Na2Ni2Fe(PO4)3 is Esseneite-derived structured and 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 8-coordinate geometry to four equivalent O(5) and four equivalent O(6) atoms. In the second Na site, Na(2) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(4), and four equivalent O(2) atoms. Fe(1) is bonded to two equivalent O(1), 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, corners with four equivalent P(2)O4 tetrahedra, and edges with two equivalent Ni(1)O6 octahedra. Ni(1) is bonded to one O(1), one O(2), one O(4), one O(5), and two equivalent O(3) atoms to form NiO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with four equivalent P(2)O4 tetrahedra,  an edgeedge with one Fe(1)O6 octahedra, and  an edgeedge with one Ni(1)O6 octahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to two equivalent O(1) and two equivalent O(5) atoms to form PO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra and corners with four equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 53-60°. In the second P site, P(2) is bonded to one O(2), one O(3), one O(4), and one O(6) atom to form PO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra and corners with four equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 38-59°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Na(2), one Fe(1), one Ni(1), and one P(1) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na(2), one Ni(1), and one P(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to two equivalent Ni(1) and one P(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Na(2), one Fe(1), one Ni(1), and one P(2) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to two equivalent Na(1), one Ni(1), and one P(1) atom. In the sixth O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na(1), one Fe(1), and one P(2) atom.
Na2Ni2Fe(PO4)3 is Esseneite-derived structured and 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 8-coordinate geometry to four equivalent O(5) and four equivalent O(6) atoms. There are two shorter (2.30 Å) and two longer (2.87 Å) Na(1)-O(5) bond lengths. There are two shorter (2.49 Å) and two longer (2.56 Å) Na(1)-O(6) bond lengths. In the second Na site, Na(2) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(4), and four equivalent O(2) atoms. Both Na(2)-O(1) bond lengths are 2.91 Å. Both Na(2)-O(4) bond lengths are 2.85 Å. There are two shorter (2.40 Å) and two longer (2.55 Å) Na(2)-O(2) bond lengths. Fe(1) is bonded to two equivalent O(1), 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, corners with four equivalent P(2)O4 tetrahedra, and edges with two equivalent Ni(1)O6 octahedra. Both Fe(1)-O(1) bond lengths are 2.13 Å. Both Fe(1)-O(4) bond lengths are 2.07 Å. Both Fe(1)-O(6) bond lengths are 2.06 Å. Ni(1) is bonded to one O(1), one O(2), one O(4), one O(5), and two equivalent O(3) atoms to form NiO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with four equivalent P(2)O4 tetrahedra,  an edgeedge with one Fe(1)O6 octahedra, and  an edgeedge with one Ni(1)O6 octahedra. The Ni(1)-O(1) bond length is 2.08 Å. The Ni(1)-O(2) bond length is 2.11 Å. The Ni(1)-O(4) bond length is 2.11 Å. The Ni(1)-O(5) bond length is 1.96 Å. There is one shorter (2.07 Å) and one longer (2.13 Å) Ni(1)-O(3) bond length. There are two inequivalent P sites. In the first P site, P(1) is bonded to two equivalent O(1) and two equivalent O(5) atoms to form PO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra and corners with four equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 53-60°. Both P(1)-O(1) bond lengths are 1.59 Å. Both P(1)-O(5) bond lengths are 1.53 Å. In the second P site, P(2) is bonded to one O(2), one O(3), one O(4), and one O(6) atom to form PO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra and corners with four equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 38-59°. The P(2)-O(2) bond length is 1.54 Å. The P(2)-O(3) bond length is 1.54 Å. The P(2)-O(4) bond length is 1.59 Å. The P(2)-O(6) bond length is 1.57 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Na(2), one Fe(1), one Ni(1), and one P(1) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na(2), one Ni(1), and one P(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to two equivalent Ni(1) and one P(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Na(2), one Fe(1), one Ni(1), and one P(2) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to two equivalent Na(1), one Ni(1), and one P(1) atom. In the sixth O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na(1), one Fe(1), and one P(2) atom.