SrAl2Si2O8 crystallizes in the monoclinic C2/c space group. Sr(1) is bonded in a 9-coordinate geometry to one O(2), one O(3), one O(4), one O(5), one O(6), one O(7), one O(8), and two equivalent O(1) atoms. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(1), one O(3), one O(5), and one O(7) atom to form AlO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra and corners with three equivalent Si(2)O4 tetrahedra. In the second Al site, Al(2) is bonded to one O(2), one O(4), one O(6), and one O(8) atom to form AlO4 tetrahedra that share  a cornercorner with one Si(2)O4 tetrahedra and corners with three equivalent Si(1)O4 tetrahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(4), one O(6), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra and corners with three equivalent Al(2)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(2), one O(3), one O(5), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(2)O4 tetrahedra and corners with three equivalent Al(1)O4 tetrahedra. There are eight inequivalent O sites. In the first O site, O(7) is bonded in a 2-coordinate geometry to one Sr(1), one Al(1), and one Si(2) atom. In the second O site, O(8) is bonded in a distorted bent 150 degrees geometry to one Sr(1), one Al(2), and one Si(1) atom. In the third O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Sr(1), one Al(1), and one Si(1) atom. In the fourth O site, O(2) is bonded in a trigonal planar geometry to one Sr(1), one Al(2), and one Si(2) atom. In the fifth O site, O(6) is bonded in a bent 120 degrees geometry to one Sr(1), one Al(2), and one Si(1) atom. In the sixth O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Sr(1), one Al(1), and one Si(2) atom. In the seventh O site, O(4) is bonded in a distorted bent 150 degrees geometry to one Sr(1), one Al(2), and one Si(1) atom. In the eighth O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Sr(1), one Al(1), and one Si(2) atom.
SrAl2Si2O8 crystallizes in the monoclinic C2/c space group. Sr(1) is bonded in a 9-coordinate geometry to one O(2), one O(3), one O(4), one O(5), one O(6), one O(7), one O(8), and two equivalent O(1) atoms. The Sr(1)-O(2) bond length is 2.45 Å. The Sr(1)-O(3) bond length is 2.87 Å. The Sr(1)-O(4) bond length is 2.77 Å. The Sr(1)-O(5) bond length is 3.14 Å. The Sr(1)-O(6) bond length is 3.26 Å. The Sr(1)-O(7) bond length is 2.77 Å. The Sr(1)-O(8) bond length is 2.80 Å. There is one shorter (2.63 Å) and one longer (2.66 Å) Sr(1)-O(1) bond length. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(1), one O(3), one O(5), and one O(7) atom to form AlO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra and corners with three equivalent Si(2)O4 tetrahedra. The Al(1)-O(1) bond length is 1.78 Å. The Al(1)-O(3) bond length is 1.76 Å. The Al(1)-O(5) bond length is 1.74 Å. The Al(1)-O(7) bond length is 1.77 Å. In the second Al site, Al(2) is bonded to one O(2), one O(4), one O(6), and one O(8) atom to form AlO4 tetrahedra that share  a cornercorner with one Si(2)O4 tetrahedra and corners with three equivalent Si(1)O4 tetrahedra. The Al(2)-O(2) bond length is 1.77 Å. The Al(2)-O(4) bond length is 1.76 Å. The Al(2)-O(6) bond length is 1.76 Å. The Al(2)-O(8) bond length is 1.75 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(4), one O(6), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra and corners with three equivalent Al(2)O4 tetrahedra. The Si(1)-O(1) bond length is 1.66 Å. The Si(1)-O(4) bond length is 1.63 Å. The Si(1)-O(6) bond length is 1.63 Å. The Si(1)-O(8) bond length is 1.64 Å. In the second Si site, Si(2) is bonded to one O(2), one O(3), one O(5), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(2)O4 tetrahedra and corners with three equivalent Al(1)O4 tetrahedra. The Si(2)-O(2) bond length is 1.66 Å. The Si(2)-O(3) bond length is 1.64 Å. The Si(2)-O(5) bond length is 1.63 Å. The Si(2)-O(7) bond length is 1.64 Å. There are eight inequivalent O sites. In the first O site, O(7) is bonded in a 2-coordinate geometry to one Sr(1), one Al(1), and one Si(2) atom. In the second O site, O(8) is bonded in a distorted bent 150 degrees geometry to one Sr(1), one Al(2), and one Si(1) atom. In the third O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Sr(1), one Al(1), and one Si(1) atom. In the fourth O site, O(2) is bonded in a trigonal planar geometry to one Sr(1), one Al(2), and one Si(2) atom. In the fifth O site, O(6) is bonded in a bent 120 degrees geometry to one Sr(1), one Al(2), and one Si(1) atom. In the sixth O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Sr(1), one Al(1), and one Si(2) atom. In the seventh O site, O(4) is bonded in a distorted bent 150 degrees geometry to one Sr(1), one Al(2), and one Si(1) atom. In the eighth O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Sr(1), one Al(1), and one Si(2) atom.