Fe3(PO4)4 crystallizes in the monoclinic P2_1 space group. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(11), one O(13), one O(7), and one O(9) atom to form distorted FeO4 tetrahedra that share  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(4)O4 tetrahedra, and corners with two equivalent P(3)O4 tetrahedra. In the second Fe site, Fe(2) is bonded to one O(1), one O(12), one O(4), one O(5), and one O(6) atom to form FeO5 trigonal bipyramids that share  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(3)O4 tetrahedra,  a cornercorner with one P(4)O4 tetrahedra, and corners with two equivalent P(2)O4 tetrahedra. In the third Fe site, Fe(3) is bonded to one O(14), one O(15), one O(16), one O(3), and one O(8) atom to form FeO5 trigonal bipyramids that share  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(3)O4 tetrahedra,  a cornercorner with one P(4)O4 tetrahedra, and corners with two equivalent P(2)O4 tetrahedra. There are four inequivalent P sites. In the first P site, P(1) is bonded to one O(10), one O(6), one O(7), and one O(8) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(1)O4 tetrahedra,  a cornercorner with one Fe(2)O5 trigonal bipyramid, and  a cornercorner with one Fe(3)O5 trigonal bipyramid. In the second P site, P(2) is bonded to one O(1), one O(12), one O(14), and one O(15) atom to form PO4 tetrahedra that share corners with two equivalent Fe(2)O5 trigonal bipyramids and corners with two equivalent Fe(3)O5 trigonal bipyramids. In the third P site, P(3) is bonded to one O(13), one O(16), one O(4), and one O(9) atom to form PO4 tetrahedra that share corners with two equivalent Fe(1)O4 tetrahedra,  a cornercorner with one Fe(2)O5 trigonal bipyramid, and  a cornercorner with one Fe(3)O5 trigonal bipyramid. In the fourth P site, P(4) is bonded to one O(11), one O(2), one O(3), and one O(5) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(1)O4 tetrahedra,  a cornercorner with one Fe(2)O5 trigonal bipyramid, and  a cornercorner with one Fe(3)O5 trigonal bipyramid. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Fe(2) and one P(2) atom. In the second O site, O(2) is bonded in a single-bond geometry to one P(4) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Fe(3) and one P(4) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Fe(2) and one P(3) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Fe(2) and one P(4) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Fe(2) and one P(1) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(1) atom. In the eighth O site, O(8) is bonded in a distorted bent 150 degrees geometry to one Fe(3) and one P(1) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(3) atom. In the tenth O site, O(10) is bonded in a single-bond geometry to one P(1) atom. In the eleventh O site, O(11) is bonded in a bent 120 degrees geometry to one Fe(1) and one P(4) atom. In the twelfth O site, O(12) is bonded in a distorted bent 150 degrees geometry to one Fe(2) and one P(2) atom. In the thirteenth O site, O(13) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(3) atom. In the fourteenth O site, O(14) is bonded in a bent 150 degrees geometry to one Fe(3) and one P(2) atom. In the fifteenth O site, O(15) is bonded in a distorted bent 150 degrees geometry to one Fe(3) and one P(2) atom. In the sixteenth O site, O(16) is bonded in a bent 120 degrees geometry to one Fe(3) and one P(3) atom.
Fe3(PO4)4 crystallizes in the monoclinic P2_1 space group. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(11), one O(13), one O(7), and one O(9) atom to form distorted FeO4 tetrahedra that share  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(4)O4 tetrahedra, and corners with two equivalent P(3)O4 tetrahedra. The Fe(1)-O(11) bond length is 1.94 Å. The Fe(1)-O(13) bond length is 1.93 Å. The Fe(1)-O(7) bond length is 1.88 Å. The Fe(1)-O(9) bond length is 1.92 Å. In the second Fe site, Fe(2) is bonded to one O(1), one O(12), one O(4), one O(5), and one O(6) atom to form FeO5 trigonal bipyramids that share  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(3)O4 tetrahedra,  a cornercorner with one P(4)O4 tetrahedra, and corners with two equivalent P(2)O4 tetrahedra. The Fe(2)-O(1) bond length is 1.88 Å. The Fe(2)-O(12) bond length is 1.89 Å. The Fe(2)-O(4) bond length is 1.99 Å. The Fe(2)-O(5) bond length is 1.90 Å. The Fe(2)-O(6) bond length is 2.06 Å. In the third Fe site, Fe(3) is bonded to one O(14), one O(15), one O(16), one O(3), and one O(8) atom to form FeO5 trigonal bipyramids that share  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(3)O4 tetrahedra,  a cornercorner with one P(4)O4 tetrahedra, and corners with two equivalent P(2)O4 tetrahedra. The Fe(3)-O(14) bond length is 1.94 Å. The Fe(3)-O(15) bond length is 2.09 Å. The Fe(3)-O(16) bond length is 1.97 Å. The Fe(3)-O(3) bond length is 2.04 Å. The Fe(3)-O(8) bond length is 1.93 Å. There are four inequivalent P sites. In the first P site, P(1) is bonded to one O(10), one O(6), one O(7), and one O(8) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(1)O4 tetrahedra,  a cornercorner with one Fe(2)O5 trigonal bipyramid, and  a cornercorner with one Fe(3)O5 trigonal bipyramid. The P(1)-O(10) bond length is 1.55 Å. The P(1)-O(6) bond length is 1.55 Å. The P(1)-O(7) bond length is 1.54 Å. The P(1)-O(8) bond length is 1.54 Å. In the second P site, P(2) is bonded to one O(1), one O(12), one O(14), and one O(15) atom to form PO4 tetrahedra that share corners with two equivalent Fe(2)O5 trigonal bipyramids and corners with two equivalent Fe(3)O5 trigonal bipyramids. The P(2)-O(1) bond length is 1.55 Å. The P(2)-O(12) bond length is 1.55 Å. The P(2)-O(14) bond length is 1.54 Å. The P(2)-O(15) bond length is 1.56 Å. In the third P site, P(3) is bonded to one O(13), one O(16), one O(4), and one O(9) atom to form PO4 tetrahedra that share corners with two equivalent Fe(1)O4 tetrahedra,  a cornercorner with one Fe(2)O5 trigonal bipyramid, and  a cornercorner with one Fe(3)O5 trigonal bipyramid. The P(3)-O(13) bond length is 1.55 Å. The P(3)-O(16) bond length is 1.55 Å. The P(3)-O(4) bond length is 1.56 Å. The P(3)-O(9) bond length is 1.55 Å. In the fourth P site, P(4) is bonded to one O(11), one O(2), one O(3), and one O(5) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(1)O4 tetrahedra,  a cornercorner with one Fe(2)O5 trigonal bipyramid, and  a cornercorner with one Fe(3)O5 trigonal bipyramid. The P(4)-O(11) bond length is 1.54 Å. The P(4)-O(2) bond length is 1.56 Å. The P(4)-O(3) bond length is 1.56 Å. The P(4)-O(5) bond length is 1.54 Å. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Fe(2) and one P(2) atom. In the second O site, O(2) is bonded in a single-bond geometry to one P(4) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Fe(3) and one P(4) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Fe(2) and one P(3) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Fe(2) and one P(4) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Fe(2) and one P(1) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(1) atom. In the eighth O site, O(8) is bonded in a distorted bent 150 degrees geometry to one Fe(3) and one P(1) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(3) atom. In the tenth O site, O(10) is bonded in a single-bond geometry to one P(1) atom. In the eleventh O site, O(11) is bonded in a bent 120 degrees geometry to one Fe(1) and one P(4) atom. In the twelfth O site, O(12) is bonded in a distorted bent 150 degrees geometry to one Fe(2) and one P(2) atom. In the thirteenth O site, O(13) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(3) atom. In the fourteenth O site, O(14) is bonded in a bent 150 degrees geometry to one Fe(3) and one P(2) atom. In the fifteenth O site, O(15) is bonded in a distorted bent 150 degrees geometry to one Fe(3) and one P(2) atom. In the sixteenth O site, O(16) is bonded in a bent 120 degrees geometry to one Fe(3) and one P(3) atom.