MgNb2 is beta-derived structured and crystallizes in the trigonal R-3m space group. Mg(1) is bonded to six equivalent Mg(1) and six equivalent Nb(1) atoms to form MgMg6Nb6 cuboctahedra that share corners with six equivalent Mg(1)Mg6Nb6 cuboctahedra, corners with twelve equivalent Nb(1)Mg3Nb9 cuboctahedra, edges with six equivalent Mg(1)Mg6Nb6 cuboctahedra, edges with twelve equivalent Nb(1)Mg3Nb9 cuboctahedra, faces with six equivalent Mg(1)Mg6Nb6 cuboctahedra, and faces with fourteen equivalent Nb(1)Mg3Nb9 cuboctahedra. Nb(1) is bonded to three equivalent Mg(1) and nine equivalent Nb(1) atoms to form NbMg3Nb9 cuboctahedra that share corners with six equivalent Mg(1)Mg6Nb6 cuboctahedra, corners with nine equivalent Nb(1)Mg3Nb9 cuboctahedra, edges with six equivalent Mg(1)Mg6Nb6 cuboctahedra, edges with fifteen equivalent Nb(1)Mg3Nb9 cuboctahedra, faces with seven equivalent Mg(1)Mg6Nb6 cuboctahedra, and faces with twelve equivalent Nb(1)Mg3Nb9 cuboctahedra.
MgNb2 is beta-derived structured and crystallizes in the trigonal R-3m space group. Mg(1) is bonded to six equivalent Mg(1) and six equivalent Nb(1) atoms to form MgMg6Nb6 cuboctahedra that share corners with six equivalent Mg(1)Mg6Nb6 cuboctahedra, corners with twelve equivalent Nb(1)Mg3Nb9 cuboctahedra, edges with six equivalent Mg(1)Mg6Nb6 cuboctahedra, edges with twelve equivalent Nb(1)Mg3Nb9 cuboctahedra, faces with six equivalent Mg(1)Mg6Nb6 cuboctahedra, and faces with fourteen equivalent Nb(1)Mg3Nb9 cuboctahedra. All Mg(1)-Mg(1) bond lengths are 2.92 Å. All Mg(1)-Nb(1) bond lengths are 3.10 Å. Nb(1) is bonded to three equivalent Mg(1) and nine equivalent Nb(1) atoms to form NbMg3Nb9 cuboctahedra that share corners with six equivalent Mg(1)Mg6Nb6 cuboctahedra, corners with nine equivalent Nb(1)Mg3Nb9 cuboctahedra, edges with six equivalent Mg(1)Mg6Nb6 cuboctahedra, edges with fifteen equivalent Nb(1)Mg3Nb9 cuboctahedra, faces with seven equivalent Mg(1)Mg6Nb6 cuboctahedra, and faces with twelve equivalent Nb(1)Mg3Nb9 cuboctahedra. There are six shorter (2.92 Å) and three longer (3.09 Å) Nb(1)-Nb(1) bond lengths.