Na4(AsO4)OH crystallizes in the orthorhombic Pnma space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one O(2), one O(4), two equivalent O(1), and two equivalent O(3) atoms. In the second Na site, Na(2) is bonded to one H(1), one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms to form distorted NaHO6 pentagonal bipyramids that share corners with two equivalent Na(2)HO6 pentagonal bipyramids, corners with four equivalent As(1)O4 tetrahedra, edges with two equivalent Na(3)H2O6 hexagonal bipyramids, and faces with two equivalent Na(3)H2O6 hexagonal bipyramids. In the third Na site, Na(3) is bonded to two equivalent H(1), two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted NaH2O6 hexagonal bipyramids that share corners with four equivalent As(1)O4 tetrahedra, edges with two equivalent Na(2)HO6 pentagonal bipyramids, faces with two equivalent Na(3)H2O6 hexagonal bipyramids, and faces with two equivalent Na(2)HO6 pentagonal bipyramids. As(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form AsO4 tetrahedra that share corners with four equivalent Na(3)H2O6 hexagonal bipyramids and corners with four equivalent Na(2)HO6 pentagonal bipyramids. H(1) is bonded in a single-bond geometry to one Na(2), two equivalent Na(3), and one O(4) atom. There are four inequivalent O sites. In the first O site, O(2) is bonded in a 6-coordinate geometry to one Na(2), two equivalent Na(1), two equivalent Na(3), and one As(1) atom. In the second O site, O(3) is bonded in a 6-coordinate geometry to one Na(2), four equivalent Na(1), and one As(1) atom. In the third O site, O(4) is bonded in a distorted single-bond geometry to two equivalent Na(1), two equivalent Na(2), two equivalent Na(3), and one H(1) atom. In the fourth O site, O(1) is bonded in a 5-coordinate geometry to one Na(2), one Na(3), two equivalent Na(1), and one As(1) atom.
Na4(AsO4)OH crystallizes in the orthorhombic Pnma space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one O(2), one O(4), two equivalent O(1), and two equivalent O(3) atoms. The Na(1)-O(2) bond length is 2.76 Å. The Na(1)-O(4) bond length is 2.40 Å. There is one shorter (2.36 Å) and one longer (2.62 Å) Na(1)-O(1) bond length. There is one shorter (2.46 Å) and one longer (2.69 Å) Na(1)-O(3) bond length. In the second Na site, Na(2) is bonded to one H(1), one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms to form distorted NaHO6 pentagonal bipyramids that share corners with two equivalent Na(2)HO6 pentagonal bipyramids, corners with four equivalent As(1)O4 tetrahedra, edges with two equivalent Na(3)H2O6 hexagonal bipyramids, and faces with two equivalent Na(3)H2O6 hexagonal bipyramids. The Na(2)-H(1) bond length is 2.47 Å. The Na(2)-O(2) bond length is 2.57 Å. The Na(2)-O(3) bond length is 2.43 Å. Both Na(2)-O(1) bond lengths are 2.37 Å. There is one shorter (2.40 Å) and one longer (2.43 Å) Na(2)-O(4) bond length. In the third Na site, Na(3) is bonded to two equivalent H(1), two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted NaH2O6 hexagonal bipyramids that share corners with four equivalent As(1)O4 tetrahedra, edges with two equivalent Na(2)HO6 pentagonal bipyramids, faces with two equivalent Na(3)H2O6 hexagonal bipyramids, and faces with two equivalent Na(2)HO6 pentagonal bipyramids. Both Na(3)-H(1) bond lengths are 2.41 Å. Both Na(3)-O(1) bond lengths are 2.33 Å. Both Na(3)-O(2) bond lengths are 2.70 Å. Both Na(3)-O(4) bond lengths are 2.52 Å. As(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form AsO4 tetrahedra that share corners with four equivalent Na(3)H2O6 hexagonal bipyramids and corners with four equivalent Na(2)HO6 pentagonal bipyramids. The As(1)-O(2) bond length is 1.72 Å. The As(1)-O(3) bond length is 1.74 Å. Both As(1)-O(1) bond lengths are 1.72 Å. H(1) is bonded in a single-bond geometry to one Na(2), two equivalent Na(3), and one O(4) atom. The H(1)-O(4) bond length is 0.97 Å. There are four inequivalent O sites. In the first O site, O(2) is bonded in a 6-coordinate geometry to one Na(2), two equivalent Na(1), two equivalent Na(3), and one As(1) atom. In the second O site, O(3) is bonded in a 6-coordinate geometry to one Na(2), four equivalent Na(1), and one As(1) atom. In the third O site, O(4) is bonded in a distorted single-bond geometry to two equivalent Na(1), two equivalent Na(2), two equivalent Na(3), and one H(1) atom. In the fourth O site, O(1) is bonded in a 5-coordinate geometry to one Na(2), one Na(3), two equivalent Na(1), and one As(1) atom.