Mn3(SiSe3)2 is Ilmenite-like structured and crystallizes in the trigonal P-31c space group. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to six equivalent Se(1) atoms to form MnSe6 octahedra that share corners with three equivalent Mn(2)Se6 octahedra, corners with six equivalent Si(1)SiSe3 tetrahedra, edges with three equivalent Mn(1)Se6 octahedra, and  a faceface with one Mn(2)Se6 octahedra. The corner-sharing octahedral tilt angles are 44°. In the second Mn site, Mn(2) is bonded to six equivalent Se(1) atoms to form MnSe6 octahedra that share corners with six equivalent Mn(1)Se6 octahedra, corners with six equivalent Si(1)SiSe3 tetrahedra, and faces with two equivalent Mn(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 44°. Si(1) is bonded to one Si(1) and three equivalent Se(1) atoms to form distorted SiSiSe3 tetrahedra that share corners with three equivalent Mn(2)Se6 octahedra, corners with six equivalent Mn(1)Se6 octahedra, and corners with three equivalent Se(1)Mn3Si trigonal pyramids. The corner-sharing octahedral tilt angles range from 59-78°. Se(1) is bonded to one Mn(2), two equivalent Mn(1), and one Si(1) atom to form distorted SeMn3Si trigonal pyramids that share  a cornercorner with one Si(1)SiSe3 tetrahedra, corners with eleven equivalent Se(1)Mn3Si trigonal pyramids, and edges with three equivalent Se(1)Mn3Si trigonal pyramids.
Mn3(SiSe3)2 is Ilmenite-like structured and crystallizes in the trigonal P-31c space group. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to six equivalent Se(1) atoms to form MnSe6 octahedra that share corners with three equivalent Mn(2)Se6 octahedra, corners with six equivalent Si(1)SiSe3 tetrahedra, edges with three equivalent Mn(1)Se6 octahedra, and  a faceface with one Mn(2)Se6 octahedra. The corner-sharing octahedral tilt angles are 44°. All Mn(1)-Se(1) bond lengths are 2.76 Å. In the second Mn site, Mn(2) is bonded to six equivalent Se(1) atoms to form MnSe6 octahedra that share corners with six equivalent Mn(1)Se6 octahedra, corners with six equivalent Si(1)SiSe3 tetrahedra, and faces with two equivalent Mn(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 44°. All Mn(2)-Se(1) bond lengths are 2.73 Å. Si(1) is bonded to one Si(1) and three equivalent Se(1) atoms to form distorted SiSiSe3 tetrahedra that share corners with three equivalent Mn(2)Se6 octahedra, corners with six equivalent Mn(1)Se6 octahedra, and corners with three equivalent Se(1)Mn3Si trigonal pyramids. The corner-sharing octahedral tilt angles range from 59-78°. The Si(1)-Si(1) bond length is 2.32 Å. All Si(1)-Se(1) bond lengths are 2.31 Å. Se(1) is bonded to one Mn(2), two equivalent Mn(1), and one Si(1) atom to form distorted SeMn3Si trigonal pyramids that share  a cornercorner with one Si(1)SiSe3 tetrahedra, corners with eleven equivalent Se(1)Mn3Si trigonal pyramids, and edges with three equivalent Se(1)Mn3Si trigonal pyramids.