MgYSe3 is Ilmenite structured and crystallizes in the trigonal R-3 space group. Mg(1) is bonded to six equivalent Se(1) atoms to form MgSe6 octahedra that share corners with nine equivalent Y(1)Se6 octahedra, edges with three equivalent Mg(1)Se6 octahedra, and  a faceface with one Y(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 40-56°. Y(1) is bonded to six equivalent Se(1) atoms to form YSe6 octahedra that share corners with nine equivalent Mg(1)Se6 octahedra, edges with three equivalent Y(1)Se6 octahedra, and  a faceface with one Mg(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 40-56°. Se(1) is bonded in a rectangular see-saw-like geometry to two equivalent Mg(1) and two equivalent Y(1) atoms.
MgYSe3 is Ilmenite structured and crystallizes in the trigonal R-3 space group. Mg(1) is bonded to six equivalent Se(1) atoms to form MgSe6 octahedra that share corners with nine equivalent Y(1)Se6 octahedra, edges with three equivalent Mg(1)Se6 octahedra, and  a faceface with one Y(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 40-56°. There are three shorter (2.70 Å) and three longer (2.77 Å) Mg(1)-Se(1) bond lengths. Y(1) is bonded to six equivalent Se(1) atoms to form YSe6 octahedra that share corners with nine equivalent Mg(1)Se6 octahedra, edges with three equivalent Y(1)Se6 octahedra, and  a faceface with one Mg(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 40-56°. There are three shorter (2.84 Å) and three longer (2.87 Å) Y(1)-Se(1) bond lengths. Se(1) is bonded in a rectangular see-saw-like geometry to two equivalent Mg(1) and two equivalent Y(1) atoms.