Al2SiO6 crystallizes in the orthorhombic Pnma space group. Al(1) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form AlO6 octahedra that share corners with two equivalent Al(1)O6 octahedra, corners with four equivalent Si(1)O4 tetrahedra, and edges with two equivalent Al(1)O6 octahedra. The corner-sharing octahedral tilt angles are 28°. Si(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form SiO4 tetrahedra that share corners with eight equivalent Al(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 49-51°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Al(1) and one Si(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Al(1) and one Si(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to two equivalent Al(1) and one Si(1) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to two equivalent Al(1) atoms.
Al2SiO6 crystallizes in the orthorhombic Pnma space group. Al(1) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form AlO6 octahedra that share corners with two equivalent Al(1)O6 octahedra, corners with four equivalent Si(1)O4 tetrahedra, and edges with two equivalent Al(1)O6 octahedra. The corner-sharing octahedral tilt angles are 28°. The Al(1)-O(1) bond length is 1.91 Å. The Al(1)-O(2) bond length is 1.98 Å. There is one shorter (1.91 Å) and one longer (1.92 Å) Al(1)-O(3) bond length. Both Al(1)-O(4) bond lengths are 1.82 Å. Si(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form SiO4 tetrahedra that share corners with eight equivalent Al(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 49-51°. The Si(1)-O(1) bond length is 1.66 Å. The Si(1)-O(2) bond length is 1.68 Å. Both Si(1)-O(3) bond lengths are 1.65 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Al(1) and one Si(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Al(1) and one Si(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to two equivalent Al(1) and one Si(1) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to two equivalent Al(1) atoms.