Fe3(PO8)2 crystallizes in the triclinic P-1 space group. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(6) atoms to form distorted FeO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra. In the second Fe site, Fe(2) is bonded to one O(1), one O(2), one O(5), one O(8), and two equivalent O(7) atoms to form FeO6 octahedra that share corners with four equivalent P(1)O4 tetrahedra and  an edgeedge with one Fe(2)O6 octahedra. P(1) is bonded to one O(1), one O(2), one O(3), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(1)O6 octahedra and corners with four equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 24-57°. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Fe(2) and one P(1) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to one Fe(2) and one P(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(1) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one Fe(1) and one O(6) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Fe(2) and one O(6) atom. In the sixth O site, O(6) is bonded in a trigonal non-coplanar geometry to one Fe(1), one O(4), and one O(5) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Fe(2) and one P(1) atom. In the eighth O site, O(8) is bonded in a single-bond geometry to one Fe(2) atom.
Fe3(PO8)2 crystallizes in the triclinic P-1 space group. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(6) atoms to form distorted FeO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra. Both Fe(1)-O(3) bond lengths are 1.84 Å. Both Fe(1)-O(4) bond lengths are 2.11 Å. Both Fe(1)-O(6) bond lengths are 2.53 Å. In the second Fe site, Fe(2) is bonded to one O(1), one O(2), one O(5), one O(8), and two equivalent O(7) atoms to form FeO6 octahedra that share corners with four equivalent P(1)O4 tetrahedra and  an edgeedge with one Fe(2)O6 octahedra. The Fe(2)-O(1) bond length is 1.98 Å. The Fe(2)-O(2) bond length is 2.00 Å. The Fe(2)-O(5) bond length is 2.21 Å. The Fe(2)-O(8) bond length is 1.90 Å. There is one shorter (2.07 Å) and one longer (2.18 Å) Fe(2)-O(7) bond length. P(1) is bonded to one O(1), one O(2), one O(3), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(1)O6 octahedra and corners with four equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 24-57°. The P(1)-O(1) bond length is 1.54 Å. The P(1)-O(2) bond length is 1.54 Å. The P(1)-O(3) bond length is 1.56 Å. The P(1)-O(7) bond length is 1.58 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Fe(2) and one P(1) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to one Fe(2) and one P(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(1) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one Fe(1) and one O(6) atom. The O(4)-O(6) bond length is 1.40 Å. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Fe(2) and one O(6) atom. The O(5)-O(6) bond length is 1.34 Å. In the sixth O site, O(6) is bonded in a trigonal non-coplanar geometry to one Fe(1), one O(4), and one O(5) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Fe(2) and one P(1) atom. In the eighth O site, O(8) is bonded in a single-bond geometry to one Fe(2) atom.