Mg14NbAl crystallizes in the hexagonal P-6m2 space group. There are seven inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(4); four Mg(1,1); four Mg(3,3); and two equivalent Al(1) atoms to form MgMg10Al2 cuboctahedra that share corners with four equivalent Nb(1)Mg12 cuboctahedra; corners with six equivalent Mg(1)Mg10Al2 cuboctahedra; corners with eight Mg(2,2)Mg10Nb2 cuboctahedra; edges with two equivalent Al(1)Mg12 cuboctahedra; edges with four Mg(1,1)Mg10Al2 cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; edges with eight Mg(3,3)Mg10NbAl cuboctahedra; faces with two equivalent Mg(2)Mg10Nb2 cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Al(1)Mg12 cuboctahedra; faces with four Mg(1,1)Mg10Al2 cuboctahedra; and faces with ten Mg(3,3)Mg10NbAl cuboctahedra. In the second Mg site, Mg(2) is bonded to two equivalent Mg(4); four Mg(2,2); four Mg(3,3); and two equivalent Nb(1) atoms to form MgMg10Nb2 cuboctahedra that share corners with four equivalent Al(1)Mg12 cuboctahedra; corners with six equivalent Mg(2)Mg10Nb2 cuboctahedra; corners with eight Mg(1,1)Mg10Al2 cuboctahedra; edges with two equivalent Nb(1)Mg12 cuboctahedra; edges with four Mg(2,2)Mg10Nb2 cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; edges with eight Mg(3,3)Mg10NbAl cuboctahedra; faces with two equivalent Mg(1)Mg10Al2 cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Nb(1)Mg12 cuboctahedra; faces with four Mg(2,2)Mg10Nb2 cuboctahedra; and faces with ten Mg(3,3)Mg10NbAl cuboctahedra. In the third Mg site, Mg(2) is bonded to two equivalent Mg(4); four equivalent Mg(2); four Mg(3,3); and two equivalent Nb(1) atoms to form MgMg10Nb2 cuboctahedra that share corners with four equivalent Al(1)Mg12 cuboctahedra; corners with six equivalent Mg(2)Mg10Nb2 cuboctahedra; corners with eight Mg(1,1)Mg10Al2 cuboctahedra; edges with two equivalent Nb(1)Mg12 cuboctahedra; edges with four equivalent Mg(2)Mg10Nb2 cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; edges with eight Mg(3,3)Mg10NbAl cuboctahedra; faces with two equivalent Mg(1)Mg10Al2 cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Nb(1)Mg12 cuboctahedra; faces with four equivalent Mg(2)Mg10Nb2 cuboctahedra; and faces with ten Mg(3,3)Mg10NbAl cuboctahedra. In the fourth Mg site, Mg(1) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Al(1) atoms to form MgMg10Al2 cuboctahedra that share corners with four equivalent Nb(1)Mg12 cuboctahedra; corners with six equivalent Mg(1)Mg10Al2 cuboctahedra; corners with eight Mg(2,2)Mg10Nb2 cuboctahedra; edges with two equivalent Al(1)Mg12 cuboctahedra; edges with four equivalent Mg(1)Mg10Al2 cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; edges with eight equivalent Mg(3)Mg10NbAl cuboctahedra; faces with two equivalent Mg(2)Mg10Nb2 cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Al(1)Mg12 cuboctahedra; faces with four equivalent Mg(1)Mg10Al2 cuboctahedra; and faces with ten Mg(3,3)Mg10NbAl cuboctahedra. In the fifth Mg site, Mg(3) is bonded to two equivalent Mg(1); two Mg(2,2); two equivalent Mg(4); four equivalent Mg(3); one Nb(1); and one Al(1) atom to form distorted MgMg10NbAl cuboctahedra that share corners with four equivalent Mg(4)Mg12 cuboctahedra; corners with fourteen Mg(3,3)Mg10NbAl cuboctahedra; edges with two equivalent Mg(4)Mg12 cuboctahedra; edges with two equivalent Nb(1)Mg12 cuboctahedra; edges with two equivalent Al(1)Mg12 cuboctahedra; edges with four equivalent Mg(1)Mg10Al2 cuboctahedra; edges with four Mg(2,2)Mg10Nb2 cuboctahedra; edges with four equivalent Mg(3)Mg10NbAl cuboctahedra;  a faceface with one Nb(1)Mg12 cuboctahedra;  a faceface with one Al(1)Mg12 cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with five Mg(1,1)Mg10Al2 cuboctahedra; faces with five Mg(2,2)Mg10Nb2 cuboctahedra; and faces with six Mg(3,3)Mg10NbAl cuboctahedra. In the sixth Mg site, Mg(3) is bonded to two Mg(1,1); two equivalent Mg(2); two equivalent Mg(4); four Mg(3,3); one Nb(1); and one Al(1) atom to form distorted MgMg10NbAl cuboctahedra that share corners with four equivalent Mg(4)Mg12 cuboctahedra; corners with fourteen Mg(3,3)Mg10NbAl cuboctahedra; edges with two equivalent Mg(4)Mg12 cuboctahedra; edges with two equivalent Nb(1)Mg12 cuboctahedra; edges with two equivalent Al(1)Mg12 cuboctahedra; edges with four Mg(1,1)Mg10Al2 cuboctahedra; edges with four equivalent Mg(2)Mg10Nb2 cuboctahedra; edges with four Mg(3,3)Mg10NbAl cuboctahedra;  a faceface with one Nb(1)Mg12 cuboctahedra;  a faceface with one Al(1)Mg12 cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with five Mg(1,1)Mg10Al2 cuboctahedra; faces with five Mg(2,2)Mg10Nb2 cuboctahedra; and faces with six Mg(3,3)Mg10NbAl cuboctahedra. In the seventh Mg site, Mg(4) is bonded to three Mg(1,1); three Mg(2,2); and six Mg(3,3) atoms to form MgMg12 cuboctahedra that share corners with six equivalent Mg(4)Mg12 cuboctahedra; corners with twelve Mg(3,3)Mg10NbAl cuboctahedra; edges with six Mg(1,1)Mg10Al2 cuboctahedra; edges with six Mg(2,2)Mg10Nb2 cuboctahedra; edges with six Mg(3,3)Mg10NbAl cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with three Mg(1,1)Mg10Al2 cuboctahedra; faces with three Mg(2,2)Mg10Nb2 cuboctahedra; faces with three equivalent Nb(1)Mg12 cuboctahedra; faces with three equivalent Al(1)Mg12 cuboctahedra; and faces with six Mg(3,3)Mg10NbAl cuboctahedra. Nb(1) is bonded to six Mg(2,2) and six Mg(3,3) atoms to form NbMg12 cuboctahedra that share corners with six equivalent Nb(1)Mg12 cuboctahedra; corners with twelve Mg(1,1)Mg10Al2 cuboctahedra; edges with six Mg(2,2)Mg10Nb2 cuboctahedra; edges with twelve Mg(3,3)Mg10NbAl cuboctahedra; faces with two equivalent Al(1)Mg12 cuboctahedra; faces with six Mg(2,2)Mg10Nb2 cuboctahedra; faces with six Mg(3,3)Mg10NbAl cuboctahedra; and faces with six equivalent Mg(4)Mg12 cuboctahedra. Al(1) is bonded to six Mg(1,1) and six Mg(3,3) atoms to form AlMg12 cuboctahedra that share corners with six equivalent Al(1)Mg12 cuboctahedra; corners with twelve Mg(2,2)Mg10Nb2 cuboctahedra; edges with six Mg(1,1)Mg10Al2 cuboctahedra; edges with twelve Mg(3,3)Mg10NbAl cuboctahedra; faces with two equivalent Nb(1)Mg12 cuboctahedra; faces with six Mg(1,1)Mg10Al2 cuboctahedra; faces with six Mg(3,3)Mg10NbAl cuboctahedra; and faces with six equivalent Mg(4)Mg12 cuboctahedra.
Mg14NbAl crystallizes in the hexagonal P-6m2 space group. There are seven inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(4); four Mg(1,1); four Mg(3,3); and two equivalent Al(1) atoms to form MgMg10Al2 cuboctahedra that share corners with four equivalent Nb(1)Mg12 cuboctahedra; corners with six equivalent Mg(1)Mg10Al2 cuboctahedra; corners with eight Mg(2,2)Mg10Nb2 cuboctahedra; edges with two equivalent Al(1)Mg12 cuboctahedra; edges with four Mg(1,1)Mg10Al2 cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; edges with eight Mg(3,3)Mg10NbAl cuboctahedra; faces with two equivalent Mg(2)Mg10Nb2 cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Al(1)Mg12 cuboctahedra; faces with four Mg(1,1)Mg10Al2 cuboctahedra; and faces with ten Mg(3,3)Mg10NbAl cuboctahedra. Both Mg(1)-Mg(4) bond lengths are 3.13 Å. There are two shorter (3.14 Å) and two longer (3.15 Å) Mg(1)-Mg(1,1) bond lengths. All Mg(1)-Mg(3,3) bond lengths are 3.14 Å. Both Mg(1)-Al(1) bond lengths are 3.14 Å. In the second Mg site, Mg(2) is bonded to two equivalent Mg(4); four Mg(2,2); four Mg(3,3); and two equivalent Nb(1) atoms to form MgMg10Nb2 cuboctahedra that share corners with four equivalent Al(1)Mg12 cuboctahedra; corners with six equivalent Mg(2)Mg10Nb2 cuboctahedra; corners with eight Mg(1,1)Mg10Al2 cuboctahedra; edges with two equivalent Nb(1)Mg12 cuboctahedra; edges with four Mg(2,2)Mg10Nb2 cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; edges with eight Mg(3,3)Mg10NbAl cuboctahedra; faces with two equivalent Mg(1)Mg10Al2 cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Nb(1)Mg12 cuboctahedra; faces with four Mg(2,2)Mg10Nb2 cuboctahedra; and faces with ten Mg(3,3)Mg10NbAl cuboctahedra. Both Mg(2)-Mg(4) bond lengths are 3.10 Å. There are two shorter (3.12 Å) and two longer (3.16 Å) Mg(2)-Mg(2,2) bond lengths. All Mg(2)-Mg(3,3) bond lengths are 3.12 Å. Both Mg(2)-Nb(1) bond lengths are 3.14 Å. In the third Mg site, Mg(2) is bonded to two equivalent Mg(4); four equivalent Mg(2); four Mg(3,3); and two equivalent Nb(1) atoms to form MgMg10Nb2 cuboctahedra that share corners with four equivalent Al(1)Mg12 cuboctahedra; corners with six equivalent Mg(2)Mg10Nb2 cuboctahedra; corners with eight Mg(1,1)Mg10Al2 cuboctahedra; edges with two equivalent Nb(1)Mg12 cuboctahedra; edges with four equivalent Mg(2)Mg10Nb2 cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; edges with eight Mg(3,3)Mg10NbAl cuboctahedra; faces with two equivalent Mg(1)Mg10Al2 cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Nb(1)Mg12 cuboctahedra; faces with four equivalent Mg(2)Mg10Nb2 cuboctahedra; and faces with ten Mg(3,3)Mg10NbAl cuboctahedra. Both Mg(2)-Mg(4) bond lengths are 3.10 Å. All Mg(2)-Mg(3,3) bond lengths are 3.12 Å. Both Mg(2)-Nb(1) bond lengths are 3.14 Å. In the fourth Mg site, Mg(1) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Al(1) atoms to form MgMg10Al2 cuboctahedra that share corners with four equivalent Nb(1)Mg12 cuboctahedra; corners with six equivalent Mg(1)Mg10Al2 cuboctahedra; corners with eight Mg(2,2)Mg10Nb2 cuboctahedra; edges with two equivalent Al(1)Mg12 cuboctahedra; edges with four equivalent Mg(1)Mg10Al2 cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; edges with eight equivalent Mg(3)Mg10NbAl cuboctahedra; faces with two equivalent Mg(2)Mg10Nb2 cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Al(1)Mg12 cuboctahedra; faces with four equivalent Mg(1)Mg10Al2 cuboctahedra; and faces with ten Mg(3,3)Mg10NbAl cuboctahedra. Both Mg(1)-Mg(4) bond lengths are 3.13 Å. All Mg(1)-Mg(3) bond lengths are 3.14 Å. Both Mg(1)-Al(1) bond lengths are 3.14 Å. In the fifth Mg site, Mg(3) is bonded to two equivalent Mg(1); two Mg(2,2); two equivalent Mg(4); four equivalent Mg(3); one Nb(1); and one Al(1) atom to form distorted MgMg10NbAl cuboctahedra that share corners with four equivalent Mg(4)Mg12 cuboctahedra; corners with fourteen Mg(3,3)Mg10NbAl cuboctahedra; edges with two equivalent Mg(4)Mg12 cuboctahedra; edges with two equivalent Nb(1)Mg12 cuboctahedra; edges with two equivalent Al(1)Mg12 cuboctahedra; edges with four equivalent Mg(1)Mg10Al2 cuboctahedra; edges with four Mg(2,2)Mg10Nb2 cuboctahedra; edges with four equivalent Mg(3)Mg10NbAl cuboctahedra;  a faceface with one Nb(1)Mg12 cuboctahedra;  a faceface with one Al(1)Mg12 cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with five Mg(1,1)Mg10Al2 cuboctahedra; faces with five Mg(2,2)Mg10Nb2 cuboctahedra; and faces with six Mg(3,3)Mg10NbAl cuboctahedra. Both Mg(3)-Mg(4) bond lengths are 3.14 Å. There are two shorter (3.04 Å) and two longer (3.24 Å) Mg(3)-Mg(3) bond lengths. The Mg(3)-Nb(1) bond length is 3.07 Å. The Mg(3)-Al(1) bond length is 3.09 Å. In the sixth Mg site, Mg(3) is bonded to two Mg(1,1); two equivalent Mg(2); two equivalent Mg(4); four Mg(3,3); one Nb(1); and one Al(1) atom to form distorted MgMg10NbAl cuboctahedra that share corners with four equivalent Mg(4)Mg12 cuboctahedra; corners with fourteen Mg(3,3)Mg10NbAl cuboctahedra; edges with two equivalent Mg(4)Mg12 cuboctahedra; edges with two equivalent Nb(1)Mg12 cuboctahedra; edges with two equivalent Al(1)Mg12 cuboctahedra; edges with four Mg(1,1)Mg10Al2 cuboctahedra; edges with four equivalent Mg(2)Mg10Nb2 cuboctahedra; edges with four Mg(3,3)Mg10NbAl cuboctahedra;  a faceface with one Nb(1)Mg12 cuboctahedra;  a faceface with one Al(1)Mg12 cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with five Mg(1,1)Mg10Al2 cuboctahedra; faces with five Mg(2,2)Mg10Nb2 cuboctahedra; and faces with six Mg(3,3)Mg10NbAl cuboctahedra. Both Mg(3)-Mg(4) bond lengths are 3.14 Å. There is one shorter (3.04 Å) and one longer (3.24 Å) Mg(3)-Mg(3) bond length. The Mg(3)-Nb(1) bond length is 3.07 Å. The Mg(3)-Al(1) bond length is 3.09 Å. In the seventh Mg site, Mg(4) is bonded to three Mg(1,1); three Mg(2,2); and six Mg(3,3) atoms to form MgMg12 cuboctahedra that share corners with six equivalent Mg(4)Mg12 cuboctahedra; corners with twelve Mg(3,3)Mg10NbAl cuboctahedra; edges with six Mg(1,1)Mg10Al2 cuboctahedra; edges with six Mg(2,2)Mg10Nb2 cuboctahedra; edges with six Mg(3,3)Mg10NbAl cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with three Mg(1,1)Mg10Al2 cuboctahedra; faces with three Mg(2,2)Mg10Nb2 cuboctahedra; faces with three equivalent Nb(1)Mg12 cuboctahedra; faces with three equivalent Al(1)Mg12 cuboctahedra; and faces with six Mg(3,3)Mg10NbAl cuboctahedra. Nb(1) is bonded to six Mg(2,2) and six Mg(3,3) atoms to form NbMg12 cuboctahedra that share corners with six equivalent Nb(1)Mg12 cuboctahedra; corners with twelve Mg(1,1)Mg10Al2 cuboctahedra; edges with six Mg(2,2)Mg10Nb2 cuboctahedra; edges with twelve Mg(3,3)Mg10NbAl cuboctahedra; faces with two equivalent Al(1)Mg12 cuboctahedra; faces with six Mg(2,2)Mg10Nb2 cuboctahedra; faces with six Mg(3,3)Mg10NbAl cuboctahedra; and faces with six equivalent Mg(4)Mg12 cuboctahedra. Al(1) is bonded to six Mg(1,1) and six Mg(3,3) atoms to form AlMg12 cuboctahedra that share corners with six equivalent Al(1)Mg12 cuboctahedra; corners with twelve Mg(2,2)Mg10Nb2 cuboctahedra; edges with six Mg(1,1)Mg10Al2 cuboctahedra; edges with twelve Mg(3,3)Mg10NbAl cuboctahedra; faces with two equivalent Nb(1)Mg12 cuboctahedra; faces with six Mg(1,1)Mg10Al2 cuboctahedra; faces with six Mg(3,3)Mg10NbAl cuboctahedra; and faces with six equivalent Mg(4)Mg12 cuboctahedra.