MgNi3 is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. Mg(1) is bonded to four equivalent Ni(1) and eight equivalent Ni(2) atoms to form MgNi12 cuboctahedra that share corners with four equivalent Mg(1)Ni12 cuboctahedra, corners with eight equivalent Ni(1)Mg4Ni8 cuboctahedra, edges with eight equivalent Mg(1)Ni12 cuboctahedra, edges with sixteen equivalent Ni(2)Mg4Ni8 cuboctahedra, faces with four equivalent Mg(1)Ni12 cuboctahedra, faces with six equivalent Ni(1)Mg4Ni8 cuboctahedra, and faces with eight equivalent Ni(2)Mg4Ni8 cuboctahedra. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to four equivalent Mg(1) and eight equivalent Ni(2) atoms to form distorted NiMg4Ni8 cuboctahedra that share corners with four equivalent Ni(1)Mg4Ni8 cuboctahedra, corners with eight equivalent Mg(1)Ni12 cuboctahedra, edges with eight equivalent Ni(1)Mg4Ni8 cuboctahedra, edges with sixteen equivalent Ni(2)Mg4Ni8 cuboctahedra, faces with four equivalent Ni(1)Mg4Ni8 cuboctahedra, faces with six equivalent Mg(1)Ni12 cuboctahedra, and faces with eight equivalent Ni(2)Mg4Ni8 cuboctahedra. In the second Ni site, Ni(2) is bonded to four equivalent Mg(1), four equivalent Ni(1), and four equivalent Ni(2) atoms to form distorted NiMg4Ni8 cuboctahedra that share corners with twelve equivalent Ni(2)Mg4Ni8 cuboctahedra, edges with eight equivalent Mg(1)Ni12 cuboctahedra, edges with eight equivalent Ni(1)Mg4Ni8 cuboctahedra, edges with eight equivalent Ni(2)Mg4Ni8 cuboctahedra, faces with four equivalent Mg(1)Ni12 cuboctahedra, faces with four equivalent Ni(1)Mg4Ni8 cuboctahedra, and faces with ten equivalent Ni(2)Mg4Ni8 cuboctahedra.
MgNi3 is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. Mg(1) is bonded to four equivalent Ni(1) and eight equivalent Ni(2) atoms to form MgNi12 cuboctahedra that share corners with four equivalent Mg(1)Ni12 cuboctahedra, corners with eight equivalent Ni(1)Mg4Ni8 cuboctahedra, edges with eight equivalent Mg(1)Ni12 cuboctahedra, edges with sixteen equivalent Ni(2)Mg4Ni8 cuboctahedra, faces with four equivalent Mg(1)Ni12 cuboctahedra, faces with six equivalent Ni(1)Mg4Ni8 cuboctahedra, and faces with eight equivalent Ni(2)Mg4Ni8 cuboctahedra. All Mg(1)-Ni(1) bond lengths are 2.59 Å. All Mg(1)-Ni(2) bond lengths are 2.57 Å. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to four equivalent Mg(1) and eight equivalent Ni(2) atoms to form distorted NiMg4Ni8 cuboctahedra that share corners with four equivalent Ni(1)Mg4Ni8 cuboctahedra, corners with eight equivalent Mg(1)Ni12 cuboctahedra, edges with eight equivalent Ni(1)Mg4Ni8 cuboctahedra, edges with sixteen equivalent Ni(2)Mg4Ni8 cuboctahedra, faces with four equivalent Ni(1)Mg4Ni8 cuboctahedra, faces with six equivalent Mg(1)Ni12 cuboctahedra, and faces with eight equivalent Ni(2)Mg4Ni8 cuboctahedra. All Ni(1)-Ni(2) bond lengths are 2.57 Å. In the second Ni site, Ni(2) is bonded to four equivalent Mg(1), four equivalent Ni(1), and four equivalent Ni(2) atoms to form distorted NiMg4Ni8 cuboctahedra that share corners with twelve equivalent Ni(2)Mg4Ni8 cuboctahedra, edges with eight equivalent Mg(1)Ni12 cuboctahedra, edges with eight equivalent Ni(1)Mg4Ni8 cuboctahedra, edges with eight equivalent Ni(2)Mg4Ni8 cuboctahedra, faces with four equivalent Mg(1)Ni12 cuboctahedra, faces with four equivalent Ni(1)Mg4Ni8 cuboctahedra, and faces with ten equivalent Ni(2)Mg4Ni8 cuboctahedra. All Ni(2)-Ni(2) bond lengths are 2.59 Å.