Ca2Fe7O11 crystallizes in the monoclinic C2/m space group. Ca(1) is bonded in a 8-coordinate geometry to one O(1), one O(5), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(3), one O(6), two equivalent O(4), and two equivalent O(5) atoms to form a mixture of distorted edge and corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 0-45°. In the second Fe site, Fe(2) is bonded to one O(4), two equivalent O(6), and three equivalent O(5) atoms to form a mixture of edge and corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 0-9°. In the third Fe site, Fe(3) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form a mixture of edge and corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles are 5°. In the fourth Fe site, Fe(4) is bonded to one O(3), two equivalent O(2), and three equivalent O(1) atoms to form a mixture of edge and corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 5-45°. There are six inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1), two equivalent Fe(3), and three equivalent Fe(4) atoms to form distorted OCaFe5 octahedra that share corners with two equivalent O(1)CaFe5 octahedra,  a cornercorner with one O(5)CaFe5 square pyramid,  a cornercorner with one O(3)Ca2Fe2 tetrahedra, corners with two equivalent O(2)Ca2Fe3 trigonal bipyramids, corners with two equivalent O(4)Ca2Fe3 trigonal bipyramids, edges with five equivalent O(1)CaFe5 octahedra, edges with two equivalent O(3)Ca2Fe2 tetrahedra, and edges with five equivalent O(2)Ca2Fe3 trigonal bipyramids. The corner-sharing octahedra are not tilted. In the second O site, O(2) is bonded to two equivalent Ca(1), one Fe(3), and two equivalent Fe(4) atoms to form distorted OCa2Fe3 trigonal bipyramids that share corners with two equivalent O(1)CaFe5 octahedra, corners with two equivalent O(5)CaFe5 square pyramids, corners with four equivalent O(3)Ca2Fe2 tetrahedra,  a cornercorner with one O(2)Ca2Fe3 trigonal bipyramid, corners with two equivalent O(4)Ca2Fe3 trigonal bipyramids, edges with five equivalent O(1)CaFe5 octahedra,  an edgeedge with one O(3)Ca2Fe2 tetrahedra,  an edgeedge with one O(4)Ca2Fe3 trigonal bipyramid, and edges with two equivalent O(2)Ca2Fe3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 12°. In the third O site, O(3) is bonded to two equivalent Ca(1), one Fe(1), and one Fe(4) atom to form distorted OCa2Fe2 tetrahedra that share  a cornercorner with one O(1)CaFe5 octahedra,  a cornercorner with one O(6)Fe6 octahedra, corners with two equivalent O(3)Ca2Fe2 tetrahedra, corners with four equivalent O(2)Ca2Fe3 trigonal bipyramids, corners with four equivalent O(4)Ca2Fe3 trigonal bipyramids, edges with two equivalent O(1)CaFe5 octahedra, edges with two equivalent O(5)CaFe5 square pyramids,  an edgeedge with one O(2)Ca2Fe3 trigonal bipyramid, and  an edgeedge with one O(4)Ca2Fe3 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 2-3°. In the fourth O site, O(4) is bonded to two equivalent Ca(1), one Fe(2), and two equivalent Fe(1) atoms to form distorted OCa2Fe3 trigonal bipyramids that share corners with two equivalent O(1)CaFe5 octahedra, corners with three equivalent O(5)CaFe5 square pyramids, corners with four equivalent O(3)Ca2Fe2 tetrahedra, corners with two equivalent O(2)Ca2Fe3 trigonal bipyramids, edges with two equivalent O(6)Fe6 octahedra, edges with three equivalent O(5)CaFe5 square pyramids,  an edgeedge with one O(3)Ca2Fe2 tetrahedra,  an edgeedge with one O(2)Ca2Fe3 trigonal bipyramid, and edges with two equivalent O(4)Ca2Fe3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 41°. In the fifth O site, O(5) is bonded to one Ca(1), two equivalent Fe(1), and three equivalent Fe(2) atoms to form distorted OCaFe5 square pyramids that share  a cornercorner with one O(1)CaFe5 octahedra, corners with two equivalent O(6)Fe6 octahedra, corners with two equivalent O(2)Ca2Fe3 trigonal bipyramids, corners with three equivalent O(4)Ca2Fe3 trigonal bipyramids, edges with three equivalent O(6)Fe6 octahedra, edges with four equivalent O(5)CaFe5 square pyramids, edges with two equivalent O(3)Ca2Fe2 tetrahedra, and edges with three equivalent O(4)Ca2Fe3 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 4-50°. In the sixth O site, O(6) is bonded to two equivalent Fe(1) and four equivalent Fe(2) atoms to form OFe6 octahedra that share corners with four equivalent O(5)CaFe5 square pyramids, corners with two equivalent O(3)Ca2Fe2 tetrahedra, edges with two equivalent O(6)Fe6 octahedra, edges with six equivalent O(5)CaFe5 square pyramids, and edges with four equivalent O(4)Ca2Fe3 trigonal bipyramids.
Ca2Fe7O11 crystallizes in the monoclinic C2/m space group. Ca(1) is bonded in a 8-coordinate geometry to one O(1), one O(5), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. The Ca(1)-O(1) bond length is 2.82 Å. The Ca(1)-O(5) bond length is 2.96 Å. Both Ca(1)-O(2) bond lengths are 2.40 Å. Both Ca(1)-O(3) bond lengths are 2.31 Å. Both Ca(1)-O(4) bond lengths are 2.41 Å. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(3), one O(6), two equivalent O(4), and two equivalent O(5) atoms to form a mixture of distorted edge and corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 0-45°. The Fe(1)-O(3) bond length is 1.94 Å. The Fe(1)-O(6) bond length is 2.32 Å. Both Fe(1)-O(4) bond lengths are 2.09 Å. Both Fe(1)-O(5) bond lengths are 2.15 Å. In the second Fe site, Fe(2) is bonded to one O(4), two equivalent O(6), and three equivalent O(5) atoms to form a mixture of edge and corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 0-9°. The Fe(2)-O(4) bond length is 1.99 Å. Both Fe(2)-O(6) bond lengths are 2.17 Å. There is one shorter (2.13 Å) and two longer (2.14 Å) Fe(2)-O(5) bond lengths. In the third Fe site, Fe(3) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form a mixture of edge and corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles are 5°. Both Fe(3)-O(2) bond lengths are 1.97 Å. All Fe(3)-O(1) bond lengths are 2.17 Å. In the fourth Fe site, Fe(4) is bonded to one O(3), two equivalent O(2), and three equivalent O(1) atoms to form a mixture of edge and corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 5-45°. The Fe(4)-O(3) bond length is 1.96 Å. Both Fe(4)-O(2) bond lengths are 2.10 Å. There are two shorter (2.13 Å) and one longer (2.24 Å) Fe(4)-O(1) bond length. There are six inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1), two equivalent Fe(3), and three equivalent Fe(4) atoms to form distorted OCaFe5 octahedra that share corners with two equivalent O(1)CaFe5 octahedra,  a cornercorner with one O(5)CaFe5 square pyramid,  a cornercorner with one O(3)Ca2Fe2 tetrahedra, corners with two equivalent O(2)Ca2Fe3 trigonal bipyramids, corners with two equivalent O(4)Ca2Fe3 trigonal bipyramids, edges with five equivalent O(1)CaFe5 octahedra, edges with two equivalent O(3)Ca2Fe2 tetrahedra, and edges with five equivalent O(2)Ca2Fe3 trigonal bipyramids. The corner-sharing octahedra are not tilted. In the second O site, O(2) is bonded to two equivalent Ca(1), one Fe(3), and two equivalent Fe(4) atoms to form distorted OCa2Fe3 trigonal bipyramids that share corners with two equivalent O(1)CaFe5 octahedra, corners with two equivalent O(5)CaFe5 square pyramids, corners with four equivalent O(3)Ca2Fe2 tetrahedra,  a cornercorner with one O(2)Ca2Fe3 trigonal bipyramid, corners with two equivalent O(4)Ca2Fe3 trigonal bipyramids, edges with five equivalent O(1)CaFe5 octahedra,  an edgeedge with one O(3)Ca2Fe2 tetrahedra,  an edgeedge with one O(4)Ca2Fe3 trigonal bipyramid, and edges with two equivalent O(2)Ca2Fe3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 12°. In the third O site, O(3) is bonded to two equivalent Ca(1), one Fe(1), and one Fe(4) atom to form distorted OCa2Fe2 tetrahedra that share  a cornercorner with one O(1)CaFe5 octahedra,  a cornercorner with one O(6)Fe6 octahedra, corners with two equivalent O(3)Ca2Fe2 tetrahedra, corners with four equivalent O(2)Ca2Fe3 trigonal bipyramids, corners with four equivalent O(4)Ca2Fe3 trigonal bipyramids, edges with two equivalent O(1)CaFe5 octahedra, edges with two equivalent O(5)CaFe5 square pyramids,  an edgeedge with one O(2)Ca2Fe3 trigonal bipyramid, and  an edgeedge with one O(4)Ca2Fe3 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 2-3°. In the fourth O site, O(4) is bonded to two equivalent Ca(1), one Fe(2), and two equivalent Fe(1) atoms to form distorted OCa2Fe3 trigonal bipyramids that share corners with two equivalent O(1)CaFe5 octahedra, corners with three equivalent O(5)CaFe5 square pyramids, corners with four equivalent O(3)Ca2Fe2 tetrahedra, corners with two equivalent O(2)Ca2Fe3 trigonal bipyramids, edges with two equivalent O(6)Fe6 octahedra, edges with three equivalent O(5)CaFe5 square pyramids,  an edgeedge with one O(3)Ca2Fe2 tetrahedra,  an edgeedge with one O(2)Ca2Fe3 trigonal bipyramid, and edges with two equivalent O(4)Ca2Fe3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 41°. In the fifth O site, O(5) is bonded to one Ca(1), two equivalent Fe(1), and three equivalent Fe(2) atoms to form distorted OCaFe5 square pyramids that share  a cornercorner with one O(1)CaFe5 octahedra, corners with two equivalent O(6)Fe6 octahedra, corners with two equivalent O(2)Ca2Fe3 trigonal bipyramids, corners with three equivalent O(4)Ca2Fe3 trigonal bipyramids, edges with three equivalent O(6)Fe6 octahedra, edges with four equivalent O(5)CaFe5 square pyramids, edges with two equivalent O(3)Ca2Fe2 tetrahedra, and edges with three equivalent O(4)Ca2Fe3 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 4-50°. In the sixth O site, O(6) is bonded to two equivalent Fe(1) and four equivalent Fe(2) atoms to form OFe6 octahedra that share corners with four equivalent O(5)CaFe5 square pyramids, corners with two equivalent O(3)Ca2Fe2 tetrahedra, edges with two equivalent O(6)Fe6 octahedra, edges with six equivalent O(5)CaFe5 square pyramids, and edges with four equivalent O(4)Ca2Fe3 trigonal bipyramids.