Ce3As2O7Cl crystallizes in the tetragonal P4_2nm space group. There are two inequivalent Ce sites. In the first Ce site, Ce(1) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. In the second Ce site, Ce(2) is bonded in a 8-coordinate geometry to one O(2), two equivalent O(1), two equivalent O(3), two equivalent O(4), and one Cl(1) atom. As(1) is bonded in a distorted T-shaped geometry to one O(2), one O(3), and one O(4) atom. There are four inequivalent O sites. In the first O site, O(3) is bonded to one Ce(1), two equivalent Ce(2), and one As(1) atom to form distorted OCe3As trigonal pyramids that share corners with two equivalent O(1)Ce4 tetrahedra, corners with three equivalent O(4)Ce3As tetrahedra, corners with three equivalent O(3)Ce3As trigonal pyramids,  an edgeedge with one O(1)Ce4 tetrahedra, and edges with two equivalent O(4)Ce3As tetrahedra. In the second O site, O(4) is bonded to one Ce(1), two equivalent Ce(2), and one As(1) atom to form distorted OCe3As tetrahedra that share corners with two equivalent O(1)Ce4 tetrahedra, corners with three equivalent O(4)Ce3As tetrahedra, corners with three equivalent O(3)Ce3As trigonal pyramids,  an edgeedge with one O(1)Ce4 tetrahedra, and edges with two equivalent O(3)Ce3As trigonal pyramids. In the third O site, O(1) is bonded to four equivalent Ce(2) atoms to form OCe4 tetrahedra that share corners with four equivalent O(4)Ce3As tetrahedra, corners with four equivalent O(3)Ce3As trigonal pyramids, edges with two equivalent O(4)Ce3As tetrahedra, edges with two equivalent O(1)Ce4 tetrahedra, and edges with two equivalent O(3)Ce3As trigonal pyramids. In the fourth O site, O(2) is bonded in a 3-coordinate geometry to one Ce(1), one Ce(2), and one As(1) atom. Cl(1) is bonded in a 2-coordinate geometry to two equivalent Ce(2) atoms.
Ce3As2O7Cl crystallizes in the tetragonal P4_2nm space group. There are two inequivalent Ce sites. In the first Ce site, Ce(1) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. Both Ce(1)-O(2) bond lengths are 2.34 Å. Both Ce(1)-O(3) bond lengths are 2.50 Å. Both Ce(1)-O(4) bond lengths are 2.41 Å. In the second Ce site, Ce(2) is bonded in a 8-coordinate geometry to one O(2), two equivalent O(1), two equivalent O(3), two equivalent O(4), and one Cl(1) atom. The Ce(2)-O(2) bond length is 2.66 Å. There is one shorter (2.33 Å) and one longer (2.38 Å) Ce(2)-O(1) bond length. There is one shorter (2.58 Å) and one longer (2.65 Å) Ce(2)-O(3) bond length. There is one shorter (2.55 Å) and one longer (2.70 Å) Ce(2)-O(4) bond length. The Ce(2)-Cl(1) bond length is 2.97 Å. As(1) is bonded in a distorted T-shaped geometry to one O(2), one O(3), and one O(4) atom. The As(1)-O(2) bond length is 1.79 Å. The As(1)-O(3) bond length is 1.82 Å. The As(1)-O(4) bond length is 1.84 Å. There are four inequivalent O sites. In the first O site, O(3) is bonded to one Ce(1), two equivalent Ce(2), and one As(1) atom to form distorted OCe3As trigonal pyramids that share corners with two equivalent O(1)Ce4 tetrahedra, corners with three equivalent O(4)Ce3As tetrahedra, corners with three equivalent O(3)Ce3As trigonal pyramids,  an edgeedge with one O(1)Ce4 tetrahedra, and edges with two equivalent O(4)Ce3As tetrahedra. In the second O site, O(4) is bonded to one Ce(1), two equivalent Ce(2), and one As(1) atom to form distorted OCe3As tetrahedra that share corners with two equivalent O(1)Ce4 tetrahedra, corners with three equivalent O(4)Ce3As tetrahedra, corners with three equivalent O(3)Ce3As trigonal pyramids,  an edgeedge with one O(1)Ce4 tetrahedra, and edges with two equivalent O(3)Ce3As trigonal pyramids. In the third O site, O(1) is bonded to four equivalent Ce(2) atoms to form OCe4 tetrahedra that share corners with four equivalent O(4)Ce3As tetrahedra, corners with four equivalent O(3)Ce3As trigonal pyramids, edges with two equivalent O(4)Ce3As tetrahedra, edges with two equivalent O(1)Ce4 tetrahedra, and edges with two equivalent O(3)Ce3As trigonal pyramids. In the fourth O site, O(2) is bonded in a 3-coordinate geometry to one Ce(1), one Ce(2), and one As(1) atom. Cl(1) is bonded in a 2-coordinate geometry to two equivalent Ce(2) atoms.