Na3Fe3(PO4)4 crystallizes in the monoclinic C2/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(4), one O(5), one O(7), and two equivalent O(8) atoms. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(5), and two equivalent O(8) atoms. There are two 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), one O(6), and one O(7) atom to form FeO6 octahedra that share corners with two equivalent Fe(2)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and  an edgeedge with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 58-59°. In the second Fe site, Fe(2) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(6) atoms to form FeO6 octahedra that share corners with four equivalent Fe(1)O6 octahedra, corners with two equivalent P(2)O4 tetrahedra, and corners with four equivalent P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 58-59°. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(3), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, and  an edgeedge with one Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 41-52°. In the second P site, P(2) is bonded to one O(2), one O(4), one O(5), and one O(8) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(2)O6 octahedra and corners with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-53°. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Na(1), one Fe(1), and one P(1) atom. In the second O site, O(2) is bonded to one Na(1), one Na(2), one Fe(1), and one P(2) atom to form distorted corner-sharing ONa2FeP tetrahedra. 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 3-coordinate geometry to one Na(1), one Fe(2), and one P(2) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Na(1), one Na(2), one Fe(1), and one P(2) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(2), and one P(1) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Na(1), one Fe(1), and one P(1) atom. In the eighth O site, O(8) is bonded in a 4-coordinate geometry to one Na(2), two equivalent Na(1), and one P(2) atom.
Na3Fe3(PO4)4 crystallizes in the monoclinic C2/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(4), one O(5), one O(7), and two equivalent O(8) atoms. The Na(1)-O(1) bond length is 2.96 Å. The Na(1)-O(2) bond length is 2.47 Å. The Na(1)-O(4) bond length is 2.61 Å. The Na(1)-O(5) bond length is 3.00 Å. The Na(1)-O(7) bond length is 2.65 Å. There is one shorter (2.34 Å) and one longer (2.53 Å) Na(1)-O(8) bond length. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(5), and two equivalent O(8) atoms. Both Na(2)-O(2) bond lengths are 2.51 Å. Both Na(2)-O(5) bond lengths are 2.50 Å. Both Na(2)-O(8) bond lengths are 2.53 Å. There are two 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), one O(6), and one O(7) atom to form FeO6 octahedra that share corners with two equivalent Fe(2)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and  an edgeedge with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 58-59°. The Fe(1)-O(1) bond length is 2.06 Å. The Fe(1)-O(2) bond length is 1.96 Å. The Fe(1)-O(3) bond length is 2.09 Å. The Fe(1)-O(5) bond length is 1.97 Å. The Fe(1)-O(6) bond length is 2.16 Å. The Fe(1)-O(7) bond length is 2.03 Å. In the second Fe site, Fe(2) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(6) atoms to form FeO6 octahedra that share corners with four equivalent Fe(1)O6 octahedra, corners with two equivalent P(2)O4 tetrahedra, and corners with four equivalent P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 58-59°. Both Fe(2)-O(3) bond lengths are 2.03 Å. Both Fe(2)-O(4) bond lengths are 1.97 Å. Both Fe(2)-O(6) bond lengths are 2.08 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(3), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, and  an edgeedge with one Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 41-52°. The P(1)-O(1) bond length is 1.53 Å. The P(1)-O(3) bond length is 1.59 Å. The P(1)-O(6) bond length is 1.58 Å. The P(1)-O(7) bond length is 1.53 Å. In the second P site, P(2) is bonded to one O(2), one O(4), one O(5), and one O(8) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(2)O6 octahedra and corners with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-53°. The P(2)-O(2) bond length is 1.58 Å. The P(2)-O(4) bond length is 1.56 Å. The P(2)-O(5) bond length is 1.56 Å. The P(2)-O(8) bond length is 1.52 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Na(1), one Fe(1), and one P(1) atom. In the second O site, O(2) is bonded to one Na(1), one Na(2), one Fe(1), and one P(2) atom to form distorted corner-sharing ONa2FeP tetrahedra. 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 3-coordinate geometry to one Na(1), one Fe(2), and one P(2) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Na(1), one Na(2), one Fe(1), and one P(2) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(2), and one P(1) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Na(1), one Fe(1), and one P(1) atom. In the eighth O site, O(8) is bonded in a 4-coordinate geometry to one Na(2), two equivalent Na(1), and one P(2) atom.