Fe7SiO10 crystallizes in the monoclinic Cm space group. There are seven inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(2), one O(5), two equivalent O(10), and two equivalent O(8) atoms to form FeO6 octahedra that share  a cornercorner with one Fe(5)O6 octahedra, corners with two equivalent Fe(7)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra, edges with two equivalent Fe(1)O6 octahedra, edges with two equivalent Fe(4)O6 octahedra, and edges with two equivalent Fe(6)O6 octahedra. The corner-sharing octahedral tilt angles are 1°. In the second Fe site, Fe(2) is bonded to one O(1), one O(6), two equivalent O(7), and two equivalent O(9) atoms to form FeO6 octahedra that share  a cornercorner with one Fe(6)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with four equivalent Fe(7)O4 tetrahedra, edges with two equivalent Fe(2)O6 octahedra, edges with two equivalent Fe(3)O6 octahedra, and edges with two equivalent Fe(5)O6 octahedra. The corner-sharing octahedral tilt angles are 4°. In the third Fe site, Fe(3) is bonded to one O(3), one O(7), two equivalent O(4), and two equivalent O(6) atoms to form FeO6 octahedra that share corners with four equivalent Fe(5)O6 octahedra,  a cornercorner with one Fe(7)O4 tetrahedra, edges with two equivalent Fe(2)O6 octahedra, edges with two equivalent Fe(3)O6 octahedra, edges with two equivalent Fe(4)O6 octahedra, edges with two equivalent Fe(5)O6 octahedra, and edges with two equivalent Fe(6)O6 octahedra. The corner-sharing octahedral tilt angles range from 3-10°. In the fourth Fe site, Fe(4) is bonded to one O(4), one O(8), two equivalent O(3), and two equivalent O(5) atoms to form FeO6 octahedra that share corners with four equivalent Fe(6)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, edges with two equivalent Fe(1)O6 octahedra, edges with two equivalent Fe(3)O6 octahedra, edges with two equivalent Fe(4)O6 octahedra, edges with two equivalent Fe(5)O6 octahedra, and edges with two equivalent Fe(6)O6 octahedra. The corner-sharing octahedral tilt angles range from 3-16°. In the fifth Fe site, Fe(5) is bonded to one O(5), one O(9), two equivalent O(4), and two equivalent O(6) atoms to form FeO6 octahedra that share  a cornercorner with one Fe(1)O6 octahedra, corners with four equivalent Fe(3)O6 octahedra,  a cornercorner with one Fe(7)O4 tetrahedra, edges with two equivalent Fe(2)O6 octahedra, edges with two equivalent Fe(3)O6 octahedra, edges with two equivalent Fe(4)O6 octahedra, edges with two equivalent Fe(5)O6 octahedra, and edges with two equivalent Fe(6)O6 octahedra. The corner-sharing octahedral tilt angles range from 1-10°. In the sixth Fe site, Fe(6) is bonded to one O(10), one O(6), two equivalent O(3), and two equivalent O(5) atoms to form FeO6 octahedra that share  a cornercorner with one Fe(2)O6 octahedra, corners with four equivalent Fe(4)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, edges with two equivalent Fe(1)O6 octahedra, edges with two equivalent Fe(3)O6 octahedra, edges with two equivalent Fe(4)O6 octahedra, edges with two equivalent Fe(5)O6 octahedra, and edges with two equivalent Fe(6)O6 octahedra. The corner-sharing octahedral tilt angles range from 3-16°. In the seventh Fe site, Fe(7) is bonded to one O(7), one O(9), and two equivalent O(2) atoms to form FeO4 tetrahedra that share  a cornercorner with one Fe(3)O6 octahedra,  a cornercorner with one Fe(5)O6 octahedra, corners with two equivalent Fe(1)O6 octahedra, corners with four equivalent Fe(2)O6 octahedra, and corners with two equivalent Fe(7)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 54-61°. Si(1) is bonded to one O(10), one O(8), and two equivalent O(1) atoms to form SiO4 tetrahedra that share  a cornercorner with one Fe(4)O6 octahedra,  a cornercorner with one Fe(6)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, corners with four equivalent Fe(1)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 53-60°. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Fe(2) and two equivalent Si(1) atoms. In the second O site, O(2) is bonded in a trigonal planar geometry to one Fe(1) and two equivalent Fe(7) atoms. In the third O site, O(3) is bonded to one Fe(3), two equivalent Fe(4), and two equivalent Fe(6) atoms to form OFe5 square pyramids that share corners with four equivalent O(5)Fe6 octahedra,  a cornercorner with one O(7)Fe4 trigonal pyramid, edges with two equivalent O(5)Fe6 octahedra, edges with two equivalent O(6)Fe6 octahedra, edges with two equivalent O(3)Fe5 square pyramids, and edges with two equivalent O(4)Fe5 square pyramids. The corner-sharing octahedral tilt angles range from 6-8°. In the fourth O site, O(4) is bonded to one Fe(4), two equivalent Fe(3), and two equivalent Fe(5) atoms to form OFe5 square pyramids that share corners with four equivalent O(6)Fe6 octahedra, corners with two equivalent O(7)Fe4 trigonal pyramids, corners with two equivalent O(9)Fe4 trigonal pyramids, edges with two equivalent O(5)Fe6 octahedra, edges with two equivalent O(6)Fe6 octahedra, edges with two equivalent O(3)Fe5 square pyramids, and edges with two equivalent O(4)Fe5 square pyramids. The corner-sharing octahedral tilt angles are 5°. In the fifth O site, O(5) is bonded to one Fe(1), one Fe(5), two equivalent Fe(4), and two equivalent Fe(6) atoms to form OFe6 octahedra that share corners with four equivalent O(3)Fe5 square pyramids,  a cornercorner with one O(9)Fe4 trigonal pyramid, edges with two equivalent O(5)Fe6 octahedra, edges with two equivalent O(6)Fe6 octahedra, edges with two equivalent O(3)Fe5 square pyramids, and edges with two equivalent O(4)Fe5 square pyramids. In the sixth O site, O(6) is bonded to one Fe(2), one Fe(6), two equivalent Fe(3), and two equivalent Fe(5) atoms to form OFe6 octahedra that share corners with four equivalent O(4)Fe5 square pyramids, edges with two equivalent O(5)Fe6 octahedra, edges with two equivalent O(6)Fe6 octahedra, edges with two equivalent O(3)Fe5 square pyramids, edges with two equivalent O(4)Fe5 square pyramids, edges with two equivalent O(7)Fe4 trigonal pyramids, and edges with two equivalent O(9)Fe4 trigonal pyramids. In the seventh O site, O(7) is bonded to one Fe(3), one Fe(7), and two equivalent Fe(2) atoms to form distorted OFe4 trigonal pyramids that share  a cornercorner with one O(3)Fe5 square pyramid, corners with two equivalent O(4)Fe5 square pyramids, corners with two equivalent O(7)Fe4 trigonal pyramids, corners with three equivalent O(9)Fe4 trigonal pyramids, edges with two equivalent O(6)Fe6 octahedra, and  an edgeedge with one O(9)Fe4 trigonal pyramid. In the eighth O site, O(8) is bonded in a distorted rectangular see-saw-like geometry to one Fe(4), two equivalent Fe(1), and one Si(1) atom. In the ninth O site, O(9) is bonded to one Fe(5), one Fe(7), and two equivalent Fe(2) atoms to form distorted OFe4 trigonal pyramids that share  a cornercorner with one O(5)Fe6 octahedra, corners with two equivalent O(4)Fe5 square pyramids, corners with two equivalent O(9)Fe4 trigonal pyramids, corners with three equivalent O(7)Fe4 trigonal pyramids, edges with two equivalent O(6)Fe6 octahedra, and  an edgeedge with one O(7)Fe4 trigonal pyramid. The corner-sharing octahedral tilt angles are 4°. In the tenth O site, O(10) is bonded in a rectangular see-saw-like geometry to one Fe(6), two equivalent Fe(1), and one Si(1) atom.
Fe7SiO10 crystallizes in the monoclinic Cm space group. There are seven inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(2), one O(5), two equivalent O(10), and two equivalent O(8) atoms to form FeO6 octahedra that share  a cornercorner with one Fe(5)O6 octahedra, corners with two equivalent Fe(7)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra, edges with two equivalent Fe(1)O6 octahedra, edges with two equivalent Fe(4)O6 octahedra, and edges with two equivalent Fe(6)O6 octahedra. The corner-sharing octahedral tilt angles are 1°. The Fe(1)-O(2) bond length is 2.02 Å. The Fe(1)-O(5) bond length is 2.22 Å. Both Fe(1)-O(10) bond lengths are 2.22 Å. Both Fe(1)-O(8) bond lengths are 2.27 Å. In the second Fe site, Fe(2) is bonded to one O(1), one O(6), two equivalent O(7), and two equivalent O(9) atoms to form FeO6 octahedra that share  a cornercorner with one Fe(6)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with four equivalent Fe(7)O4 tetrahedra, edges with two equivalent Fe(2)O6 octahedra, edges with two equivalent Fe(3)O6 octahedra, and edges with two equivalent Fe(5)O6 octahedra. The corner-sharing octahedral tilt angles are 4°. The Fe(2)-O(1) bond length is 2.35 Å. The Fe(2)-O(6) bond length is 2.32 Å. Both Fe(2)-O(7) bond lengths are 2.13 Å. Both Fe(2)-O(9) bond lengths are 2.11 Å. In the third Fe site, Fe(3) is bonded to one O(3), one O(7), two equivalent O(4), and two equivalent O(6) atoms to form FeO6 octahedra that share corners with four equivalent Fe(5)O6 octahedra,  a cornercorner with one Fe(7)O4 tetrahedra, edges with two equivalent Fe(2)O6 octahedra, edges with two equivalent Fe(3)O6 octahedra, edges with two equivalent Fe(4)O6 octahedra, edges with two equivalent Fe(5)O6 octahedra, and edges with two equivalent Fe(6)O6 octahedra. The corner-sharing octahedral tilt angles range from 3-10°. The Fe(3)-O(3) bond length is 2.00 Å. The Fe(3)-O(7) bond length is 2.03 Å. Both Fe(3)-O(4) bond lengths are 2.09 Å. Both Fe(3)-O(6) bond lengths are 2.11 Å. In the fourth Fe site, Fe(4) is bonded to one O(4), one O(8), two equivalent O(3), and two equivalent O(5) atoms to form FeO6 octahedra that share corners with four equivalent Fe(6)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, edges with two equivalent Fe(1)O6 octahedra, edges with two equivalent Fe(3)O6 octahedra, edges with two equivalent Fe(4)O6 octahedra, edges with two equivalent Fe(5)O6 octahedra, and edges with two equivalent Fe(6)O6 octahedra. The corner-sharing octahedral tilt angles range from 3-16°. The Fe(4)-O(4) bond length is 2.14 Å. The Fe(4)-O(8) bond length is 2.08 Å. Both Fe(4)-O(3) bond lengths are 2.17 Å. Both Fe(4)-O(5) bond lengths are 2.22 Å. In the fifth Fe site, Fe(5) is bonded to one O(5), one O(9), two equivalent O(4), and two equivalent O(6) atoms to form FeO6 octahedra that share  a cornercorner with one Fe(1)O6 octahedra, corners with four equivalent Fe(3)O6 octahedra,  a cornercorner with one Fe(7)O4 tetrahedra, edges with two equivalent Fe(2)O6 octahedra, edges with two equivalent Fe(3)O6 octahedra, edges with two equivalent Fe(4)O6 octahedra, edges with two equivalent Fe(5)O6 octahedra, and edges with two equivalent Fe(6)O6 octahedra. The corner-sharing octahedral tilt angles range from 1-10°. The Fe(5)-O(5) bond length is 2.35 Å. The Fe(5)-O(9) bond length is 2.07 Å. Both Fe(5)-O(4) bond lengths are 2.20 Å. Both Fe(5)-O(6) bond lengths are 2.24 Å. In the sixth Fe site, Fe(6) is bonded to one O(10), one O(6), two equivalent O(3), and two equivalent O(5) atoms to form FeO6 octahedra that share  a cornercorner with one Fe(2)O6 octahedra, corners with four equivalent Fe(4)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, edges with two equivalent Fe(1)O6 octahedra, edges with two equivalent Fe(3)O6 octahedra, edges with two equivalent Fe(4)O6 octahedra, edges with two equivalent Fe(5)O6 octahedra, and edges with two equivalent Fe(6)O6 octahedra. The corner-sharing octahedral tilt angles range from 3-16°. The Fe(6)-O(10) bond length is 2.17 Å. The Fe(6)-O(6) bond length is 2.28 Å. Both Fe(6)-O(3) bond lengths are 2.10 Å. Both Fe(6)-O(5) bond lengths are 2.16 Å. In the seventh Fe site, Fe(7) is bonded to one O(7), one O(9), and two equivalent O(2) atoms to form FeO4 tetrahedra that share  a cornercorner with one Fe(3)O6 octahedra,  a cornercorner with one Fe(5)O6 octahedra, corners with two equivalent Fe(1)O6 octahedra, corners with four equivalent Fe(2)O6 octahedra, and corners with two equivalent Fe(7)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 54-61°. The Fe(7)-O(7) bond length is 1.91 Å. The Fe(7)-O(9) bond length is 1.90 Å. Both Fe(7)-O(2) bond lengths are 1.89 Å. Si(1) is bonded to one O(10), one O(8), and two equivalent O(1) atoms to form SiO4 tetrahedra that share  a cornercorner with one Fe(4)O6 octahedra,  a cornercorner with one Fe(6)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, corners with four equivalent Fe(1)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 53-60°. The Si(1)-O(10) bond length is 1.63 Å. The Si(1)-O(8) bond length is 1.64 Å. Both Si(1)-O(1) bond lengths are 1.75 Å. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Fe(2) and two equivalent Si(1) atoms. In the second O site, O(2) is bonded in a trigonal planar geometry to one Fe(1) and two equivalent Fe(7) atoms. In the third O site, O(3) is bonded to one Fe(3), two equivalent Fe(4), and two equivalent Fe(6) atoms to form OFe5 square pyramids that share corners with four equivalent O(5)Fe6 octahedra,  a cornercorner with one O(7)Fe4 trigonal pyramid, edges with two equivalent O(5)Fe6 octahedra, edges with two equivalent O(6)Fe6 octahedra, edges with two equivalent O(3)Fe5 square pyramids, and edges with two equivalent O(4)Fe5 square pyramids. The corner-sharing octahedral tilt angles range from 6-8°. In the fourth O site, O(4) is bonded to one Fe(4), two equivalent Fe(3), and two equivalent Fe(5) atoms to form OFe5 square pyramids that share corners with four equivalent O(6)Fe6 octahedra, corners with two equivalent O(7)Fe4 trigonal pyramids, corners with two equivalent O(9)Fe4 trigonal pyramids, edges with two equivalent O(5)Fe6 octahedra, edges with two equivalent O(6)Fe6 octahedra, edges with two equivalent O(3)Fe5 square pyramids, and edges with two equivalent O(4)Fe5 square pyramids. The corner-sharing octahedral tilt angles are 5°. In the fifth O site, O(5) is bonded to one Fe(1), one Fe(5), two equivalent Fe(4), and two equivalent Fe(6) atoms to form OFe6 octahedra that share corners with four equivalent O(3)Fe5 square pyramids,  a cornercorner with one O(9)Fe4 trigonal pyramid, edges with two equivalent O(5)Fe6 octahedra, edges with two equivalent O(6)Fe6 octahedra, edges with two equivalent O(3)Fe5 square pyramids, and edges with two equivalent O(4)Fe5 square pyramids. In the sixth O site, O(6) is bonded to one Fe(2), one Fe(6), two equivalent Fe(3), and two equivalent Fe(5) atoms to form OFe6 octahedra that share corners with four equivalent O(4)Fe5 square pyramids, edges with two equivalent O(5)Fe6 octahedra, edges with two equivalent O(6)Fe6 octahedra, edges with two equivalent O(3)Fe5 square pyramids, edges with two equivalent O(4)Fe5 square pyramids, edges with two equivalent O(7)Fe4 trigonal pyramids, and edges with two equivalent O(9)Fe4 trigonal pyramids. In the seventh O site, O(7) is bonded to one Fe(3), one Fe(7), and two equivalent Fe(2) atoms to form distorted OFe4 trigonal pyramids that share  a cornercorner with one O(3)Fe5 square pyramid, corners with two equivalent O(4)Fe5 square pyramids, corners with two equivalent O(7)Fe4 trigonal pyramids, corners with three equivalent O(9)Fe4 trigonal pyramids, edges with two equivalent O(6)Fe6 octahedra, and  an edgeedge with one O(9)Fe4 trigonal pyramid. In the eighth O site, O(8) is bonded in a distorted rectangular see-saw-like geometry to one Fe(4), two equivalent Fe(1), and one Si(1) atom. In the ninth O site, O(9) is bonded to one Fe(5), one Fe(7), and two equivalent Fe(2) atoms to form distorted OFe4 trigonal pyramids that share  a cornercorner with one O(5)Fe6 octahedra, corners with two equivalent O(4)Fe5 square pyramids, corners with two equivalent O(9)Fe4 trigonal pyramids, corners with three equivalent O(7)Fe4 trigonal pyramids, edges with two equivalent O(6)Fe6 octahedra, and  an edgeedge with one O(7)Fe4 trigonal pyramid. The corner-sharing octahedral tilt angles are 4°. In the tenth O site, O(10) is bonded in a rectangular see-saw-like geometry to one Fe(6), two equivalent Fe(1), and one Si(1) atom.