Li5Mg crystallizes in the hexagonal P-6m2 space group. There are four inequivalent Li sites. In the first Li site, Li(1) is bonded to three equivalent Li(2), six equivalent Li(1), and three equivalent Mg(1) atoms to form LiLi9Mg3 cuboctahedra that share corners with six equivalent Li(3)Li12 cuboctahedra, corners with twelve equivalent Li(1)Li9Mg3 cuboctahedra, edges with six equivalent Li(2)Li12 cuboctahedra, edges with six equivalent Li(1)Li9Mg3 cuboctahedra, edges with six equivalent Mg(1)Li6Mg6 cuboctahedra,  a faceface with one Li(3)Li12 cuboctahedra, faces with six equivalent Li(2)Li12 cuboctahedra, faces with six equivalent Mg(1)Li6Mg6 cuboctahedra, and faces with seven equivalent Li(1)Li9Mg3 cuboctahedra. In the second Li site, Li(2) is bonded to three equivalent Li(1), three equivalent Li(3), and six equivalent Li(2) atoms to form LiLi12 cuboctahedra that share corners with six equivalent Mg(1)Li6Mg6 cuboctahedra; corners with twelve Li(2,2)Li12 cuboctahedra; edges with six equivalent Li(2)Li12 cuboctahedra; edges with six equivalent Li(3)Li12 cuboctahedra; edges with six equivalent Li(1)Li9Mg3 cuboctahedra;  a faceface with one Mg(1)Li6Mg6 cuboctahedra; faces with six equivalent Li(3)Li12 cuboctahedra; faces with six equivalent Li(1)Li9Mg3 cuboctahedra; and faces with seven Li(2,2)Li12 cuboctahedra. In the third Li site, Li(3) is bonded to six Li(2,2) and six equivalent Li(3) atoms to form LiLi12 cuboctahedra that share corners with six equivalent Li(3)Li12 cuboctahedra; corners with twelve equivalent Li(1)Li9Mg3 cuboctahedra; edges with six equivalent Li(3)Li12 cuboctahedra; edges with twelve Li(2,2)Li12 cuboctahedra; faces with two equivalent Li(1)Li9Mg3 cuboctahedra; faces with six equivalent Li(3)Li12 cuboctahedra; and faces with twelve Li(2,2)Li12 cuboctahedra. In the fourth Li site, Li(2) is bonded to three equivalent Li(1), three equivalent Li(3), and six equivalent Li(2) atoms to form LiLi12 cuboctahedra that share corners with six equivalent Mg(1)Li6Mg6 cuboctahedra; corners with twelve Li(2,2)Li12 cuboctahedra; edges with six equivalent Li(2)Li12 cuboctahedra; edges with six equivalent Li(3)Li12 cuboctahedra; edges with six equivalent Li(1)Li9Mg3 cuboctahedra;  a faceface with one Mg(1)Li6Mg6 cuboctahedra; faces with six equivalent Li(3)Li12 cuboctahedra; faces with six equivalent Li(1)Li9Mg3 cuboctahedra; and faces with seven Li(2,2)Li12 cuboctahedra. Mg(1) is bonded to six equivalent Li(1) and six equivalent Mg(1) atoms to form MgLi6Mg6 cuboctahedra that share corners with six equivalent Mg(1)Li6Mg6 cuboctahedra; corners with twelve Li(2,2)Li12 cuboctahedra; edges with six equivalent Mg(1)Li6Mg6 cuboctahedra; edges with twelve equivalent Li(1)Li9Mg3 cuboctahedra; faces with two Li(2,2)Li12 cuboctahedra; faces with six equivalent Mg(1)Li6Mg6 cuboctahedra; and faces with twelve equivalent Li(1)Li9Mg3 cuboctahedra.
Li5Mg crystallizes in the hexagonal P-6m2 space group. There are four inequivalent Li sites. In the first Li site, Li(1) is bonded to three equivalent Li(2), six equivalent Li(1), and three equivalent Mg(1) atoms to form LiLi9Mg3 cuboctahedra that share corners with six equivalent Li(3)Li12 cuboctahedra, corners with twelve equivalent Li(1)Li9Mg3 cuboctahedra, edges with six equivalent Li(2)Li12 cuboctahedra, edges with six equivalent Li(1)Li9Mg3 cuboctahedra, edges with six equivalent Mg(1)Li6Mg6 cuboctahedra,  a faceface with one Li(3)Li12 cuboctahedra, faces with six equivalent Li(2)Li12 cuboctahedra, faces with six equivalent Mg(1)Li6Mg6 cuboctahedra, and faces with seven equivalent Li(1)Li9Mg3 cuboctahedra. All Li(1)-Li(2) bond lengths are 3.07 Å. All Li(1)-Li(1) bond lengths are 3.06 Å. All Li(1)-Mg(1) bond lengths are 3.15 Å. In the second Li site, Li(2) is bonded to three equivalent Li(1), three equivalent Li(3), and six equivalent Li(2) atoms to form LiLi12 cuboctahedra that share corners with six equivalent Mg(1)Li6Mg6 cuboctahedra; corners with twelve Li(2,2)Li12 cuboctahedra; edges with six equivalent Li(2)Li12 cuboctahedra; edges with six equivalent Li(3)Li12 cuboctahedra; edges with six equivalent Li(1)Li9Mg3 cuboctahedra;  a faceface with one Mg(1)Li6Mg6 cuboctahedra; faces with six equivalent Li(3)Li12 cuboctahedra; faces with six equivalent Li(1)Li9Mg3 cuboctahedra; and faces with seven Li(2,2)Li12 cuboctahedra. All Li(2)-Li(3) bond lengths are 3.11 Å. All Li(2)-Li(2) bond lengths are 3.06 Å. In the third Li site, Li(3) is bonded to six Li(2,2) and six equivalent Li(3) atoms to form LiLi12 cuboctahedra that share corners with six equivalent Li(3)Li12 cuboctahedra; corners with twelve equivalent Li(1)Li9Mg3 cuboctahedra; edges with six equivalent Li(3)Li12 cuboctahedra; edges with twelve Li(2,2)Li12 cuboctahedra; faces with two equivalent Li(1)Li9Mg3 cuboctahedra; faces with six equivalent Li(3)Li12 cuboctahedra; and faces with twelve Li(2,2)Li12 cuboctahedra. All Li(3)-Li(2) bond lengths are 3.11 Å. All Li(3)-Li(3) bond lengths are 3.06 Å. In the fourth Li site, Li(2) is bonded to three equivalent Li(1), three equivalent Li(3), and six equivalent Li(2) atoms to form LiLi12 cuboctahedra that share corners with six equivalent Mg(1)Li6Mg6 cuboctahedra; corners with twelve Li(2,2)Li12 cuboctahedra; edges with six equivalent Li(2)Li12 cuboctahedra; edges with six equivalent Li(3)Li12 cuboctahedra; edges with six equivalent Li(1)Li9Mg3 cuboctahedra;  a faceface with one Mg(1)Li6Mg6 cuboctahedra; faces with six equivalent Li(3)Li12 cuboctahedra; faces with six equivalent Li(1)Li9Mg3 cuboctahedra; and faces with seven Li(2,2)Li12 cuboctahedra. All Li(2)-Li(1) bond lengths are 3.07 Å. All Li(2)-Li(2) bond lengths are 3.06 Å. Mg(1) is bonded to six equivalent Li(1) and six equivalent Mg(1) atoms to form MgLi6Mg6 cuboctahedra that share corners with six equivalent Mg(1)Li6Mg6 cuboctahedra; corners with twelve Li(2,2)Li12 cuboctahedra; edges with six equivalent Mg(1)Li6Mg6 cuboctahedra; edges with twelve equivalent Li(1)Li9Mg3 cuboctahedra; faces with two Li(2,2)Li12 cuboctahedra; faces with six equivalent Mg(1)Li6Mg6 cuboctahedra; and faces with twelve equivalent Li(1)Li9Mg3 cuboctahedra. All Mg(1)-Mg(1) bond lengths are 3.06 Å.