Mg14NiSb crystallizes in the orthorhombic Amm2 space group. There are seven inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(2), two equivalent Mg(6), four equivalent Mg(4), and four equivalent Mg(5) atoms to form MgMg12 cuboctahedra that share corners with four equivalent Sb(1)Mg10Ni2 cuboctahedra, corners with six equivalent Mg(1)Mg12 cuboctahedra, corners with eight equivalent Mg(5)Mg6NiSb cuboctahedra, corners with eight equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra, edges with two equivalent Mg(2)Mg12 cuboctahedra, edges with four equivalent Mg(4)Mg12 cuboctahedra, edges with four equivalent Mg(5)Mg6NiSb cuboctahedra, faces with two equivalent Mg(2)Mg12 cuboctahedra, faces with two equivalent Ni(1)Mg10Sb2 cuboctahedra, faces with four equivalent Mg(4)Mg12 cuboctahedra, and faces with six equivalent Mg(7)Mg11Sb cuboctahedra. In the second Mg site, Mg(2) is bonded to two equivalent Mg(1), two equivalent Mg(7), four equivalent Mg(4), and four equivalent Mg(5) atoms to form MgMg12 cuboctahedra that share corners with four equivalent Mg(5)Mg6NiSb cuboctahedra, corners with four equivalent Ni(1)Mg10Sb2 cuboctahedra, corners with six equivalent Mg(2)Mg12 cuboctahedra, corners with eight equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra, edges with two equivalent Mg(1)Mg12 cuboctahedra, edges with four equivalent Mg(7)Mg11Sb cuboctahedra, edges with four equivalent Mg(4)Mg12 cuboctahedra, edges with four equivalent Mg(5)Mg6NiSb cuboctahedra, faces with two equivalent Mg(7)Mg11Sb cuboctahedra, faces with two equivalent Mg(1)Mg12 cuboctahedra, faces with two equivalent Sb(1)Mg10Ni2 cuboctahedra, faces with four equivalent Mg(4)Mg12 cuboctahedra, and faces with four equivalent Mg(5)Mg6NiSb cuboctahedra. In the third Mg site, Mg(3) is bonded to two equivalent Mg(3), two equivalent Mg(5), two equivalent Mg(6), two equivalent Mg(7), two equivalent Ni(1), and two equivalent Sb(1) atoms to form distorted MgMg8Ni2Sb2 cuboctahedra that share corners with two equivalent Mg(5)Mg6NiSb cuboctahedra, corners with four equivalent Mg(1)Mg12 cuboctahedra, corners with four equivalent Mg(2)Mg12 cuboctahedra, corners with four equivalent Mg(4)Mg12 cuboctahedra, corners with six equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra, edges with two equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra, edges with two equivalent Ni(1)Mg10Sb2 cuboctahedra, edges with two equivalent Sb(1)Mg10Ni2 cuboctahedra, edges with four equivalent Mg(7)Mg11Sb cuboctahedra, edges with four equivalent Mg(5)Mg6NiSb cuboctahedra, faces with two equivalent Mg(7)Mg11Sb cuboctahedra, faces with two equivalent Mg(4)Mg12 cuboctahedra, faces with two equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra, faces with two equivalent Ni(1)Mg10Sb2 cuboctahedra, faces with two equivalent Sb(1)Mg10Ni2 cuboctahedra, and faces with six equivalent Mg(5)Mg6NiSb cuboctahedra. In the fourth Mg site, Mg(4) is bonded to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(4), two equivalent Mg(5), two equivalent Mg(6), and two equivalent Mg(7) atoms to form MgMg12 cuboctahedra that share corners with two equivalent Mg(5)Mg6NiSb cuboctahedra, corners with four equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra, corners with four equivalent Ni(1)Mg10Sb2 cuboctahedra, corners with four equivalent Sb(1)Mg10Ni2 cuboctahedra, corners with six equivalent Mg(4)Mg12 cuboctahedra, edges with two equivalent Mg(1)Mg12 cuboctahedra, edges with two equivalent Mg(2)Mg12 cuboctahedra, edges with two equivalent Mg(4)Mg12 cuboctahedra, edges with four equivalent Mg(7)Mg11Sb cuboctahedra, edges with four equivalent Mg(5)Mg6NiSb cuboctahedra, faces with two equivalent Mg(7)Mg11Sb cuboctahedra, faces with two equivalent Mg(1)Mg12 cuboctahedra, faces with two equivalent Mg(2)Mg12 cuboctahedra, faces with two equivalent Mg(4)Mg12 cuboctahedra, faces with two equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra, and faces with six equivalent Mg(5)Mg6NiSb cuboctahedra. In the fifth Mg site, Mg(5) is bonded to one Mg(1), one Mg(2), one Mg(3), one Mg(4), two equivalent Mg(7), one Ni(1), and one Sb(1) atom to form distorted MgMg6NiSb cuboctahedra that share  a cornercorner with one Mg(2)Mg12 cuboctahedra,  a cornercorner with one Mg(4)Mg12 cuboctahedra,  a cornercorner with one Mg(3)Mg8Ni2Sb2 cuboctahedra,  a cornercorner with one Sb(1)Mg10Ni2 cuboctahedra, corners with two equivalent Mg(1)Mg12 cuboctahedra, corners with two equivalent Ni(1)Mg10Sb2 cuboctahedra, corners with four equivalent Mg(7)Mg11Sb cuboctahedra, corners with eight equivalent Mg(5)Mg6NiSb cuboctahedra,  an edgeedge with one Mg(1)Mg12 cuboctahedra,  an edgeedge with one Mg(2)Mg12 cuboctahedra,  an edgeedge with one Ni(1)Mg10Sb2 cuboctahedra,  an edgeedge with one Sb(1)Mg10Ni2 cuboctahedra, edges with two equivalent Mg(7)Mg11Sb cuboctahedra, edges with two equivalent Mg(4)Mg12 cuboctahedra, edges with two equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra,  a faceface with one Mg(2)Mg12 cuboctahedra,  a faceface with one Sb(1)Mg10Ni2 cuboctahedra, faces with three equivalent Mg(4)Mg12 cuboctahedra, faces with three equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra, and faces with four equivalent Mg(5)Mg6NiSb cuboctahedra. In the sixth Mg site, Mg(6) is bonded in a distorted single-bond geometry to one Mg(1), two equivalent Mg(3), two equivalent Mg(4), two equivalent Mg(7), and one Ni(1) atom. In the seventh Mg site, Mg(7) is bonded to one Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Mg(6), four equivalent Mg(5), and one Sb(1) atom to form distorted MgMg11Sb cuboctahedra that share corners with six equivalent Mg(7)Mg11Sb cuboctahedra, corners with eight equivalent Mg(5)Mg6NiSb cuboctahedra, edges with two equivalent Mg(2)Mg12 cuboctahedra, edges with two equivalent Sb(1)Mg10Ni2 cuboctahedra, edges with four equivalent Mg(4)Mg12 cuboctahedra, edges with four equivalent Mg(5)Mg6NiSb cuboctahedra, edges with four equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra,  a faceface with one Mg(2)Mg12 cuboctahedra,  a faceface with one Sb(1)Mg10Ni2 cuboctahedra, faces with two equivalent Mg(7)Mg11Sb cuboctahedra, faces with two equivalent Mg(4)Mg12 cuboctahedra, faces with two equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra, faces with three equivalent Mg(1)Mg12 cuboctahedra, and faces with three equivalent Ni(1)Mg10Sb2 cuboctahedra. Ni(1) is bonded to two equivalent Mg(6), four equivalent Mg(3), four equivalent Mg(5), and two equivalent Sb(1) atoms to form NiMg10Sb2 cuboctahedra that share corners with four equivalent Mg(2)Mg12 cuboctahedra, corners with six equivalent Ni(1)Mg10Sb2 cuboctahedra, corners with eight equivalent Mg(4)Mg12 cuboctahedra, corners with eight equivalent Mg(5)Mg6NiSb cuboctahedra, edges with two equivalent Sb(1)Mg10Ni2 cuboctahedra, edges with four equivalent Mg(5)Mg6NiSb cuboctahedra, edges with four equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra, faces with two equivalent Mg(1)Mg12 cuboctahedra, faces with two equivalent Sb(1)Mg10Ni2 cuboctahedra, faces with four equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra, and faces with six equivalent Mg(7)Mg11Sb cuboctahedra. Sb(1) is bonded to two equivalent Mg(7), four equivalent Mg(3), four equivalent Mg(5), and two equivalent Ni(1) atoms to form SbMg10Ni2 cuboctahedra that share corners with four equivalent Mg(1)Mg12 cuboctahedra, corners with four equivalent Mg(5)Mg6NiSb cuboctahedra, corners with six equivalent Sb(1)Mg10Ni2 cuboctahedra, corners with eight equivalent Mg(4)Mg12 cuboctahedra, edges with two equivalent Ni(1)Mg10Sb2 cuboctahedra, edges with four equivalent Mg(7)Mg11Sb cuboctahedra, edges with four equivalent Mg(5)Mg6NiSb cuboctahedra, edges with four equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra, faces with two equivalent Mg(7)Mg11Sb cuboctahedra, faces with two equivalent Mg(2)Mg12 cuboctahedra, faces with two equivalent Ni(1)Mg10Sb2 cuboctahedra, faces with four equivalent Mg(5)Mg6NiSb cuboctahedra, and faces with four equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra.
Mg14NiSb crystallizes in the orthorhombic Amm2 space group. There are seven inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(2), two equivalent Mg(6), four equivalent Mg(4), and four equivalent Mg(5) atoms to form MgMg12 cuboctahedra that share corners with four equivalent Sb(1)Mg10Ni2 cuboctahedra, corners with six equivalent Mg(1)Mg12 cuboctahedra, corners with eight equivalent Mg(5)Mg6NiSb cuboctahedra, corners with eight equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra, edges with two equivalent Mg(2)Mg12 cuboctahedra, edges with four equivalent Mg(4)Mg12 cuboctahedra, edges with four equivalent Mg(5)Mg6NiSb cuboctahedra, faces with two equivalent Mg(2)Mg12 cuboctahedra, faces with two equivalent Ni(1)Mg10Sb2 cuboctahedra, faces with four equivalent Mg(4)Mg12 cuboctahedra, and faces with six equivalent Mg(7)Mg11Sb cuboctahedra. Both Mg(1)-Mg(2) bond lengths are 3.15 Å. Both Mg(1)-Mg(6) bond lengths are 3.19 Å. There are two shorter (3.11 Å) and two longer (3.13 Å) Mg(1)-Mg(4) bond lengths. All Mg(1)-Mg(5) bond lengths are 3.21 Å. In the second Mg site, Mg(2) is bonded to two equivalent Mg(1), two equivalent Mg(7), four equivalent Mg(4), and four equivalent Mg(5) atoms to form MgMg12 cuboctahedra that share corners with four equivalent Mg(5)Mg6NiSb cuboctahedra, corners with four equivalent Ni(1)Mg10Sb2 cuboctahedra, corners with six equivalent Mg(2)Mg12 cuboctahedra, corners with eight equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra, edges with two equivalent Mg(1)Mg12 cuboctahedra, edges with four equivalent Mg(7)Mg11Sb cuboctahedra, edges with four equivalent Mg(4)Mg12 cuboctahedra, edges with four equivalent Mg(5)Mg6NiSb cuboctahedra, faces with two equivalent Mg(7)Mg11Sb cuboctahedra, faces with two equivalent Mg(1)Mg12 cuboctahedra, faces with two equivalent Sb(1)Mg10Ni2 cuboctahedra, faces with four equivalent Mg(4)Mg12 cuboctahedra, and faces with four equivalent Mg(5)Mg6NiSb cuboctahedra. Both Mg(2)-Mg(7) bond lengths are 3.11 Å. There are two shorter (3.10 Å) and two longer (3.15 Å) Mg(2)-Mg(4) bond lengths. All Mg(2)-Mg(5) bond lengths are 3.26 Å. In the third Mg site, Mg(3) is bonded to two equivalent Mg(3), two equivalent Mg(5), two equivalent Mg(6), two equivalent Mg(7), two equivalent Ni(1), and two equivalent Sb(1) atoms to form distorted MgMg8Ni2Sb2 cuboctahedra that share corners with two equivalent Mg(5)Mg6NiSb cuboctahedra, corners with four equivalent Mg(1)Mg12 cuboctahedra, corners with four equivalent Mg(2)Mg12 cuboctahedra, corners with four equivalent Mg(4)Mg12 cuboctahedra, corners with six equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra, edges with two equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra, edges with two equivalent Ni(1)Mg10Sb2 cuboctahedra, edges with two equivalent Sb(1)Mg10Ni2 cuboctahedra, edges with four equivalent Mg(7)Mg11Sb cuboctahedra, edges with four equivalent Mg(5)Mg6NiSb cuboctahedra, faces with two equivalent Mg(7)Mg11Sb cuboctahedra, faces with two equivalent Mg(4)Mg12 cuboctahedra, faces with two equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra, faces with two equivalent Ni(1)Mg10Sb2 cuboctahedra, faces with two equivalent Sb(1)Mg10Ni2 cuboctahedra, and faces with six equivalent Mg(5)Mg6NiSb cuboctahedra. There is one shorter (3.14 Å) and one longer (3.16 Å) Mg(3)-Mg(3) bond length. Both Mg(3)-Mg(5) bond lengths are 3.07 Å. Both Mg(3)-Mg(6) bond lengths are 3.07 Å. Both Mg(3)-Mg(7) bond lengths are 3.17 Å. There is one shorter (3.09 Å) and one longer (3.16 Å) Mg(3)-Ni(1) bond length. There is one shorter (3.06 Å) and one longer (3.18 Å) Mg(3)-Sb(1) bond length. In the fourth Mg site, Mg(4) is bonded to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(4), two equivalent Mg(5), two equivalent Mg(6), and two equivalent Mg(7) atoms to form MgMg12 cuboctahedra that share corners with two equivalent Mg(5)Mg6NiSb cuboctahedra, corners with four equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra, corners with four equivalent Ni(1)Mg10Sb2 cuboctahedra, corners with four equivalent Sb(1)Mg10Ni2 cuboctahedra, corners with six equivalent Mg(4)Mg12 cuboctahedra, edges with two equivalent Mg(1)Mg12 cuboctahedra, edges with two equivalent Mg(2)Mg12 cuboctahedra, edges with two equivalent Mg(4)Mg12 cuboctahedra, edges with four equivalent Mg(7)Mg11Sb cuboctahedra, edges with four equivalent Mg(5)Mg6NiSb cuboctahedra, faces with two equivalent Mg(7)Mg11Sb cuboctahedra, faces with two equivalent Mg(1)Mg12 cuboctahedra, faces with two equivalent Mg(2)Mg12 cuboctahedra, faces with two equivalent Mg(4)Mg12 cuboctahedra, faces with two equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra, and faces with six equivalent Mg(5)Mg6NiSb cuboctahedra. There is one shorter (3.13 Å) and one longer (3.17 Å) Mg(4)-Mg(4) bond length. Both Mg(4)-Mg(5) bond lengths are 3.24 Å. Both Mg(4)-Mg(6) bond lengths are 3.23 Å. Both Mg(4)-Mg(7) bond lengths are 3.10 Å. In the fifth Mg site, Mg(5) is bonded to one Mg(1), one Mg(2), one Mg(3), one Mg(4), two equivalent Mg(7), one Ni(1), and one Sb(1) atom to form distorted MgMg6NiSb cuboctahedra that share  a cornercorner with one Mg(2)Mg12 cuboctahedra,  a cornercorner with one Mg(4)Mg12 cuboctahedra,  a cornercorner with one Mg(3)Mg8Ni2Sb2 cuboctahedra,  a cornercorner with one Sb(1)Mg10Ni2 cuboctahedra, corners with two equivalent Mg(1)Mg12 cuboctahedra, corners with two equivalent Ni(1)Mg10Sb2 cuboctahedra, corners with four equivalent Mg(7)Mg11Sb cuboctahedra, corners with eight equivalent Mg(5)Mg6NiSb cuboctahedra,  an edgeedge with one Mg(1)Mg12 cuboctahedra,  an edgeedge with one Mg(2)Mg12 cuboctahedra,  an edgeedge with one Ni(1)Mg10Sb2 cuboctahedra,  an edgeedge with one Sb(1)Mg10Ni2 cuboctahedra, edges with two equivalent Mg(7)Mg11Sb cuboctahedra, edges with two equivalent Mg(4)Mg12 cuboctahedra, edges with two equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra,  a faceface with one Mg(2)Mg12 cuboctahedra,  a faceface with one Sb(1)Mg10Ni2 cuboctahedra, faces with three equivalent Mg(4)Mg12 cuboctahedra, faces with three equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra, and faces with four equivalent Mg(5)Mg6NiSb cuboctahedra. There is one shorter (3.11 Å) and one longer (3.15 Å) Mg(5)-Mg(7) bond length. The Mg(5)-Ni(1) bond length is 3.01 Å. The Mg(5)-Sb(1) bond length is 3.07 Å. In the sixth Mg site, Mg(6) is bonded in a distorted single-bond geometry to one Mg(1), two equivalent Mg(3), two equivalent Mg(4), two equivalent Mg(7), and one Ni(1) atom. Both Mg(6)-Mg(7) bond lengths are 3.15 Å. The Mg(6)-Ni(1) bond length is 3.02 Å. In the seventh Mg site, Mg(7) is bonded to one Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Mg(6), four equivalent Mg(5), and one Sb(1) atom to form distorted MgMg11Sb cuboctahedra that share corners with six equivalent Mg(7)Mg11Sb cuboctahedra, corners with eight equivalent Mg(5)Mg6NiSb cuboctahedra, edges with two equivalent Mg(2)Mg12 cuboctahedra, edges with two equivalent Sb(1)Mg10Ni2 cuboctahedra, edges with four equivalent Mg(4)Mg12 cuboctahedra, edges with four equivalent Mg(5)Mg6NiSb cuboctahedra, edges with four equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra,  a faceface with one Mg(2)Mg12 cuboctahedra,  a faceface with one Sb(1)Mg10Ni2 cuboctahedra, faces with two equivalent Mg(7)Mg11Sb cuboctahedra, faces with two equivalent Mg(4)Mg12 cuboctahedra, faces with two equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra, faces with three equivalent Mg(1)Mg12 cuboctahedra, and faces with three equivalent Ni(1)Mg10Sb2 cuboctahedra. The Mg(7)-Sb(1) bond length is 3.17 Å. Ni(1) is bonded to two equivalent Mg(6), four equivalent Mg(3), four equivalent Mg(5), and two equivalent Sb(1) atoms to form NiMg10Sb2 cuboctahedra that share corners with four equivalent Mg(2)Mg12 cuboctahedra, corners with six equivalent Ni(1)Mg10Sb2 cuboctahedra, corners with eight equivalent Mg(4)Mg12 cuboctahedra, corners with eight equivalent Mg(5)Mg6NiSb cuboctahedra, edges with two equivalent Sb(1)Mg10Ni2 cuboctahedra, edges with four equivalent Mg(5)Mg6NiSb cuboctahedra, edges with four equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra, faces with two equivalent Mg(1)Mg12 cuboctahedra, faces with two equivalent Sb(1)Mg10Ni2 cuboctahedra, faces with four equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra, and faces with six equivalent Mg(7)Mg11Sb cuboctahedra. Both Ni(1)-Sb(1) bond lengths are 3.15 Å. Sb(1) is bonded to two equivalent Mg(7), four equivalent Mg(3), four equivalent Mg(5), and two equivalent Ni(1) atoms to form SbMg10Ni2 cuboctahedra that share corners with four equivalent Mg(1)Mg12 cuboctahedra, corners with four equivalent Mg(5)Mg6NiSb cuboctahedra, corners with six equivalent Sb(1)Mg10Ni2 cuboctahedra, corners with eight equivalent Mg(4)Mg12 cuboctahedra, edges with two equivalent Ni(1)Mg10Sb2 cuboctahedra, edges with four equivalent Mg(7)Mg11Sb cuboctahedra, edges with four equivalent Mg(5)Mg6NiSb cuboctahedra, edges with four equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra, faces with two equivalent Mg(7)Mg11Sb cuboctahedra, faces with two equivalent Mg(2)Mg12 cuboctahedra, faces with two equivalent Ni(1)Mg10Sb2 cuboctahedra, faces with four equivalent Mg(5)Mg6NiSb cuboctahedra, and faces with four equivalent Mg(3)Mg8Ni2Sb2 cuboctahedra.