Mg14NbB crystallizes in the hexagonal P-6m2 space group. There are six inequivalent Mg sites. In the first 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 distorted MgMg10Nb2 cuboctahedra that share corners with six equivalent Mg(1)Mg10Nb2 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, faces with two equivalent Mg(4)Mg12 cuboctahedra, faces with two equivalent Nb(1)Mg12 cuboctahedra, and faces with four equivalent Mg(1)Mg10Nb2 cuboctahedra. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to two equivalent Mg(4) and four equivalent Mg(3) atoms. In the third Mg site, Mg(1) is bonded to two equivalent Mg(4); four Mg(1,1); four Mg(3,3); and two equivalent Nb(1) atoms to form distorted MgMg10Nb2 cuboctahedra that share corners with six equivalent Mg(1)Mg10Nb2 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; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Nb(1)Mg12 cuboctahedra; and faces with four Mg(1,1)Mg10Nb2 cuboctahedra. In the fourth Mg site, Mg(3) is bonded in a 12-coordinate geometry to two Mg(1,1); two equivalent Mg(2); two equivalent Mg(4); four Mg(3,3); one Nb(1); and one B(1) atom. In the fifth Mg site, Mg(3) is bonded in a 12-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(4), four equivalent Mg(3), one Nb(1), and one B(1) atom. In the sixth Mg site, Mg(4) is bonded to three Mg(1,1); three equivalent Mg(2); and six Mg(3,3) atoms to form MgMg12 cuboctahedra that share corners with six equivalent Mg(4)Mg12 cuboctahedra; edges with six Mg(1,1)Mg10Nb2 cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with three Mg(1,1)Mg10Nb2 cuboctahedra; and faces with three equivalent Nb(1)Mg12 cuboctahedra. Nb(1) is bonded to six Mg(1,1) and six Mg(3,3) atoms to form NbMg12 cuboctahedra that share corners with six equivalent Nb(1)Mg12 cuboctahedra; edges with six Mg(1,1)Mg10Nb2 cuboctahedra; faces with six Mg(1,1)Mg10Nb2 cuboctahedra; and faces with six equivalent Mg(4)Mg12 cuboctahedra. B(1) is bonded in a 6-coordinate geometry to six Mg(3,3) atoms.
Mg14NbB crystallizes in the hexagonal P-6m2 space group. There are six inequivalent Mg sites. In the first 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 distorted MgMg10Nb2 cuboctahedra that share corners with six equivalent Mg(1)Mg10Nb2 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, faces with two equivalent Mg(4)Mg12 cuboctahedra, faces with two equivalent Nb(1)Mg12 cuboctahedra, and faces with four equivalent Mg(1)Mg10Nb2 cuboctahedra. Both Mg(1)-Mg(4) bond lengths are 3.02 Å. There are two shorter (3.04 Å) and two longer (3.17 Å) Mg(1)-Mg(1) bond lengths. All Mg(1)-Mg(3) bond lengths are 3.14 Å. Both Mg(1)-Nb(1) bond lengths are 3.11 Å. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to two equivalent Mg(4) and four equivalent Mg(3) atoms. Both Mg(2)-Mg(4) bond lengths are 3.11 Å. All Mg(2)-Mg(3) bond lengths are 3.04 Å. In the third Mg site, Mg(1) is bonded to two equivalent Mg(4); four Mg(1,1); four Mg(3,3); and two equivalent Nb(1) atoms to form distorted MgMg10Nb2 cuboctahedra that share corners with six equivalent Mg(1)Mg10Nb2 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; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with two equivalent Nb(1)Mg12 cuboctahedra; and faces with four Mg(1,1)Mg10Nb2 cuboctahedra. Both Mg(1)-Mg(4) bond lengths are 3.02 Å. There is one shorter (3.04 Å) and one longer (3.17 Å) Mg(1)-Mg(1) bond length. All Mg(1)-Mg(3,3) bond lengths are 3.14 Å. Both Mg(1)-Nb(1) bond lengths are 3.11 Å. In the fourth Mg site, Mg(3) is bonded in a 12-coordinate geometry to two Mg(1,1); two equivalent Mg(2); two equivalent Mg(4); four Mg(3,3); one Nb(1); and one B(1) atom. Both Mg(3)-Mg(4) bond lengths are 3.11 Å. There are two shorter (2.92 Å) and two longer (3.29 Å) Mg(3)-Mg(3,3) bond lengths. The Mg(3)-Nb(1) bond length is 3.05 Å. The Mg(3)-B(1) bond length is 2.94 Å. In the fifth Mg site, Mg(3) is bonded in a 12-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(4), four equivalent Mg(3), one Nb(1), and one B(1) atom. Both Mg(3)-Mg(2) bond lengths are 3.04 Å. Both Mg(3)-Mg(4) bond lengths are 3.11 Å. The Mg(3)-Nb(1) bond length is 3.05 Å. The Mg(3)-B(1) bond length is 2.94 Å. In the sixth Mg site, Mg(4) is bonded to three Mg(1,1); three equivalent Mg(2); and six Mg(3,3) atoms to form MgMg12 cuboctahedra that share corners with six equivalent Mg(4)Mg12 cuboctahedra; edges with six Mg(1,1)Mg10Nb2 cuboctahedra; faces with two equivalent Mg(4)Mg12 cuboctahedra; faces with three Mg(1,1)Mg10Nb2 cuboctahedra; and faces with three equivalent Nb(1)Mg12 cuboctahedra. Nb(1) is bonded to six Mg(1,1) and six Mg(3,3) atoms to form NbMg12 cuboctahedra that share corners with six equivalent Nb(1)Mg12 cuboctahedra; edges with six Mg(1,1)Mg10Nb2 cuboctahedra; faces with six Mg(1,1)Mg10Nb2 cuboctahedra; and faces with six equivalent Mg(4)Mg12 cuboctahedra. B(1) is bonded in a 6-coordinate geometry to six Mg(3,3) atoms.