SrAl2Si2O8 crystallizes in the trigonal P-3c1 space group. Sr(1) is bonded to six equivalent O(2) atoms to form SrO6 octahedra that share corners with six equivalent Al(1)O4 tetrahedra and corners with six equivalent Si(1)O4 tetrahedra. Al(1) is bonded to one O(1) and three equivalent O(2) atoms to form AlO4 tetrahedra that share corners with three equivalent Sr(1)O6 octahedra and corners with four equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 64°. Si(1) is bonded to one O(1) and three equivalent O(2) atoms to form SiO4 tetrahedra that share corners with three equivalent Sr(1)O6 octahedra and corners with four equivalent Al(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 62°. There are two inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to one Al(1) and one Si(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Sr(1), one Al(1), and one Si(1) atom.
SrAl2Si2O8 crystallizes in the trigonal P-3c1 space group. Sr(1) is bonded to six equivalent O(2) atoms to form SrO6 octahedra that share corners with six equivalent Al(1)O4 tetrahedra and corners with six equivalent Si(1)O4 tetrahedra. All Sr(1)-O(2) bond lengths are 2.63 Å. Al(1) is bonded to one O(1) and three equivalent O(2) atoms to form AlO4 tetrahedra that share corners with three equivalent Sr(1)O6 octahedra and corners with four equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 64°. The Al(1)-O(1) bond length is 1.71 Å. All Al(1)-O(2) bond lengths are 1.78 Å. Si(1) is bonded to one O(1) and three equivalent O(2) atoms to form SiO4 tetrahedra that share corners with three equivalent Sr(1)O6 octahedra and corners with four equivalent Al(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 62°. The Si(1)-O(1) bond length is 1.60 Å. All Si(1)-O(2) bond lengths are 1.65 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to one Al(1) and one Si(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Sr(1), one Al(1), and one Si(1) atom.