Na3Fe(PO4)2 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 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to one O(1), one O(3), two equivalent O(2), and two equivalent O(4) atoms. Fe(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form FeO6 octahedra that share corners with six equivalent P(1)O4 tetrahedra. P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 28-51°. There are four inequivalent O sites. In the first O site, O(3) is bonded in a 3-coordinate geometry to one Na(2), one Fe(1), and one P(1) atom. In the second O site, O(4) is bonded in a 4-coordinate geometry to one Na(1), two equivalent Na(2), and one P(1) atom. In the third O site, O(1) is bonded in a 3-coordinate geometry to one Na(1), one Na(2), one Fe(1), and one P(1) atom. In the fourth O site, O(2) is bonded in a 5-coordinate geometry to one Na(1), two equivalent Na(2), one Fe(1), and one P(1) atom.
Na3Fe(PO4)2 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 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms. Both Na(1)-O(1) bond lengths are 2.87 Å. Both Na(1)-O(2) bond lengths are 2.43 Å. Both Na(1)-O(4) bond lengths are 2.35 Å. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to one O(1), one O(3), two equivalent O(2), and two equivalent O(4) atoms. The Na(2)-O(1) bond length is 2.35 Å. The Na(2)-O(3) bond length is 2.54 Å. There is one shorter (2.56 Å) and one longer (2.73 Å) Na(2)-O(2) bond length. There is one shorter (2.34 Å) and one longer (2.54 Å) Na(2)-O(4) bond length. Fe(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form FeO6 octahedra that share corners with six equivalent P(1)O4 tetrahedra. Both Fe(1)-O(1) bond lengths are 2.01 Å. Both Fe(1)-O(2) bond lengths are 2.11 Å. Both Fe(1)-O(3) bond lengths are 2.02 Å. P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 28-51°. The P(1)-O(1) bond length is 1.57 Å. The P(1)-O(2) bond length is 1.57 Å. The P(1)-O(3) bond length is 1.55 Å. The P(1)-O(4) bond length is 1.53 Å. There are four inequivalent O sites. In the first O site, O(3) is bonded in a 3-coordinate geometry to one Na(2), one Fe(1), and one P(1) atom. In the second O site, O(4) is bonded in a 4-coordinate geometry to one Na(1), two equivalent Na(2), and one P(1) atom. In the third O site, O(1) is bonded in a 3-coordinate geometry to one Na(1), one Na(2), one Fe(1), and one P(1) atom. In the fourth O site, O(2) is bonded in a 5-coordinate geometry to one Na(1), two equivalent Na(2), one Fe(1), and one P(1) atom.