Li10Cu4S9 crystallizes in the tetragonal P4_2/nmc space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded to two equivalent S(1) and two equivalent S(2) atoms to form distorted LiS4 tetrahedra that share corners with two equivalent Li(2)S4 tetrahedra, corners with four equivalent Cu(1)S4 tetrahedra, corners with six equivalent Li(1)S4 tetrahedra,  an edgeedge with one Li(2)S4 tetrahedra,  an edgeedge with one Cu(1)S4 tetrahedra, and edges with three equivalent Li(1)S4 tetrahedra. In the second Li site, Li(2) is bonded to four equivalent S(2) atoms to form LiS4 tetrahedra that share corners with four equivalent Cu(1)S4 tetrahedra, corners with eight equivalent Li(1)S4 tetrahedra, edges with two equivalent Li(2)S4 tetrahedra, and edges with four equivalent Li(1)S4 tetrahedra. Cu(1) is bonded to one S(2), one S(3), and two equivalent S(1) atoms to form CuS4 tetrahedra that share corners with two equivalent Li(2)S4 tetrahedra, corners with five equivalent Cu(1)S4 tetrahedra, corners with eight equivalent Li(1)S4 tetrahedra, and edges with two equivalent Li(1)S4 tetrahedra. There are three inequivalent S sites. In the first S site, S(1) is bonded to four equivalent Li(1) and two equivalent Cu(1) atoms to form distorted SLi4Cu2 octahedra that share corners with two equivalent S(1)Li4Cu2 octahedra, corners with two equivalent S(2)Li6Cu pentagonal bipyramids, corners with two equivalent S(3)Cu4 tetrahedra, edges with two equivalent S(1)Li4Cu2 octahedra, and edges with four equivalent S(2)Li6Cu pentagonal bipyramids. The corner-sharing octahedral tilt angles are 73°. In the second S site, S(2) is bonded to two equivalent Li(2), four equivalent Li(1), and one Cu(1) atom to form distorted SLi6Cu pentagonal bipyramids that share corners with two equivalent S(1)Li4Cu2 octahedra,  a cornercorner with one S(3)Cu4 tetrahedra, edges with four equivalent S(1)Li4Cu2 octahedra, and edges with five equivalent S(2)Li6Cu pentagonal bipyramids. The corner-sharing octahedral tilt angles are 56°. In the third S site, S(3) is bonded to four equivalent Cu(1) atoms to form SCu4 tetrahedra that share corners with eight equivalent S(1)Li4Cu2 octahedra and corners with four equivalent S(2)Li6Cu pentagonal bipyramids. The corner-sharing octahedral tilt angles are 67°.
Li10Cu4S9 crystallizes in the tetragonal P4_2/nmc space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded to two equivalent S(1) and two equivalent S(2) atoms to form distorted LiS4 tetrahedra that share corners with two equivalent Li(2)S4 tetrahedra, corners with four equivalent Cu(1)S4 tetrahedra, corners with six equivalent Li(1)S4 tetrahedra,  an edgeedge with one Li(2)S4 tetrahedra,  an edgeedge with one Cu(1)S4 tetrahedra, and edges with three equivalent Li(1)S4 tetrahedra. There is one shorter (2.41 Å) and one longer (2.54 Å) Li(1)-S(1) bond length. There is one shorter (2.39 Å) and one longer (2.46 Å) Li(1)-S(2) bond length. In the second Li site, Li(2) is bonded to four equivalent S(2) atoms to form LiS4 tetrahedra that share corners with four equivalent Cu(1)S4 tetrahedra, corners with eight equivalent Li(1)S4 tetrahedra, edges with two equivalent Li(2)S4 tetrahedra, and edges with four equivalent Li(1)S4 tetrahedra. There are two shorter (2.39 Å) and two longer (2.40 Å) Li(2)-S(2) bond lengths. Cu(1) is bonded to one S(2), one S(3), and two equivalent S(1) atoms to form CuS4 tetrahedra that share corners with two equivalent Li(2)S4 tetrahedra, corners with five equivalent Cu(1)S4 tetrahedra, corners with eight equivalent Li(1)S4 tetrahedra, and edges with two equivalent Li(1)S4 tetrahedra. The Cu(1)-S(2) bond length is 2.31 Å. The Cu(1)-S(3) bond length is 2.30 Å. Both Cu(1)-S(1) bond lengths are 2.31 Å. There are three inequivalent S sites. In the first S site, S(1) is bonded to four equivalent Li(1) and two equivalent Cu(1) atoms to form distorted SLi4Cu2 octahedra that share corners with two equivalent S(1)Li4Cu2 octahedra, corners with two equivalent S(2)Li6Cu pentagonal bipyramids, corners with two equivalent S(3)Cu4 tetrahedra, edges with two equivalent S(1)Li4Cu2 octahedra, and edges with four equivalent S(2)Li6Cu pentagonal bipyramids. The corner-sharing octahedral tilt angles are 73°. In the second S site, S(2) is bonded to two equivalent Li(2), four equivalent Li(1), and one Cu(1) atom to form distorted SLi6Cu pentagonal bipyramids that share corners with two equivalent S(1)Li4Cu2 octahedra,  a cornercorner with one S(3)Cu4 tetrahedra, edges with four equivalent S(1)Li4Cu2 octahedra, and edges with five equivalent S(2)Li6Cu pentagonal bipyramids. The corner-sharing octahedral tilt angles are 56°. In the third S site, S(3) is bonded to four equivalent Cu(1) atoms to form SCu4 tetrahedra that share corners with eight equivalent S(1)Li4Cu2 octahedra and corners with four equivalent S(2)Li6Cu pentagonal bipyramids. The corner-sharing octahedral tilt angles are 67°.