MnCdSe2 is Enargite-like structured and crystallizes in the trigonal P3m1 space group. Mn(1) is bonded to one Se(2) and three equivalent Se(1) atoms to form MnSe4 tetrahedra that share corners with six equivalent Mn(1)Se4 tetrahedra and corners with six equivalent Cd(1)Se4 tetrahedra. Cd(1) is bonded to one Se(1) and three equivalent Se(2) atoms to form CdSe4 tetrahedra that share corners with six equivalent Mn(1)Se4 tetrahedra and corners with six equivalent Cd(1)Se4 tetrahedra. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to three equivalent Mn(1) and one Cd(1) atom to form SeMn3Cd tetrahedra that share corners with six equivalent Se(1)Mn3Cd tetrahedra and corners with six equivalent Se(2)MnCd3 tetrahedra. In the second Se site, Se(2) is bonded to one Mn(1) and three equivalent Cd(1) atoms to form SeMnCd3 tetrahedra that share corners with six equivalent Se(1)Mn3Cd tetrahedra and corners with six equivalent Se(2)MnCd3 tetrahedra.
MnCdSe2 is Enargite-like structured and crystallizes in the trigonal P3m1 space group. Mn(1) is bonded to one Se(2) and three equivalent Se(1) atoms to form MnSe4 tetrahedra that share corners with six equivalent Mn(1)Se4 tetrahedra and corners with six equivalent Cd(1)Se4 tetrahedra. The Mn(1)-Se(2) bond length is 2.54 Å. All Mn(1)-Se(1) bond lengths are 2.58 Å. Cd(1) is bonded to one Se(1) and three equivalent Se(2) atoms to form CdSe4 tetrahedra that share corners with six equivalent Mn(1)Se4 tetrahedra and corners with six equivalent Cd(1)Se4 tetrahedra. The Cd(1)-Se(1) bond length is 2.66 Å. All Cd(1)-Se(2) bond lengths are 2.65 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to three equivalent Mn(1) and one Cd(1) atom to form SeMn3Cd tetrahedra that share corners with six equivalent Se(1)Mn3Cd tetrahedra and corners with six equivalent Se(2)MnCd3 tetrahedra. In the second Se site, Se(2) is bonded to one Mn(1) and three equivalent Cd(1) atoms to form SeMnCd3 tetrahedra that share corners with six equivalent Se(1)Mn3Cd tetrahedra and corners with six equivalent Se(2)MnCd3 tetrahedra.