K3Fe2S4 crystallizes in the orthorhombic Pnma space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 6-coordinate geometry to one S(2), two equivalent S(3), and three equivalent S(1) atoms. In the second K site, K(2) is bonded to two equivalent S(2) and four equivalent S(1) atoms to form distorted KS6 octahedra that share corners with eight equivalent Fe(1)S4 tetrahedra, edges with two equivalent Fe(1)S4 tetrahedra, and faces with two equivalent K(2)S6 octahedra. Fe(1) is bonded to one S(2), one S(3), and two equivalent S(1) atoms to form FeS4 tetrahedra that share corners with four equivalent K(2)S6 octahedra,  an edgeedge with one K(2)S6 octahedra, and edges with two equivalent Fe(1)S4 tetrahedra. The corner-sharing octahedral tilt angles range from 19-64°. There are three inequivalent S sites. In the first S site, S(3) is bonded in a 6-coordinate geometry to four equivalent K(1) and two equivalent Fe(1) atoms. In the second S site, S(1) is bonded in a 7-coordinate geometry to two equivalent K(2), three equivalent K(1), and two equivalent Fe(1) atoms. In the third S site, S(2) is bonded in a 6-coordinate geometry to two equivalent K(1), two equivalent K(2), and two equivalent Fe(1) atoms.
K3Fe2S4 crystallizes in the orthorhombic Pnma space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 6-coordinate geometry to one S(2), two equivalent S(3), and three equivalent S(1) atoms. The K(1)-S(2) bond length is 3.39 Å. There is one shorter (3.13 Å) and one longer (3.22 Å) K(1)-S(3) bond length. There are two shorter (3.31 Å) and one longer (3.59 Å) K(1)-S(1) bond length. In the second K site, K(2) is bonded to two equivalent S(2) and four equivalent S(1) atoms to form distorted KS6 octahedra that share corners with eight equivalent Fe(1)S4 tetrahedra, edges with two equivalent Fe(1)S4 tetrahedra, and faces with two equivalent K(2)S6 octahedra. There is one shorter (3.12 Å) and one longer (3.16 Å) K(2)-S(2) bond length. There are two shorter (3.21 Å) and two longer (3.32 Å) K(2)-S(1) bond lengths. Fe(1) is bonded to one S(2), one S(3), and two equivalent S(1) atoms to form FeS4 tetrahedra that share corners with four equivalent K(2)S6 octahedra,  an edgeedge with one K(2)S6 octahedra, and edges with two equivalent Fe(1)S4 tetrahedra. The corner-sharing octahedral tilt angles range from 19-64°. The Fe(1)-S(2) bond length is 2.30 Å. The Fe(1)-S(3) bond length is 2.26 Å. There is one shorter (2.27 Å) and one longer (2.31 Å) Fe(1)-S(1) bond length. There are three inequivalent S sites. In the first S site, S(3) is bonded in a 6-coordinate geometry to four equivalent K(1) and two equivalent Fe(1) atoms. In the second S site, S(1) is bonded in a 7-coordinate geometry to two equivalent K(2), three equivalent K(1), and two equivalent Fe(1) atoms. In the third S site, S(2) is bonded in a 6-coordinate geometry to two equivalent K(1), two equivalent K(2), and two equivalent Fe(1) atoms.