CeSe2 crystallizes in the monoclinic C2/c space group. There are two inequivalent Ce sites. In the first Ce site, Ce(1) is bonded to one Se(1), one Se(3), one Se(4), and one Se(5) atom to form distorted corner-sharing CeSe4 trigonal pyramids. In the second Ce site, Ce(2) is bonded to one Se(2), one Se(3), one Se(4), and one Se(5) atom to form distorted corner-sharing CeSe4 trigonal pyramids. There are five inequivalent Se sites. In the first Se site, Se(1) is bonded in a linear geometry to two equivalent Ce(1) atoms. In the second Se site, Se(2) is bonded in a linear geometry to two equivalent Ce(2) atoms. In the third Se site, Se(3) is bonded in a bent 120 degrees geometry to one Ce(1) and one Ce(2) atom. In the fourth Se site, Se(4) is bonded in a 3-coordinate geometry to one Ce(1), one Ce(2), and one Se(4) atom. In the fifth Se site, Se(5) is bonded in a bent 120 degrees geometry to one Ce(1) and one Ce(2) atom.
CeSe2 crystallizes in the monoclinic C2/c space group. There are two inequivalent Ce sites. In the first Ce site, Ce(1) is bonded to one Se(1), one Se(3), one Se(4), and one Se(5) atom to form distorted corner-sharing CeSe4 trigonal pyramids. The Ce(1)-Se(1) bond length is 2.75 Å. The Ce(1)-Se(3) bond length is 2.73 Å. The Ce(1)-Se(4) bond length is 2.90 Å. The Ce(1)-Se(5) bond length is 2.73 Å. In the second Ce site, Ce(2) is bonded to one Se(2), one Se(3), one Se(4), and one Se(5) atom to form distorted corner-sharing CeSe4 trigonal pyramids. The Ce(2)-Se(2) bond length is 2.75 Å. The Ce(2)-Se(3) bond length is 2.73 Å. The Ce(2)-Se(4) bond length is 2.91 Å. The Ce(2)-Se(5) bond length is 2.73 Å. There are five inequivalent Se sites. In the first Se site, Se(1) is bonded in a linear geometry to two equivalent Ce(1) atoms. In the second Se site, Se(2) is bonded in a linear geometry to two equivalent Ce(2) atoms. In the third Se site, Se(3) is bonded in a bent 120 degrees geometry to one Ce(1) and one Ce(2) atom. In the fourth Se site, Se(4) is bonded in a 3-coordinate geometry to one Ce(1), one Ce(2), and one Se(4) atom. The Se(4)-Se(4) bond length is 2.46 Å. In the fifth Se site, Se(5) is bonded in a bent 120 degrees geometry to one Ce(1) and one Ce(2) atom.