Fe9(PO4)8 crystallizes in the triclinic P-1 space group. There are six inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(12), one O(15), one O(3), one O(8), and one O(9) atom to form FeO5 trigonal bipyramids that share  a cornercorner with one Fe(5)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(2)O4 tetrahedra,  a cornercorner with one P(4)O4 tetrahedra, and  an edgeedge with one P(3)O4 tetrahedra. The corner-sharing octahedral tilt angles are 63°. In the second Fe site, Fe(2) is bonded to one O(10), one O(14), one O(16), one O(2), one O(5), and one O(7) atom to form distorted FeO6 octahedra that share  a cornercorner with one Fe(5)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(3)O4 tetrahedra, corners with two equivalent P(4)O4 tetrahedra, corners with two equivalent Fe(3)O5 trigonal bipyramids, and  an edgeedge with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 51°. In the third Fe site, Fe(3) is bonded to one O(1), one O(11), one O(14), one O(4), and one O(5) atom to form FeO5 trigonal bipyramids that share corners with two equivalent Fe(2)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra,  a cornercorner with one P(3)O4 tetrahedra,  a cornercorner with one P(4)O4 tetrahedra, and corners with two equivalent P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 61-66°. In the fourth Fe site, Fe(4) is bonded in a square co-planar geometry to two equivalent O(12) and two equivalent O(4) atoms. In the fifth Fe site, Fe(5) is bonded to two equivalent O(13), two equivalent O(15), and two equivalent O(16) atoms to form distorted FeO6 octahedra that share corners with two equivalent Fe(2)O6 octahedra, corners with two equivalent P(2)O4 tetrahedra, corners with two equivalent Fe(1)O5 trigonal bipyramids, and edges with two equivalent P(3)O4 tetrahedra. The corner-sharing octahedral tilt angles are 51°. In the sixth Fe site, Fe(6) is bonded in a square co-planar geometry to two equivalent O(3) and two equivalent O(6) atoms. There are four inequivalent P sites. In the first P site, P(1) is bonded to one O(10), one O(14), one O(5), and one O(9) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(2)O6 octahedra,  a cornercorner with one Fe(1)O5 trigonal bipyramid, corners with two equivalent Fe(3)O5 trigonal bipyramids, and  an edgeedge with one Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles are 42°. In the second P site, P(2) is bonded to one O(1), one O(13), one O(6), and one O(8) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(5)O6 octahedra,  a cornercorner with one Fe(1)O5 trigonal bipyramid, and  a cornercorner with one Fe(3)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 39°. In the third P site, P(3) is bonded to one O(11), one O(12), one O(15), and one O(16) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(2)O6 octahedra,  a cornercorner with one Fe(3)O5 trigonal bipyramid,  an edgeedge with one Fe(5)O6 octahedra, and  an edgeedge with one Fe(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 49°. In the fourth P site, P(4) is bonded to one O(2), one O(3), one O(4), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent Fe(2)O6 octahedra,  a cornercorner with one Fe(1)O5 trigonal bipyramid, and  a cornercorner with one Fe(3)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 43-45°. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Fe(3) and one P(2) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Fe(2) and one P(4) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(6), and one P(4) atom. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one Fe(3), one Fe(4), and one P(4) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Fe(2), one Fe(3), and one P(1) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Fe(6) and one P(2) atom. In the seventh O site, O(7) is bonded in a distorted bent 150 degrees geometry to one Fe(2) and one P(4) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one Fe(1) and one P(2) atom. In the ninth O site, O(9) is bonded in a distorted bent 120 degrees geometry to one Fe(1) and one P(1) atom. In the tenth O site, O(10) is bonded in a distorted bent 150 degrees geometry to one Fe(2) and one P(1) atom. In the eleventh O site, O(11) is bonded in a bent 150 degrees geometry to one Fe(3) and one P(3) atom. In the twelfth O site, O(12) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(4), and one P(3) atom. In the thirteenth O site, O(13) is bonded in a bent 150 degrees geometry to one Fe(5) and one P(2) atom. In the fourteenth O site, O(14) is bonded in a distorted trigonal planar geometry to one Fe(2), one Fe(3), and one P(1) atom. In the fifteenth O site, O(15) is bonded in a 3-coordinate geometry to one Fe(1), one Fe(5), and one P(3) atom. In the sixteenth O site, O(16) is bonded in a 3-coordinate geometry to one Fe(2), one Fe(5), and one P(3) atom.
Fe9(PO4)8 crystallizes in the triclinic P-1 space group. There are six inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(12), one O(15), one O(3), one O(8), and one O(9) atom to form FeO5 trigonal bipyramids that share  a cornercorner with one Fe(5)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(2)O4 tetrahedra,  a cornercorner with one P(4)O4 tetrahedra, and  an edgeedge with one P(3)O4 tetrahedra. The corner-sharing octahedral tilt angles are 63°. The Fe(1)-O(12) bond length is 2.12 Å. The Fe(1)-O(15) bond length is 2.06 Å. The Fe(1)-O(3) bond length is 2.06 Å. The Fe(1)-O(8) bond length is 1.88 Å. The Fe(1)-O(9) bond length is 1.94 Å. In the second Fe site, Fe(2) is bonded to one O(10), one O(14), one O(16), one O(2), one O(5), and one O(7) atom to form distorted FeO6 octahedra that share  a cornercorner with one Fe(5)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(3)O4 tetrahedra, corners with two equivalent P(4)O4 tetrahedra, corners with two equivalent Fe(3)O5 trigonal bipyramids, and  an edgeedge with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 51°. The Fe(2)-O(10) bond length is 1.97 Å. The Fe(2)-O(14) bond length is 2.11 Å. The Fe(2)-O(16) bond length is 1.99 Å. The Fe(2)-O(2) bond length is 1.97 Å. The Fe(2)-O(5) bond length is 2.48 Å. The Fe(2)-O(7) bond length is 1.94 Å. In the third Fe site, Fe(3) is bonded to one O(1), one O(11), one O(14), one O(4), and one O(5) atom to form FeO5 trigonal bipyramids that share corners with two equivalent Fe(2)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra,  a cornercorner with one P(3)O4 tetrahedra,  a cornercorner with one P(4)O4 tetrahedra, and corners with two equivalent P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 61-66°. The Fe(3)-O(1) bond length is 1.88 Å. The Fe(3)-O(11) bond length is 1.97 Å. The Fe(3)-O(14) bond length is 2.08 Å. The Fe(3)-O(4) bond length is 2.00 Å. The Fe(3)-O(5) bond length is 1.99 Å. In the fourth Fe site, Fe(4) is bonded in a square co-planar geometry to two equivalent O(12) and two equivalent O(4) atoms. Both Fe(4)-O(12) bond lengths are 2.01 Å. Both Fe(4)-O(4) bond lengths are 2.10 Å. In the fifth Fe site, Fe(5) is bonded to two equivalent O(13), two equivalent O(15), and two equivalent O(16) atoms to form distorted FeO6 octahedra that share corners with two equivalent Fe(2)O6 octahedra, corners with two equivalent P(2)O4 tetrahedra, corners with two equivalent Fe(1)O5 trigonal bipyramids, and edges with two equivalent P(3)O4 tetrahedra. The corner-sharing octahedral tilt angles are 51°. Both Fe(5)-O(13) bond lengths are 2.05 Å. Both Fe(5)-O(15) bond lengths are 2.35 Å. Both Fe(5)-O(16) bond lengths are 2.31 Å. In the sixth Fe site, Fe(6) is bonded in a square co-planar geometry to two equivalent O(3) and two equivalent O(6) atoms. Both Fe(6)-O(3) bond lengths are 2.16 Å. Both Fe(6)-O(6) bond lengths are 1.99 Å. There are four inequivalent P sites. In the first P site, P(1) is bonded to one O(10), one O(14), one O(5), and one O(9) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(2)O6 octahedra,  a cornercorner with one Fe(1)O5 trigonal bipyramid, corners with two equivalent Fe(3)O5 trigonal bipyramids, and  an edgeedge with one Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles are 42°. The P(1)-O(10) bond length is 1.53 Å. The P(1)-O(14) bond length is 1.59 Å. The P(1)-O(5) bond length is 1.57 Å. The P(1)-O(9) bond length is 1.53 Å. In the second P site, P(2) is bonded to one O(1), one O(13), one O(6), and one O(8) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(5)O6 octahedra,  a cornercorner with one Fe(1)O5 trigonal bipyramid, and  a cornercorner with one Fe(3)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 39°. The P(2)-O(1) bond length is 1.59 Å. The P(2)-O(13) bond length is 1.53 Å. The P(2)-O(6) bond length is 1.53 Å. The P(2)-O(8) bond length is 1.57 Å. In the third P site, P(3) is bonded to one O(11), one O(12), one O(15), and one O(16) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(2)O6 octahedra,  a cornercorner with one Fe(3)O5 trigonal bipyramid,  an edgeedge with one Fe(5)O6 octahedra, and  an edgeedge with one Fe(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 49°. The P(3)-O(11) bond length is 1.52 Å. The P(3)-O(12) bond length is 1.58 Å. The P(3)-O(15) bond length is 1.56 Å. The P(3)-O(16) bond length is 1.56 Å. In the fourth P site, P(4) is bonded to one O(2), one O(3), one O(4), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent Fe(2)O6 octahedra,  a cornercorner with one Fe(1)O5 trigonal bipyramid, and  a cornercorner with one Fe(3)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 43-45°. The P(4)-O(2) bond length is 1.54 Å. The P(4)-O(3) bond length is 1.57 Å. The P(4)-O(4) bond length is 1.57 Å. The P(4)-O(7) bond length is 1.53 Å. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Fe(3) and one P(2) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Fe(2) and one P(4) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(6), and one P(4) atom. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one Fe(3), one Fe(4), and one P(4) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Fe(2), one Fe(3), and one P(1) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Fe(6) and one P(2) atom. In the seventh O site, O(7) is bonded in a distorted bent 150 degrees geometry to one Fe(2) and one P(4) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one Fe(1) and one P(2) atom. In the ninth O site, O(9) is bonded in a distorted bent 120 degrees geometry to one Fe(1) and one P(1) atom. In the tenth O site, O(10) is bonded in a distorted bent 150 degrees geometry to one Fe(2) and one P(1) atom. In the eleventh O site, O(11) is bonded in a bent 150 degrees geometry to one Fe(3) and one P(3) atom. In the twelfth O site, O(12) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(4), and one P(3) atom. In the thirteenth O site, O(13) is bonded in a bent 150 degrees geometry to one Fe(5) and one P(2) atom. In the fourteenth O site, O(14) is bonded in a distorted trigonal planar geometry to one Fe(2), one Fe(3), and one P(1) atom. In the fifteenth O site, O(15) is bonded in a 3-coordinate geometry to one Fe(1), one Fe(5), and one P(3) atom. In the sixteenth O site, O(16) is bonded in a 3-coordinate geometry to one Fe(2), one Fe(5), and one P(3) atom.