Na3VCAsO7 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 6-coordinate geometry to one O(2), one O(3), two equivalent O(1), and two equivalent O(6) atoms. In the second Na site, Na(2) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), and two equivalent O(6) atoms. V(1) is bonded to one O(2), one O(3), one O(4), one O(5), and two equivalent O(6) atoms to form VO6 octahedra that share corners with four equivalent As(1)O4 tetrahedra. C(1) is bonded in a trigonal planar geometry to one O(1), one O(2), and one O(3) atom. As(1) is bonded to one O(4), one O(5), and two equivalent O(6) atoms to form AsO4 tetrahedra that share corners with four equivalent V(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-59°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Na(1), two equivalent Na(2), and one C(1) atom. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Na(1), two equivalent Na(2), one V(1), and one C(1) atom. In the third O site, O(3) is bonded to one Na(1), two equivalent Na(2), one V(1), and one C(1) atom to form a mixture of distorted corner and edge-sharing ONa3VC trigonal bipyramids. In the fourth O site, O(4) is bonded to two equivalent Na(2), one V(1), and one As(1) atom to form distorted ONa2VAs tetrahedra that share corners with three equivalent O(3)Na3VC trigonal bipyramids and corners with four equivalent O(5)Na2VAs trigonal pyramids. In the fifth O site, O(5) is bonded to two equivalent Na(2), one V(1), and one As(1) atom to form distorted ONa2VAs trigonal pyramids that share corners with four equivalent O(4)Na2VAs tetrahedra,  a cornercorner with one O(3)Na3VC trigonal bipyramid, and  an edgeedge with one O(3)Na3VC trigonal bipyramid. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Na(1), two equivalent Na(2), one V(1), and one As(1) atom.
Na3VCAsO7 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 6-coordinate geometry to one O(2), one O(3), two equivalent O(1), and two equivalent O(6) atoms. The Na(1)-O(2) bond length is 2.33 Å. The Na(1)-O(3) bond length is 2.60 Å. There is one shorter (2.44 Å) and one longer (2.88 Å) Na(1)-O(1) bond length. Both Na(1)-O(6) bond lengths are 2.47 Å. In the second Na site, Na(2) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), and two equivalent O(6) atoms. The Na(2)-O(1) bond length is 2.37 Å. The Na(2)-O(2) bond length is 2.84 Å. The Na(2)-O(3) bond length is 2.53 Å. The Na(2)-O(4) bond length is 2.47 Å. The Na(2)-O(5) bond length is 2.34 Å. There is one shorter (2.49 Å) and one longer (2.92 Å) Na(2)-O(6) bond length. V(1) is bonded to one O(2), one O(3), one O(4), one O(5), and two equivalent O(6) atoms to form VO6 octahedra that share corners with four equivalent As(1)O4 tetrahedra. The V(1)-O(2) bond length is 2.20 Å. The V(1)-O(3) bond length is 2.28 Å. The V(1)-O(4) bond length is 2.17 Å. The V(1)-O(5) bond length is 2.14 Å. Both V(1)-O(6) bond lengths are 2.17 Å. C(1) is bonded in a trigonal planar geometry to one O(1), one O(2), and one O(3) atom. The C(1)-O(1) bond length is 1.29 Å. The C(1)-O(2) bond length is 1.31 Å. The C(1)-O(3) bond length is 1.31 Å. As(1) is bonded to one O(4), one O(5), and two equivalent O(6) atoms to form AsO4 tetrahedra that share corners with four equivalent V(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-59°. The As(1)-O(4) bond length is 1.73 Å. The As(1)-O(5) bond length is 1.72 Å. Both As(1)-O(6) bond lengths are 1.73 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Na(1), two equivalent Na(2), and one C(1) atom. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Na(1), two equivalent Na(2), one V(1), and one C(1) atom. In the third O site, O(3) is bonded to one Na(1), two equivalent Na(2), one V(1), and one C(1) atom to form a mixture of distorted corner and edge-sharing ONa3VC trigonal bipyramids. In the fourth O site, O(4) is bonded to two equivalent Na(2), one V(1), and one As(1) atom to form distorted ONa2VAs tetrahedra that share corners with three equivalent O(3)Na3VC trigonal bipyramids and corners with four equivalent O(5)Na2VAs trigonal pyramids. In the fifth O site, O(5) is bonded to two equivalent Na(2), one V(1), and one As(1) atom to form distorted ONa2VAs trigonal pyramids that share corners with four equivalent O(4)Na2VAs tetrahedra,  a cornercorner with one O(3)Na3VC trigonal bipyramid, and  an edgeedge with one O(3)Na3VC trigonal bipyramid. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Na(1), two equivalent Na(2), one V(1), and one As(1) atom.