Al2(SO4)3 crystallizes in the trigonal R-3 space group. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to three equivalent O(2) and three equivalent O(3) atoms to form AlO6 octahedra that share corners with six equivalent S(1)O4 tetrahedra. In the second Al site, Al(2) is bonded to three equivalent O(1) and three equivalent O(4) atoms to form AlO6 octahedra that share corners with six equivalent S(1)O4 tetrahedra. S(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SO4 tetrahedra that share corners with two equivalent Al(1)O6 octahedra and corners with two equivalent Al(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 25-38°. There are four inequivalent O sites. In the first O site, O(2) is bonded in a bent 150 degrees geometry to one Al(1) and one S(1) atom. In the second O site, O(3) is bonded in a bent 150 degrees geometry to one Al(1) and one S(1) atom. In the third O site, O(4) is bonded in a bent 150 degrees geometry to one Al(2) and one S(1) atom. In the fourth O site, O(1) is bonded in a bent 150 degrees geometry to one Al(2) and one S(1) atom.
Al2(SO4)3 crystallizes in the trigonal R-3 space group. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to three equivalent O(2) and three equivalent O(3) atoms to form AlO6 octahedra that share corners with six equivalent S(1)O4 tetrahedra. All Al(1)-O(2) bond lengths are 1.87 Å. All Al(1)-O(3) bond lengths are 1.87 Å. In the second Al site, Al(2) is bonded to three equivalent O(1) and three equivalent O(4) atoms to form AlO6 octahedra that share corners with six equivalent S(1)O4 tetrahedra. All Al(2)-O(1) bond lengths are 1.88 Å. All Al(2)-O(4) bond lengths are 1.88 Å. S(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SO4 tetrahedra that share corners with two equivalent Al(1)O6 octahedra and corners with two equivalent Al(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 25-38°. The S(1)-O(1) bond length is 1.46 Å. The S(1)-O(2) bond length is 1.45 Å. The S(1)-O(3) bond length is 1.46 Å. The S(1)-O(4) bond length is 1.47 Å. There are four inequivalent O sites. In the first O site, O(2) is bonded in a bent 150 degrees geometry to one Al(1) and one S(1) atom. In the second O site, O(3) is bonded in a bent 150 degrees geometry to one Al(1) and one S(1) atom. In the third O site, O(4) is bonded in a bent 150 degrees geometry to one Al(2) and one S(1) atom. In the fourth O site, O(1) is bonded in a bent 150 degrees geometry to one Al(2) and one S(1) atom.