FeFe3Si2Sn7O16 crystallizes in the monoclinic C2/m space group. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(3) and four equivalent O(9) atoms to form distorted FeO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra, edges with two equivalent Sn(1)O6 octahedra, and edges with four equivalent Fe(2)O6 octahedra. In the second Fe site, Fe(2) is bonded to one O(10), one O(11), one O(12), one O(3), one O(4), and one O(9) atom to form distorted FeO6 octahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  an edgeedge with one Fe(1)O6 octahedra,  an edgeedge with one Fe(4)O6 octahedra,  an edgeedge with one Sn(1)O6 octahedra,  an edgeedge with one Sn(2)O6 octahedra, and edges with two equivalent Fe(2)O6 octahedra. In the third Fe site, Fe(3) is bonded to one Sn(3), one Sn(4), two equivalent Sn(5), and two equivalent Sn(6) atoms to form FeSn6 octahedra that share  a cornercorner with one O(11)Fe2Sn2 tetrahedra,  a cornercorner with one O(12)Fe2Sn2 tetrahedra, corners with two equivalent O(10)Fe2Sn2 tetrahedra, and corners with two equivalent O(9)Fe2Sn2 tetrahedra. In the fourth Fe site, Fe(4) is bonded to two equivalent O(4) and four equivalent O(10) atoms to form distorted FeO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, edges with two equivalent Sn(2)O6 octahedra, and edges with four equivalent Fe(2)O6 octahedra. There are six inequivalent Sn sites. In the first Sn site, Sn(1) is bonded to two equivalent O(11) and four equivalent O(9) atoms to form SnO6 octahedra that share edges with two equivalent Fe(1)O6 octahedra and edges with four equivalent Fe(2)O6 octahedra. In the second Sn site, Sn(2) is bonded to two equivalent O(12) and four equivalent O(10) atoms to form SnO6 octahedra that share edges with two equivalent Fe(4)O6 octahedra and edges with four equivalent Fe(2)O6 octahedra. In the third Sn site, Sn(3) is bonded in a 5-coordinate geometry to one Fe(3), one O(1), one O(11), and two equivalent O(8) atoms. In the fourth Sn site, Sn(4) is bonded in a 5-coordinate geometry to one Fe(3), one O(12), one O(2), and two equivalent O(7) atoms. In the fifth Sn site, Sn(5) is bonded in a 5-coordinate geometry to one Fe(3), one O(1), one O(10), one O(5), and one O(8) atom. In the sixth Sn site, Sn(6) is bonded in a 5-coordinate geometry to one Fe(3), one O(2), one O(6), one O(7), and one O(9) atom. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(4), one O(5), and two equivalent O(7) atoms to form SiO4 tetrahedra that share  a cornercorner with one Fe(4)O6 octahedra and corners with two equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 68-69°. In the second Si site, Si(2) is bonded to one O(3), one O(6), and two equivalent O(8) atoms to form SiO4 tetrahedra that share  a cornercorner with one Fe(1)O6 octahedra and corners with two equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 68-69°. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Sn(3) and two equivalent Sn(5) atoms. In the second O site, O(2) is bonded in a trigonal planar geometry to one Sn(4) and two equivalent Sn(6) atoms. In the third O site, O(3) is bonded to one Fe(1), two equivalent Fe(2), and one Si(2) atom to form OFe3Si tetrahedra that share  a cornercorner with one O(3)Fe3Si tetrahedra, corners with two equivalent O(10)Fe2Sn2 tetrahedra, corners with two equivalent O(11)Fe2Sn2 tetrahedra, corners with two equivalent O(9)Fe2Sn2 tetrahedra, corners with two equivalent O(4)Fe3Si tetrahedra,  an edgeedge with one O(12)Fe2Sn2 tetrahedra, and edges with two equivalent O(9)Fe2Sn2 tetrahedra. In the fourth O site, O(4) is bonded to one Fe(4), two equivalent Fe(2), and one Si(1) atom to form OFe3Si tetrahedra that share  a cornercorner with one O(4)Fe3Si tetrahedra, corners with two equivalent O(10)Fe2Sn2 tetrahedra, corners with two equivalent O(12)Fe2Sn2 tetrahedra, corners with two equivalent O(9)Fe2Sn2 tetrahedra, corners with two equivalent O(3)Fe3Si tetrahedra,  an edgeedge with one O(11)Fe2Sn2 tetrahedra, and edges with two equivalent O(10)Fe2Sn2 tetrahedra. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to two equivalent Sn(5) and one Si(1) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to two equivalent Sn(6) and one Si(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Sn(4), one Sn(6), and one Si(1) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Sn(3), one Sn(5), and one Si(2) atom. In the ninth O site, O(9) is bonded to one Fe(1), one Fe(2), one Sn(1), and one Sn(6) atom to form OFe2Sn2 tetrahedra that share  a cornercorner with one Fe(3)Sn6 octahedra,  a cornercorner with one O(10)Fe2Sn2 tetrahedra,  a cornercorner with one O(11)Fe2Sn2 tetrahedra,  a cornercorner with one O(12)Fe2Sn2 tetrahedra,  a cornercorner with one O(3)Fe3Si tetrahedra,  a cornercorner with one O(4)Fe3Si tetrahedra, corners with four equivalent O(9)Fe2Sn2 tetrahedra,  an edgeedge with one O(11)Fe2Sn2 tetrahedra,  an edgeedge with one O(9)Fe2Sn2 tetrahedra, and  an edgeedge with one O(3)Fe3Si tetrahedra. The corner-sharing octahedral tilt angles are 56°. In the tenth O site, O(10) is bonded to one Fe(2), one Fe(4), one Sn(2), and one Sn(5) atom to form OFe2Sn2 tetrahedra that share  a cornercorner with one Fe(3)Sn6 octahedra,  a cornercorner with one O(11)Fe2Sn2 tetrahedra,  a cornercorner with one O(12)Fe2Sn2 tetrahedra,  a cornercorner with one O(9)Fe2Sn2 tetrahedra,  a cornercorner with one O(3)Fe3Si tetrahedra,  a cornercorner with one O(4)Fe3Si tetrahedra, corners with four equivalent O(10)Fe2Sn2 tetrahedra,  an edgeedge with one O(10)Fe2Sn2 tetrahedra,  an edgeedge with one O(12)Fe2Sn2 tetrahedra, and  an edgeedge with one O(4)Fe3Si tetrahedra. The corner-sharing octahedral tilt angles are 56°. In the eleventh O site, O(11) is bonded to two equivalent Fe(2), one Sn(1), and one Sn(3) atom to form OFe2Sn2 tetrahedra that share  a cornercorner with one Fe(3)Sn6 octahedra,  a cornercorner with one O(11)Fe2Sn2 tetrahedra, corners with two equivalent O(10)Fe2Sn2 tetrahedra, corners with two equivalent O(12)Fe2Sn2 tetrahedra, corners with two equivalent O(9)Fe2Sn2 tetrahedra, corners with two equivalent O(3)Fe3Si tetrahedra,  an edgeedge with one O(4)Fe3Si tetrahedra, and edges with two equivalent O(9)Fe2Sn2 tetrahedra. The corner-sharing octahedral tilt angles are 56°. In the twelfth O site, O(12) is bonded to two equivalent Fe(2), one Sn(2), and one Sn(4) atom to form OFe2Sn2 tetrahedra that share  a cornercorner with one Fe(3)Sn6 octahedra,  a cornercorner with one O(12)Fe2Sn2 tetrahedra, corners with two equivalent O(10)Fe2Sn2 tetrahedra, corners with two equivalent O(11)Fe2Sn2 tetrahedra, corners with two equivalent O(9)Fe2Sn2 tetrahedra, corners with two equivalent O(4)Fe3Si tetrahedra,  an edgeedge with one O(3)Fe3Si tetrahedra, and edges with two equivalent O(10)Fe2Sn2 tetrahedra. The corner-sharing octahedral tilt angles are 56°.
FeFe3Si2Sn7O16 crystallizes in the monoclinic C2/m space group. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(3) and four equivalent O(9) atoms to form distorted FeO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra, edges with two equivalent Sn(1)O6 octahedra, and edges with four equivalent Fe(2)O6 octahedra. Both Fe(1)-O(3) bond lengths are 2.16 Å. All Fe(1)-O(9) bond lengths are 2.33 Å. In the second Fe site, Fe(2) is bonded to one O(10), one O(11), one O(12), one O(3), one O(4), and one O(9) atom to form distorted FeO6 octahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  an edgeedge with one Fe(1)O6 octahedra,  an edgeedge with one Fe(4)O6 octahedra,  an edgeedge with one Sn(1)O6 octahedra,  an edgeedge with one Sn(2)O6 octahedra, and edges with two equivalent Fe(2)O6 octahedra. The Fe(2)-O(10) bond length is 2.34 Å. The Fe(2)-O(11) bond length is 2.33 Å. The Fe(2)-O(12) bond length is 2.34 Å. The Fe(2)-O(3) bond length is 2.15 Å. The Fe(2)-O(4) bond length is 2.16 Å. The Fe(2)-O(9) bond length is 2.34 Å. In the third Fe site, Fe(3) is bonded to one Sn(3), one Sn(4), two equivalent Sn(5), and two equivalent Sn(6) atoms to form FeSn6 octahedra that share  a cornercorner with one O(11)Fe2Sn2 tetrahedra,  a cornercorner with one O(12)Fe2Sn2 tetrahedra, corners with two equivalent O(10)Fe2Sn2 tetrahedra, and corners with two equivalent O(9)Fe2Sn2 tetrahedra. The Fe(3)-Sn(3) bond length is 2.53 Å. The Fe(3)-Sn(4) bond length is 2.53 Å. Both Fe(3)-Sn(5) bond lengths are 2.53 Å. Both Fe(3)-Sn(6) bond lengths are 2.53 Å. In the fourth Fe site, Fe(4) is bonded to two equivalent O(4) and four equivalent O(10) atoms to form distorted FeO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, edges with two equivalent Sn(2)O6 octahedra, and edges with four equivalent Fe(2)O6 octahedra. Both Fe(4)-O(4) bond lengths are 2.15 Å. All Fe(4)-O(10) bond lengths are 2.34 Å. There are six inequivalent Sn sites. In the first Sn site, Sn(1) is bonded to two equivalent O(11) and four equivalent O(9) atoms to form SnO6 octahedra that share edges with two equivalent Fe(1)O6 octahedra and edges with four equivalent Fe(2)O6 octahedra. Both Sn(1)-O(11) bond lengths are 2.14 Å. All Sn(1)-O(9) bond lengths are 2.14 Å. In the second Sn site, Sn(2) is bonded to two equivalent O(12) and four equivalent O(10) atoms to form SnO6 octahedra that share edges with two equivalent Fe(4)O6 octahedra and edges with four equivalent Fe(2)O6 octahedra. Both Sn(2)-O(12) bond lengths are 2.13 Å. All Sn(2)-O(10) bond lengths are 2.14 Å. In the third Sn site, Sn(3) is bonded in a 5-coordinate geometry to one Fe(3), one O(1), one O(11), and two equivalent O(8) atoms. The Sn(3)-O(1) bond length is 2.04 Å. The Sn(3)-O(11) bond length is 2.09 Å. Both Sn(3)-O(8) bond lengths are 2.27 Å. In the fourth Sn site, Sn(4) is bonded in a 5-coordinate geometry to one Fe(3), one O(12), one O(2), and two equivalent O(7) atoms. The Sn(4)-O(12) bond length is 2.09 Å. The Sn(4)-O(2) bond length is 2.04 Å. Both Sn(4)-O(7) bond lengths are 2.27 Å. In the fifth Sn site, Sn(5) is bonded in a 5-coordinate geometry to one Fe(3), one O(1), one O(10), one O(5), and one O(8) atom. The Sn(5)-O(1) bond length is 2.04 Å. The Sn(5)-O(10) bond length is 2.09 Å. The Sn(5)-O(5) bond length is 2.27 Å. The Sn(5)-O(8) bond length is 2.27 Å. In the sixth Sn site, Sn(6) is bonded in a 5-coordinate geometry to one Fe(3), one O(2), one O(6), one O(7), and one O(9) atom. The Sn(6)-O(2) bond length is 2.04 Å. The Sn(6)-O(6) bond length is 2.27 Å. The Sn(6)-O(7) bond length is 2.27 Å. The Sn(6)-O(9) bond length is 2.09 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(4), one O(5), and two equivalent O(7) atoms to form SiO4 tetrahedra that share  a cornercorner with one Fe(4)O6 octahedra and corners with two equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 68-69°. The Si(1)-O(4) bond length is 1.68 Å. The Si(1)-O(5) bond length is 1.63 Å. Both Si(1)-O(7) bond lengths are 1.63 Å. In the second Si site, Si(2) is bonded to one O(3), one O(6), and two equivalent O(8) atoms to form SiO4 tetrahedra that share  a cornercorner with one Fe(1)O6 octahedra and corners with two equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 68-69°. The Si(2)-O(3) bond length is 1.67 Å. The Si(2)-O(6) bond length is 1.63 Å. Both Si(2)-O(8) bond lengths are 1.63 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Sn(3) and two equivalent Sn(5) atoms. In the second O site, O(2) is bonded in a trigonal planar geometry to one Sn(4) and two equivalent Sn(6) atoms. In the third O site, O(3) is bonded to one Fe(1), two equivalent Fe(2), and one Si(2) atom to form OFe3Si tetrahedra that share  a cornercorner with one O(3)Fe3Si tetrahedra, corners with two equivalent O(10)Fe2Sn2 tetrahedra, corners with two equivalent O(11)Fe2Sn2 tetrahedra, corners with two equivalent O(9)Fe2Sn2 tetrahedra, corners with two equivalent O(4)Fe3Si tetrahedra,  an edgeedge with one O(12)Fe2Sn2 tetrahedra, and edges with two equivalent O(9)Fe2Sn2 tetrahedra. In the fourth O site, O(4) is bonded to one Fe(4), two equivalent Fe(2), and one Si(1) atom to form OFe3Si tetrahedra that share  a cornercorner with one O(4)Fe3Si tetrahedra, corners with two equivalent O(10)Fe2Sn2 tetrahedra, corners with two equivalent O(12)Fe2Sn2 tetrahedra, corners with two equivalent O(9)Fe2Sn2 tetrahedra, corners with two equivalent O(3)Fe3Si tetrahedra,  an edgeedge with one O(11)Fe2Sn2 tetrahedra, and edges with two equivalent O(10)Fe2Sn2 tetrahedra. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to two equivalent Sn(5) and one Si(1) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to two equivalent Sn(6) and one Si(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Sn(4), one Sn(6), and one Si(1) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Sn(3), one Sn(5), and one Si(2) atom. In the ninth O site, O(9) is bonded to one Fe(1), one Fe(2), one Sn(1), and one Sn(6) atom to form OFe2Sn2 tetrahedra that share  a cornercorner with one Fe(3)Sn6 octahedra,  a cornercorner with one O(10)Fe2Sn2 tetrahedra,  a cornercorner with one O(11)Fe2Sn2 tetrahedra,  a cornercorner with one O(12)Fe2Sn2 tetrahedra,  a cornercorner with one O(3)Fe3Si tetrahedra,  a cornercorner with one O(4)Fe3Si tetrahedra, corners with four equivalent O(9)Fe2Sn2 tetrahedra,  an edgeedge with one O(11)Fe2Sn2 tetrahedra,  an edgeedge with one O(9)Fe2Sn2 tetrahedra, and  an edgeedge with one O(3)Fe3Si tetrahedra. The corner-sharing octahedral tilt angles are 56°. In the tenth O site, O(10) is bonded to one Fe(2), one Fe(4), one Sn(2), and one Sn(5) atom to form OFe2Sn2 tetrahedra that share  a cornercorner with one Fe(3)Sn6 octahedra,  a cornercorner with one O(11)Fe2Sn2 tetrahedra,  a cornercorner with one O(12)Fe2Sn2 tetrahedra,  a cornercorner with one O(9)Fe2Sn2 tetrahedra,  a cornercorner with one O(3)Fe3Si tetrahedra,  a cornercorner with one O(4)Fe3Si tetrahedra, corners with four equivalent O(10)Fe2Sn2 tetrahedra,  an edgeedge with one O(10)Fe2Sn2 tetrahedra,  an edgeedge with one O(12)Fe2Sn2 tetrahedra, and  an edgeedge with one O(4)Fe3Si tetrahedra. The corner-sharing octahedral tilt angles are 56°. In the eleventh O site, O(11) is bonded to two equivalent Fe(2), one Sn(1), and one Sn(3) atom to form OFe2Sn2 tetrahedra that share  a cornercorner with one Fe(3)Sn6 octahedra,  a cornercorner with one O(11)Fe2Sn2 tetrahedra, corners with two equivalent O(10)Fe2Sn2 tetrahedra, corners with two equivalent O(12)Fe2Sn2 tetrahedra, corners with two equivalent O(9)Fe2Sn2 tetrahedra, corners with two equivalent O(3)Fe3Si tetrahedra,  an edgeedge with one O(4)Fe3Si tetrahedra, and edges with two equivalent O(9)Fe2Sn2 tetrahedra. The corner-sharing octahedral tilt angles are 56°. In the twelfth O site, O(12) is bonded to two equivalent Fe(2), one Sn(2), and one Sn(4) atom to form OFe2Sn2 tetrahedra that share  a cornercorner with one Fe(3)Sn6 octahedra,  a cornercorner with one O(12)Fe2Sn2 tetrahedra, corners with two equivalent O(10)Fe2Sn2 tetrahedra, corners with two equivalent O(11)Fe2Sn2 tetrahedra, corners with two equivalent O(9)Fe2Sn2 tetrahedra, corners with two equivalent O(4)Fe3Si tetrahedra,  an edgeedge with one O(3)Fe3Si tetrahedra, and edges with two equivalent O(10)Fe2Sn2 tetrahedra. The corner-sharing octahedral tilt angles are 56°.