Na2CoP2O7 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 5-coordinate geometry to one O(2), one O(4), one O(5), two equivalent O(1), and two equivalent O(6) atoms. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom. Co(1) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(6) atom to form CoO5 trigonal bipyramids that share corners with two equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(3), one O(4), one O(5), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one P(2)O4 tetrahedra and corners with two equivalent Co(1)O5 trigonal bipyramids. 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  a cornercorner with one P(1)O4 tetrahedra and corners with three equivalent Co(1)O5 trigonal bipyramids. There are seven inequivalent O sites. In the first O site, O(4) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Co(1), and one P(1) atom. In the second O site, O(5) is bonded in a 3-coordinate geometry to one Na(1), one Na(2), and one P(1) atom. In the third O site, O(6) is bonded in a 5-coordinate geometry to one Na(2), two equivalent Na(1), one Co(1), and one P(2) atom. In the fourth O site, O(7) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the fifth O site, O(1) is bonded in a 5-coordinate geometry to one Na(2), two equivalent Na(1), one Co(1), and one P(2) atom. In the sixth O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Na(2), one Co(1), and one P(2) atom. In the seventh O site, O(3) is bonded in a distorted trigonal planar geometry to one Na(2), one Co(1), and one P(1) atom.
Na2CoP2O7 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 5-coordinate geometry to one O(2), one O(4), one O(5), two equivalent O(1), and two equivalent O(6) atoms. The Na(1)-O(2) bond length is 2.41 Å. The Na(1)-O(4) bond length is 2.56 Å. The Na(1)-O(5) bond length is 2.27 Å. There is one shorter (2.39 Å) and one longer (2.89 Å) Na(1)-O(1) bond length. There is one shorter (2.45 Å) and one longer (2.82 Å) Na(1)-O(6) bond length. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom. The Na(2)-O(1) bond length is 2.76 Å. The Na(2)-O(2) bond length is 2.46 Å. The Na(2)-O(3) bond length is 2.49 Å. The Na(2)-O(4) bond length is 2.51 Å. The Na(2)-O(5) bond length is 2.42 Å. The Na(2)-O(6) bond length is 2.52 Å. Co(1) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(6) atom to form CoO5 trigonal bipyramids that share corners with two equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. The Co(1)-O(1) bond length is 2.06 Å. The Co(1)-O(2) bond length is 2.17 Å. The Co(1)-O(3) bond length is 1.99 Å. The Co(1)-O(4) bond length is 2.07 Å. The Co(1)-O(6) bond length is 2.10 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(3), one O(4), one O(5), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one P(2)O4 tetrahedra and corners with two equivalent Co(1)O5 trigonal bipyramids. The P(1)-O(3) bond length is 1.55 Å. The P(1)-O(4) bond length is 1.56 Å. The P(1)-O(5) bond length is 1.50 Å. The P(1)-O(7) bond length is 1.66 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  a cornercorner with one P(1)O4 tetrahedra and corners with three equivalent Co(1)O5 trigonal bipyramids. The P(2)-O(1) bond length is 1.55 Å. The P(2)-O(2) bond length is 1.53 Å. The P(2)-O(6) bond length is 1.54 Å. The P(2)-O(7) bond length is 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(1), one Na(2), one Co(1), and one P(1) atom. In the second O site, O(5) is bonded in a 3-coordinate geometry to one Na(1), one Na(2), and one P(1) atom. In the third O site, O(6) is bonded in a 5-coordinate geometry to one Na(2), two equivalent Na(1), one Co(1), and one P(2) atom. In the fourth O site, O(7) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the fifth O site, O(1) is bonded in a 5-coordinate geometry to one Na(2), two equivalent Na(1), one Co(1), and one P(2) atom. In the sixth O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Na(2), one Co(1), and one P(2) atom. In the seventh O site, O(3) is bonded in a distorted trigonal planar geometry to one Na(2), one Co(1), and one P(1) atom.