Cs2CeO3 crystallizes in the orthorhombic Cmc2_1 space group. There are four inequivalent Cs sites. In the first Cs site, Cs(1) is bonded to one O(2), one O(3), one O(5), two equivalent O(1), and two equivalent O(4) atoms to form distorted CsO7 pentagonal bipyramids that share corners with two equivalent Cs(1)O7 pentagonal bipyramids,  a cornercorner with one Ce(2)O4 tetrahedra, edges with two equivalent Ce(1)O4 tetrahedra, and edges with two equivalent Ce(2)O4 tetrahedra. In the second Cs site, Cs(2) is bonded in a 5-coordinate geometry to one O(2), one O(3), one O(4), and two equivalent O(5) atoms. In the third Cs site, Cs(3) is bonded in a 5-coordinate geometry to one O(2), one O(4), one O(5), and two equivalent O(3) atoms. In the fourth Cs site, Cs(4) is bonded in a 7-coordinate geometry to one O(3), one O(4), one O(5), two equivalent O(1), and two equivalent O(2) atoms. There are two inequivalent Ce sites. In the first Ce site, Ce(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form CeO4 tetrahedra that share corners with two equivalent Ce(2)O4 tetrahedra and edges with two equivalent Cs(1)O7 pentagonal bipyramids. In the second Ce site, Ce(2) is bonded to one O(4), one O(5), and two equivalent O(1) atoms to form CeO4 tetrahedra that share  a cornercorner with one Cs(1)O7 pentagonal bipyramid, corners with two equivalent Ce(1)O4 tetrahedra, and edges with two equivalent Cs(1)O7 pentagonal bipyramids. There are five inequivalent O sites. In the first O site, O(5) is bonded in a 6-coordinate geometry to one Cs(1), one Cs(3), one Cs(4), two equivalent Cs(2), and one Ce(2) atom. In the second O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Cs(1), one Cs(4), one Ce(1), and one Ce(2) atom. In the third O site, O(2) is bonded in a 6-coordinate geometry to one Cs(1), one Cs(2), one Cs(3), two equivalent Cs(4), and one Ce(1) atom. In the fourth O site, O(3) is bonded in a 6-coordinate geometry to one Cs(1), one Cs(2), one Cs(4), two equivalent Cs(3), and one Ce(1) atom. In the fifth O site, O(4) is bonded in a 6-coordinate geometry to one Cs(2), one Cs(3), one Cs(4), two equivalent Cs(1), and one Ce(2) atom.
Cs2CeO3 crystallizes in the orthorhombic Cmc2_1 space group. There are four inequivalent Cs sites. In the first Cs site, Cs(1) is bonded to one O(2), one O(3), one O(5), two equivalent O(1), and two equivalent O(4) atoms to form distorted CsO7 pentagonal bipyramids that share corners with two equivalent Cs(1)O7 pentagonal bipyramids,  a cornercorner with one Ce(2)O4 tetrahedra, edges with two equivalent Ce(1)O4 tetrahedra, and edges with two equivalent Ce(2)O4 tetrahedra. The Cs(1)-O(2) bond length is 3.47 Å. The Cs(1)-O(3) bond length is 3.17 Å. The Cs(1)-O(5) bond length is 3.02 Å. Both Cs(1)-O(1) bond lengths are 3.30 Å. Both Cs(1)-O(4) bond lengths are 3.49 Å. In the second Cs site, Cs(2) is bonded in a 5-coordinate geometry to one O(2), one O(3), one O(4), and two equivalent O(5) atoms. The Cs(2)-O(2) bond length is 3.08 Å. The Cs(2)-O(3) bond length is 3.46 Å. The Cs(2)-O(4) bond length is 3.06 Å. Both Cs(2)-O(5) bond lengths are 3.48 Å. In the third Cs site, Cs(3) is bonded in a 5-coordinate geometry to one O(2), one O(4), one O(5), and two equivalent O(3) atoms. The Cs(3)-O(2) bond length is 3.03 Å. The Cs(3)-O(4) bond length is 3.18 Å. The Cs(3)-O(5) bond length is 3.42 Å. Both Cs(3)-O(3) bond lengths are 3.49 Å. In the fourth Cs site, Cs(4) is bonded in a 7-coordinate geometry to one O(3), one O(4), one O(5), two equivalent O(1), and two equivalent O(2) atoms. The Cs(4)-O(3) bond length is 2.96 Å. The Cs(4)-O(4) bond length is 3.51 Å. The Cs(4)-O(5) bond length is 3.17 Å. Both Cs(4)-O(1) bond lengths are 3.28 Å. Both Cs(4)-O(2) bond lengths are 3.50 Å. There are two inequivalent Ce sites. In the first Ce site, Ce(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form CeO4 tetrahedra that share corners with two equivalent Ce(2)O4 tetrahedra and edges with two equivalent Cs(1)O7 pentagonal bipyramids. The Ce(1)-O(2) bond length is 2.05 Å. The Ce(1)-O(3) bond length is 2.04 Å. Both Ce(1)-O(1) bond lengths are 2.21 Å. In the second Ce site, Ce(2) is bonded to one O(4), one O(5), and two equivalent O(1) atoms to form CeO4 tetrahedra that share  a cornercorner with one Cs(1)O7 pentagonal bipyramid, corners with two equivalent Ce(1)O4 tetrahedra, and edges with two equivalent Cs(1)O7 pentagonal bipyramids. The Ce(2)-O(4) bond length is 2.05 Å. The Ce(2)-O(5) bond length is 2.01 Å. Both Ce(2)-O(1) bond lengths are 2.24 Å. There are five inequivalent O sites. In the first O site, O(5) is bonded in a 6-coordinate geometry to one Cs(1), one Cs(3), one Cs(4), two equivalent Cs(2), and one Ce(2) atom. In the second O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Cs(1), one Cs(4), one Ce(1), and one Ce(2) atom. In the third O site, O(2) is bonded in a 6-coordinate geometry to one Cs(1), one Cs(2), one Cs(3), two equivalent Cs(4), and one Ce(1) atom. In the fourth O site, O(3) is bonded in a 6-coordinate geometry to one Cs(1), one Cs(2), one Cs(4), two equivalent Cs(3), and one Ce(1) atom. In the fifth O site, O(4) is bonded in a 6-coordinate geometry to one Cs(2), one Cs(3), one Cs(4), two equivalent Cs(1), and one Ce(2) atom.