Mg6NbCo crystallizes in the orthorhombic Amm2 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 12-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Nb(1), and two equivalent Co(1) atoms. In the second Mg site, Mg(2) is bonded in a 12-coordinate geometry to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Co(1) atoms. In the third Mg site, Mg(3) is bonded to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Nb(1), and two equivalent Co(1) atoms to form distorted MgMg8Nb2Co2 cuboctahedra that share corners with four equivalent Mg(4)Mg10Nb2 cuboctahedra, corners with four equivalent Nb(1)Mg10Co2 cuboctahedra, corners with ten equivalent Mg(3)Mg8Nb2Co2 cuboctahedra, edges with two equivalent Mg(4)Mg10Nb2 cuboctahedra, edges with two equivalent Mg(3)Mg8Nb2Co2 cuboctahedra, edges with two equivalent Nb(1)Mg10Co2 cuboctahedra, faces with two equivalent Mg(4)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Co2 cuboctahedra, and faces with four equivalent Mg(3)Mg8Nb2Co2 cuboctahedra. In the fourth Mg site, Mg(4) is bonded to two equivalent Mg(2), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Nb(1) atoms to form distorted MgMg10Nb2 cuboctahedra that share corners with four equivalent Nb(1)Mg10Co2 cuboctahedra, corners with six equivalent Mg(4)Mg10Nb2 cuboctahedra, corners with eight equivalent Mg(3)Mg8Nb2Co2 cuboctahedra, edges with two equivalent Nb(1)Mg10Co2 cuboctahedra, edges with four equivalent Mg(3)Mg8Nb2Co2 cuboctahedra, faces with two equivalent Mg(4)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Co2 cuboctahedra, and faces with four equivalent Mg(3)Mg8Nb2Co2 cuboctahedra. Nb(1) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Co(1) atoms to form distorted NbMg10Co2 cuboctahedra that share corners with four equivalent Mg(4)Mg10Nb2 cuboctahedra, corners with six equivalent Nb(1)Mg10Co2 cuboctahedra, corners with eight equivalent Mg(3)Mg8Nb2Co2 cuboctahedra, edges with two equivalent Mg(4)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(3)Mg8Nb2Co2 cuboctahedra, faces with two equivalent Mg(4)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Co2 cuboctahedra, and faces with four equivalent Mg(3)Mg8Nb2Co2 cuboctahedra. Co(1) is bonded in a 10-coordinate geometry to two equivalent Mg(2), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Nb(1) atoms.
Mg6NbCo crystallizes in the orthorhombic Amm2 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 12-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Nb(1), and two equivalent Co(1) atoms. There is one shorter (2.86 Å) and one longer (3.11 Å) Mg(1)-Mg(1) bond length. There is one shorter (3.10 Å) and one longer (3.16 Å) Mg(1)-Mg(2) bond length. Both Mg(1)-Mg(3) bond lengths are 2.94 Å. Both Mg(1)-Mg(4) bond lengths are 2.99 Å. Both Mg(1)-Nb(1) bond lengths are 3.02 Å. There is one shorter (2.80 Å) and one longer (3.46 Å) Mg(1)-Co(1) bond length. In the second Mg site, Mg(2) is bonded in a 12-coordinate geometry to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Co(1) atoms. Both Mg(2)-Mg(4) bond lengths are 2.93 Å. All Mg(2)-Mg(3) bond lengths are 3.02 Å. Both Mg(2)-Co(1) bond lengths are 3.00 Å. In the third Mg site, Mg(3) is bonded to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Nb(1), and two equivalent Co(1) atoms to form distorted MgMg8Nb2Co2 cuboctahedra that share corners with four equivalent Mg(4)Mg10Nb2 cuboctahedra, corners with four equivalent Nb(1)Mg10Co2 cuboctahedra, corners with ten equivalent Mg(3)Mg8Nb2Co2 cuboctahedra, edges with two equivalent Mg(4)Mg10Nb2 cuboctahedra, edges with two equivalent Mg(3)Mg8Nb2Co2 cuboctahedra, edges with two equivalent Nb(1)Mg10Co2 cuboctahedra, faces with two equivalent Mg(4)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Co2 cuboctahedra, and faces with four equivalent Mg(3)Mg8Nb2Co2 cuboctahedra. There is one shorter (2.89 Å) and one longer (3.08 Å) Mg(3)-Mg(3) bond length. There is one shorter (3.06 Å) and one longer (3.20 Å) Mg(3)-Mg(4) bond length. There is one shorter (2.92 Å) and one longer (3.34 Å) Mg(3)-Nb(1) bond length. Both Mg(3)-Co(1) bond lengths are 3.08 Å. In the fourth Mg site, Mg(4) is bonded to two equivalent Mg(2), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Nb(1) atoms to form distorted MgMg10Nb2 cuboctahedra that share corners with four equivalent Nb(1)Mg10Co2 cuboctahedra, corners with six equivalent Mg(4)Mg10Nb2 cuboctahedra, corners with eight equivalent Mg(3)Mg8Nb2Co2 cuboctahedra, edges with two equivalent Nb(1)Mg10Co2 cuboctahedra, edges with four equivalent Mg(3)Mg8Nb2Co2 cuboctahedra, faces with two equivalent Mg(4)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Co2 cuboctahedra, and faces with four equivalent Mg(3)Mg8Nb2Co2 cuboctahedra. Both Mg(4)-Nb(1) bond lengths are 3.00 Å. Nb(1) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Co(1) atoms to form distorted NbMg10Co2 cuboctahedra that share corners with four equivalent Mg(4)Mg10Nb2 cuboctahedra, corners with six equivalent Nb(1)Mg10Co2 cuboctahedra, corners with eight equivalent Mg(3)Mg8Nb2Co2 cuboctahedra, edges with two equivalent Mg(4)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(3)Mg8Nb2Co2 cuboctahedra, faces with two equivalent Mg(4)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Co2 cuboctahedra, and faces with four equivalent Mg(3)Mg8Nb2Co2 cuboctahedra. Both Nb(1)-Co(1) bond lengths are 2.64 Å. Co(1) is bonded in a 10-coordinate geometry to two equivalent Mg(2), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Nb(1) atoms.