FeCo3S8 is Pyrite-derived structured and crystallizes in the trigonal R-3 space group. Fe(1) is bonded to six equivalent S(1) atoms to form FeS6 octahedra that share corners with twelve equivalent Co(1)S6 octahedra and corners with six equivalent S(1)FeCo2S tetrahedra. The corner-sharing octahedral tilt angles range from 64-65°. Co(1) is bonded to two equivalent S(2) and four equivalent S(1) atoms to form CoS6 octahedra that share corners with four equivalent Fe(1)S6 octahedra, corners with eight equivalent Co(1)S6 octahedra, corners with two equivalent S(2)Co3S tetrahedra, and corners with four equivalent S(1)FeCo2S tetrahedra. The corner-sharing octahedral tilt angles range from 64-66°. There are two inequivalent S sites. In the first S site, S(1) is bonded to one Fe(1), two equivalent Co(1), and one S(1) atom to form distorted SFeCo2S tetrahedra that share  a cornercorner with one Fe(1)S6 octahedra, corners with two equivalent Co(1)S6 octahedra, corners with four equivalent S(2)Co3S tetrahedra, and corners with eleven equivalent S(1)FeCo2S tetrahedra. The corner-sharing octahedral tilt angles range from 75-78°. In the second S site, S(2) is bonded to three equivalent Co(1) and one S(2) atom to form distorted SCo3S tetrahedra that share corners with three equivalent Co(1)S6 octahedra, corners with three equivalent S(2)Co3S tetrahedra, and corners with twelve equivalent S(1)FeCo2S tetrahedra. The corner-sharing octahedral tilt angles are 76°.
FeCo3S8 is Pyrite-derived structured and crystallizes in the trigonal R-3 space group. Fe(1) is bonded to six equivalent S(1) atoms to form FeS6 octahedra that share corners with twelve equivalent Co(1)S6 octahedra and corners with six equivalent S(1)FeCo2S tetrahedra. The corner-sharing octahedral tilt angles range from 64-65°. All Fe(1)-S(1) bond lengths are 2.27 Å. Co(1) is bonded to two equivalent S(2) and four equivalent S(1) atoms to form CoS6 octahedra that share corners with four equivalent Fe(1)S6 octahedra, corners with eight equivalent Co(1)S6 octahedra, corners with two equivalent S(2)Co3S tetrahedra, and corners with four equivalent S(1)FeCo2S tetrahedra. The corner-sharing octahedral tilt angles range from 64-66°. Both Co(1)-S(2) bond lengths are 2.31 Å. All Co(1)-S(1) bond lengths are 2.32 Å. There are two inequivalent S sites. In the first S site, S(1) is bonded to one Fe(1), two equivalent Co(1), and one S(1) atom to form distorted SFeCo2S tetrahedra that share  a cornercorner with one Fe(1)S6 octahedra, corners with two equivalent Co(1)S6 octahedra, corners with four equivalent S(2)Co3S tetrahedra, and corners with eleven equivalent S(1)FeCo2S tetrahedra. The corner-sharing octahedral tilt angles range from 75-78°. The S(1)-S(1) bond length is 2.12 Å. In the second S site, S(2) is bonded to three equivalent Co(1) and one S(2) atom to form distorted SCo3S tetrahedra that share corners with three equivalent Co(1)S6 octahedra, corners with three equivalent S(2)Co3S tetrahedra, and corners with twelve equivalent S(1)FeCo2S tetrahedra. The corner-sharing octahedral tilt angles are 76°. The S(2)-S(2) bond length is 2.08 Å.