Mg14NbCd crystallizes in the hexagonal P-6m2 space group. There are five inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(4); four Mg(1,1); four equivalent Mg(3); and two equivalent Nb(1) atoms to form MgMg10Nb2 cuboctahedra that share corners with four equivalent Cd(1)Mg12 cuboctahedra; corners with six equivalent Mg(1)Mg10Nb2 cuboctahedra; corners with eight equivalent Mg(2)Mg10Cd2 cuboctahedra; edges with two equivalent Nb(1)Mg12 cuboctahedra; edges with four Mg(1,1)Mg10Nb2 cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; edges with eight equivalent Mg(3)Mg10NbCd cuboctahedra; faces with two equivalent Mg(2)Mg10Cd2 cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Nb(1)Mg12 cuboctahedra; faces with four Mg(1,1)Mg10Nb2 cuboctahedra; and faces with ten equivalent Mg(3)Mg10NbCd cuboctahedra. In the second Mg site, Mg(2) is bonded to two equivalent Mg(4), four equivalent Mg(2), four equivalent Mg(3), and two equivalent Cd(1) atoms to form MgMg10Cd2 cuboctahedra that share corners with four equivalent Nb(1)Mg12 cuboctahedra; corners with six equivalent Mg(2)Mg10Cd2 cuboctahedra; corners with eight Mg(1,1)Mg10Nb2 cuboctahedra; edges with two equivalent Cd(1)Mg12 cuboctahedra; edges with four equivalent Mg(2)Mg10Cd2 cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; edges with eight equivalent Mg(3)Mg10NbCd cuboctahedra; faces with two equivalent Mg(1)Mg10Nb2 cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Cd(1)Mg12 cuboctahedra; faces with four equivalent Mg(2)Mg10Cd2 cuboctahedra; and faces with ten equivalent Mg(3)Mg10NbCd cuboctahedra. In the third Mg site, Mg(1) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Nb(1) atoms to form MgMg10Nb2 cuboctahedra that share corners with four equivalent Cd(1)Mg12 cuboctahedra, corners with six equivalent Mg(1)Mg10Nb2 cuboctahedra, corners with eight equivalent Mg(2)Mg10Cd2 cuboctahedra, edges with two equivalent Nb(1)Mg12 cuboctahedra, edges with four equivalent Mg(1)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(4)Mg12 cuboctahedra, edges with eight equivalent Mg(3)Mg10NbCd cuboctahedra, faces with two equivalent Mg(2)Mg10Cd2 cuboctahedra, faces with two equivalent Mg(4)Mg12 cuboctahedra, faces with two equivalent Nb(1)Mg12 cuboctahedra, faces with four equivalent Mg(1)Mg10Nb2 cuboctahedra, and faces with ten equivalent Mg(3)Mg10NbCd cuboctahedra. In the fourth Mg site, Mg(3) is bonded to two Mg(1,1); two equivalent Mg(2); two equivalent Mg(4); four equivalent Mg(3); one Nb(1); and one Cd(1) atom to form distorted MgMg10NbCd cuboctahedra that share corners with four equivalent Mg(4)Mg12 cuboctahedra; corners with fourteen equivalent Mg(3)Mg10NbCd cuboctahedra; edges with two equivalent Mg(4)Mg12 cuboctahedra; edges with two equivalent Nb(1)Mg12 cuboctahedra; edges with two equivalent Cd(1)Mg12 cuboctahedra; edges with four equivalent Mg(2)Mg10Cd2 cuboctahedra; edges with four Mg(1,1)Mg10Nb2 cuboctahedra; edges with four equivalent Mg(3)Mg10NbCd cuboctahedra;  a faceface with one Nb(1)Mg12 cuboctahedra;  a faceface with one Cd(1)Mg12 cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with five equivalent Mg(2)Mg10Cd2 cuboctahedra; faces with five Mg(1,1)Mg10Nb2 cuboctahedra; and faces with six equivalent Mg(3)Mg10NbCd cuboctahedra. In the fifth Mg site, Mg(4) is bonded to three Mg(1,1); three equivalent Mg(2); and six equivalent Mg(3) atoms to form MgMg12 cuboctahedra that share corners with six equivalent Mg(4)Mg12 cuboctahedra; corners with twelve equivalent Mg(3)Mg10NbCd cuboctahedra; edges with six equivalent Mg(2)Mg10Cd2 cuboctahedra; edges with six Mg(1,1)Mg10Nb2 cuboctahedra; edges with six equivalent Mg(3)Mg10NbCd cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with three equivalent Mg(2)Mg10Cd2 cuboctahedra; faces with three Mg(1,1)Mg10Nb2 cuboctahedra; faces with three equivalent Nb(1)Mg12 cuboctahedra; faces with three equivalent Cd(1)Mg12 cuboctahedra; and faces with six equivalent Mg(3)Mg10NbCd cuboctahedra. Nb(1) is bonded to six Mg(1,1) and six equivalent Mg(3) atoms to form NbMg12 cuboctahedra that share corners with six equivalent Nb(1)Mg12 cuboctahedra; corners with twelve equivalent Mg(2)Mg10Cd2 cuboctahedra; edges with six Mg(1,1)Mg10Nb2 cuboctahedra; edges with twelve equivalent Mg(3)Mg10NbCd cuboctahedra; faces with two equivalent Cd(1)Mg12 cuboctahedra; faces with six Mg(1,1)Mg10Nb2 cuboctahedra; faces with six equivalent Mg(3)Mg10NbCd cuboctahedra; and faces with six equivalent Mg(4)Mg12 cuboctahedra. Cd(1) is bonded to six equivalent Mg(2) and six equivalent Mg(3) atoms to form CdMg12 cuboctahedra that share corners with six equivalent Cd(1)Mg12 cuboctahedra; corners with twelve Mg(1,1)Mg10Nb2 cuboctahedra; edges with six equivalent Mg(2)Mg10Cd2 cuboctahedra; edges with twelve equivalent Mg(3)Mg10NbCd cuboctahedra; faces with two equivalent Nb(1)Mg12 cuboctahedra; faces with six equivalent Mg(2)Mg10Cd2 cuboctahedra; faces with six equivalent Mg(3)Mg10NbCd cuboctahedra; and faces with six equivalent Mg(4)Mg12 cuboctahedra.
Mg14NbCd crystallizes in the hexagonal P-6m2 space group. There are five inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(4); four Mg(1,1); four equivalent Mg(3); and two equivalent Nb(1) atoms to form MgMg10Nb2 cuboctahedra that share corners with four equivalent Cd(1)Mg12 cuboctahedra; corners with six equivalent Mg(1)Mg10Nb2 cuboctahedra; corners with eight equivalent Mg(2)Mg10Cd2 cuboctahedra; edges with two equivalent Nb(1)Mg12 cuboctahedra; edges with four Mg(1,1)Mg10Nb2 cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; edges with eight equivalent Mg(3)Mg10NbCd cuboctahedra; faces with two equivalent Mg(2)Mg10Cd2 cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Nb(1)Mg12 cuboctahedra; faces with four Mg(1,1)Mg10Nb2 cuboctahedra; and faces with ten equivalent Mg(3)Mg10NbCd cuboctahedra. Both Mg(1)-Mg(4) bond lengths are 3.10 Å. There are two shorter (3.15 Å) and two longer (3.22 Å) Mg(1)-Mg(1,1) bond lengths. All Mg(1)-Mg(3) bond lengths are 3.08 Å. Both Mg(1)-Nb(1) bond lengths are 3.18 Å. In the second Mg site, Mg(2) is bonded to two equivalent Mg(4), four equivalent Mg(2), four equivalent Mg(3), and two equivalent Cd(1) atoms to form MgMg10Cd2 cuboctahedra that share corners with four equivalent Nb(1)Mg12 cuboctahedra; corners with six equivalent Mg(2)Mg10Cd2 cuboctahedra; corners with eight Mg(1,1)Mg10Nb2 cuboctahedra; edges with two equivalent Cd(1)Mg12 cuboctahedra; edges with four equivalent Mg(2)Mg10Cd2 cuboctahedra; edges with four equivalent Mg(4)Mg12 cuboctahedra; edges with eight equivalent Mg(3)Mg10NbCd cuboctahedra; faces with two equivalent Mg(1)Mg10Nb2 cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Cd(1)Mg12 cuboctahedra; faces with four equivalent Mg(2)Mg10Cd2 cuboctahedra; and faces with ten equivalent Mg(3)Mg10NbCd cuboctahedra. Both Mg(2)-Mg(4) bond lengths are 3.12 Å. There are two shorter (3.17 Å) and two longer (3.19 Å) Mg(2)-Mg(2) bond lengths. All Mg(2)-Mg(3) bond lengths are 3.16 Å. Both Mg(2)-Cd(1) bond lengths are 3.18 Å. In the third Mg site, Mg(1) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Nb(1) atoms to form MgMg10Nb2 cuboctahedra that share corners with four equivalent Cd(1)Mg12 cuboctahedra, corners with six equivalent Mg(1)Mg10Nb2 cuboctahedra, corners with eight equivalent Mg(2)Mg10Cd2 cuboctahedra, edges with two equivalent Nb(1)Mg12 cuboctahedra, edges with four equivalent Mg(1)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(4)Mg12 cuboctahedra, edges with eight equivalent Mg(3)Mg10NbCd cuboctahedra, faces with two equivalent Mg(2)Mg10Cd2 cuboctahedra, faces with two equivalent Mg(4)Mg12 cuboctahedra, faces with two equivalent Nb(1)Mg12 cuboctahedra, faces with four equivalent Mg(1)Mg10Nb2 cuboctahedra, and faces with ten equivalent Mg(3)Mg10NbCd cuboctahedra. Both Mg(1)-Mg(4) bond lengths are 3.10 Å. All Mg(1)-Mg(3) bond lengths are 3.08 Å. Both Mg(1)-Nb(1) bond lengths are 3.18 Å. In the fourth Mg site, Mg(3) is bonded to two Mg(1,1); two equivalent Mg(2); two equivalent Mg(4); four equivalent Mg(3); one Nb(1); and one Cd(1) atom to form distorted MgMg10NbCd cuboctahedra that share corners with four equivalent Mg(4)Mg12 cuboctahedra; corners with fourteen equivalent Mg(3)Mg10NbCd cuboctahedra; edges with two equivalent Mg(4)Mg12 cuboctahedra; edges with two equivalent Nb(1)Mg12 cuboctahedra; edges with two equivalent Cd(1)Mg12 cuboctahedra; edges with four equivalent Mg(2)Mg10Cd2 cuboctahedra; edges with four Mg(1,1)Mg10Nb2 cuboctahedra; edges with four equivalent Mg(3)Mg10NbCd cuboctahedra;  a faceface with one Nb(1)Mg12 cuboctahedra;  a faceface with one Cd(1)Mg12 cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with five equivalent Mg(2)Mg10Cd2 cuboctahedra; faces with five Mg(1,1)Mg10Nb2 cuboctahedra; and faces with six equivalent Mg(3)Mg10NbCd cuboctahedra. Both Mg(3)-Mg(4) bond lengths are 3.18 Å. There are two shorter (3.08 Å) and two longer (3.29 Å) Mg(3)-Mg(3) bond lengths. The Mg(3)-Nb(1) bond length is 3.03 Å. The Mg(3)-Cd(1) bond length is 3.10 Å. In the fifth Mg site, Mg(4) is bonded to three Mg(1,1); three equivalent Mg(2); and six equivalent Mg(3) atoms to form MgMg12 cuboctahedra that share corners with six equivalent Mg(4)Mg12 cuboctahedra; corners with twelve equivalent Mg(3)Mg10NbCd cuboctahedra; edges with six equivalent Mg(2)Mg10Cd2 cuboctahedra; edges with six Mg(1,1)Mg10Nb2 cuboctahedra; edges with six equivalent Mg(3)Mg10NbCd cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with three equivalent Mg(2)Mg10Cd2 cuboctahedra; faces with three Mg(1,1)Mg10Nb2 cuboctahedra; faces with three equivalent Nb(1)Mg12 cuboctahedra; faces with three equivalent Cd(1)Mg12 cuboctahedra; and faces with six equivalent Mg(3)Mg10NbCd cuboctahedra. Nb(1) is bonded to six Mg(1,1) and six equivalent Mg(3) atoms to form NbMg12 cuboctahedra that share corners with six equivalent Nb(1)Mg12 cuboctahedra; corners with twelve equivalent Mg(2)Mg10Cd2 cuboctahedra; edges with six Mg(1,1)Mg10Nb2 cuboctahedra; edges with twelve equivalent Mg(3)Mg10NbCd cuboctahedra; faces with two equivalent Cd(1)Mg12 cuboctahedra; faces with six Mg(1,1)Mg10Nb2 cuboctahedra; faces with six equivalent Mg(3)Mg10NbCd cuboctahedra; and faces with six equivalent Mg(4)Mg12 cuboctahedra. Cd(1) is bonded to six equivalent Mg(2) and six equivalent Mg(3) atoms to form CdMg12 cuboctahedra that share corners with six equivalent Cd(1)Mg12 cuboctahedra; corners with twelve Mg(1,1)Mg10Nb2 cuboctahedra; edges with six equivalent Mg(2)Mg10Cd2 cuboctahedra; edges with twelve equivalent Mg(3)Mg10NbCd cuboctahedra; faces with two equivalent Nb(1)Mg12 cuboctahedra; faces with six equivalent Mg(2)Mg10Cd2 cuboctahedra; faces with six equivalent Mg(3)Mg10NbCd cuboctahedra; and faces with six equivalent Mg(4)Mg12 cuboctahedra.