Cs2Al2As2O7 crystallizes in the orthorhombic Imm2 space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 5-coordinate geometry to one O(2) and four equivalent O(1) atoms. In the second Cs site, Cs(2) is bonded to four equivalent O(1) and four equivalent O(3) atoms to form distorted CsO8 hexagonal bipyramids that share corners with four equivalent Al(1)O4 tetrahedra, edges with two equivalent Cs(2)O8 hexagonal bipyramids, and edges with two equivalent Al(1)O4 tetrahedra. Al(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form AlO4 tetrahedra that share corners with two equivalent Cs(2)O8 hexagonal bipyramids,  a cornercorner with one Al(1)O4 tetrahedra, and  an edgeedge with one Cs(2)O8 hexagonal bipyramid. As(1) is bonded in a 3-coordinate geometry to one O(3) and two equivalent O(1) atoms. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Cs(1), one Cs(2), one Al(1), and one As(1) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Cs(1) and two equivalent Al(1) atoms. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to two equivalent Cs(2), one Al(1), and one As(1) atom.
Cs2Al2As2O7 crystallizes in the orthorhombic Imm2 space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 5-coordinate geometry to one O(2) and four equivalent O(1) atoms. The Cs(1)-O(2) bond length is 3.12 Å. All Cs(1)-O(1) bond lengths are 3.18 Å. In the second Cs site, Cs(2) is bonded to four equivalent O(1) and four equivalent O(3) atoms to form distorted CsO8 hexagonal bipyramids that share corners with four equivalent Al(1)O4 tetrahedra, edges with two equivalent Cs(2)O8 hexagonal bipyramids, and edges with two equivalent Al(1)O4 tetrahedra. All Cs(2)-O(1) bond lengths are 3.40 Å. All Cs(2)-O(3) bond lengths are 3.25 Å. Al(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form AlO4 tetrahedra that share corners with two equivalent Cs(2)O8 hexagonal bipyramids,  a cornercorner with one Al(1)O4 tetrahedra, and  an edgeedge with one Cs(2)O8 hexagonal bipyramid. The Al(1)-O(2) bond length is 1.74 Å. The Al(1)-O(3) bond length is 1.79 Å. Both Al(1)-O(1) bond lengths are 1.79 Å. As(1) is bonded in a 3-coordinate geometry to one O(3) and two equivalent O(1) atoms. The As(1)-O(3) bond length is 1.79 Å. Both As(1)-O(1) bond lengths are 1.80 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Cs(1), one Cs(2), one Al(1), and one As(1) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Cs(1) and two equivalent Al(1) atoms. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to two equivalent Cs(2), one Al(1), and one As(1) atom.