KCr3O8 crystallizes in the monoclinic C2/m space group. K(1) is bonded in a 10-coordinate geometry to four equivalent O(3) and six equivalent O(2) atoms. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form corner-sharing CrO6 octahedra. In the second Cr site, Cr(2) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form corner-sharing CrO4 tetrahedra. The corner-sharing octahedral tilt angles range from 32-44°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Cr(1) and one Cr(2) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to three equivalent K(1) and one Cr(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one K(1), one Cr(1), and one Cr(2) atom.
KCr3O8 crystallizes in the monoclinic C2/m space group. K(1) is bonded in a 10-coordinate geometry to four equivalent O(3) and six equivalent O(2) atoms. All K(1)-O(3) bond lengths are 2.77 Å. There are two shorter (2.88 Å) and four longer (3.20 Å) K(1)-O(2) bond lengths. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form corner-sharing CrO6 octahedra. Both Cr(1)-O(1) bond lengths are 1.93 Å. All Cr(1)-O(3) bond lengths are 1.95 Å. In the second Cr site, Cr(2) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form corner-sharing CrO4 tetrahedra. The corner-sharing octahedral tilt angles range from 32-44°. The Cr(2)-O(1) bond length is 1.64 Å. The Cr(2)-O(2) bond length is 1.61 Å. Both Cr(2)-O(3) bond lengths are 1.68 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Cr(1) and one Cr(2) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to three equivalent K(1) and one Cr(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one K(1), one Cr(1), and one Cr(2) atom.