KMg6Nb is beta Cu3Ti-derived structured and crystallizes in the orthorhombic Amm2 space group. K(1) is bonded to two equivalent Mg(2), two equivalent Mg(4), four equivalent Mg(1), and four equivalent Mg(3) atoms to form KMg12 cuboctahedra that share corners with six equivalent K(1)Mg12 cuboctahedra, edges with four equivalent Mg(4)K2Mg8Nb2 cuboctahedra, faces with two equivalent K(1)Mg12 cuboctahedra, faces with two equivalent Mg(4)K2Mg8Nb2 cuboctahedra, and faces with six equivalent Nb(1)Mg12 cuboctahedra. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 4-coordinate geometry to two equivalent K(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), and two equivalent Nb(1) atoms. In the second Mg site, Mg(2) is bonded in a 12-coordinate geometry to two equivalent K(1), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Nb(1) atoms. In the third Mg site, Mg(3) is bonded in a 12-coordinate geometry to two equivalent K(1), two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), and two equivalent Nb(1) atoms. In the fourth Mg site, Mg(4) is bonded to two equivalent K(1), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Nb(1) atoms to form distorted MgK2Mg8Nb2 cuboctahedra that share corners with four equivalent Nb(1)Mg12 cuboctahedra, corners with six equivalent Mg(4)K2Mg8Nb2 cuboctahedra, edges with two equivalent Nb(1)Mg12 cuboctahedra, edges with four equivalent K(1)Mg12 cuboctahedra, faces with two equivalent K(1)Mg12 cuboctahedra, faces with two equivalent Mg(4)K2Mg8Nb2 cuboctahedra, and faces with two equivalent Nb(1)Mg12 cuboctahedra. Nb(1) is bonded to two equivalent Mg(2), two equivalent Mg(4), four equivalent Mg(1), and four equivalent Mg(3) atoms to form NbMg12 cuboctahedra that share corners with four equivalent Mg(4)K2Mg8Nb2 cuboctahedra, corners with six equivalent Nb(1)Mg12 cuboctahedra, edges with two equivalent Mg(4)K2Mg8Nb2 cuboctahedra, faces with two equivalent Mg(4)K2Mg8Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg12 cuboctahedra, and faces with six equivalent K(1)Mg12 cuboctahedra.
KMg6Nb is beta Cu3Ti-derived structured and crystallizes in the orthorhombic Amm2 space group. K(1) is bonded to two equivalent Mg(2), two equivalent Mg(4), four equivalent Mg(1), and four equivalent Mg(3) atoms to form KMg12 cuboctahedra that share corners with six equivalent K(1)Mg12 cuboctahedra, edges with four equivalent Mg(4)K2Mg8Nb2 cuboctahedra, faces with two equivalent K(1)Mg12 cuboctahedra, faces with two equivalent Mg(4)K2Mg8Nb2 cuboctahedra, and faces with six equivalent Nb(1)Mg12 cuboctahedra. Both K(1)-Mg(2) bond lengths are 3.27 Å. Both K(1)-Mg(4) bond lengths are 3.26 Å. There are two shorter (3.24 Å) and two longer (3.27 Å) K(1)-Mg(1) bond lengths. All K(1)-Mg(3) bond lengths are 3.23 Å. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 4-coordinate geometry to two equivalent K(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), and two equivalent Nb(1) atoms. There is one shorter (3.04 Å) and one longer (3.47 Å) Mg(1)-Mg(2) bond length. Both Mg(1)-Mg(3) bond lengths are 3.23 Å. Both Mg(1)-Mg(4) bond lengths are 3.20 Å. Both Mg(1)-Nb(1) bond lengths are 3.09 Å. In the second Mg site, Mg(2) is bonded in a 12-coordinate geometry to two equivalent K(1), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Nb(1) atoms. All Mg(2)-Mg(3) bond lengths are 3.17 Å. Both Mg(2)-Nb(1) bond lengths are 3.13 Å. In the third Mg site, Mg(3) is bonded in a 12-coordinate geometry to two equivalent K(1), two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), and two equivalent Nb(1) atoms. There is one shorter (3.12 Å) and one longer (3.42 Å) Mg(3)-Mg(3) bond length. There is one shorter (3.08 Å) and one longer (3.42 Å) Mg(3)-Mg(4) bond length. There is one shorter (3.22 Å) and one longer (3.28 Å) Mg(3)-Nb(1) bond length. In the fourth Mg site, Mg(4) is bonded to two equivalent K(1), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Nb(1) atoms to form distorted MgK2Mg8Nb2 cuboctahedra that share corners with four equivalent Nb(1)Mg12 cuboctahedra, corners with six equivalent Mg(4)K2Mg8Nb2 cuboctahedra, edges with two equivalent Nb(1)Mg12 cuboctahedra, edges with four equivalent K(1)Mg12 cuboctahedra, faces with two equivalent K(1)Mg12 cuboctahedra, faces with two equivalent Mg(4)K2Mg8Nb2 cuboctahedra, and faces with two equivalent Nb(1)Mg12 cuboctahedra. Both Mg(4)-Nb(1) bond lengths are 3.28 Å. Nb(1) is bonded to two equivalent Mg(2), two equivalent Mg(4), four equivalent Mg(1), and four equivalent Mg(3) atoms to form NbMg12 cuboctahedra that share corners with four equivalent Mg(4)K2Mg8Nb2 cuboctahedra, corners with six equivalent Nb(1)Mg12 cuboctahedra, edges with two equivalent Mg(4)K2Mg8Nb2 cuboctahedra, faces with two equivalent Mg(4)K2Mg8Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg12 cuboctahedra, and faces with six equivalent K(1)Mg12 cuboctahedra.