Fe4(PO5)3 crystallizes in the monoclinic C2/c space group. There are two 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), one O(6), and one O(7) atom to form FeO6 octahedra that share  a cornercorner with one Fe(1)O6 octahedra,  a cornercorner with one Fe(2)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and  a faceface with one Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 38-51°. In the second Fe site, Fe(2) is bonded to one O(5), one O(6), one O(7), one O(8), and two equivalent O(2) atoms to form FeO6 octahedra that share  a cornercorner with one Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra, and  a faceface with one Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 51°. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(4), one O(5), one O(6), and one O(8) atom to form PO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra and corners with three equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 27-50°. In the second P site, P(2) is bonded to two equivalent O(3) and two equivalent O(7) atoms to form PO4 tetrahedra that share corners with two equivalent Fe(2)O6 octahedra and corners with four equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 41-44°. There are eight inequivalent O sites. In the first O site, O(3) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(2) atom. In the second O site, O(4) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(1) atom. In the third O site, O(5) is bonded in a bent 150 degrees geometry to one Fe(2) and one P(1) atom. In the fourth O site, O(6) is bonded in a 3-coordinate geometry to one Fe(1), one Fe(2), and one P(1) atom. In the fifth O site, O(7) is bonded in a 3-coordinate geometry to one Fe(1), one Fe(2), and one P(2) atom. In the sixth O site, O(8) is bonded in a bent 150 degrees geometry to one Fe(2) and one P(1) atom. In the seventh O site, O(1) is bonded in a bent 150 degrees geometry to two equivalent Fe(1) atoms. In the eighth O site, O(2) is bonded in a distorted trigonal planar geometry to one Fe(1) and two equivalent Fe(2) atoms.
Fe4(PO5)3 crystallizes in the monoclinic C2/c space group. There are two 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), one O(6), and one O(7) atom to form FeO6 octahedra that share  a cornercorner with one Fe(1)O6 octahedra,  a cornercorner with one Fe(2)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and  a faceface with one Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 38-51°. The Fe(1)-O(1) bond length is 1.99 Å. The Fe(1)-O(2) bond length is 1.99 Å. The Fe(1)-O(3) bond length is 1.92 Å. The Fe(1)-O(4) bond length is 1.93 Å. The Fe(1)-O(6) bond length is 2.04 Å. The Fe(1)-O(7) bond length is 2.16 Å. In the second Fe site, Fe(2) is bonded to one O(5), one O(6), one O(7), one O(8), and two equivalent O(2) atoms to form FeO6 octahedra that share  a cornercorner with one Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra, and  a faceface with one Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 51°. The Fe(2)-O(5) bond length is 1.91 Å. The Fe(2)-O(6) bond length is 2.11 Å. The Fe(2)-O(7) bond length is 2.14 Å. The Fe(2)-O(8) bond length is 1.94 Å. There is one shorter (1.97 Å) and one longer (2.06 Å) Fe(2)-O(2) bond length. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(4), one O(5), one O(6), and one O(8) atom to form PO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra and corners with three equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 27-50°. The P(1)-O(4) bond length is 1.53 Å. The P(1)-O(5) bond length is 1.54 Å. The P(1)-O(6) bond length is 1.58 Å. The P(1)-O(8) bond length is 1.53 Å. In the second P site, P(2) is bonded to two equivalent O(3) and two equivalent O(7) atoms to form PO4 tetrahedra that share corners with two equivalent Fe(2)O6 octahedra and corners with four equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 41-44°. Both P(2)-O(3) bond lengths are 1.54 Å. Both P(2)-O(7) bond lengths are 1.54 Å. There are eight inequivalent O sites. In the first O site, O(3) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(2) atom. In the second O site, O(4) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(1) atom. In the third O site, O(5) is bonded in a bent 150 degrees geometry to one Fe(2) and one P(1) atom. In the fourth O site, O(6) is bonded in a 3-coordinate geometry to one Fe(1), one Fe(2), and one P(1) atom. In the fifth O site, O(7) is bonded in a 3-coordinate geometry to one Fe(1), one Fe(2), and one P(2) atom. In the sixth O site, O(8) is bonded in a bent 150 degrees geometry to one Fe(2) and one P(1) atom. In the seventh O site, O(1) is bonded in a bent 150 degrees geometry to two equivalent Fe(1) atoms. In the eighth O site, O(2) is bonded in a distorted trigonal planar geometry to one Fe(1) and two equivalent Fe(2) atoms.