Na3VP2O9 crystallizes in the monoclinic P2_1/m 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(3), one O(5), one O(6), and two equivalent O(7) atoms. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to one O(3), one O(6), two equivalent O(2), and two equivalent O(7) atoms. V(1) is bonded to one O(1), one O(3), one O(4), one O(5), and two equivalent O(2) atoms to form VO6 octahedra that share  a cornercorner with one P(2)O4 tetrahedra and corners with four equivalent P(1)O4 tetrahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(4), and two equivalent O(2) atoms to form PO4 tetrahedra that share corners with four equivalent V(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 34-53°. In the second P site, P(2) is bonded to one O(5), one O(6), and two equivalent O(7) atoms to form PO4 tetrahedra that share  a cornercorner with one V(1)O6 octahedra. The corner-sharing octahedral tilt angles are 51°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Na(1), one V(1), and one P(1) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one V(1), and one P(1) atom. In the third O site, O(3) is bonded in a single-bond geometry to one Na(2), two equivalent Na(1), and one V(1) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one V(1) and one P(1) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to two equivalent Na(1), one V(1), and one P(2) atom. In the sixth O site, O(6) is bonded in a distorted trigonal pyramidal geometry to one Na(2), two equivalent Na(1), and one P(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Na(2), two equivalent Na(1), and one P(2) atom.
Na3VP2O9 crystallizes in the monoclinic P2_1/m 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(3), one O(5), one O(6), and two equivalent O(7) atoms. The Na(1)-O(1) bond length is 2.50 Å. The Na(1)-O(2) bond length is 2.83 Å. The Na(1)-O(3) bond length is 2.86 Å. The Na(1)-O(5) bond length is 2.56 Å. The Na(1)-O(6) bond length is 2.29 Å. There is one shorter (2.28 Å) and one longer (2.81 Å) Na(1)-O(7) bond length. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to one O(3), one O(6), two equivalent O(2), and two equivalent O(7) atoms. The Na(2)-O(3) bond length is 2.98 Å. The Na(2)-O(6) bond length is 2.23 Å. Both Na(2)-O(2) bond lengths are 2.67 Å. Both Na(2)-O(7) bond lengths are 2.26 Å. V(1) is bonded to one O(1), one O(3), one O(4), one O(5), and two equivalent O(2) atoms to form VO6 octahedra that share  a cornercorner with one P(2)O4 tetrahedra and corners with four equivalent P(1)O4 tetrahedra. The V(1)-O(1) bond length is 2.02 Å. The V(1)-O(3) bond length is 1.66 Å. The V(1)-O(4) bond length is 1.87 Å. The V(1)-O(5) bond length is 2.01 Å. Both V(1)-O(2) bond lengths are 2.01 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(4), and two equivalent O(2) atoms to form PO4 tetrahedra that share corners with four equivalent V(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 34-53°. The P(1)-O(1) bond length is 1.55 Å. The P(1)-O(4) bond length is 1.55 Å. Both P(1)-O(2) bond lengths are 1.55 Å. In the second P site, P(2) is bonded to one O(5), one O(6), and two equivalent O(7) atoms to form PO4 tetrahedra that share  a cornercorner with one V(1)O6 octahedra. The corner-sharing octahedral tilt angles are 51°. The P(2)-O(5) bond length is 1.63 Å. The P(2)-O(6) bond length is 1.55 Å. Both P(2)-O(7) bond lengths are 1.54 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Na(1), one V(1), and one P(1) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one V(1), and one P(1) atom. In the third O site, O(3) is bonded in a single-bond geometry to one Na(2), two equivalent Na(1), and one V(1) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one V(1) and one P(1) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to two equivalent Na(1), one V(1), and one P(2) atom. In the sixth O site, O(6) is bonded in a distorted trigonal pyramidal geometry to one Na(2), two equivalent Na(1), and one P(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Na(2), two equivalent Na(1), and one P(2) atom.