Fe21HO32 crystallizes in the trigonal R3m space group. There are eight inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(2), one O(4), two equivalent O(5), and two equivalent O(8) atoms to form FeO6 octahedra that share  a cornercorner with one Fe(5)O4 tetrahedra,  a cornercorner with one Fe(7)O4 tetrahedra, corners with two equivalent Fe(4)O4 tetrahedra, corners with two equivalent Fe(6)O4 tetrahedra,  an edgeedge with one Fe(2)O6 octahedra, and edges with four equivalent Fe(3)O6 octahedra. In the second Fe site, Fe(2) is bonded to one O(1), one O(3), two equivalent O(5), and two equivalent O(7) atoms to form FeO6 octahedra that share  a cornercorner with one Fe(7)O4 tetrahedra, corners with two equivalent Fe(4)O4 tetrahedra, corners with three equivalent Fe(6)O4 tetrahedra,  an edgeedge with one Fe(1)O6 octahedra, edges with two equivalent Fe(2)O6 octahedra, and edges with two equivalent Fe(3)O6 octahedra. In the third Fe site, Fe(3) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(8) atom to form FeO6 octahedra that share  a cornercorner with one Fe(5)O4 tetrahedra,  a cornercorner with one Fe(7)O4 tetrahedra, corners with two equivalent Fe(4)O4 tetrahedra, corners with two equivalent Fe(6)O4 tetrahedra,  an edgeedge with one Fe(2)O6 octahedra, edges with two equivalent Fe(1)O6 octahedra, and edges with two equivalent Fe(3)O6 octahedra. In the fourth Fe site, Fe(4) is bonded to one O(6), one O(7), and two equivalent O(8) atoms to form corner-sharing FeO4 tetrahedra. The corner-sharing octahedral tilt angles range from 52-59°. In the fifth Fe site, Fe(5) is bonded to one O(9) and three equivalent O(4) atoms to form FeO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra, corners with six equivalent Fe(3)O6 octahedra, and  a cornercorner with one Fe(8)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 58-64°. In the sixth Fe site, Fe(6) is bonded to one O(10), one O(3), and two equivalent O(5) atoms to form FeO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with three equivalent Fe(2)O6 octahedra, corners with four equivalent Fe(3)O6 octahedra, and  a cornercorner with one Fe(8)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 54-62°. In the seventh Fe site, Fe(7) is bonded to one O(1) and three equivalent O(2) atoms to form corner-sharing FeO4 tetrahedra. The corner-sharing octahedral tilt angles range from 54-56°. In the eighth Fe site, Fe(8) is bonded to one O(9) and three equivalent O(10) atoms to form corner-sharing FeO4 tetrahedra. H(1) is bonded in a trigonal non-coplanar geometry to three equivalent O(7) atoms. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Fe(7) and three equivalent Fe(2) atoms. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Fe(1), one Fe(7), and two equivalent Fe(3) atoms. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Fe(2), one Fe(6), and two equivalent Fe(3) atoms. In the fourth O site, O(4) is bonded to one Fe(1), one Fe(5), and two equivalent Fe(3) atoms to form distorted corner-sharing OFe4 trigonal pyramids. In the fifth O site, O(5) is bonded in a rectangular see-saw-like geometry to one Fe(1), one Fe(2), one Fe(3), and one Fe(6) atom. In the sixth O site, O(6) is bonded in a trigonal planar geometry to one Fe(4) and two equivalent Fe(3) atoms. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Fe(4), two equivalent Fe(2), and one H(1) atom. In the eighth O site, O(8) is bonded in a trigonal planar geometry to one Fe(1), one Fe(3), and one Fe(4) atom. In the ninth O site, O(9) is bonded in a linear geometry to one Fe(5) and one Fe(8) atom. In the tenth O site, O(10) is bonded in a linear geometry to one Fe(6) and one Fe(8) atom.
Fe21HO32 crystallizes in the trigonal R3m space group. There are eight inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(2), one O(4), two equivalent O(5), and two equivalent O(8) atoms to form FeO6 octahedra that share  a cornercorner with one Fe(5)O4 tetrahedra,  a cornercorner with one Fe(7)O4 tetrahedra, corners with two equivalent Fe(4)O4 tetrahedra, corners with two equivalent Fe(6)O4 tetrahedra,  an edgeedge with one Fe(2)O6 octahedra, and edges with four equivalent Fe(3)O6 octahedra. The Fe(1)-O(2) bond length is 2.13 Å. The Fe(1)-O(4) bond length is 2.02 Å. Both Fe(1)-O(5) bond lengths are 2.15 Å. Both Fe(1)-O(8) bond lengths are 1.98 Å. In the second Fe site, Fe(2) is bonded to one O(1), one O(3), two equivalent O(5), and two equivalent O(7) atoms to form FeO6 octahedra that share  a cornercorner with one Fe(7)O4 tetrahedra, corners with two equivalent Fe(4)O4 tetrahedra, corners with three equivalent Fe(6)O4 tetrahedra,  an edgeedge with one Fe(1)O6 octahedra, edges with two equivalent Fe(2)O6 octahedra, and edges with two equivalent Fe(3)O6 octahedra. The Fe(2)-O(1) bond length is 2.11 Å. The Fe(2)-O(3) bond length is 2.03 Å. Both Fe(2)-O(5) bond lengths are 2.03 Å. Both Fe(2)-O(7) bond lengths are 2.01 Å. In the third Fe site, Fe(3) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(8) atom to form FeO6 octahedra that share  a cornercorner with one Fe(5)O4 tetrahedra,  a cornercorner with one Fe(7)O4 tetrahedra, corners with two equivalent Fe(4)O4 tetrahedra, corners with two equivalent Fe(6)O4 tetrahedra,  an edgeedge with one Fe(2)O6 octahedra, edges with two equivalent Fe(1)O6 octahedra, and edges with two equivalent Fe(3)O6 octahedra. The Fe(3)-O(2) bond length is 2.12 Å. The Fe(3)-O(3) bond length is 2.09 Å. The Fe(3)-O(4) bond length is 2.11 Å. The Fe(3)-O(5) bond length is 2.05 Å. The Fe(3)-O(6) bond length is 1.97 Å. The Fe(3)-O(8) bond length is 1.99 Å. In the fourth Fe site, Fe(4) is bonded to one O(6), one O(7), and two equivalent O(8) atoms to form corner-sharing FeO4 tetrahedra. The corner-sharing octahedral tilt angles range from 52-59°. The Fe(4)-O(6) bond length is 1.91 Å. The Fe(4)-O(7) bond length is 1.99 Å. Both Fe(4)-O(8) bond lengths are 1.92 Å. In the fifth Fe site, Fe(5) is bonded to one O(9) and three equivalent O(4) atoms to form FeO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra, corners with six equivalent Fe(3)O6 octahedra, and  a cornercorner with one Fe(8)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 58-64°. The Fe(5)-O(9) bond length is 1.79 Å. All Fe(5)-O(4) bond lengths are 2.00 Å. In the sixth Fe site, Fe(6) is bonded to one O(10), one O(3), and two equivalent O(5) atoms to form FeO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with three equivalent Fe(2)O6 octahedra, corners with four equivalent Fe(3)O6 octahedra, and  a cornercorner with one Fe(8)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 54-62°. The Fe(6)-O(10) bond length is 1.79 Å. The Fe(6)-O(3) bond length is 2.01 Å. Both Fe(6)-O(5) bond lengths are 2.00 Å. In the seventh Fe site, Fe(7) is bonded to one O(1) and three equivalent O(2) atoms to form corner-sharing FeO4 tetrahedra. The corner-sharing octahedral tilt angles range from 54-56°. The Fe(7)-O(1) bond length is 1.95 Å. All Fe(7)-O(2) bond lengths are 1.94 Å. In the eighth Fe site, Fe(8) is bonded to one O(9) and three equivalent O(10) atoms to form corner-sharing FeO4 tetrahedra. The Fe(8)-O(9) bond length is 1.86 Å. All Fe(8)-O(10) bond lengths are 1.89 Å. H(1) is bonded in a trigonal non-coplanar geometry to three equivalent O(7) atoms. All H(1)-O(7) bond lengths are 1.55 Å. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Fe(7) and three equivalent Fe(2) atoms. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Fe(1), one Fe(7), and two equivalent Fe(3) atoms. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Fe(2), one Fe(6), and two equivalent Fe(3) atoms. In the fourth O site, O(4) is bonded to one Fe(1), one Fe(5), and two equivalent Fe(3) atoms to form distorted corner-sharing OFe4 trigonal pyramids. In the fifth O site, O(5) is bonded in a rectangular see-saw-like geometry to one Fe(1), one Fe(2), one Fe(3), and one Fe(6) atom. In the sixth O site, O(6) is bonded in a trigonal planar geometry to one Fe(4) and two equivalent Fe(3) atoms. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Fe(4), two equivalent Fe(2), and one H(1) atom. In the eighth O site, O(8) is bonded in a trigonal planar geometry to one Fe(1), one Fe(3), and one Fe(4) atom. In the ninth O site, O(9) is bonded in a linear geometry to one Fe(5) and one Fe(8) atom. In the tenth O site, O(10) is bonded in a linear geometry to one Fe(6) and one Fe(8) atom.