Mg6NiSb crystallizes in the orthorhombic Amm2 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Ni(1), and two equivalent Sb(1) atoms to form distorted MgMg8Ni2Sb2 cuboctahedra that share corners with four equivalent Ni(1)Mg10Sb2 cuboctahedra, corners with four equivalent Sb(1)Mg10Ni2 cuboctahedra, corners with ten equivalent Mg(1)Mg8Ni2Sb2 cuboctahedra, edges with two equivalent Mg(1)Mg8Ni2Sb2 cuboctahedra, edges with two equivalent Ni(1)Mg10Sb2 cuboctahedra, edges with two equivalent Sb(1)Mg10Ni2 cuboctahedra, faces with two equivalent Ni(1)Mg10Sb2 cuboctahedra, faces with two equivalent Sb(1)Mg10Ni2 cuboctahedra, and faces with four equivalent Mg(1)Mg8Ni2Sb2 cuboctahedra. In the second Mg site, Mg(2) is bonded in a 4-coordinate geometry to two equivalent Mg(1), two equivalent Ni(1), and two equivalent Sb(1) atoms. In the third Mg site, Mg(3) is bonded in a 2-coordinate geometry to four equivalent Mg(1) and two equivalent Ni(1) atoms. In the fourth Mg site, Mg(4) is bonded in a distorted water-like geometry to four equivalent Mg(1) and two equivalent Sb(1) atoms. Ni(1) is bonded to two equivalent Mg(3), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Sb(1) atoms to form distorted NiMg10Sb2 cuboctahedra that share corners with four equivalent Sb(1)Mg10Ni2 cuboctahedra, corners with six equivalent Ni(1)Mg10Sb2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Ni2Sb2 cuboctahedra, edges with two equivalent Sb(1)Mg10Ni2 cuboctahedra, edges with four equivalent Mg(1)Mg8Ni2Sb2 cuboctahedra, faces with two equivalent Ni(1)Mg10Sb2 cuboctahedra, faces with two equivalent Sb(1)Mg10Ni2 cuboctahedra, and faces with four equivalent Mg(1)Mg8Ni2Sb2 cuboctahedra. Sb(1) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Ni(1) atoms to form distorted SbMg10Ni2 cuboctahedra that share corners with four equivalent Ni(1)Mg10Sb2 cuboctahedra, corners with six equivalent Sb(1)Mg10Ni2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Ni2Sb2 cuboctahedra, edges with two equivalent Ni(1)Mg10Sb2 cuboctahedra, edges with four equivalent Mg(1)Mg8Ni2Sb2 cuboctahedra, faces with two equivalent Ni(1)Mg10Sb2 cuboctahedra, faces with two equivalent Sb(1)Mg10Ni2 cuboctahedra, and faces with four equivalent Mg(1)Mg8Ni2Sb2 cuboctahedra.
Mg6NiSb crystallizes in the orthorhombic Amm2 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Ni(1), and two equivalent Sb(1) atoms to form distorted MgMg8Ni2Sb2 cuboctahedra that share corners with four equivalent Ni(1)Mg10Sb2 cuboctahedra, corners with four equivalent Sb(1)Mg10Ni2 cuboctahedra, corners with ten equivalent Mg(1)Mg8Ni2Sb2 cuboctahedra, edges with two equivalent Mg(1)Mg8Ni2Sb2 cuboctahedra, edges with two equivalent Ni(1)Mg10Sb2 cuboctahedra, edges with two equivalent Sb(1)Mg10Ni2 cuboctahedra, faces with two equivalent Ni(1)Mg10Sb2 cuboctahedra, faces with two equivalent Sb(1)Mg10Ni2 cuboctahedra, and faces with four equivalent Mg(1)Mg8Ni2Sb2 cuboctahedra. There is one shorter (3.16 Å) and one longer (3.24 Å) Mg(1)-Mg(1) bond length. Both Mg(1)-Mg(2) bond lengths are 3.05 Å. Both Mg(1)-Mg(3) bond lengths are 3.05 Å. Both Mg(1)-Mg(4) bond lengths are 3.03 Å. There is one shorter (3.09 Å) and one longer (3.13 Å) Mg(1)-Ni(1) bond length. Both Mg(1)-Sb(1) bond lengths are 3.11 Å. In the second Mg site, Mg(2) is bonded in a 4-coordinate geometry to two equivalent Mg(1), two equivalent Ni(1), and two equivalent Sb(1) atoms. Both Mg(2)-Ni(1) bond lengths are 2.95 Å. Both Mg(2)-Sb(1) bond lengths are 3.10 Å. In the third Mg site, Mg(3) is bonded in a 2-coordinate geometry to four equivalent Mg(1) and two equivalent Ni(1) atoms. Both Mg(3)-Ni(1) bond lengths are 2.96 Å. In the fourth Mg site, Mg(4) is bonded in a distorted water-like geometry to four equivalent Mg(1) and two equivalent Sb(1) atoms. Both Mg(4)-Sb(1) bond lengths are 3.04 Å. Ni(1) is bonded to two equivalent Mg(3), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Sb(1) atoms to form distorted NiMg10Sb2 cuboctahedra that share corners with four equivalent Sb(1)Mg10Ni2 cuboctahedra, corners with six equivalent Ni(1)Mg10Sb2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Ni2Sb2 cuboctahedra, edges with two equivalent Sb(1)Mg10Ni2 cuboctahedra, edges with four equivalent Mg(1)Mg8Ni2Sb2 cuboctahedra, faces with two equivalent Ni(1)Mg10Sb2 cuboctahedra, faces with two equivalent Sb(1)Mg10Ni2 cuboctahedra, and faces with four equivalent Mg(1)Mg8Ni2Sb2 cuboctahedra. Both Ni(1)-Sb(1) bond lengths are 3.20 Å. Sb(1) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Ni(1) atoms to form distorted SbMg10Ni2 cuboctahedra that share corners with four equivalent Ni(1)Mg10Sb2 cuboctahedra, corners with six equivalent Sb(1)Mg10Ni2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Ni2Sb2 cuboctahedra, edges with two equivalent Ni(1)Mg10Sb2 cuboctahedra, edges with four equivalent Mg(1)Mg8Ni2Sb2 cuboctahedra, faces with two equivalent Ni(1)Mg10Sb2 cuboctahedra, faces with two equivalent Sb(1)Mg10Ni2 cuboctahedra, and faces with four equivalent Mg(1)Mg8Ni2Sb2 cuboctahedra.