Na2VP2O8 crystallizes in the monoclinic P2_1/c 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(5), one O(6), one O(7), and two equivalent O(3) atoms. In the second Na site, Na(2) is bonded to one O(4), two equivalent O(1), and two equivalent O(8) atoms to form distorted NaO5 trigonal bipyramids that share corners with three equivalent V(1)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and edges with two equivalent Na(2)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 44-60°. V(1) is bonded to one O(3), one O(4), one O(5), one O(6), one O(7), and one O(8) atom to form distorted VO6 octahedra that share corners with two equivalent P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra, and corners with three equivalent Na(2)O5 trigonal bipyramids. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form PO4 tetrahedra that share corners with three equivalent V(1)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra, and  a cornercorner with one Na(2)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 43-50°. In the second P site, P(2) is bonded to one O(1), one O(2), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent V(1)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, and corners with two equivalent Na(2)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 41-48°. There are eight inequivalent O sites. In the first O site, O(4) is bonded in a 3-coordinate geometry to one Na(2), one V(1), and one P(1) atom. In the second O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Na(1), one V(1), and one P(1) atom. In the third O site, O(6) is bonded in a distorted trigonal planar geometry to one Na(1), one V(1), and one P(2) atom. In the fourth O site, O(7) is bonded in a 3-coordinate geometry to one Na(1), one V(1), and one P(2) atom. In the fifth O site, O(8) is bonded in a 3-coordinate geometry to two equivalent Na(2) and one V(1) atom. In the sixth O site, O(1) is bonded to one Na(1), two equivalent Na(2), and one P(2) atom to form distorted corner-sharing ONa3P tetrahedra. In the seventh O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Na(1), one P(1), and one P(2) atom. In the eighth O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Na(1), one V(1), and one P(1) atom.
Na2VP2O8 crystallizes in the monoclinic P2_1/c 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(5), one O(6), one O(7), and two equivalent O(3) atoms. The Na(1)-O(1) bond length is 2.33 Å. The Na(1)-O(2) bond length is 2.89 Å. The Na(1)-O(5) bond length is 3.00 Å. The Na(1)-O(6) bond length is 2.38 Å. The Na(1)-O(7) bond length is 2.47 Å. There is one shorter (2.37 Å) and one longer (2.72 Å) Na(1)-O(3) bond length. In the second Na site, Na(2) is bonded to one O(4), two equivalent O(1), and two equivalent O(8) atoms to form distorted NaO5 trigonal bipyramids that share corners with three equivalent V(1)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and edges with two equivalent Na(2)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 44-60°. The Na(2)-O(4) bond length is 2.66 Å. There is one shorter (2.38 Å) and one longer (2.45 Å) Na(2)-O(1) bond length. There is one shorter (2.40 Å) and one longer (2.44 Å) Na(2)-O(8) bond length. V(1) is bonded to one O(3), one O(4), one O(5), one O(6), one O(7), and one O(8) atom to form distorted VO6 octahedra that share corners with two equivalent P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra, and corners with three equivalent Na(2)O5 trigonal bipyramids. The V(1)-O(3) bond length is 2.08 Å. The V(1)-O(4) bond length is 2.08 Å. The V(1)-O(5) bond length is 2.04 Å. The V(1)-O(6) bond length is 2.16 Å. The V(1)-O(7) bond length is 2.04 Å. The V(1)-O(8) bond length is 1.66 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form PO4 tetrahedra that share corners with three equivalent V(1)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra, and  a cornercorner with one Na(2)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 43-50°. The P(1)-O(2) bond length is 1.61 Å. The P(1)-O(3) bond length is 1.54 Å. The P(1)-O(4) bond length is 1.53 Å. The P(1)-O(5) bond length is 1.53 Å. In the second P site, P(2) is bonded to one O(1), one O(2), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent V(1)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, and corners with two equivalent Na(2)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 41-48°. The P(2)-O(1) bond length is 1.52 Å. The P(2)-O(2) bond length is 1.65 Å. The P(2)-O(6) bond length is 1.53 Å. The P(2)-O(7) bond length is 1.54 Å. There are eight inequivalent O sites. In the first O site, O(4) is bonded in a 3-coordinate geometry to one Na(2), one V(1), and one P(1) atom. In the second O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Na(1), one V(1), and one P(1) atom. In the third O site, O(6) is bonded in a distorted trigonal planar geometry to one Na(1), one V(1), and one P(2) atom. In the fourth O site, O(7) is bonded in a 3-coordinate geometry to one Na(1), one V(1), and one P(2) atom. In the fifth O site, O(8) is bonded in a 3-coordinate geometry to two equivalent Na(2) and one V(1) atom. In the sixth O site, O(1) is bonded to one Na(1), two equivalent Na(2), and one P(2) atom to form distorted corner-sharing ONa3P tetrahedra. In the seventh O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Na(1), one P(1), and one P(2) atom. In the eighth O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Na(1), one V(1), and one P(1) atom.