Mg(CuS)2 crystallizes in the trigonal R3m space group. Mg(1) is bonded to one S(2) and three equivalent S(1) atoms to form distorted MgS4 tetrahedra that share corners with four equivalent Cu(1)S4 tetrahedra, corners with six equivalent Mg(1)S4 tetrahedra, and edges with three equivalent Cu(1)S4 tetrahedra. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one S(2) and three equivalent S(1) atoms to form CuS4 tetrahedra that share corners with four equivalent Mg(1)S4 tetrahedra, corners with six equivalent Cu(1)S4 tetrahedra, and edges with three equivalent Mg(1)S4 tetrahedra. In the second Cu site, Cu(2) is bonded in a trigonal planar geometry to three equivalent S(2) atoms. There are two inequivalent S sites. In the first S site, S(1) is bonded to three equivalent Mg(1) and three equivalent Cu(1) atoms to form distorted SMg3Cu3 octahedra that share corners with six equivalent S(2)MgCu4 trigonal bipyramids and edges with six equivalent S(1)Mg3Cu3 octahedra. In the second S site, S(2) is bonded to one Mg(1), one Cu(1), and three equivalent Cu(2) atoms to form SMgCu4 trigonal bipyramids that share corners with six equivalent S(1)Mg3Cu3 octahedra and corners with six equivalent S(2)MgCu4 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 62-67°.
Mg(CuS)2 crystallizes in the trigonal R3m space group. Mg(1) is bonded to one S(2) and three equivalent S(1) atoms to form distorted MgS4 tetrahedra that share corners with four equivalent Cu(1)S4 tetrahedra, corners with six equivalent Mg(1)S4 tetrahedra, and edges with three equivalent Cu(1)S4 tetrahedra. The Mg(1)-S(2) bond length is 2.40 Å. All Mg(1)-S(1) bond lengths are 2.53 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one S(2) and three equivalent S(1) atoms to form CuS4 tetrahedra that share corners with four equivalent Mg(1)S4 tetrahedra, corners with six equivalent Cu(1)S4 tetrahedra, and edges with three equivalent Mg(1)S4 tetrahedra. The Cu(1)-S(2) bond length is 2.28 Å. All Cu(1)-S(1) bond lengths are 2.43 Å. In the second Cu site, Cu(2) is bonded in a trigonal planar geometry to three equivalent S(2) atoms. All Cu(2)-S(2) bond lengths are 2.24 Å. There are two inequivalent S sites. In the first S site, S(1) is bonded to three equivalent Mg(1) and three equivalent Cu(1) atoms to form distorted SMg3Cu3 octahedra that share corners with six equivalent S(2)MgCu4 trigonal bipyramids and edges with six equivalent S(1)Mg3Cu3 octahedra. In the second S site, S(2) is bonded to one Mg(1), one Cu(1), and three equivalent Cu(2) atoms to form SMgCu4 trigonal bipyramids that share corners with six equivalent S(1)Mg3Cu3 octahedra and corners with six equivalent S(2)MgCu4 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 62-67°.