Fe5(PO4)4 crystallizes in the triclinic P-1 space group. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(2), one O(3), one O(5), and one O(7) atom to form distorted FeO5 trigonal bipyramids that share corners with two equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and edges with two equivalent Fe(2)O6 octahedra. In the second Fe site, Fe(2) is bonded to one O(1), one O(3), one O(5), one O(6), one O(7), and one O(8) atom to form FeO6 octahedra that share  a cornercorner with one P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra,  an edgeedge with one Fe(3)O6 octahedra,  an edgeedge with one P(2)O4 tetrahedra, and edges with two equivalent Fe(1)O5 trigonal bipyramids. In the third Fe site, Fe(3) is bonded to two equivalent O(4), two equivalent O(6), and two equivalent O(8) atoms to form FeO6 octahedra that share corners with two equivalent P(2)O4 tetrahedra, corners with four equivalent P(1)O4 tetrahedra, and edges with two equivalent Fe(2)O6 octahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(3), one O(4), one O(7), and one O(8) atom to form PO4 tetrahedra that share corners with two equivalent Fe(3)O6 octahedra, corners with three equivalent Fe(2)O6 octahedra, and corners with two equivalent Fe(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 39-53°. In the second P site, P(2) is bonded to one O(1), one O(2), one O(5), and one O(6) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(2)O6 octahedra,  a cornercorner with one Fe(3)O6 octahedra, corners with three equivalent Fe(1)O5 trigonal bipyramids, and  an edgeedge with one Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-55°. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Fe(1), one Fe(2), and one P(2) atom. In the second O site, O(2) is bonded in a linear geometry to one Fe(1) and one P(2) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(2), and one P(1) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Fe(3) and one P(1) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Fe(1), one Fe(2), and one P(2) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Fe(2), one Fe(3), and one P(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(2), and one P(1) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Fe(2), one Fe(3), and one P(1) atom.
Fe5(PO4)4 crystallizes in the triclinic P-1 space group. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(2), one O(3), one O(5), and one O(7) atom to form distorted FeO5 trigonal bipyramids that share corners with two equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and edges with two equivalent Fe(2)O6 octahedra. The Fe(1)-O(1) bond length is 2.11 Å. The Fe(1)-O(2) bond length is 1.97 Å. The Fe(1)-O(3) bond length is 2.16 Å. The Fe(1)-O(5) bond length is 2.10 Å. The Fe(1)-O(7) bond length is 2.21 Å. In the second Fe site, Fe(2) is bonded to one O(1), one O(3), one O(5), one O(6), one O(7), and one O(8) atom to form FeO6 octahedra that share  a cornercorner with one P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra,  an edgeedge with one Fe(3)O6 octahedra,  an edgeedge with one P(2)O4 tetrahedra, and edges with two equivalent Fe(1)O5 trigonal bipyramids. The Fe(2)-O(1) bond length is 2.07 Å. The Fe(2)-O(3) bond length is 2.02 Å. The Fe(2)-O(5) bond length is 2.13 Å. The Fe(2)-O(6) bond length is 2.03 Å. The Fe(2)-O(7) bond length is 2.06 Å. The Fe(2)-O(8) bond length is 2.02 Å. In the third Fe site, Fe(3) is bonded to two equivalent O(4), two equivalent O(6), and two equivalent O(8) atoms to form FeO6 octahedra that share corners with two equivalent P(2)O4 tetrahedra, corners with four equivalent P(1)O4 tetrahedra, and edges with two equivalent Fe(2)O6 octahedra. Both Fe(3)-O(4) bond lengths are 2.00 Å. Both Fe(3)-O(6) bond lengths are 2.23 Å. Both Fe(3)-O(8) bond lengths are 2.40 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(3), one O(4), one O(7), and one O(8) atom to form PO4 tetrahedra that share corners with two equivalent Fe(3)O6 octahedra, corners with three equivalent Fe(2)O6 octahedra, and corners with two equivalent Fe(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 39-53°. The P(1)-O(3) bond length is 1.58 Å. The P(1)-O(4) bond length is 1.52 Å. The P(1)-O(7) bond length is 1.56 Å. The P(1)-O(8) bond length is 1.57 Å. In the second P site, P(2) is bonded to one O(1), one O(2), one O(5), and one O(6) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(2)O6 octahedra,  a cornercorner with one Fe(3)O6 octahedra, corners with three equivalent Fe(1)O5 trigonal bipyramids, and  an edgeedge with one Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-55°. The P(2)-O(1) bond length is 1.58 Å. The P(2)-O(2) bond length is 1.52 Å. The P(2)-O(5) bond length is 1.56 Å. The P(2)-O(6) bond length is 1.55 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Fe(1), one Fe(2), and one P(2) atom. In the second O site, O(2) is bonded in a linear geometry to one Fe(1) and one P(2) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(2), and one P(1) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Fe(3) and one P(1) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Fe(1), one Fe(2), and one P(2) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Fe(2), one Fe(3), and one P(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(2), and one P(1) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Fe(2), one Fe(3), and one P(1) atom.