Al5O8 is beta indium sulfide-like structured and 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 48°. 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 48°. 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 58-61°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to three equivalent Al(1) atoms. In the second O site, O(2) is bonded to one Al(2), one Al(3), and two equivalent Al(1) atoms to form a mixture of distorted corner and edge-sharing OAl4 tetrahedra. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Al(2) and two equivalent Al(1) atoms. In the fourth O site, O(4) is bonded to one Al(3) and three equivalent Al(1) atoms to form a mixture of distorted corner and edge-sharing OAl4 tetrahedra.
Al5O8 is beta indium sulfide-like structured and 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 48°. The Al(1)-O(1) bond length is 1.82 Å. The Al(1)-O(4) bond length is 1.93 Å. Both Al(1)-O(2) bond lengths are 1.97 Å. Both Al(1)-O(3) bond lengths are 1.89 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 48°. All Al(2)-O(2) bond lengths are 2.00 Å. All Al(2)-O(3) bond lengths are 1.87 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 58-61°. The Al(3)-O(4) bond length is 1.82 Å. All Al(3)-O(2) bond lengths are 1.82 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to three equivalent Al(1) atoms. In the second O site, O(2) is bonded to one Al(2), one Al(3), and two equivalent Al(1) atoms to form a mixture of distorted corner and edge-sharing OAl4 tetrahedra. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Al(2) and two equivalent Al(1) atoms. In the fourth O site, O(4) is bonded to one Al(3) and three equivalent Al(1) atoms to form a mixture of distorted corner and edge-sharing OAl4 tetrahedra.