Al2(SeO4)3 crystallizes in the trigonal R3c space group. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded in an octahedral geometry to three equivalent O(1) and three equivalent O(3) atoms. In the second Al site, Al(2) is bonded in an octahedral geometry to three equivalent O(2) and three equivalent O(4) atoms. Se(1) is bonded in a distorted trigonal non-coplanar geometry to one O(1), one O(2), and one O(3) atom. There are four inequivalent O sites. In the first O site, O(2) is bonded in a bent 120 degrees geometry to one Al(2) and one Se(1) atom. In the second O site, O(3) is bonded in a bent 120 degrees geometry to one Al(1) and one Se(1) atom. In the third O site, O(4) is bonded in a single-bond geometry to one Al(2) atom. In the fourth O site, O(1) is bonded in a bent 120 degrees geometry to one Al(1) and one Se(1) atom.
Al2(SeO4)3 crystallizes in the trigonal R3c space group. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded in an octahedral geometry to three equivalent O(1) and three equivalent O(3) atoms. All Al(1)-O(1) bond lengths are 1.90 Å. All Al(1)-O(3) bond lengths are 1.91 Å. In the second Al site, Al(2) is bonded in an octahedral geometry to three equivalent O(2) and three equivalent O(4) atoms. All Al(2)-O(2) bond lengths are 1.87 Å. All Al(2)-O(4) bond lengths are 1.88 Å. Se(1) is bonded in a distorted trigonal non-coplanar geometry to one O(1), one O(2), and one O(3) atom. The Se(1)-O(1) bond length is 1.70 Å. The Se(1)-O(2) bond length is 1.77 Å. The Se(1)-O(3) bond length is 1.72 Å. There are four inequivalent O sites. In the first O site, O(2) is bonded in a bent 120 degrees geometry to one Al(2) and one Se(1) atom. In the second O site, O(3) is bonded in a bent 120 degrees geometry to one Al(1) and one Se(1) atom. In the third O site, O(4) is bonded in a single-bond geometry to one Al(2) atom. In the fourth O site, O(1) is bonded in a bent 120 degrees geometry to one Al(1) and one Se(1) atom.