mg10ZrNb cuboctahedra, edges with four equivalent Mg(4)Mg12 cuboctahedra, edges with four equivalent Mg(3)Mg8Zr2Nb2 cuboctahedra,  a faceface with one Mg(1)Mg12 cuboctahedra,  a faceface with one Zr(1)Mg10Nb2 cuboctahedra, faces with two equivalent Mg(7)Mg11Nb cuboctahedra, faces with two equivalent Mg(6)Mg11Zr cuboctahedra, faces with two equivalent Mg(4)Mg12 cuboctahedra, faces with two equivalent Mg(3)Mg8Zr2Nb2 cuboctahedra, faces with three equivalent Mg(2)Mg12 cuboctahedra, faces with three equivalent Nb(1)Mg10Zr2 cuboctahedra, and faces with four equivalent Mg(5)Mg10ZrNb cuboctahedra. Both Mg(6)-Mg(7) bond lengths are 3.07 Å. The Mg(6)-Zr(1) bond length is 3.12 Å. In the seventh Mg site, Mg(7) is bonded to one Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Mg(6), four equivalent Mg(5), and one Nb(1) atom to form distorted MgMg11Nb cuboctahedra that share corners with four equivalent Mg(6)Mg11Zr cuboctahedra, corners with six equivalent Mg(7)Mg11Nb cuboctahedra, corners with eight equivalent Mg(5)Mg10ZrNb cuboctahedra, edges with two equivalent Mg(6)Mg11Zr cuboctahedra, edges with two equivalent Mg(2)Mg12 cuboctahedra, edges with two equivalent Nb(1)Mg10Zr2 cuboctahedra, edges with four equivalent Mg(5)Mg10ZrNb cuboctahedra, edges with four equivalent Mg(4)Mg12 cuboctahedra, edges with four equivalent Mg(3)Mg8Zr2Nb2 cuboctahedra,  a faceface with one Mg(2)Mg12 cuboctahedra,  a faceface with one Nb(1)Mg10Zr2 cuboctahedra, faces with two equivalent Mg(7)Mg11Nb cuboctahedra, faces with two equivalent Mg(6)Mg11Zr cuboctahedra, faces with two equivalent Mg(4)Mg12 cuboctahedra, faces with two equivalent Mg(3)Mg8Zr2Nb2 cuboctahedra, faces with three equivalent Mg(1)Mg12 cuboctahedra, faces with three equivalent Zr(1)Mg10Nb2 cuboctahedra, and faces with four equivalent Mg(5)Mg10ZrNb cuboctahedra. The Mg(7)-Nb(1) bond length is 3.04 Å. Zr(1) is bonded to two equivalent Mg(6), four equivalent Mg(3), four equivalent Mg(5), and two equivalent Nb(1) atoms to form ZrMg10Nb2 cuboctahedra that share corners with four equivalent Mg(2)Mg12 cuboctahedra, corners with six equivalent Zr(1)Mg10Nb2 cuboctahedra, corners with eight equivalent Mg(4)Mg12 cuboctahedra, edges with two equivalent Nb(1)Mg10Zr2 cuboctahedra, edges with four equivalent Mg(6)Mg11Zr cuboctahedra, edges with four equivalent Mg(3)Mg8Zr2Nb2 cuboctahedra, edges with eight equivalent Mg(5)Mg10ZrNb cuboctahedra, faces with two equivalent Mg(6)Mg11Zr cuboctahedra, faces with two equivalent Mg(1)Mg12 cuboctahedra, faces with two equivalent Nb(1)Mg10Zr2 cuboctahedra, faces with four equivalent Mg(5)Mg10ZrNb cuboctahedra, faces with four equivalent Mg(3)Mg8Zr2Nb2 cuboctahedra, and faces with six equivalent Mg(7)Mg11Nb cuboctahedra. Both Zr(1)-Nb(1) bond lengths are 3.07 Å. Nb(1) is bonded to two equivalent Mg(7), four equivalent Mg(3), four equivalent Mg(5), and two equivalent Zr(1) atoms to form NbMg10Zr2 cuboctahedra that share corners with four equivalent Mg(1)Mg12 cuboctahedra, corners with six equivalent Nb(1)Mg10Zr2 cuboctahedra, corners with eight equivalent Mg(4)Mg12 cuboctahedra, edges with two equivalent Zr(1)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(7)Mg11Nb cuboctahedra, edges with four equivalent Mg(3)Mg8Zr2Nb2 cuboctahedra, edges with eight equivalent Mg(5)Mg10ZrNb cuboctahedra, faces with two equivalent Mg(7)Mg11Nb cuboctahedra, faces with two equivalent Mg(2)Mg12 cuboctahedra, faces with two equivalent Zr(1)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(5)Mg10ZrNb cuboctahedra, faces with four equivalent Mg(3)Mg8Zr2Nb2 cuboctahedra, and faces with six equivalent Mg(6)Mg11Zr cuboctahedra.