K3FeO3 crystallizes in the monoclinic C2/m space group. There are three inequivalent K sites. In the first K site, K(1) is bonded in a 5-coordinate geometry to one O(2) and four equivalent O(1) atoms. In the second K site, K(2) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form distorted KO6 octahedra that share corners with four equivalent Fe(1)O4 tetrahedra, edges with three equivalent K(2)O6 octahedra, and edges with two equivalent Fe(1)O4 tetrahedra. In the third K site, K(3) is bonded in a 4-coordinate geometry to four equivalent O(1) atoms. Fe(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form FeO4 tetrahedra that share corners with four equivalent K(2)O6 octahedra, edges with two equivalent K(2)O6 octahedra, and  an edgeedge with one Fe(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 10-44°. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 7-coordinate geometry to two equivalent K(1), two equivalent K(2), two equivalent K(3), and one Fe(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one K(1), two equivalent K(2), and two equivalent Fe(1) atoms.
K3FeO3 crystallizes in the monoclinic C2/m space group. There are three inequivalent K sites. In the first K site, K(1) is bonded in a 5-coordinate geometry to one O(2) and four equivalent O(1) atoms. The K(1)-O(2) bond length is 2.54 Å. There are two shorter (2.77 Å) and two longer (2.85 Å) K(1)-O(1) bond lengths. In the second K site, K(2) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form distorted KO6 octahedra that share corners with four equivalent Fe(1)O4 tetrahedra, edges with three equivalent K(2)O6 octahedra, and edges with two equivalent Fe(1)O4 tetrahedra. Both K(2)-O(2) bond lengths are 2.98 Å. There are two shorter (2.69 Å) and two longer (2.89 Å) K(2)-O(1) bond lengths. In the third K site, K(3) is bonded in a 4-coordinate geometry to four equivalent O(1) atoms. There are two shorter (2.74 Å) and two longer (2.78 Å) K(3)-O(1) bond lengths. Fe(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form FeO4 tetrahedra that share corners with four equivalent K(2)O6 octahedra, edges with two equivalent K(2)O6 octahedra, and  an edgeedge with one Fe(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 10-44°. Both Fe(1)-O(1) bond lengths are 1.85 Å. There is one shorter (1.95 Å) and one longer (1.96 Å) Fe(1)-O(2) bond length. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 7-coordinate geometry to two equivalent K(1), two equivalent K(2), two equivalent K(3), and one Fe(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one K(1), two equivalent K(2), and two equivalent Fe(1) atoms.