Ba8Fe8O21 crystallizes in the triclinic P-1 space group. There are five inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a distorted q6 geometry to one O(2), one O(4), one O(6), one O(7), one O(9), two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms. In the second Ba site, Ba(2) is bonded in a distorted q6 geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms. In the third Ba site, Ba(3) is bonded in a distorted q6 geometry to two equivalent O(10), two equivalent O(11), two equivalent O(12), two equivalent O(13), and two equivalent O(8) atoms. In the fourth Ba site, Ba(4) is bonded in a distorted q6 geometry to one O(10), one O(11), one O(6), one O(7), one O(8), one O(9), two equivalent O(12), and two equivalent O(13) atoms. In the fifth Ba site, Ba(5) is bonded in a distorted q6 geometry to one O(1), one O(12), one O(13), one O(3), one O(5), two equivalent O(6), two equivalent O(7), and two equivalent O(9) atoms. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(5) atom to form FeO5 square pyramids that share corners with three equivalent Fe(3)O6 octahedra and corners with two equivalent Fe(1)O5 square pyramids. The corner-sharing octahedral tilt angles range from 1-15°. In the second Fe site, Fe(2) is bonded to one O(12), one O(13), one O(6), one O(7), and one O(9) atom to form FeO5 square pyramids that share corners with three equivalent Fe(3)O6 octahedra and corners with two equivalent Fe(4)O5 square pyramids. The corner-sharing octahedral tilt angles range from 0-17°. In the third Fe site, Fe(3) is bonded to one O(1), one O(3), one O(5), one O(6), one O(7), and one O(9) atom to form corner-sharing FeO6 octahedra. In the fourth Fe site, Fe(4) is bonded to one O(10), one O(11), one O(12), one O(13), and one O(8) atom to form corner-sharing FeO5 square pyramids. There are thirteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to one Ba(2), one Ba(5), two equivalent Ba(1), one Fe(1), and one Fe(3) atom. In the second O site, O(2) is bonded to two equivalent Ba(1), two equivalent Ba(2), and two equivalent Fe(1) atoms to form a mixture of distorted face and corner-sharing OBa4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-62°. In the third O site, O(3) is bonded in a 6-coordinate geometry to one Ba(2), one Ba(5), two equivalent Ba(1), one Fe(1), and one Fe(3) atom. In the fourth O site, O(4) is bonded to two equivalent Ba(1), two equivalent Ba(2), and two equivalent Fe(1) atoms to form a mixture of distorted face, corner, and edge-sharing OBa4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-60°. In the fifth O site, O(5) is bonded to one Ba(2), one Ba(5), two equivalent Ba(1), one Fe(1), and one Fe(3) atom to form a mixture of distorted face, corner, and edge-sharing OBa4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-62°. In the sixth O site, O(6) is bonded in a 6-coordinate geometry to one Ba(1), one Ba(4), two equivalent Ba(5), one Fe(2), and one Fe(3) atom. In the seventh O site, O(7) is bonded to one Ba(1), one Ba(4), two equivalent Ba(5), one Fe(2), and one Fe(3) atom to form a mixture of distorted face, corner, and edge-sharing OBa4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 2-62°. In the eighth O site, O(8) is bonded in a distorted linear geometry to two equivalent Ba(3), two equivalent Ba(4), and two equivalent Fe(4) atoms. In the ninth O site, O(9) is bonded in a distorted linear geometry to one Ba(1), one Ba(4), two equivalent Ba(5), one Fe(2), and one Fe(3) atom. In the tenth O site, O(10) is bonded to two equivalent Ba(3), two equivalent Ba(4), and two equivalent Fe(4) atoms to form a mixture of distorted face, corner, and edge-sharing OBa4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-61°. In the eleventh O site, O(11) is bonded to two equivalent Ba(3), two equivalent Ba(4), and two equivalent Fe(4) atoms to form a mixture of distorted face, corner, and edge-sharing OBa4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-60°. In the twelfth O site, O(12) is bonded to one Ba(3), one Ba(5), two equivalent Ba(4), one Fe(2), and one Fe(4) atom to form a mixture of distorted face, corner, and edge-sharing OBa4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-61°. In the thirteenth O site, O(13) is bonded to one Ba(3), one Ba(5), two equivalent Ba(4), one Fe(2), and one Fe(4) atom to form a mixture of distorted face, corner, and edge-sharing OBa4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-62°.
Ba8Fe8O21 crystallizes in the triclinic P-1 space group. There are five inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a distorted q6 geometry to one O(2), one O(4), one O(6), one O(7), one O(9), two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms. The Ba(1)-O(2) bond length is 2.94 Å. The Ba(1)-O(4) bond length is 2.90 Å. The Ba(1)-O(6) bond length is 2.97 Å. The Ba(1)-O(7) bond length is 2.84 Å. The Ba(1)-O(9) bond length is 2.87 Å. There is one shorter (2.85 Å) and one longer (2.94 Å) Ba(1)-O(1) bond length. There is one shorter (2.86 Å) and one longer (2.97 Å) Ba(1)-O(3) bond length. There is one shorter (2.87 Å) and one longer (2.88 Å) Ba(1)-O(5) bond length. In the second Ba site, Ba(2) is bonded in a distorted q6 geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms. Both Ba(2)-O(1) bond lengths are 2.85 Å. Both Ba(2)-O(2) bond lengths are 2.91 Å. Both Ba(2)-O(3) bond lengths are 2.82 Å. Both Ba(2)-O(4) bond lengths are 2.87 Å. Both Ba(2)-O(5) bond lengths are 2.87 Å. In the third Ba site, Ba(3) is bonded in a distorted q6 geometry to two equivalent O(10), two equivalent O(11), two equivalent O(12), two equivalent O(13), and two equivalent O(8) atoms. Both Ba(3)-O(10) bond lengths are 2.91 Å. Both Ba(3)-O(11) bond lengths are 2.89 Å. Both Ba(3)-O(12) bond lengths are 2.91 Å. Both Ba(3)-O(13) bond lengths are 2.91 Å. Both Ba(3)-O(8) bond lengths are 2.87 Å. In the fourth Ba site, Ba(4) is bonded in a distorted q6 geometry to one O(10), one O(11), one O(6), one O(7), one O(8), one O(9), two equivalent O(12), and two equivalent O(13) atoms. The Ba(4)-O(10) bond length is 2.96 Å. The Ba(4)-O(11) bond length is 2.95 Å. The Ba(4)-O(6) bond length is 2.75 Å. The Ba(4)-O(7) bond length is 2.83 Å. The Ba(4)-O(8) bond length is 2.89 Å. The Ba(4)-O(9) bond length is 2.81 Å. There is one shorter (2.85 Å) and one longer (2.93 Å) Ba(4)-O(12) bond length. Both Ba(4)-O(13) bond lengths are 2.91 Å. In the fifth Ba site, Ba(5) is bonded in a distorted q6 geometry to one O(1), one O(12), one O(13), one O(3), one O(5), two equivalent O(6), two equivalent O(7), and two equivalent O(9) atoms. The Ba(5)-O(1) bond length is 2.86 Å. The Ba(5)-O(12) bond length is 2.92 Å. The Ba(5)-O(13) bond length is 2.95 Å. The Ba(5)-O(3) bond length is 2.93 Å. The Ba(5)-O(5) bond length is 2.82 Å. There is one shorter (2.87 Å) and one longer (2.97 Å) Ba(5)-O(6) bond length. There is one shorter (2.89 Å) and one longer (2.90 Å) Ba(5)-O(7) bond length. There is one shorter (2.84 Å) and one longer (2.91 Å) Ba(5)-O(9) bond length. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(5) atom to form FeO5 square pyramids that share corners with three equivalent Fe(3)O6 octahedra and corners with two equivalent Fe(1)O5 square pyramids. The corner-sharing octahedral tilt angles range from 1-15°. The Fe(1)-O(1) bond length is 1.89 Å. The Fe(1)-O(2) bond length is 2.02 Å. The Fe(1)-O(3) bond length is 1.94 Å. The Fe(1)-O(4) bond length is 2.05 Å. The Fe(1)-O(5) bond length is 2.06 Å. In the second Fe site, Fe(2) is bonded to one O(12), one O(13), one O(6), one O(7), and one O(9) atom to form FeO5 square pyramids that share corners with three equivalent Fe(3)O6 octahedra and corners with two equivalent Fe(4)O5 square pyramids. The corner-sharing octahedral tilt angles range from 0-17°. The Fe(2)-O(12) bond length is 2.09 Å. The Fe(2)-O(13) bond length is 2.01 Å. The Fe(2)-O(6) bond length is 1.93 Å. The Fe(2)-O(7) bond length is 2.04 Å. The Fe(2)-O(9) bond length is 1.89 Å. In the third Fe site, Fe(3) is bonded to one O(1), one O(3), one O(5), one O(6), one O(7), and one O(9) atom to form corner-sharing FeO6 octahedra. The Fe(3)-O(1) bond length is 1.99 Å. The Fe(3)-O(3) bond length is 2.13 Å. The Fe(3)-O(5) bond length is 2.04 Å. The Fe(3)-O(6) bond length is 2.19 Å. The Fe(3)-O(7) bond length is 2.03 Å. The Fe(3)-O(9) bond length is 2.01 Å. In the fourth Fe site, Fe(4) is bonded to one O(10), one O(11), one O(12), one O(13), and one O(8) atom to form corner-sharing FeO5 square pyramids. The Fe(4)-O(10) bond length is 2.02 Å. The Fe(4)-O(11) bond length is 2.04 Å. The Fe(4)-O(12) bond length is 2.00 Å. The Fe(4)-O(13) bond length is 2.04 Å. The Fe(4)-O(8) bond length is 1.88 Å. There are thirteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to one Ba(2), one Ba(5), two equivalent Ba(1), one Fe(1), and one Fe(3) atom. In the second O site, O(2) is bonded to two equivalent Ba(1), two equivalent Ba(2), and two equivalent Fe(1) atoms to form a mixture of distorted face and corner-sharing OBa4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-62°. In the third O site, O(3) is bonded in a 6-coordinate geometry to one Ba(2), one Ba(5), two equivalent Ba(1), one Fe(1), and one Fe(3) atom. In the fourth O site, O(4) is bonded to two equivalent Ba(1), two equivalent Ba(2), and two equivalent Fe(1) atoms to form a mixture of distorted face, corner, and edge-sharing OBa4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-60°. In the fifth O site, O(5) is bonded to one Ba(2), one Ba(5), two equivalent Ba(1), one Fe(1), and one Fe(3) atom to form a mixture of distorted face, corner, and edge-sharing OBa4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-62°. In the sixth O site, O(6) is bonded in a 6-coordinate geometry to one Ba(1), one Ba(4), two equivalent Ba(5), one Fe(2), and one Fe(3) atom. In the seventh O site, O(7) is bonded to one Ba(1), one Ba(4), two equivalent Ba(5), one Fe(2), and one Fe(3) atom to form a mixture of distorted face, corner, and edge-sharing OBa4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 2-62°. In the eighth O site, O(8) is bonded in a distorted linear geometry to two equivalent Ba(3), two equivalent Ba(4), and two equivalent Fe(4) atoms. In the ninth O site, O(9) is bonded in a distorted linear geometry to one Ba(1), one Ba(4), two equivalent Ba(5), one Fe(2), and one Fe(3) atom. In the tenth O site, O(10) is bonded to two equivalent Ba(3), two equivalent Ba(4), and two equivalent Fe(4) atoms to form a mixture of distorted face, corner, and edge-sharing OBa4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-61°. In the eleventh O site, O(11) is bonded to two equivalent Ba(3), two equivalent Ba(4), and two equivalent Fe(4) atoms to form a mixture of distorted face, corner, and edge-sharing OBa4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-60°. In the twelfth O site, O(12) is bonded to one Ba(3), one Ba(5), two equivalent Ba(4), one Fe(2), and one Fe(4) atom to form a mixture of distorted face, corner, and edge-sharing OBa4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-61°. In the thirteenth O site, O(13) is bonded to one Ba(3), one Ba(5), two equivalent Ba(4), one Fe(2), and one Fe(4) atom to form a mixture of distorted face, corner, and edge-sharing OBa4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-62°.