Na3VP2O9 crystallizes in the monoclinic C2/m space group. There are three 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(3), and two equivalent O(5) atoms. In the second Na site, Na(2) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(7), and two equivalent O(4) atoms. In the third Na site, Na(3) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(6) atoms to form distorted NaO6 octahedra that share corners with two equivalent V(1)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, edges with two equivalent Na(3)O6 octahedra, and edges with two equivalent P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 67°. V(1) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(7) atoms to form VO6 octahedra that share corners with two equivalent Na(3)O6 octahedra, corners with two equivalent V(1)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, and corners with two equivalent P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 38-67°. 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 corners with two equivalent Na(3)O6 octahedra and corners with two equivalent V(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 43-63°. 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 two equivalent V(1)O6 octahedra and edges with two equivalent Na(3)O6 octahedra. The corner-sharing octahedral tilt angles are 43°. There are seven inequivalent O sites. In the first O site, O(4) is bonded in a 4-coordinate geometry to one Na(2), one Na(3), one V(1), and one P(2) atom. In the second O site, O(5) is bonded in a 3-coordinate geometry to two equivalent Na(1) and one P(2) atom. In the third O site, O(6) is bonded in a distorted single-bond geometry to two equivalent Na(3) and one P(2) atom. In the fourth O site, O(7) is bonded in a distorted bent 150 degrees geometry to one Na(2) and two equivalent V(1) atoms. In the fifth O site, O(1) is bonded in a 4-coordinate geometry to one Na(2), two equivalent Na(1), and one P(1) atom. In the sixth O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Na(2), two equivalent Na(3), and one P(1) atom. In the seventh O site, O(3) is bonded in a 3-coordinate geometry to one Na(1), one V(1), and one P(1) atom.
Na3VP2O9 crystallizes in the monoclinic C2/m space group. There are three 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(3), and two equivalent O(5) atoms. Both Na(1)-O(1) bond lengths are 2.48 Å. Both Na(1)-O(3) bond lengths are 2.59 Å. Both Na(1)-O(5) bond lengths are 2.31 Å. In the second Na site, Na(2) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(7), and two equivalent O(4) atoms. The Na(2)-O(1) bond length is 2.23 Å. The Na(2)-O(2) bond length is 2.29 Å. The Na(2)-O(7) bond length is 2.78 Å. Both Na(2)-O(4) bond lengths are 2.56 Å. In the third Na site, Na(3) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(6) atoms to form distorted NaO6 octahedra that share corners with two equivalent V(1)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, edges with two equivalent Na(3)O6 octahedra, and edges with two equivalent P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 67°. Both Na(3)-O(2) bond lengths are 2.33 Å. Both Na(3)-O(4) bond lengths are 2.53 Å. Both Na(3)-O(6) bond lengths are 2.52 Å. V(1) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(7) atoms to form VO6 octahedra that share corners with two equivalent Na(3)O6 octahedra, corners with two equivalent V(1)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, and corners with two equivalent P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 38-67°. Both V(1)-O(3) bond lengths are 1.93 Å. Both V(1)-O(4) bond lengths are 1.91 Å. Both V(1)-O(7) bond lengths are 1.85 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 corners with two equivalent Na(3)O6 octahedra and corners with two equivalent V(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 43-63°. The P(1)-O(1) bond length is 1.52 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 two equivalent V(1)O6 octahedra and edges with two equivalent Na(3)O6 octahedra. The corner-sharing octahedral tilt angles are 43°. The P(2)-O(5) bond length is 1.51 Å. The P(2)-O(6) bond length is 1.50 Å. Both P(2)-O(4) bond lengths are 1.62 Å. There are seven inequivalent O sites. In the first O site, O(4) is bonded in a 4-coordinate geometry to one Na(2), one Na(3), one V(1), and one P(2) atom. In the second O site, O(5) is bonded in a 3-coordinate geometry to two equivalent Na(1) and one P(2) atom. In the third O site, O(6) is bonded in a distorted single-bond geometry to two equivalent Na(3) and one P(2) atom. In the fourth O site, O(7) is bonded in a distorted bent 150 degrees geometry to one Na(2) and two equivalent V(1) atoms. In the fifth O site, O(1) is bonded in a 4-coordinate geometry to one Na(2), two equivalent Na(1), and one P(1) atom. In the sixth O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Na(2), two equivalent Na(3), and one P(1) atom. In the seventh O site, O(3) is bonded in a 3-coordinate geometry to one Na(1), one V(1), and one P(1) atom.