Cs3As5O9 crystallizes in the trigonal P31m space group. Cs(1) is bonded in a 7-coordinate geometry to three equivalent O(2) and four equivalent O(1) atoms. There are two inequivalent As sites. In the first As site, As(1) is bonded in a distorted T-shaped geometry to three equivalent O(1) atoms. In the second As site, As(2) is bonded in a trigonal non-coplanar geometry to one O(2) and two equivalent O(1) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to two equivalent Cs(1), one As(1), and one As(2) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to three equivalent Cs(1) and one As(2) atom.
Cs3As5O9 crystallizes in the trigonal P31m space group. Cs(1) is bonded in a 7-coordinate geometry to three equivalent O(2) and four equivalent O(1) atoms. There is one shorter (3.04 Å) and two longer (3.30 Å) Cs(1)-O(2) bond lengths. There are two shorter (3.11 Å) and two longer (3.41 Å) Cs(1)-O(1) bond lengths. There are two inequivalent As sites. In the first As site, As(1) is bonded in a distorted T-shaped geometry to three equivalent O(1) atoms. All As(1)-O(1) bond lengths are 1.79 Å. In the second As site, As(2) is bonded in a trigonal non-coplanar geometry to one O(2) and two equivalent O(1) atoms. The As(2)-O(2) bond length is 1.69 Å. Both As(2)-O(1) bond lengths are 1.86 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to two equivalent Cs(1), one As(1), and one As(2) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to three equivalent Cs(1) and one As(2) atom.