Na4NiP2O7F2 crystallizes in the orthorhombic Imma 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(2), two equivalent O(3), and two equivalent F(2) atoms. In the second Na site, Na(2) is bonded in a 5-coordinate geometry to one O(2), two equivalent O(3), one F(1), and one F(2) atom. Ni(1) is bonded to four equivalent O(3) and two equivalent F(1) atoms to form NiO4F2 octahedra that share corners with two equivalent Ni(1)O4F2 octahedra and corners with four equivalent P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 54°. P(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form PO4 tetrahedra that share corners with two equivalent Ni(1)O4F2 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 58°. There are three inequivalent O sites. In the first O site, O(3) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Ni(1), and one P(1) atom. In the second O site, O(1) is bonded in a bent 120 degrees geometry to two equivalent P(1) atoms. In the third O site, O(2) is bonded in a rectangular see-saw-like geometry to one Na(2), two equivalent Na(1), and one P(1) atom. There are two inequivalent F sites. In the first F site, F(1) is bonded to two equivalent Na(2) and two equivalent Ni(1) atoms to form FNa2Ni2 tetrahedra that share corners with two equivalent F(2)Na6 octahedra and corners with two equivalent F(1)Na2Ni2 tetrahedra. The corner-sharing octahedral tilt angles are 51°. In the second F site, F(2) is bonded to two equivalent Na(2) and four equivalent Na(1) atoms to form FNa6 octahedra that share corners with four equivalent F(2)Na6 octahedra and corners with two equivalent F(1)Na2Ni2 tetrahedra. The corner-sharing octahedral tilt angles are 11°.
Na4NiP2O7F2 crystallizes in the orthorhombic Imma 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(2), two equivalent O(3), and two equivalent F(2) atoms. Both Na(1)-O(2) bond lengths are 2.44 Å. Both Na(1)-O(3) bond lengths are 2.48 Å. Both Na(1)-F(2) bond lengths are 2.67 Å. In the second Na site, Na(2) is bonded in a 5-coordinate geometry to one O(2), two equivalent O(3), one F(1), and one F(2) atom. The Na(2)-O(2) bond length is 2.33 Å. Both Na(2)-O(3) bond lengths are 2.51 Å. The Na(2)-F(1) bond length is 2.21 Å. The Na(2)-F(2) bond length is 2.14 Å. Ni(1) is bonded to four equivalent O(3) and two equivalent F(1) atoms to form NiO4F2 octahedra that share corners with two equivalent Ni(1)O4F2 octahedra and corners with four equivalent P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 54°. All Ni(1)-O(3) bond lengths are 2.09 Å. Both Ni(1)-F(1) bond lengths are 2.01 Å. P(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form PO4 tetrahedra that share corners with two equivalent Ni(1)O4F2 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 58°. The P(1)-O(1) bond length is 1.66 Å. The P(1)-O(2) bond length is 1.52 Å. Both P(1)-O(3) bond lengths are 1.54 Å. There are three inequivalent O sites. In the first O site, O(3) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Ni(1), and one P(1) atom. In the second O site, O(1) is bonded in a bent 120 degrees geometry to two equivalent P(1) atoms. In the third O site, O(2) is bonded in a rectangular see-saw-like geometry to one Na(2), two equivalent Na(1), and one P(1) atom. There are two inequivalent F sites. In the first F site, F(1) is bonded to two equivalent Na(2) and two equivalent Ni(1) atoms to form FNa2Ni2 tetrahedra that share corners with two equivalent F(2)Na6 octahedra and corners with two equivalent F(1)Na2Ni2 tetrahedra. The corner-sharing octahedral tilt angles are 51°. In the second F site, F(2) is bonded to two equivalent Na(2) and four equivalent Na(1) atoms to form FNa6 octahedra that share corners with four equivalent F(2)Na6 octahedra and corners with two equivalent F(1)Na2Ni2 tetrahedra. The corner-sharing octahedral tilt angles are 11°.