MgFeCuS2 crystallizes in the trigonal P3m1 space group. Mg(1) is bonded to three equivalent S(1) and three equivalent S(2) atoms to form edge-sharing MgS6 octahedra. Fe(1) is bonded in a 4-coordinate geometry to three equivalent Cu(1), one S(1), and three equivalent S(2) atoms. Cu(1) is bonded in a 7-coordinate geometry to three equivalent Fe(1), one S(2), and three equivalent S(1) atoms. There are two inequivalent S sites. In the first S site, S(1) is bonded to three equivalent Mg(1), one Fe(1), and three equivalent Cu(1) atoms to form distorted edge-sharing SMg3FeCu3 pentagonal bipyramids. In the second S site, S(2) is bonded in a 7-coordinate geometry to three equivalent Mg(1), three equivalent Fe(1), and one Cu(1) atom.
MgFeCuS2 crystallizes in the trigonal P3m1 space group. Mg(1) is bonded to three equivalent S(1) and three equivalent S(2) atoms to form edge-sharing MgS6 octahedra. All Mg(1)-S(1) bond lengths are 2.63 Å. All Mg(1)-S(2) bond lengths are 2.61 Å. Fe(1) is bonded in a 4-coordinate geometry to three equivalent Cu(1), one S(1), and three equivalent S(2) atoms. All Fe(1)-Cu(1) bond lengths are 2.60 Å. The Fe(1)-S(1) bond length is 2.42 Å. All Fe(1)-S(2) bond lengths are 2.40 Å. Cu(1) is bonded in a 7-coordinate geometry to three equivalent Fe(1), one S(2), and three equivalent S(1) atoms. The Cu(1)-S(2) bond length is 2.56 Å. All Cu(1)-S(1) bond lengths are 2.34 Å. There are two inequivalent S sites. In the first S site, S(1) is bonded to three equivalent Mg(1), one Fe(1), and three equivalent Cu(1) atoms to form distorted edge-sharing SMg3FeCu3 pentagonal bipyramids. In the second S site, S(2) is bonded in a 7-coordinate geometry to three equivalent Mg(1), three equivalent Fe(1), and one Cu(1) atom.