Fe3(PO4)2 crystallizes in the monoclinic P2_1/c 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(4), one O(6), and one O(8) atom to form distorted FeO5 square pyramids that share corners with two equivalent P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra, and  a cornercorner with one Fe(2)O5 trigonal bipyramid. In the second Fe site, Fe(2) is bonded to one O(1), two equivalent O(3), and two equivalent O(7) atoms to form distorted FeO5 trigonal bipyramids that share  a cornercorner with one Fe(1)O5 square pyramid, corners with two equivalent P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra, and edges with two equivalent Fe(2)O5 trigonal bipyramids. In the third Fe site, Fe(3) is bonded in a 5-coordinate geometry to one O(4), one O(6), one O(8), and two equivalent O(5) atoms. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(3), one O(4), and one O(6) atom to form PO4 tetrahedra that share corners with three equivalent Fe(1)O5 square pyramids and corners with three equivalent Fe(2)O5 trigonal bipyramids. In the second P site, P(2) is bonded to one O(2), one O(5), one O(7), and one O(8) atom to form PO4 tetrahedra that share corners with two equivalent Fe(1)O5 square pyramids and corners with two equivalent Fe(2)O5 trigonal bipyramids. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(2), and one P(1) atom. In the second O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Fe(1) and one P(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to two equivalent Fe(2) and one P(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(3), and one P(1) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to two equivalent Fe(3) and one P(2) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Fe(1), one Fe(3), and one P(1) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Fe(2) and one P(2) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(3), and one P(2) atom.
Fe3(PO4)2 crystallizes in the monoclinic P2_1/c 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(4), one O(6), and one O(8) atom to form distorted FeO5 square pyramids that share corners with two equivalent P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra, and  a cornercorner with one Fe(2)O5 trigonal bipyramid. The Fe(1)-O(1) bond length is 2.36 Å. The Fe(1)-O(2) bond length is 2.07 Å. The Fe(1)-O(4) bond length is 1.98 Å. The Fe(1)-O(6) bond length is 1.98 Å. The Fe(1)-O(8) bond length is 2.41 Å. In the second Fe site, Fe(2) is bonded to one O(1), two equivalent O(3), and two equivalent O(7) atoms to form distorted FeO5 trigonal bipyramids that share  a cornercorner with one Fe(1)O5 square pyramid, corners with two equivalent P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra, and edges with two equivalent Fe(2)O5 trigonal bipyramids. The Fe(2)-O(1) bond length is 2.08 Å. There is one shorter (2.10 Å) and one longer (2.27 Å) Fe(2)-O(3) bond length. There is one shorter (2.03 Å) and one longer (2.19 Å) Fe(2)-O(7) bond length. In the third Fe site, Fe(3) is bonded in a 5-coordinate geometry to one O(4), one O(6), one O(8), and two equivalent O(5) atoms. The Fe(3)-O(4) bond length is 2.18 Å. The Fe(3)-O(6) bond length is 2.34 Å. The Fe(3)-O(8) bond length is 2.02 Å. There is one shorter (2.05 Å) and one longer (2.18 Å) Fe(3)-O(5) bond length. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(3), one O(4), and one O(6) atom to form PO4 tetrahedra that share corners with three equivalent Fe(1)O5 square pyramids and corners with three equivalent Fe(2)O5 trigonal bipyramids. The P(1)-O(1) bond length is 1.56 Å. The P(1)-O(3) bond length is 1.54 Å. The P(1)-O(4) bond length is 1.56 Å. The P(1)-O(6) bond length is 1.56 Å. In the second P site, P(2) is bonded to one O(2), one O(5), one O(7), and one O(8) atom to form PO4 tetrahedra that share corners with two equivalent Fe(1)O5 square pyramids and corners with two equivalent Fe(2)O5 trigonal bipyramids. The P(2)-O(2) bond length is 1.53 Å. The P(2)-O(5) bond length is 1.57 Å. The P(2)-O(7) bond length is 1.56 Å. The P(2)-O(8) bond length is 1.56 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(2), and one P(1) atom. In the second O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Fe(1) and one P(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to two equivalent Fe(2) and one P(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(3), and one P(1) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to two equivalent Fe(3) and one P(2) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Fe(1), one Fe(3), and one P(1) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Fe(2) and one P(2) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(3), and one P(2) atom.