NaAlP2O7 crystallizes in the monoclinic P2_1/c space group. Na(1) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(4), one O(5), one O(6), one O(7), and two equivalent O(3) atoms. Al(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(6), and one O(7) atom to form AlO6 octahedra that share corners with three 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(2), one O(4), one O(5), and one O(7) atom to form PO4 tetrahedra that share corners with three equivalent Al(1)O6 octahedra and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 18-48°. In the second P site, P(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form PO4 tetrahedra that share corners with three equivalent Al(1)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 32-51°. There are seven inequivalent O sites. In the first O site, O(5) is bonded in a 3-coordinate geometry to one Na(1), one P(1), and one P(2) atom. In the second O site, O(6) is bonded in a 3-coordinate geometry to one Na(1), one Al(1), and one P(2) atom. In the third O site, O(7) is bonded in a distorted bent 150 degrees geometry to one Na(1), one Al(1), and one P(1) atom. In the fourth O site, O(1) is bonded in a 3-coordinate geometry to one Na(1), one Al(1), and one P(2) atom. In the fifth O site, O(2) is bonded in a 3-coordinate geometry to one Na(1), one Al(1), and one P(1) atom. In the sixth O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Na(1), one Al(1), and one P(2) atom. In the seventh O site, O(4) is bonded in a 3-coordinate geometry to one Na(1), one Al(1), and one P(1) atom.
NaAlP2O7 crystallizes in the monoclinic P2_1/c space group. Na(1) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(4), one O(5), one O(6), one O(7), and two equivalent O(3) atoms. The Na(1)-O(1) bond length is 2.72 Å. The Na(1)-O(2) bond length is 2.61 Å. The Na(1)-O(4) bond length is 2.42 Å. The Na(1)-O(5) bond length is 2.50 Å. The Na(1)-O(6) bond length is 2.37 Å. The Na(1)-O(7) bond length is 2.94 Å. There is one shorter (2.46 Å) and one longer (2.90 Å) Na(1)-O(3) bond length. Al(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(6), and one O(7) atom to form AlO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. The Al(1)-O(1) bond length is 1.97 Å. The Al(1)-O(2) bond length is 1.91 Å. The Al(1)-O(3) bond length is 1.99 Å. The Al(1)-O(4) bond length is 1.91 Å. The Al(1)-O(6) bond length is 1.88 Å. The Al(1)-O(7) bond length is 1.87 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(2), one O(4), one O(5), and one O(7) atom to form PO4 tetrahedra that share corners with three equivalent Al(1)O6 octahedra and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 18-48°. The P(1)-O(2) bond length is 1.52 Å. The P(1)-O(4) bond length is 1.54 Å. The P(1)-O(5) bond length is 1.63 Å. The P(1)-O(7) bond length is 1.51 Å. In the second P site, P(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form PO4 tetrahedra that share corners with three equivalent Al(1)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 32-51°. The P(2)-O(1) bond length is 1.52 Å. The P(2)-O(3) bond length is 1.54 Å. The P(2)-O(5) bond length is 1.63 Å. The P(2)-O(6) bond length is 1.52 Å. There are seven inequivalent O sites. In the first O site, O(5) is bonded in a 3-coordinate geometry to one Na(1), one P(1), and one P(2) atom. In the second O site, O(6) is bonded in a 3-coordinate geometry to one Na(1), one Al(1), and one P(2) atom. In the third O site, O(7) is bonded in a distorted bent 150 degrees geometry to one Na(1), one Al(1), and one P(1) atom. In the fourth O site, O(1) is bonded in a 3-coordinate geometry to one Na(1), one Al(1), and one P(2) atom. In the fifth O site, O(2) is bonded in a 3-coordinate geometry to one Na(1), one Al(1), and one P(1) atom. In the sixth O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Na(1), one Al(1), and one P(2) atom. In the seventh O site, O(4) is bonded in a 3-coordinate geometry to one Na(1), one Al(1), and one P(1) atom.