CeSe2 crystallizes in the monoclinic Cc space group. There are two inequivalent Ce sites. In the first Ce site, Ce(1) is bonded to one Se(1), one Se(4), and two equivalent Se(2) atoms to form corner-sharing CeSe4 tetrahedra. In the second Ce site, Ce(2) is bonded to one Se(1), one Se(4), and two equivalent Se(3) atoms to form corner-sharing CeSe4 tetrahedra. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded in a bent 150 degrees geometry to one Ce(1) and one Ce(2) atom. In the second Se site, Se(2) is bonded in a bent 120 degrees geometry to two equivalent Ce(1) atoms. In the third Se site, Se(3) is bonded in a bent 150 degrees geometry to two equivalent Ce(2) atoms. In the fourth Se site, Se(4) is bonded in a bent 150 degrees geometry to one Ce(1) and one Ce(2) atom.
CeSe2 crystallizes in the monoclinic Cc space group. There are two inequivalent Ce sites. In the first Ce site, Ce(1) is bonded to one Se(1), one Se(4), and two equivalent Se(2) atoms to form corner-sharing CeSe4 tetrahedra. The Ce(1)-Se(1) bond length is 2.72 Å. The Ce(1)-Se(4) bond length is 2.72 Å. Both Ce(1)-Se(2) bond lengths are 2.73 Å. In the second Ce site, Ce(2) is bonded to one Se(1), one Se(4), and two equivalent Se(3) atoms to form corner-sharing CeSe4 tetrahedra. The Ce(2)-Se(1) bond length is 2.73 Å. The Ce(2)-Se(4) bond length is 2.72 Å. There is one shorter (2.72 Å) and one longer (2.73 Å) Ce(2)-Se(3) bond length. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded in a bent 150 degrees geometry to one Ce(1) and one Ce(2) atom. In the second Se site, Se(2) is bonded in a bent 120 degrees geometry to two equivalent Ce(1) atoms. In the third Se site, Se(3) is bonded in a bent 150 degrees geometry to two equivalent Ce(2) atoms. In the fourth Se site, Se(4) is bonded in a bent 150 degrees geometry to one Ce(1) and one Ce(2) atom.