MnCdSe4 is Pyrite-derived structured and crystallizes in the monoclinic P2_1/c space group. Mn(1) is bonded to two equivalent Se(2) and four equivalent Se(1) atoms to form MnSe6 octahedra that share corners with four equivalent Mn(1)Se6 octahedra, corners with eight equivalent Cd(1)Se6 octahedra, corners with two equivalent Se(2)MnCd2Se tetrahedra, and corners with four equivalent Se(1)Mn2CdSe tetrahedra. The corner-sharing octahedral tilt angles range from 62-69°. Cd(1) is bonded to two equivalent Se(1) and four equivalent Se(2) atoms to form CdSe6 octahedra that share corners with four equivalent Cd(1)Se6 octahedra, corners with eight equivalent Mn(1)Se6 octahedra, corners with two equivalent Se(1)Mn2CdSe tetrahedra, and corners with four equivalent Se(2)MnCd2Se tetrahedra. The corner-sharing octahedral tilt angles range from 64-70°. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Mn(1), one Cd(1), and one Se(1) atom to form distorted SeMn2CdSe tetrahedra that share  a cornercorner with one Cd(1)Se6 octahedra, corners with two equivalent Mn(1)Se6 octahedra, corners with seven equivalent Se(1)Mn2CdSe tetrahedra, and corners with eight equivalent Se(2)MnCd2Se tetrahedra. The corner-sharing octahedral tilt angles range from 72-81°. In the second Se site, Se(2) is bonded to one Mn(1), two equivalent Cd(1), and one Se(2) atom to form distorted SeMnCd2Se tetrahedra that share  a cornercorner with one Mn(1)Se6 octahedra, corners with two equivalent Cd(1)Se6 octahedra, corners with seven equivalent Se(2)MnCd2Se tetrahedra, and corners with eight equivalent Se(1)Mn2CdSe tetrahedra. The corner-sharing octahedral tilt angles range from 70-79°.
MnCdSe4 is Pyrite-derived structured and crystallizes in the monoclinic P2_1/c space group. Mn(1) is bonded to two equivalent Se(2) and four equivalent Se(1) atoms to form MnSe6 octahedra that share corners with four equivalent Mn(1)Se6 octahedra, corners with eight equivalent Cd(1)Se6 octahedra, corners with two equivalent Se(2)MnCd2Se tetrahedra, and corners with four equivalent Se(1)Mn2CdSe tetrahedra. The corner-sharing octahedral tilt angles range from 62-69°. Both Mn(1)-Se(2) bond lengths are 2.68 Å. All Mn(1)-Se(1) bond lengths are 2.72 Å. Cd(1) is bonded to two equivalent Se(1) and four equivalent Se(2) atoms to form CdSe6 octahedra that share corners with four equivalent Cd(1)Se6 octahedra, corners with eight equivalent Mn(1)Se6 octahedra, corners with two equivalent Se(1)Mn2CdSe tetrahedra, and corners with four equivalent Se(2)MnCd2Se tetrahedra. The corner-sharing octahedral tilt angles range from 64-70°. Both Cd(1)-Se(1) bond lengths are 2.88 Å. There are two shorter (2.83 Å) and two longer (2.84 Å) Cd(1)-Se(2) bond lengths. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Mn(1), one Cd(1), and one Se(1) atom to form distorted SeMn2CdSe tetrahedra that share  a cornercorner with one Cd(1)Se6 octahedra, corners with two equivalent Mn(1)Se6 octahedra, corners with seven equivalent Se(1)Mn2CdSe tetrahedra, and corners with eight equivalent Se(2)MnCd2Se tetrahedra. The corner-sharing octahedral tilt angles range from 72-81°. The Se(1)-Se(1) bond length is 2.43 Å. In the second Se site, Se(2) is bonded to one Mn(1), two equivalent Cd(1), and one Se(2) atom to form distorted SeMnCd2Se tetrahedra that share  a cornercorner with one Mn(1)Se6 octahedra, corners with two equivalent Cd(1)Se6 octahedra, corners with seven equivalent Se(2)MnCd2Se tetrahedra, and corners with eight equivalent Se(1)Mn2CdSe tetrahedra. The corner-sharing octahedral tilt angles range from 70-79°. The Se(2)-Se(2) bond length is 2.40 Å.