TaCu3Se3S is Sulvanite-derived structured and crystallizes in the trigonal R3m space group. Ta(1) is bonded to three equivalent Se(1) and one S(1) atom to form distorted TaSe3S tetrahedra that share edges with six equivalent Cu(1)Se3S tetrahedra. Cu(1) is bonded to three equivalent Se(1) and one S(1) atom to form distorted CuSe3S tetrahedra that share corners with eight equivalent Cu(1)Se3S tetrahedra and edges with two equivalent Ta(1)Se3S tetrahedra. Se(1) is bonded to one Ta(1) and three equivalent Cu(1) atoms to form SeTaCu3 tetrahedra that share corners with two equivalent S(1)TaCu3 tetrahedra, corners with four equivalent Se(1)TaCu3 tetrahedra,  an edgeedge with one S(1)TaCu3 tetrahedra, and edges with two equivalent Se(1)TaCu3 tetrahedra. S(1) is bonded to one Ta(1) and three equivalent Cu(1) atoms to form distorted STaCu3 tetrahedra that share corners with six equivalent Se(1)TaCu3 tetrahedra and edges with three equivalent Se(1)TaCu3 tetrahedra.
TaCu3Se3S is Sulvanite-derived structured and crystallizes in the trigonal R3m space group. Ta(1) is bonded to three equivalent Se(1) and one S(1) atom to form distorted TaSe3S tetrahedra that share edges with six equivalent Cu(1)Se3S tetrahedra. All Ta(1)-Se(1) bond lengths are 2.46 Å. The Ta(1)-S(1) bond length is 2.32 Å. Cu(1) is bonded to three equivalent Se(1) and one S(1) atom to form distorted CuSe3S tetrahedra that share corners with eight equivalent Cu(1)Se3S tetrahedra and edges with two equivalent Ta(1)Se3S tetrahedra. There are two shorter (2.47 Å) and one longer (2.49 Å) Cu(1)-Se(1) bond length. The Cu(1)-S(1) bond length is 2.35 Å. Se(1) is bonded to one Ta(1) and three equivalent Cu(1) atoms to form SeTaCu3 tetrahedra that share corners with two equivalent S(1)TaCu3 tetrahedra, corners with four equivalent Se(1)TaCu3 tetrahedra,  an edgeedge with one S(1)TaCu3 tetrahedra, and edges with two equivalent Se(1)TaCu3 tetrahedra. S(1) is bonded to one Ta(1) and three equivalent Cu(1) atoms to form distorted STaCu3 tetrahedra that share corners with six equivalent Se(1)TaCu3 tetrahedra and edges with three equivalent Se(1)TaCu3 tetrahedra.