Na2HPO4 crystallizes in the monoclinic P2_1 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(1), one O(2), one O(3), and two equivalent O(4) atoms. In the second Na site, Na(2) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted NaO6 octahedra that share corners with six equivalent P(1)O4 tetrahedra and edges with two equivalent Na(2)O6 octahedra. P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share corners with six equivalent Na(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-52°. H(1) is bonded in a distorted linear geometry to one O(1) and one O(2) atom. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Na(1), one Na(2), one P(1), and one H(1) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Na(2), one P(1), and one H(1) atom. In the third O site, O(3) is bonded to one Na(1), two equivalent Na(2), and one P(1) atom to form distorted corner-sharing ONa3P trigonal pyramids. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to two equivalent Na(1), two equivalent Na(2), and one P(1) atom.
Na2HPO4 crystallizes in the monoclinic P2_1 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(1), one O(2), one O(3), and two equivalent O(4) atoms. The Na(1)-O(1) bond length is 2.40 Å. The Na(1)-O(2) bond length is 2.32 Å. The Na(1)-O(3) bond length is 2.35 Å. There is one shorter (2.72 Å) and one longer (2.80 Å) Na(1)-O(4) bond length. In the second Na site, Na(2) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted NaO6 octahedra that share corners with six equivalent P(1)O4 tetrahedra and edges with two equivalent Na(2)O6 octahedra. The Na(2)-O(1) bond length is 2.58 Å. The Na(2)-O(2) bond length is 2.39 Å. There is one shorter (2.33 Å) and one longer (2.37 Å) Na(2)-O(3) bond length. There is one shorter (2.49 Å) and one longer (2.56 Å) Na(2)-O(4) bond length. P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share corners with six equivalent Na(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-52°. The P(1)-O(1) bond length is 1.65 Å. The P(1)-O(2) bond length is 1.55 Å. The P(1)-O(3) bond length is 1.53 Å. The P(1)-O(4) bond length is 1.52 Å. H(1) is bonded in a distorted linear geometry to one O(1) and one O(2) atom. The H(1)-O(1) bond length is 1.03 Å. The H(1)-O(2) bond length is 1.58 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Na(1), one Na(2), one P(1), and one H(1) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Na(2), one P(1), and one H(1) atom. In the third O site, O(3) is bonded to one Na(1), two equivalent Na(2), and one P(1) atom to form distorted corner-sharing ONa3P trigonal pyramids. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to two equivalent Na(1), two equivalent Na(2), and one P(1) atom.