HAl5O8 crystallizes in the hexagonal P6_3mc space group. There are three inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms to form AlO6 octahedra that share corners with two equivalent Al(2)O6 octahedra, corners with three equivalent Al(3)O4 tetrahedra,  an edgeedge with one Al(2)O6 octahedra, and edges with four equivalent Al(1)O6 octahedra. The corner-sharing octahedral tilt angles are 52°. In the second Al site, Al(2) is bonded to three equivalent O(2) and three equivalent O(3) atoms to form AlO6 octahedra that share corners with six equivalent Al(1)O6 octahedra, corners with three equivalent Al(3)O4 tetrahedra, and edges with three equivalent Al(1)O6 octahedra. The corner-sharing octahedral tilt angles are 52°. In the third Al site, Al(3) is bonded to one O(4) and three equivalent O(2) atoms to form corner-sharing AlO4 tetrahedra. The corner-sharing octahedral tilt angles range from 56-62°. H(1) is bonded in a single-bond geometry to one O(1) atom. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to three equivalent Al(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 Al(2), one Al(3), and two equivalent Al(1) atoms. In the third O site, O(3) is bonded in a trigonal planar geometry to one Al(2) and two equivalent Al(1) atoms. In the fourth O site, O(4) is bonded in a distorted trigonal pyramidal geometry to one Al(3) and three equivalent Al(1) atoms.
HAl5O8 crystallizes in the hexagonal P6_3mc space group. There are three inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms to form AlO6 octahedra that share corners with two equivalent Al(2)O6 octahedra, corners with three equivalent Al(3)O4 tetrahedra,  an edgeedge with one Al(2)O6 octahedra, and edges with four equivalent Al(1)O6 octahedra. The corner-sharing octahedral tilt angles are 52°. The Al(1)-O(1) bond length is 1.91 Å. The Al(1)-O(4) bond length is 1.89 Å. Both Al(1)-O(2) bond lengths are 1.95 Å. Both Al(1)-O(3) bond lengths are 1.84 Å. In the second Al site, Al(2) is bonded to three equivalent O(2) and three equivalent O(3) atoms to form AlO6 octahedra that share corners with six equivalent Al(1)O6 octahedra, corners with three equivalent Al(3)O4 tetrahedra, and edges with three equivalent Al(1)O6 octahedra. The corner-sharing octahedral tilt angles are 52°. All Al(2)-O(2) bond lengths are 2.01 Å. All Al(2)-O(3) bond lengths are 1.86 Å. In the third Al site, Al(3) is bonded to one O(4) and three equivalent O(2) atoms to form corner-sharing AlO4 tetrahedra. The corner-sharing octahedral tilt angles range from 56-62°. The Al(3)-O(4) bond length is 1.81 Å. All Al(3)-O(2) bond lengths are 1.80 Å. H(1) is bonded in a single-bond geometry to one O(1) atom. The H(1)-O(1) bond length is 0.98 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to three equivalent Al(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 Al(2), one Al(3), and two equivalent Al(1) atoms. In the third O site, O(3) is bonded in a trigonal planar geometry to one Al(2) and two equivalent Al(1) atoms. In the fourth O site, O(4) is bonded in a distorted trigonal pyramidal geometry to one Al(3) and three equivalent Al(1) atoms.