CeSe2 crystallizes in the triclinic P-1 space group. There are eight inequivalent Ce sites. In the first Ce site, Ce(1) is bonded to one Se(15), one Se(2), one Se(7), and one Se(8) atom to form corner-sharing CeSe4 tetrahedra. In the second Ce site, Ce(2) is bonded to one Se(8), one Se(9), and two equivalent Se(4) atoms to form a mixture of edge and corner-sharing CeSe4 tetrahedra. In the third Ce site, Ce(3) is bonded to one Se(11), one Se(12), one Se(13), and one Se(16) atom to form corner-sharing CeSe4 tetrahedra. In the fourth Ce site, Ce(4) is bonded to one Se(12), one Se(14), one Se(3), and one Se(7) atom to form corner-sharing CeSe4 tetrahedra. In the fifth Ce site, Ce(5) is bonded to one Se(11), one Se(5), and two equivalent Se(1) atoms to form a mixture of edge and corner-sharing CeSe4 tetrahedra. In the sixth Ce site, Ce(6) is bonded to one Se(14), one Se(2), and two equivalent Se(10) atoms to form a mixture of edge and corner-sharing CeSe4 tetrahedra. In the seventh Ce site, Ce(7) is bonded to one Se(16), one Se(3), and two equivalent Se(6) atoms to form a mixture of edge and corner-sharing CeSe4 tetrahedra. In the eighth Ce site, Ce(8) is bonded to one Se(13), one Se(15), one Se(5), and one Se(9) atom to form corner-sharing CeSe4 tetrahedra. There are sixteen inequivalent Se sites. In the first Se site, Se(1) is bonded in a water-like geometry to two equivalent Ce(5) atoms. In the second Se site, Se(2) is bonded in a bent 120 degrees geometry to one Ce(1) and one Ce(6) atom. In the third Se site, Se(3) is bonded in a bent 120 degrees geometry to one Ce(4) and one Ce(7) atom. In the fourth Se site, Se(4) is bonded in an L-shaped geometry to two equivalent Ce(2) atoms. In the fifth Se site, Se(5) is bonded in a bent 120 degrees geometry to one Ce(5) and one Ce(8) atom. In the sixth Se site, Se(6) is bonded in an L-shaped geometry to two equivalent Ce(7) atoms. In the seventh Se site, Se(7) is bonded in a bent 120 degrees geometry to one Ce(1) and one Ce(4) atom. In the eighth Se site, Se(8) is bonded in a bent 120 degrees geometry to one Ce(1) and one Ce(2) atom. In the ninth Se site, Se(9) is bonded in a bent 120 degrees geometry to one Ce(2) and one Ce(8) atom. In the tenth Se site, Se(10) is bonded in a water-like geometry to two equivalent Ce(6) atoms. In the eleventh Se site, Se(11) is bonded in a bent 120 degrees geometry to one Ce(3) and one Ce(5) atom. In the twelfth Se site, Se(12) is bonded in a bent 120 degrees geometry to one Ce(3) and one Ce(4) atom. In the thirteenth Se site, Se(13) is bonded in a bent 120 degrees geometry to one Ce(3) and one Ce(8) atom. In the fourteenth Se site, Se(14) is bonded in a bent 120 degrees geometry to one Ce(4) and one Ce(6) atom. In the fifteenth Se site, Se(15) is bonded in a bent 120 degrees geometry to one Ce(1) and one Ce(8) atom. In the sixteenth Se site, Se(16) is bonded in a bent 120 degrees geometry to one Ce(3) and one Ce(7) atom.
CeSe2 crystallizes in the triclinic P-1 space group. There are eight inequivalent Ce sites. In the first Ce site, Ce(1) is bonded to one Se(15), one Se(2), one Se(7), and one Se(8) atom to form corner-sharing CeSe4 tetrahedra. The Ce(1)-Se(15) bond length is 2.74 Å. The Ce(1)-Se(2) bond length is 2.72 Å. The Ce(1)-Se(7) bond length is 2.74 Å. The Ce(1)-Se(8) bond length is 2.72 Å. In the second Ce site, Ce(2) is bonded to one Se(8), one Se(9), and two equivalent Se(4) atoms to form a mixture of edge and corner-sharing CeSe4 tetrahedra. The Ce(2)-Se(8) bond length is 2.73 Å. The Ce(2)-Se(9) bond length is 2.74 Å. Both Ce(2)-Se(4) bond lengths are 2.73 Å. In the third Ce site, Ce(3) is bonded to one Se(11), one Se(12), one Se(13), and one Se(16) atom to form corner-sharing CeSe4 tetrahedra. The Ce(3)-Se(11) bond length is 2.73 Å. The Ce(3)-Se(12) bond length is 2.73 Å. The Ce(3)-Se(13) bond length is 2.74 Å. The Ce(3)-Se(16) bond length is 2.73 Å. In the fourth Ce site, Ce(4) is bonded to one Se(12), one Se(14), one Se(3), and one Se(7) atom to form corner-sharing CeSe4 tetrahedra. The Ce(4)-Se(12) bond length is 2.74 Å. The Ce(4)-Se(14) bond length is 2.72 Å. The Ce(4)-Se(3) bond length is 2.72 Å. The Ce(4)-Se(7) bond length is 2.74 Å. In the fifth Ce site, Ce(5) is bonded to one Se(11), one Se(5), and two equivalent Se(1) atoms to form a mixture of edge and corner-sharing CeSe4 tetrahedra. The Ce(5)-Se(11) bond length is 2.74 Å. The Ce(5)-Se(5) bond length is 2.74 Å. Both Ce(5)-Se(1) bond lengths are 2.73 Å. In the sixth Ce site, Ce(6) is bonded to one Se(14), one Se(2), and two equivalent Se(10) atoms to form a mixture of edge and corner-sharing CeSe4 tetrahedra. The Ce(6)-Se(14) bond length is 2.75 Å. The Ce(6)-Se(2) bond length is 2.75 Å. There is one shorter (2.71 Å) and one longer (2.75 Å) Ce(6)-Se(10) bond length. In the seventh Ce site, Ce(7) is bonded to one Se(16), one Se(3), and two equivalent Se(6) atoms to form a mixture of edge and corner-sharing CeSe4 tetrahedra. The Ce(7)-Se(16) bond length is 2.74 Å. The Ce(7)-Se(3) bond length is 2.73 Å. Both Ce(7)-Se(6) bond lengths are 2.73 Å. In the eighth Ce site, Ce(8) is bonded to one Se(13), one Se(15), one Se(5), and one Se(9) atom to form corner-sharing CeSe4 tetrahedra. The Ce(8)-Se(13) bond length is 2.73 Å. The Ce(8)-Se(15) bond length is 2.73 Å. The Ce(8)-Se(5) bond length is 2.73 Å. The Ce(8)-Se(9) bond length is 2.73 Å. There are sixteen inequivalent Se sites. In the first Se site, Se(1) is bonded in a water-like geometry to two equivalent Ce(5) atoms. In the second Se site, Se(2) is bonded in a bent 120 degrees geometry to one Ce(1) and one Ce(6) atom. In the third Se site, Se(3) is bonded in a bent 120 degrees geometry to one Ce(4) and one Ce(7) atom. In the fourth Se site, Se(4) is bonded in an L-shaped geometry to two equivalent Ce(2) atoms. In the fifth Se site, Se(5) is bonded in a bent 120 degrees geometry to one Ce(5) and one Ce(8) atom. In the sixth Se site, Se(6) is bonded in an L-shaped geometry to two equivalent Ce(7) atoms. In the seventh Se site, Se(7) is bonded in a bent 120 degrees geometry to one Ce(1) and one Ce(4) atom. In the eighth Se site, Se(8) is bonded in a bent 120 degrees geometry to one Ce(1) and one Ce(2) atom. In the ninth Se site, Se(9) is bonded in a bent 120 degrees geometry to one Ce(2) and one Ce(8) atom. In the tenth Se site, Se(10) is bonded in a water-like geometry to two equivalent Ce(6) atoms. In the eleventh Se site, Se(11) is bonded in a bent 120 degrees geometry to one Ce(3) and one Ce(5) atom. In the twelfth Se site, Se(12) is bonded in a bent 120 degrees geometry to one Ce(3) and one Ce(4) atom. In the thirteenth Se site, Se(13) is bonded in a bent 120 degrees geometry to one Ce(3) and one Ce(8) atom. In the fourteenth Se site, Se(14) is bonded in a bent 120 degrees geometry to one Ce(4) and one Ce(6) atom. In the fifteenth Se site, Se(15) is bonded in a bent 120 degrees geometry to one Ce(1) and one Ce(8) atom. In the sixteenth Se site, Se(16) is bonded in a bent 120 degrees geometry to one Ce(3) and one Ce(7) atom.