MgCeSe3 is Ilmenite-like structured and crystallizes in the monoclinic C2/m space group. Mg(1) is bonded to two equivalent Se(2) and four equivalent Se(1) atoms to form distorted edge-sharing MgSe6 octahedra. Ce(1) is bonded in a 6-coordinate geometry to two equivalent Se(2) and four equivalent Se(1) atoms. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Mg(1) and two equivalent Ce(1) atoms. In the second Se site, Se(2) is bonded to two equivalent Mg(1) and two equivalent Ce(1) atoms to form edge-sharing SeCe2Mg2 trigonal pyramids.
MgCeSe3 is Ilmenite-like structured and crystallizes in the monoclinic C2/m space group. Mg(1) is bonded to two equivalent Se(2) and four equivalent Se(1) atoms to form distorted edge-sharing MgSe6 octahedra. Both Mg(1)-Se(2) bond lengths are 2.73 Å. There are two shorter (2.67 Å) and two longer (2.92 Å) Mg(1)-Se(1) bond lengths. Ce(1) is bonded in a 6-coordinate geometry to two equivalent Se(2) and four equivalent Se(1) atoms. There is one shorter (2.84 Å) and one longer (2.86 Å) Ce(1)-Se(2) bond length. There are two shorter (2.76 Å) and two longer (3.22 Å) Ce(1)-Se(1) bond lengths. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Mg(1) and two equivalent Ce(1) atoms. In the second Se site, Se(2) is bonded to two equivalent Mg(1) and two equivalent Ce(1) atoms to form edge-sharing SeCe2Mg2 trigonal pyramids.