FeCoS4 is Pyrite-derived structured and crystallizes in the monoclinic P2_1/c space group. Fe(1) is bonded to two equivalent S(2) and four equivalent S(1) atoms to form FeS6 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)FeCo2S tetrahedra, and corners with four equivalent S(1)Fe2CoS tetrahedra. The corner-sharing octahedral tilt angles range from 63-65°. Co(1) is bonded to two equivalent S(1) and four equivalent S(2) atoms to form CoS6 octahedra that share corners with four equivalent Co(1)S6 octahedra, corners with eight equivalent Fe(1)S6 octahedra, corners with two equivalent S(1)Fe2CoS tetrahedra, and corners with four equivalent S(2)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 two equivalent Fe(1), one Co(1), and one S(1) atom to form distorted SFe2CoS tetrahedra that share  a cornercorner with one Co(1)S6 octahedra, corners with two equivalent Fe(1)S6 octahedra, corners with seven equivalent S(1)Fe2CoS tetrahedra, and corners with eight equivalent S(2)FeCo2S tetrahedra. The corner-sharing octahedral tilt angles range from 77-80°. In the second S site, S(2) is bonded to one Fe(1), two equivalent Co(1), and one S(2) 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 seven equivalent S(2)FeCo2S tetrahedra, and corners with eight equivalent S(1)Fe2CoS tetrahedra. The corner-sharing octahedral tilt angles range from 76-79°.
FeCoS4 is Pyrite-derived structured and crystallizes in the monoclinic P2_1/c space group. Fe(1) is bonded to two equivalent S(2) and four equivalent S(1) atoms to form FeS6 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)FeCo2S tetrahedra, and corners with four equivalent S(1)Fe2CoS tetrahedra. The corner-sharing octahedral tilt angles range from 63-65°. Both Fe(1)-S(2) bond lengths are 2.25 Å. There are two shorter (2.26 Å) and two longer (2.27 Å) Fe(1)-S(1) bond lengths. Co(1) is bonded to two equivalent S(1) and four equivalent S(2) atoms to form CoS6 octahedra that share corners with four equivalent Co(1)S6 octahedra, corners with eight equivalent Fe(1)S6 octahedra, corners with two equivalent S(1)Fe2CoS tetrahedra, and corners with four equivalent S(2)FeCo2S tetrahedra. The corner-sharing octahedral tilt angles range from 64-66°. Both Co(1)-S(1) bond lengths are 2.30 Å. There are two shorter (2.29 Å) and two longer (2.30 Å) Co(1)-S(2) bond lengths. There are two inequivalent S sites. In the first S site, S(1) is bonded to two equivalent Fe(1), one Co(1), and one S(1) atom to form distorted SFe2CoS tetrahedra that share  a cornercorner with one Co(1)S6 octahedra, corners with two equivalent Fe(1)S6 octahedra, corners with seven equivalent S(1)Fe2CoS tetrahedra, and corners with eight equivalent S(2)FeCo2S tetrahedra. The corner-sharing octahedral tilt angles range from 77-80°. The S(1)-S(1) bond length is 2.21 Å. In the second S site, S(2) is bonded to one Fe(1), two equivalent Co(1), and one S(2) 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 seven equivalent S(2)FeCo2S tetrahedra, and corners with eight equivalent S(1)Fe2CoS tetrahedra. The corner-sharing octahedral tilt angles range from 76-79°. The S(2)-S(2) bond length is 2.16 Å.