KNb4AsO13 crystallizes in the orthorhombic Cmc2_1 space group. K(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(7), and one O(8) atom to form NbO6 octahedra that share  a cornercorner with one Nb(1)O6 octahedra, corners with four equivalent Nb(2)O6 octahedra, and  a cornercorner with one As(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 20-42°. In the second Nb site, Nb(2) is bonded to one O(3), one O(4), one O(5), one O(6), one O(7), and one O(8) atom to form distorted NbO6 octahedra that share corners with four equivalent Nb(1)O6 octahedra, corners with two equivalent As(1)O4 tetrahedra, and  an edgeedge with one Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 20-28°. As(1) is bonded to one O(5), one O(6), and two equivalent O(2) atoms to form AsO4 tetrahedra that share corners with two equivalent Nb(1)O6 octahedra and corners with four equivalent Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-54°. There are eight inequivalent O sites. In the first O site, O(5) is bonded in a trigonal planar geometry to two equivalent Nb(2) and one As(1) atom. In the second O site, O(6) is bonded in a trigonal planar geometry to two equivalent Nb(2) and one As(1) atom. In the third O site, O(7) is bonded in a bent 150 degrees geometry to one Nb(1) and one Nb(2) atom. In the fourth O site, O(8) is bonded in a bent 150 degrees geometry to one Nb(1) and one Nb(2) atom. In the fifth O site, O(1) is bonded in a 2-coordinate geometry to two equivalent K(1) and two equivalent Nb(1) atoms. In the sixth O site, O(2) is bonded in a 3-coordinate geometry to one K(1), one Nb(1), and one As(1) atom. In the seventh O site, O(3) is bonded in a 3-coordinate geometry to one K(1), one Nb(1), and one Nb(2) atom. In the eighth O site, O(4) is bonded in a 3-coordinate geometry to one K(1), one Nb(1), and one Nb(2) atom.
KNb4AsO13 crystallizes in the orthorhombic Cmc2_1 space group. K(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. There is one shorter (3.01 Å) and one longer (3.33 Å) K(1)-O(1) bond length. Both K(1)-O(2) bond lengths are 3.04 Å. Both K(1)-O(3) bond lengths are 2.81 Å. Both K(1)-O(4) bond lengths are 2.94 Å. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(7), and one O(8) atom to form NbO6 octahedra that share  a cornercorner with one Nb(1)O6 octahedra, corners with four equivalent Nb(2)O6 octahedra, and  a cornercorner with one As(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 20-42°. The Nb(1)-O(1) bond length is 1.95 Å. The Nb(1)-O(2) bond length is 2.17 Å. The Nb(1)-O(3) bond length is 2.14 Å. The Nb(1)-O(4) bond length is 2.14 Å. The Nb(1)-O(7) bond length is 1.87 Å. The Nb(1)-O(8) bond length is 1.88 Å. In the second Nb site, Nb(2) is bonded to one O(3), one O(4), one O(5), one O(6), one O(7), and one O(8) atom to form distorted NbO6 octahedra that share corners with four equivalent Nb(1)O6 octahedra, corners with two equivalent As(1)O4 tetrahedra, and  an edgeedge with one Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 20-28°. The Nb(2)-O(3) bond length is 1.84 Å. The Nb(2)-O(4) bond length is 1.84 Å. The Nb(2)-O(5) bond length is 2.28 Å. The Nb(2)-O(6) bond length is 2.27 Å. The Nb(2)-O(7) bond length is 2.03 Å. The Nb(2)-O(8) bond length is 2.01 Å. As(1) is bonded to one O(5), one O(6), and two equivalent O(2) atoms to form AsO4 tetrahedra that share corners with two equivalent Nb(1)O6 octahedra and corners with four equivalent Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-54°. The As(1)-O(5) bond length is 1.74 Å. The As(1)-O(6) bond length is 1.73 Å. Both As(1)-O(2) bond lengths are 1.71 Å. There are eight inequivalent O sites. In the first O site, O(5) is bonded in a trigonal planar geometry to two equivalent Nb(2) and one As(1) atom. In the second O site, O(6) is bonded in a trigonal planar geometry to two equivalent Nb(2) and one As(1) atom. In the third O site, O(7) is bonded in a bent 150 degrees geometry to one Nb(1) and one Nb(2) atom. In the fourth O site, O(8) is bonded in a bent 150 degrees geometry to one Nb(1) and one Nb(2) atom. In the fifth O site, O(1) is bonded in a 2-coordinate geometry to two equivalent K(1) and two equivalent Nb(1) atoms. In the sixth O site, O(2) is bonded in a 3-coordinate geometry to one K(1), one Nb(1), and one As(1) atom. In the seventh O site, O(3) is bonded in a 3-coordinate geometry to one K(1), one Nb(1), and one Nb(2) atom. In the eighth O site, O(4) is bonded in a 3-coordinate geometry to one K(1), one Nb(1), and one Nb(2) atom.