Fe7Se3 crystallizes in the triclinic P-1 space group. There are fourteen inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 2-coordinate geometry to one Se(1), one Se(3), and one Se(4) atom. In the second Fe site, Fe(2) is bonded in a 3-coordinate geometry to two equivalent Se(1) and two equivalent Se(3) atoms. In the third Fe site, Fe(3) is bonded in a 2-coordinate geometry to one Se(4) and one Se(5) atom. In the fourth Fe site, Fe(4) is bonded in a 3-coordinate geometry to two equivalent Se(2) and two equivalent Se(5) atoms. In the fifth Fe site, Fe(5) is bonded in a 2-coordinate geometry to one Se(2), one Se(3), and one Se(4) atom. In the sixth Fe site, Fe(6) is bonded in a 4-coordinate geometry to one Se(1), one Se(2), one Se(3), and one Se(6) atom. In the seventh Fe site, Fe(7) is bonded in a 3-coordinate geometry to one Se(2), one Se(4), and one Se(5) atom. In the eighth Fe site, Fe(8) is bonded in a 2-coordinate geometry to one Se(1), one Se(5), and one Se(6) atom. In the ninth Fe site, Fe(9) is bonded in a 3-coordinate geometry to one Se(1), one Se(2), one Se(4), and one Se(5) atom. In the tenth Fe site, Fe(10) is bonded in a 2-coordinate geometry to one Se(2), one Se(5), and one Se(6) atom. In the eleventh Fe site, Fe(11) is bonded in a 3-coordinate geometry to two equivalent Se(2) and two equivalent Se(4) atoms. In the twelfth Fe site, Fe(12) is bonded in a 3-coordinate geometry to two equivalent Se(1) and two equivalent Se(6) atoms. In the thirteenth Fe site, Fe(13) is bonded in a 4-coordinate geometry to one Se(3), one Se(4), one Se(5), and one Se(6) atom. In the fourteenth Fe site, Fe(14) is bonded in a 3-coordinate geometry to one Se(1), one Se(3), and one Se(6) atom. There are six inequivalent Se sites. In the first Se site, Se(1) is bonded in a 9-coordinate geometry to one Fe(1), one Fe(14), one Fe(6), one Fe(8), one Fe(9), two equivalent Fe(12), and two equivalent Fe(2) atoms. In the second Se site, Se(2) is bonded in a 9-coordinate geometry to one Fe(10), one Fe(5), one Fe(6), one Fe(7), one Fe(9), two equivalent Fe(11), and two equivalent Fe(4) atoms. In the third Se site, Se(3) is bonded in a 7-coordinate geometry to one Fe(1), one Fe(13), one Fe(14), one Fe(5), one Fe(6), and two equivalent Fe(2) atoms. In the fourth Se site, Se(4) is bonded in a 8-coordinate geometry to one Fe(1), one Fe(13), one Fe(3), one Fe(5), one Fe(7), one Fe(9), and two equivalent Fe(11) atoms. In the fifth Se site, Se(5) is bonded in a 8-coordinate geometry to one Fe(10), one Fe(13), one Fe(3), one Fe(7), one Fe(8), one Fe(9), and two equivalent Fe(4) atoms. In the sixth Se site, Se(6) is bonded in a 7-coordinate geometry to one Fe(10), one Fe(13), one Fe(14), one Fe(6), one Fe(8), and two equivalent Fe(12) atoms.
Fe7Se3 crystallizes in the triclinic P-1 space group. There are fourteen inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 2-coordinate geometry to one Se(1), one Se(3), and one Se(4) atom. The Fe(1)-Se(1) bond length is 2.40 Å. The Fe(1)-Se(3) bond length is 2.64 Å. The Fe(1)-Se(4) bond length is 2.42 Å. In the second Fe site, Fe(2) is bonded in a 3-coordinate geometry to two equivalent Se(1) and two equivalent Se(3) atoms. There is one shorter (2.65 Å) and one longer (2.96 Å) Fe(2)-Se(1) bond length. There is one shorter (2.49 Å) and one longer (2.61 Å) Fe(2)-Se(3) bond length. In the third Fe site, Fe(3) is bonded in a 2-coordinate geometry to one Se(4) and one Se(5) atom. The Fe(3)-Se(4) bond length is 2.63 Å. The Fe(3)-Se(5) bond length is 2.63 Å. In the fourth Fe site, Fe(4) is bonded in a 3-coordinate geometry to two equivalent Se(2) and two equivalent Se(5) atoms. There is one shorter (2.54 Å) and one longer (2.98 Å) Fe(4)-Se(2) bond length. There is one shorter (2.51 Å) and one longer (2.68 Å) Fe(4)-Se(5) bond length. In the fifth Fe site, Fe(5) is bonded in a 2-coordinate geometry to one Se(2), one Se(3), and one Se(4) atom. The Fe(5)-Se(2) bond length is 2.39 Å. The Fe(5)-Se(3) bond length is 2.34 Å. The Fe(5)-Se(4) bond length is 2.64 Å. In the sixth Fe site, Fe(6) is bonded in a 4-coordinate geometry to one Se(1), one Se(2), one Se(3), and one Se(6) atom. The Fe(6)-Se(1) bond length is 2.70 Å. The Fe(6)-Se(2) bond length is 2.63 Å. The Fe(6)-Se(3) bond length is 2.51 Å. The Fe(6)-Se(6) bond length is 2.51 Å. In the seventh Fe site, Fe(7) is bonded in a 3-coordinate geometry to one Se(2), one Se(4), and one Se(5) atom. The Fe(7)-Se(2) bond length is 2.44 Å. The Fe(7)-Se(4) bond length is 2.51 Å. The Fe(7)-Se(5) bond length is 2.51 Å. In the eighth Fe site, Fe(8) is bonded in a 2-coordinate geometry to one Se(1), one Se(5), and one Se(6) atom. The Fe(8)-Se(1) bond length is 2.40 Å. The Fe(8)-Se(5) bond length is 2.42 Å. The Fe(8)-Se(6) bond length is 2.65 Å. In the ninth Fe site, Fe(9) is bonded in a 3-coordinate geometry to one Se(1), one Se(2), one Se(4), and one Se(5) atom. The Fe(9)-Se(1) bond length is 2.62 Å. The Fe(9)-Se(2) bond length is 2.71 Å. The Fe(9)-Se(4) bond length is 2.52 Å. The Fe(9)-Se(5) bond length is 2.52 Å. In the tenth Fe site, Fe(10) is bonded in a 2-coordinate geometry to one Se(2), one Se(5), and one Se(6) atom. The Fe(10)-Se(2) bond length is 2.39 Å. The Fe(10)-Se(5) bond length is 2.63 Å. The Fe(10)-Se(6) bond length is 2.34 Å. In the eleventh Fe site, Fe(11) is bonded in a 3-coordinate geometry to two equivalent Se(2) and two equivalent Se(4) atoms. There is one shorter (2.54 Å) and one longer (2.98 Å) Fe(11)-Se(2) bond length. There is one shorter (2.51 Å) and one longer (2.68 Å) Fe(11)-Se(4) bond length. In the twelfth Fe site, Fe(12) is bonded in a 3-coordinate geometry to two equivalent Se(1) and two equivalent Se(6) atoms. There is one shorter (2.65 Å) and one longer (2.94 Å) Fe(12)-Se(1) bond length. There is one shorter (2.49 Å) and one longer (2.60 Å) Fe(12)-Se(6) bond length. In the thirteenth Fe site, Fe(13) is bonded in a 4-coordinate geometry to one Se(3), one Se(4), one Se(5), and one Se(6) atom. The Fe(13)-Se(3) bond length is 2.70 Å. The Fe(13)-Se(4) bond length is 2.64 Å. The Fe(13)-Se(5) bond length is 2.64 Å. The Fe(13)-Se(6) bond length is 2.70 Å. In the fourteenth Fe site, Fe(14) is bonded in a 3-coordinate geometry to one Se(1), one Se(3), and one Se(6) atom. The Fe(14)-Se(1) bond length is 2.47 Å. The Fe(14)-Se(3) bond length is 2.48 Å. The Fe(14)-Se(6) bond length is 2.48 Å. There are six inequivalent Se sites. In the first Se site, Se(1) is bonded in a 9-coordinate geometry to one Fe(1), one Fe(14), one Fe(6), one Fe(8), one Fe(9), two equivalent Fe(12), and two equivalent Fe(2) atoms. In the second Se site, Se(2) is bonded in a 9-coordinate geometry to one Fe(10), one Fe(5), one Fe(6), one Fe(7), one Fe(9), two equivalent Fe(11), and two equivalent Fe(4) atoms. In the third Se site, Se(3) is bonded in a 7-coordinate geometry to one Fe(1), one Fe(13), one Fe(14), one Fe(5), one Fe(6), and two equivalent Fe(2) atoms. In the fourth Se site, Se(4) is bonded in a 8-coordinate geometry to one Fe(1), one Fe(13), one Fe(3), one Fe(5), one Fe(7), one Fe(9), and two equivalent Fe(11) atoms. In the fifth Se site, Se(5) is bonded in a 8-coordinate geometry to one Fe(10), one Fe(13), one Fe(3), one Fe(7), one Fe(8), one Fe(9), and two equivalent Fe(4) atoms. In the sixth Se site, Se(6) is bonded in a 7-coordinate geometry to one Fe(10), one Fe(13), one Fe(14), one Fe(6), one Fe(8), and two equivalent Fe(12) atoms.