MnNiSe2 crystallizes in the trigonal P-3m1 space group. Mn(1) is bonded to two equivalent Ni(1) and six equivalent Se(1) atoms to form a mixture of distorted corner and edge-sharing MnNi2Se6 octahedra. The corner-sharing octahedra are not tilted. Ni(1) is bonded in a 8-coordinate geometry to two equivalent Mn(1) and six equivalent Se(1) atoms. Se(1) is bonded in a 6-coordinate geometry to three equivalent Mn(1) and three equivalent Ni(1) atoms.
MnNiSe2 crystallizes in the trigonal P-3m1 space group. Mn(1) is bonded to two equivalent Ni(1) and six equivalent Se(1) atoms to form a mixture of distorted corner and edge-sharing MnNi2Se6 octahedra. The corner-sharing octahedra are not tilted. Both Mn(1)-Ni(1) bond lengths are 2.66 Å. All Mn(1)-Se(1) bond lengths are 2.46 Å. Ni(1) is bonded in a 8-coordinate geometry to two equivalent Mn(1) and six equivalent Se(1) atoms. All Ni(1)-Se(1) bond lengths are 2.51 Å. Se(1) is bonded in a 6-coordinate geometry to three equivalent Mn(1) and three equivalent Ni(1) atoms.