KNb3O8 crystallizes in the orthorhombic Cmcm space group. K(1) is bonded to two equivalent O(1) and four equivalent O(5) atoms to form distorted face-sharing KO6 pentagonal pyramids. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. In the second Nb site, Nb(2) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(3), one O(5), and two equivalent O(4) atoms. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent K(1) and two equivalent Nb(2) atoms to form distorted corner-sharing OK2Nb2 tetrahedra. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to two equivalent Nb(1) and two equivalent Nb(2) atoms. In the third O site, O(3) is bonded in a linear geometry to one Nb(1) and one Nb(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Nb(1) and two equivalent Nb(2) atoms. In the fifth O site, O(5) is bonded in a distorted single-bond geometry to two equivalent K(1) and one Nb(2) atom.
KNb3O8 crystallizes in the orthorhombic Cmcm space group. K(1) is bonded to two equivalent O(1) and four equivalent O(5) atoms to form distorted face-sharing KO6 pentagonal pyramids. Both K(1)-O(1) bond lengths are 2.89 Å. All K(1)-O(5) bond lengths are 2.76 Å. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. Both Nb(1)-O(2) bond lengths are 2.00 Å. Both Nb(1)-O(3) bond lengths are 1.83 Å. Both Nb(1)-O(4) bond lengths are 2.31 Å. In the second Nb site, Nb(2) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(3), one O(5), and two equivalent O(4) atoms. The Nb(2)-O(1) bond length is 1.99 Å. The Nb(2)-O(2) bond length is 2.48 Å. The Nb(2)-O(3) bond length is 2.08 Å. The Nb(2)-O(5) bond length is 1.77 Å. Both Nb(2)-O(4) bond lengths are 2.02 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent K(1) and two equivalent Nb(2) atoms to form distorted corner-sharing OK2Nb2 tetrahedra. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to two equivalent Nb(1) and two equivalent Nb(2) atoms. In the third O site, O(3) is bonded in a linear geometry to one Nb(1) and one Nb(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Nb(1) and two equivalent Nb(2) atoms. In the fifth O site, O(5) is bonded in a distorted single-bond geometry to two equivalent K(1) and one Nb(2) atom.