NbFe(PO4)2 crystallizes in the monoclinic P2_1/m space group. Nb(1) is bonded to one O(1), one O(5), two equivalent O(3), and two equivalent O(4) atoms to form NbO6 pentagonal pyramids that share corners with four equivalent Fe(1)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra, and  an edgeedge with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 47-54°. Fe(1) is bonded to one O(2), one O(6), two equivalent O(3), and two equivalent O(4) atoms to form distorted FeO6 octahedra that share corners with four equivalent Nb(1)O6 pentagonal pyramids,  a cornercorner with one P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and  an edgeedge with one P(1)O4 tetrahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form PO4 tetrahedra that share  a cornercorner with one Fe(1)O6 octahedra, corners with three equivalent Nb(1)O6 pentagonal pyramids, and  an edgeedge with one Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 52°. In the second P site, P(2) is bonded to one O(5), one O(6), and two equivalent O(4) atoms to form PO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra,  a cornercorner with one Nb(1)O6 pentagonal pyramid, and  an edgeedge with one Nb(1)O6 pentagonal pyramid. The corner-sharing octahedral tilt angles range from 38-58°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one Nb(1) and one P(1) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to one Fe(1) and one P(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Nb(1), one Fe(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Nb(1), one Fe(1), and one P(2) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Nb(1) and one P(2) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(2) atom.
NbFe(PO4)2 crystallizes in the monoclinic P2_1/m space group. Nb(1) is bonded to one O(1), one O(5), two equivalent O(3), and two equivalent O(4) atoms to form NbO6 pentagonal pyramids that share corners with four equivalent Fe(1)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra, and  an edgeedge with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 47-54°. The Nb(1)-O(1) bond length is 2.11 Å. The Nb(1)-O(5) bond length is 2.07 Å. Both Nb(1)-O(3) bond lengths are 2.06 Å. Both Nb(1)-O(4) bond lengths are 2.16 Å. Fe(1) is bonded to one O(2), one O(6), two equivalent O(3), and two equivalent O(4) atoms to form distorted FeO6 octahedra that share corners with four equivalent Nb(1)O6 pentagonal pyramids,  a cornercorner with one P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and  an edgeedge with one P(1)O4 tetrahedra. The Fe(1)-O(2) bond length is 2.01 Å. The Fe(1)-O(6) bond length is 1.98 Å. Both Fe(1)-O(3) bond lengths are 2.43 Å. Both Fe(1)-O(4) bond lengths are 2.22 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form PO4 tetrahedra that share  a cornercorner with one Fe(1)O6 octahedra, corners with three equivalent Nb(1)O6 pentagonal pyramids, and  an edgeedge with one Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 52°. The P(1)-O(1) bond length is 1.54 Å. The P(1)-O(2) bond length is 1.52 Å. Both P(1)-O(3) bond lengths are 1.59 Å. In the second P site, P(2) is bonded to one O(5), one O(6), and two equivalent O(4) atoms to form PO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra,  a cornercorner with one Nb(1)O6 pentagonal pyramid, and  an edgeedge with one Nb(1)O6 pentagonal pyramid. The corner-sharing octahedral tilt angles range from 38-58°. The P(2)-O(5) bond length is 1.54 Å. The P(2)-O(6) bond length is 1.51 Å. Both P(2)-O(4) bond lengths are 1.59 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one Nb(1) and one P(1) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to one Fe(1) and one P(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Nb(1), one Fe(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Nb(1), one Fe(1), and one P(2) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Nb(1) and one P(2) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(2) atom.