Na3CoCAsO7 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 to one O(1), one O(2), one O(3), one O(4), one O(5), and two equivalent O(6) atoms to form distorted NaO7 pentagonal bipyramids that share  a cornercorner with one Co(1)O6 octahedra, corners with two equivalent Na(2)O7 pentagonal bipyramids, corners with two equivalent As(1)O4 tetrahedra,  an edgeedge with one Co(1)O6 octahedra,  an edgeedge with one Na(2)O7 pentagonal bipyramid,  an edgeedge with one As(1)O4 tetrahedra,  a faceface with one Co(1)O6 octahedra, and  a faceface with one Na(2)O7 pentagonal bipyramid. The corner-sharing octahedral tilt angles are 58°. Co(1) is bonded to one O(2), one O(3), one O(4), one O(5), and two equivalent O(6) atoms to form distorted CoO6 octahedra that share corners with two equivalent Na(2)O7 pentagonal bipyramids, corners with four equivalent As(1)O4 tetrahedra, edges with two equivalent Na(2)O7 pentagonal bipyramids, and faces with two equivalent Na(2)O7 pentagonal bipyramids. 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 Co(1)O6 octahedra, corners with four equivalent Na(2)O7 pentagonal bipyramids, and edges with two equivalent Na(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 43-59°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 5-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 Co(1), and one C(1) atom. In the third O site, O(3) is bonded in a distorted trigonal bipyramidal geometry to one Na(1), two equivalent Na(2), one Co(1), and one C(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to two equivalent Na(2), one Co(1), and one As(1) atom. In the fifth O site, O(5) is bonded in a rectangular see-saw-like geometry to two equivalent Na(2), one Co(1), and one As(1) atom. In the sixth O site, O(6) is bonded in a 5-coordinate geometry to one Na(1), two equivalent Na(2), one Co(1), and one As(1) atom.
Na3CoCAsO7 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 2.36 Å. The Na(1)-O(3) bond length is 2.57 Å. There is one shorter (2.47 Å) and one longer (2.79 Å) Na(1)-O(1) bond length. Both Na(1)-O(6) bond lengths are 2.48 Å. In the second Na site, Na(2) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and two equivalent O(6) atoms to form distorted NaO7 pentagonal bipyramids that share  a cornercorner with one Co(1)O6 octahedra, corners with two equivalent Na(2)O7 pentagonal bipyramids, corners with two equivalent As(1)O4 tetrahedra,  an edgeedge with one Co(1)O6 octahedra,  an edgeedge with one Na(2)O7 pentagonal bipyramid,  an edgeedge with one As(1)O4 tetrahedra,  a faceface with one Co(1)O6 octahedra, and  a faceface with one Na(2)O7 pentagonal bipyramid. The corner-sharing octahedral tilt angles are 58°. The Na(2)-O(1) bond length is 2.35 Å. The Na(2)-O(2) bond length is 2.70 Å. The Na(2)-O(3) bond length is 2.49 Å. The Na(2)-O(4) bond length is 2.50 Å. The Na(2)-O(5) bond length is 2.32 Å. There is one shorter (2.54 Å) and one longer (2.84 Å) Na(2)-O(6) bond length. Co(1) is bonded to one O(2), one O(3), one O(4), one O(5), and two equivalent O(6) atoms to form distorted CoO6 octahedra that share corners with two equivalent Na(2)O7 pentagonal bipyramids, corners with four equivalent As(1)O4 tetrahedra, edges with two equivalent Na(2)O7 pentagonal bipyramids, and faces with two equivalent Na(2)O7 pentagonal bipyramids. The Co(1)-O(2) bond length is 2.20 Å. The Co(1)-O(3) bond length is 2.28 Å. The Co(1)-O(4) bond length is 2.10 Å. The Co(1)-O(5) bond length is 2.08 Å. Both Co(1)-O(6) bond lengths are 2.10 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 1.30 Å. The C(1)-O(2) bond length is 1.31 Å. The C(1)-O(3) bond length is 1.30 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 Co(1)O6 octahedra, corners with four equivalent Na(2)O7 pentagonal bipyramids, and edges with two equivalent Na(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 43-59°. The As(1)-O(4) bond length is 1.73 Å. The As(1)-O(5) bond length is 1.71 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 5-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 Co(1), and one C(1) atom. In the third O site, O(3) is bonded in a distorted trigonal bipyramidal geometry to one Na(1), two equivalent Na(2), one Co(1), and one C(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to two equivalent Na(2), one Co(1), and one As(1) atom. In the fifth O site, O(5) is bonded in a rectangular see-saw-like geometry to two equivalent Na(2), one Co(1), and one As(1) atom. In the sixth O site, O(6) is bonded in a 5-coordinate geometry to one Na(1), two equivalent Na(2), one Co(1), and one As(1) atom.