FeFeS crystallizes in the monoclinic Cm space group. There are fourteen inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a distorted bent 150 degrees geometry to one S(1) and one S(2) atom. In the second Fe site, Fe(2) is bonded in a 2-coordinate geometry to one S(7) and two equivalent S(1) atoms. In the third Fe site, Fe(3) is bonded in a 2-coordinate geometry to one S(4) and three equivalent S(3) atoms. In the fourth Fe site, Fe(4) is bonded in a 3-coordinate geometry to one S(3) and two equivalent S(2) atoms. In the fifth Fe site, Fe(5) is bonded in a 3-coordinate geometry to one S(4) and two equivalent S(3) atoms. In the sixth Fe site, Fe(6) is bonded in a 3-coordinate geometry to one S(3) and two equivalent S(2) atoms. In the seventh Fe site, Fe(7) is bonded in a 3-coordinate geometry to one S(5) and two equivalent S(4) atoms. In the eighth Fe site, Fe(8) is bonded in a 3-coordinate geometry to one S(5) and two equivalent S(4) atoms. In the ninth Fe site, Fe(9) is bonded in a 3-coordinate geometry to one S(6) and two equivalent S(5) atoms. In the tenth Fe site, Fe(10) is bonded in a 4-coordinate geometry to one S(6) and three equivalent S(5) atoms. In the eleventh Fe site, Fe(11) is bonded in a 3-coordinate geometry to one S(7) and two equivalent S(6) atoms. In the twelfth Fe site, Fe(12) is bonded in a distorted trigonal non-coplanar geometry to one S(7) and two equivalent S(6) atoms. In the thirteenth Fe site, Fe(13) is bonded in a distorted rectangular see-saw-like geometry to two equivalent S(1) and two equivalent S(7) atoms. In the fourteenth Fe site, Fe(14) is bonded in a 3-coordinate geometry to three equivalent S(7) atoms. There are seven inequivalent S sites. In the first S site, S(1) is bonded in a 5-coordinate geometry to one Fe(1), two equivalent Fe(13), and two equivalent Fe(2) atoms. In the second S site, S(2) is bonded in a 5-coordinate geometry to one Fe(1), two equivalent Fe(4), and two equivalent Fe(6) atoms. In the third S site, S(3) is bonded in a 7-coordinate geometry to one Fe(4), one Fe(6), two equivalent Fe(5), and three equivalent Fe(3) atoms. In the fourth S site, S(4) is bonded in a 6-coordinate geometry to one Fe(3), one Fe(5), two equivalent Fe(7), and two equivalent Fe(8) atoms. In the fifth S site, S(5) is bonded in a 7-coordinate geometry to one Fe(7), one Fe(8), two equivalent Fe(9), and three equivalent Fe(10) atoms. In the sixth S site, S(6) is bonded in a 6-coordinate geometry to one Fe(10), one Fe(9), two equivalent Fe(11), and two equivalent Fe(12) atoms. In the seventh S site, S(7) is bonded in a 8-coordinate geometry to one Fe(11), one Fe(12), one Fe(2), two equivalent Fe(13), and three equivalent Fe(14) atoms.
FeFeS crystallizes in the monoclinic Cm space group. There are fourteen inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a distorted bent 150 degrees geometry to one S(1) and one S(2) atom. The Fe(1)-S(1) bond length is 2.23 Å. The Fe(1)-S(2) bond length is 2.28 Å. In the second Fe site, Fe(2) is bonded in a 2-coordinate geometry to one S(7) and two equivalent S(1) atoms. The Fe(2)-S(7) bond length is 2.64 Å. Both Fe(2)-S(1) bond lengths are 2.30 Å. In the third Fe site, Fe(3) is bonded in a 2-coordinate geometry to one S(4) and three equivalent S(3) atoms. The Fe(3)-S(4) bond length is 2.28 Å. There is one shorter (2.26 Å) and two longer (2.62 Å) Fe(3)-S(3) bond lengths. In the fourth Fe site, Fe(4) is bonded in a 3-coordinate geometry to one S(3) and two equivalent S(2) atoms. The Fe(4)-S(3) bond length is 2.32 Å. Both Fe(4)-S(2) bond lengths are 2.30 Å. In the fifth Fe site, Fe(5) is bonded in a 3-coordinate geometry to one S(4) and two equivalent S(3) atoms. The Fe(5)-S(4) bond length is 2.21 Å. Both Fe(5)-S(3) bond lengths are 2.15 Å. In the sixth Fe site, Fe(6) is bonded in a 3-coordinate geometry to one S(3) and two equivalent S(2) atoms. The Fe(6)-S(3) bond length is 2.23 Å. Both Fe(6)-S(2) bond lengths are 2.29 Å. In the seventh Fe site, Fe(7) is bonded in a 3-coordinate geometry to one S(5) and two equivalent S(4) atoms. The Fe(7)-S(5) bond length is 2.28 Å. Both Fe(7)-S(4) bond lengths are 2.37 Å. In the eighth Fe site, Fe(8) is bonded in a 3-coordinate geometry to one S(5) and two equivalent S(4) atoms. The Fe(8)-S(5) bond length is 2.25 Å. Both Fe(8)-S(4) bond lengths are 2.25 Å. In the ninth Fe site, Fe(9) is bonded in a 3-coordinate geometry to one S(6) and two equivalent S(5) atoms. The Fe(9)-S(6) bond length is 2.34 Å. Both Fe(9)-S(5) bond lengths are 2.24 Å. In the tenth Fe site, Fe(10) is bonded in a 4-coordinate geometry to one S(6) and three equivalent S(5) atoms. The Fe(10)-S(6) bond length is 2.25 Å. There is one shorter (2.37 Å) and two longer (2.55 Å) Fe(10)-S(5) bond lengths. In the eleventh Fe site, Fe(11) is bonded in a 3-coordinate geometry to one S(7) and two equivalent S(6) atoms. The Fe(11)-S(7) bond length is 2.32 Å. Both Fe(11)-S(6) bond lengths are 2.47 Å. In the twelfth Fe site, Fe(12) is bonded in a distorted trigonal non-coplanar geometry to one S(7) and two equivalent S(6) atoms. The Fe(12)-S(7) bond length is 2.16 Å. Both Fe(12)-S(6) bond lengths are 2.20 Å. In the thirteenth Fe site, Fe(13) is bonded in a distorted rectangular see-saw-like geometry to two equivalent S(1) and two equivalent S(7) atoms. Both Fe(13)-S(1) bond lengths are 2.22 Å. Both Fe(13)-S(7) bond lengths are 2.21 Å. In the fourteenth Fe site, Fe(14) is bonded in a 3-coordinate geometry to three equivalent S(7) atoms. There is one shorter (2.34 Å) and two longer (2.59 Å) Fe(14)-S(7) bond lengths. There are seven inequivalent S sites. In the first S site, S(1) is bonded in a 5-coordinate geometry to one Fe(1), two equivalent Fe(13), and two equivalent Fe(2) atoms. In the second S site, S(2) is bonded in a 5-coordinate geometry to one Fe(1), two equivalent Fe(4), and two equivalent Fe(6) atoms. In the third S site, S(3) is bonded in a 7-coordinate geometry to one Fe(4), one Fe(6), two equivalent Fe(5), and three equivalent Fe(3) atoms. In the fourth S site, S(4) is bonded in a 6-coordinate geometry to one Fe(3), one Fe(5), two equivalent Fe(7), and two equivalent Fe(8) atoms. In the fifth S site, S(5) is bonded in a 7-coordinate geometry to one Fe(7), one Fe(8), two equivalent Fe(9), and three equivalent Fe(10) atoms. In the sixth S site, S(6) is bonded in a 6-coordinate geometry to one Fe(10), one Fe(9), two equivalent Fe(11), and two equivalent Fe(12) atoms. In the seventh S site, S(7) is bonded in a 8-coordinate geometry to one Fe(11), one Fe(12), one Fe(2), two equivalent Fe(13), and three equivalent Fe(14) atoms.