Fe3(Se2S)2 is Marcasite-derived structured and crystallizes in the monoclinic Pm space group. There are six inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one Se(2), two equivalent Se(5), two equivalent Se(8), and one S(3) atom to form FeSe5S octahedra that share corners with two equivalent Fe(6)Se2S4 octahedra, corners with two equivalent Fe(5)Se4S2 octahedra, corners with four equivalent Fe(4)Se4S2 octahedra,  a cornercorner with one Se(1)Fe3S tetrahedra, and edges with two equivalent Fe(1)Se5S octahedra. The corner-sharing octahedral tilt angles range from 57-58°. In the second Fe site, Fe(2) is bonded to two equivalent Se(3), two equivalent Se(6), one S(1), and one S(4) atom to form FeSe4S2 octahedra that share corners with two equivalent Fe(6)Se2S4 octahedra, corners with two equivalent Fe(4)Se4S2 octahedra, corners with four equivalent Fe(5)Se4S2 octahedra,  a cornercorner with one Se(2)Fe3S tetrahedra, and edges with two equivalent Fe(2)Se4S2 octahedra. The corner-sharing octahedral tilt angles range from 56-58°. In the third Fe site, Fe(3) is bonded to one Se(1), two equivalent Se(4), two equivalent Se(7), and one S(2) atom to form FeSe5S octahedra that share corners with two equivalent Fe(4)Se4S2 octahedra, corners with two equivalent Fe(5)Se4S2 octahedra, corners with four equivalent Fe(6)Se2S4 octahedra, and edges with two equivalent Fe(3)Se5S octahedra. The corner-sharing octahedral tilt angles range from 56-59°. In the fourth Fe site, Fe(4) is bonded to one Se(5), one Se(8), two equivalent Se(1), and two equivalent S(1) atoms to form FeSe4S2 octahedra that share corners with two equivalent Fe(2)Se4S2 octahedra, corners with two equivalent Fe(3)Se5S octahedra, corners with four equivalent Fe(1)Se5S octahedra, corners with two equivalent Se(2)Fe3S tetrahedra, and edges with two equivalent Fe(4)Se4S2 octahedra. The corner-sharing octahedral tilt angles range from 57-58°. In the fifth Fe site, Fe(5) is bonded to one Se(3), one Se(6), two equivalent Se(2), and two equivalent S(2) atoms to form FeSe4S2 octahedra that share corners with two equivalent Fe(1)Se5S octahedra, corners with two equivalent Fe(3)Se5S octahedra, corners with four equivalent Fe(2)Se4S2 octahedra, and edges with two equivalent Fe(5)Se4S2 octahedra. The corner-sharing octahedral tilt angles range from 56-59°. In the sixth Fe site, Fe(6) is bonded to one Se(4), one Se(7), two equivalent S(3), and two equivalent S(4) atoms to form FeSe2S4 octahedra that share corners with two equivalent Fe(2)Se4S2 octahedra, corners with two equivalent Fe(1)Se5S octahedra, corners with four equivalent Fe(3)Se5S octahedra, corners with two equivalent Se(1)Fe3S tetrahedra, and edges with two equivalent Fe(6)Se2S4 octahedra. The corner-sharing octahedral tilt angles range from 56-58°. There are eight inequivalent Se sites. In the first Se site, Se(1) is bonded to one Fe(3), two equivalent Fe(4), and one S(3) atom to form distorted SeFe3S tetrahedra that share  a cornercorner with one Fe(1)Se5S octahedra, corners with two equivalent Fe(6)Se2S4 octahedra, and corners with two equivalent Se(1)Fe3S tetrahedra. The corner-sharing octahedral tilt angles range from 74-80°. In the second Se site, Se(2) is bonded to one Fe(1), two equivalent Fe(5), and one S(1) atom to form distorted SeFe3S tetrahedra that share  a cornercorner with one Fe(2)Se4S2 octahedra, corners with two equivalent Fe(4)Se4S2 octahedra, and corners with two equivalent Se(2)Fe3S tetrahedra. The corner-sharing octahedral tilt angles range from 75-79°. In the third Se site, Se(3) is bonded in a 3-coordinate geometry to one Fe(5) and two equivalent Fe(2) atoms. In the fourth Se site, Se(4) is bonded in a 3-coordinate geometry to one Fe(6) and two equivalent Fe(3) atoms. In the fifth Se site, Se(5) is bonded in a 3-coordinate geometry to one Fe(4) and two equivalent Fe(1) atoms. In the sixth Se site, Se(6) is bonded in a 3-coordinate geometry to one Fe(5) and two equivalent Fe(2) atoms. In the seventh Se site, Se(7) is bonded in a 3-coordinate geometry to one Fe(6) and two equivalent Fe(3) atoms. In the eighth Se site, Se(8) is bonded in a 3-coordinate geometry to one Fe(4) and two equivalent Fe(1) atoms. There are four inequivalent S sites. In the first S site, S(1) is bonded in a 3-coordinate geometry to one Fe(2), two equivalent Fe(4), and one Se(2) atom. In the second S site, S(2) is bonded in a distorted trigonal planar geometry to one Fe(3) and two equivalent Fe(5) atoms. In the third S site, S(3) is bonded in a 4-coordinate geometry to one Fe(1), two equivalent Fe(6), and one Se(1) atom. In the fourth S site, S(4) is bonded in a 3-coordinate geometry to one Fe(2) and two equivalent Fe(6) atoms.
Fe3(Se2S)2 is Marcasite-derived structured and crystallizes in the monoclinic Pm space group. There are six inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one Se(2), two equivalent Se(5), two equivalent Se(8), and one S(3) atom to form FeSe5S octahedra that share corners with two equivalent Fe(6)Se2S4 octahedra, corners with two equivalent Fe(5)Se4S2 octahedra, corners with four equivalent Fe(4)Se4S2 octahedra,  a cornercorner with one Se(1)Fe3S tetrahedra, and edges with two equivalent Fe(1)Se5S octahedra. The corner-sharing octahedral tilt angles range from 57-58°. The Fe(1)-Se(2) bond length is 2.37 Å. Both Fe(1)-Se(5) bond lengths are 2.35 Å. Both Fe(1)-Se(8) bond lengths are 2.35 Å. The Fe(1)-S(3) bond length is 2.26 Å. In the second Fe site, Fe(2) is bonded to two equivalent Se(3), two equivalent Se(6), one S(1), and one S(4) atom to form FeSe4S2 octahedra that share corners with two equivalent Fe(6)Se2S4 octahedra, corners with two equivalent Fe(4)Se4S2 octahedra, corners with four equivalent Fe(5)Se4S2 octahedra,  a cornercorner with one Se(2)Fe3S tetrahedra, and edges with two equivalent Fe(2)Se4S2 octahedra. The corner-sharing octahedral tilt angles range from 56-58°. Both Fe(2)-Se(3) bond lengths are 2.35 Å. Both Fe(2)-Se(6) bond lengths are 2.34 Å. The Fe(2)-S(1) bond length is 2.28 Å. The Fe(2)-S(4) bond length is 2.29 Å. In the third Fe site, Fe(3) is bonded to one Se(1), two equivalent Se(4), two equivalent Se(7), and one S(2) atom to form FeSe5S octahedra that share corners with two equivalent Fe(4)Se4S2 octahedra, corners with two equivalent Fe(5)Se4S2 octahedra, corners with four equivalent Fe(6)Se2S4 octahedra, and edges with two equivalent Fe(3)Se5S octahedra. The corner-sharing octahedral tilt angles range from 56-59°. The Fe(3)-Se(1) bond length is 2.36 Å. Both Fe(3)-Se(4) bond lengths are 2.34 Å. Both Fe(3)-Se(7) bond lengths are 2.35 Å. The Fe(3)-S(2) bond length is 2.23 Å. In the fourth Fe site, Fe(4) is bonded to one Se(5), one Se(8), two equivalent Se(1), and two equivalent S(1) atoms to form FeSe4S2 octahedra that share corners with two equivalent Fe(2)Se4S2 octahedra, corners with two equivalent Fe(3)Se5S octahedra, corners with four equivalent Fe(1)Se5S octahedra, corners with two equivalent Se(2)Fe3S tetrahedra, and edges with two equivalent Fe(4)Se4S2 octahedra. The corner-sharing octahedral tilt angles range from 57-58°. The Fe(4)-Se(5) bond length is 2.33 Å. The Fe(4)-Se(8) bond length is 2.35 Å. Both Fe(4)-Se(1) bond lengths are 2.37 Å. Both Fe(4)-S(1) bond lengths are 2.29 Å. In the fifth Fe site, Fe(5) is bonded to one Se(3), one Se(6), two equivalent Se(2), and two equivalent S(2) atoms to form FeSe4S2 octahedra that share corners with two equivalent Fe(1)Se5S octahedra, corners with two equivalent Fe(3)Se5S octahedra, corners with four equivalent Fe(2)Se4S2 octahedra, and edges with two equivalent Fe(5)Se4S2 octahedra. The corner-sharing octahedral tilt angles range from 56-59°. The Fe(5)-Se(3) bond length is 2.35 Å. The Fe(5)-Se(6) bond length is 2.33 Å. Both Fe(5)-Se(2) bond lengths are 2.37 Å. Both Fe(5)-S(2) bond lengths are 2.28 Å. In the sixth Fe site, Fe(6) is bonded to one Se(4), one Se(7), two equivalent S(3), and two equivalent S(4) atoms to form FeSe2S4 octahedra that share corners with two equivalent Fe(2)Se4S2 octahedra, corners with two equivalent Fe(1)Se5S octahedra, corners with four equivalent Fe(3)Se5S octahedra, corners with two equivalent Se(1)Fe3S tetrahedra, and edges with two equivalent Fe(6)Se2S4 octahedra. The corner-sharing octahedral tilt angles range from 56-58°. The Fe(6)-Se(4) bond length is 2.33 Å. The Fe(6)-Se(7) bond length is 2.35 Å. Both Fe(6)-S(3) bond lengths are 2.30 Å. Both Fe(6)-S(4) bond lengths are 2.31 Å. There are eight inequivalent Se sites. In the first Se site, Se(1) is bonded to one Fe(3), two equivalent Fe(4), and one S(3) atom to form distorted SeFe3S tetrahedra that share  a cornercorner with one Fe(1)Se5S octahedra, corners with two equivalent Fe(6)Se2S4 octahedra, and corners with two equivalent Se(1)Fe3S tetrahedra. The corner-sharing octahedral tilt angles range from 74-80°. The Se(1)-S(3) bond length is 2.56 Å. In the second Se site, Se(2) is bonded to one Fe(1), two equivalent Fe(5), and one S(1) atom to form distorted SeFe3S tetrahedra that share  a cornercorner with one Fe(2)Se4S2 octahedra, corners with two equivalent Fe(4)Se4S2 octahedra, and corners with two equivalent Se(2)Fe3S tetrahedra. The corner-sharing octahedral tilt angles range from 75-79°. The Se(2)-S(1) bond length is 2.55 Å. In the third Se site, Se(3) is bonded in a 3-coordinate geometry to one Fe(5) and two equivalent Fe(2) atoms. In the fourth Se site, Se(4) is bonded in a 3-coordinate geometry to one Fe(6) and two equivalent Fe(3) atoms. In the fifth Se site, Se(5) is bonded in a 3-coordinate geometry to one Fe(4) and two equivalent Fe(1) atoms. In the sixth Se site, Se(6) is bonded in a 3-coordinate geometry to one Fe(5) and two equivalent Fe(2) atoms. In the seventh Se site, Se(7) is bonded in a 3-coordinate geometry to one Fe(6) and two equivalent Fe(3) atoms. In the eighth Se site, Se(8) is bonded in a 3-coordinate geometry to one Fe(4) and two equivalent Fe(1) atoms. There are four inequivalent S sites. In the first S site, S(1) is bonded in a 3-coordinate geometry to one Fe(2), two equivalent Fe(4), and one Se(2) atom. In the second S site, S(2) is bonded in a distorted trigonal planar geometry to one Fe(3) and two equivalent Fe(5) atoms. In the third S site, S(3) is bonded in a 4-coordinate geometry to one Fe(1), two equivalent Fe(6), and one Se(1) atom. In the fourth S site, S(4) is bonded in a 3-coordinate geometry to one Fe(2) and two equivalent Fe(6) atoms.