K6Ti2O7 crystallizes in the monoclinic Pc space group. There are six inequivalent K sites. In the first K site, K(1) is bonded in a 5-coordinate geometry to one O(1), one O(4), one O(5), one O(6), and one O(7) atom. In the second K site, K(2) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(5) atom to form distorted KO5 square pyramids that share  a cornercorner with one Ti(1)O4 tetrahedra, corners with two equivalent Ti(2)O4 tetrahedra, edges with two equivalent K(5)O5 square pyramids, and  an edgeedge with one Ti(1)O4 tetrahedra. In the third K site, K(3) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(3), one O(6), and one O(7) atom. In the fourth K site, K(4) is bonded in a 6-coordinate geometry to one O(3), one O(4), one O(6), one O(7), and two equivalent O(2) atoms. In the fifth K site, K(5) is bonded to one O(2), one O(3), one O(4), one O(5), and one O(7) atom to form distorted KO5 square pyramids that share  a cornercorner with one Ti(2)O4 tetrahedra, corners with two equivalent Ti(1)O4 tetrahedra, edges with two equivalent K(2)O5 square pyramids, and  an edgeedge with one Ti(2)O4 tetrahedra. In the sixth K site, K(6) is bonded in a 6-coordinate geometry to one O(1), one O(3), one O(4), one O(6), and two equivalent O(5) atoms. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(1), one O(4), one O(5), and one O(6) atom to form TiO4 tetrahedra that share  a cornercorner with one K(2)O5 square pyramid, corners with two equivalent K(5)O5 square pyramids,  a cornercorner with one Ti(2)O4 tetrahedra, and  an edgeedge with one K(2)O5 square pyramid. In the second Ti site, Ti(2) is bonded to one O(2), one O(3), one O(6), and one O(7) atom to form TiO4 tetrahedra that share  a cornercorner with one K(5)O5 square pyramid, corners with two equivalent K(2)O5 square pyramids,  a cornercorner with one Ti(1)O4 tetrahedra, and  an edgeedge with one K(5)O5 square pyramid. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 1-coordinate geometry to one K(1), one K(2), one K(3), one K(6), and one Ti(1) atom. In the second O site, O(2) is bonded in a 1-coordinate geometry to one K(2), one K(3), one K(5), two equivalent K(4), and one Ti(2) atom. In the third O site, O(3) is bonded in a 6-coordinate geometry to one K(2), one K(3), one K(4), one K(5), one K(6), and one Ti(2) atom. In the fourth O site, O(4) is bonded in a 6-coordinate geometry to one K(1), one K(2), one K(4), one K(5), one K(6), and one Ti(1) atom. In the fifth O site, O(5) is bonded in a 1-coordinate geometry to one K(1), one K(2), one K(5), two equivalent K(6), and one Ti(1) atom. In the sixth O site, O(6) is bonded in a distorted linear geometry to one K(1), one K(3), one K(4), one K(6), one Ti(1), and one Ti(2) atom. In the seventh O site, O(7) is bonded in a 1-coordinate geometry to one K(1), one K(3), one K(4), one K(5), and one Ti(2) atom.
K6Ti2O7 crystallizes in the monoclinic Pc space group. There are six inequivalent K sites. In the first K site, K(1) is bonded in a 5-coordinate geometry to one O(1), one O(4), one O(5), one O(6), and one O(7) atom. The K(1)-O(1) bond length is 2.70 Å. The K(1)-O(4) bond length is 2.85 Å. The K(1)-O(5) bond length is 2.77 Å. The K(1)-O(6) bond length is 3.06 Å. The K(1)-O(7) bond length is 3.16 Å. In the second K site, K(2) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(5) atom to form distorted KO5 square pyramids that share  a cornercorner with one Ti(1)O4 tetrahedra, corners with two equivalent Ti(2)O4 tetrahedra, edges with two equivalent K(5)O5 square pyramids, and  an edgeedge with one Ti(1)O4 tetrahedra. The K(2)-O(1) bond length is 2.98 Å. The K(2)-O(2) bond length is 2.70 Å. The K(2)-O(3) bond length is 2.73 Å. The K(2)-O(4) bond length is 2.70 Å. The K(2)-O(5) bond length is 2.69 Å. In the third K site, K(3) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(3), one O(6), and one O(7) atom. The K(3)-O(1) bond length is 3.21 Å. The K(3)-O(2) bond length is 2.83 Å. The K(3)-O(3) bond length is 2.87 Å. The K(3)-O(6) bond length is 2.93 Å. The K(3)-O(7) bond length is 2.69 Å. In the fourth K site, K(4) is bonded in a 6-coordinate geometry to one O(3), one O(4), one O(6), one O(7), and two equivalent O(2) atoms. The K(4)-O(3) bond length is 2.90 Å. The K(4)-O(4) bond length is 3.05 Å. The K(4)-O(6) bond length is 2.91 Å. The K(4)-O(7) bond length is 2.72 Å. There is one shorter (2.73 Å) and one longer (3.23 Å) K(4)-O(2) bond length. In the fifth K site, K(5) is bonded to one O(2), one O(3), one O(4), one O(5), and one O(7) atom to form distorted KO5 square pyramids that share  a cornercorner with one Ti(2)O4 tetrahedra, corners with two equivalent Ti(1)O4 tetrahedra, edges with two equivalent K(2)O5 square pyramids, and  an edgeedge with one Ti(2)O4 tetrahedra. The K(5)-O(2) bond length is 2.68 Å. The K(5)-O(3) bond length is 2.73 Å. The K(5)-O(4) bond length is 2.71 Å. The K(5)-O(5) bond length is 2.69 Å. The K(5)-O(7) bond length is 3.02 Å. In the sixth K site, K(6) is bonded in a 6-coordinate geometry to one O(1), one O(3), one O(4), one O(6), and two equivalent O(5) atoms. The K(6)-O(1) bond length is 2.71 Å. The K(6)-O(3) bond length is 2.97 Å. The K(6)-O(4) bond length is 2.88 Å. The K(6)-O(6) bond length is 3.01 Å. There is one shorter (2.77 Å) and one longer (3.16 Å) K(6)-O(5) bond length. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(1), one O(4), one O(5), and one O(6) atom to form TiO4 tetrahedra that share  a cornercorner with one K(2)O5 square pyramid, corners with two equivalent K(5)O5 square pyramids,  a cornercorner with one Ti(2)O4 tetrahedra, and  an edgeedge with one K(2)O5 square pyramid. The Ti(1)-O(1) bond length is 1.82 Å. The Ti(1)-O(4) bond length is 1.82 Å. The Ti(1)-O(5) bond length is 1.82 Å. The Ti(1)-O(6) bond length is 1.91 Å. In the second Ti site, Ti(2) is bonded to one O(2), one O(3), one O(6), and one O(7) atom to form TiO4 tetrahedra that share  a cornercorner with one K(5)O5 square pyramid, corners with two equivalent K(2)O5 square pyramids,  a cornercorner with one Ti(1)O4 tetrahedra, and  an edgeedge with one K(5)O5 square pyramid. The Ti(2)-O(2) bond length is 1.82 Å. The Ti(2)-O(3) bond length is 1.82 Å. The Ti(2)-O(6) bond length is 1.91 Å. The Ti(2)-O(7) bond length is 1.82 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 1-coordinate geometry to one K(1), one K(2), one K(3), one K(6), and one Ti(1) atom. In the second O site, O(2) is bonded in a 1-coordinate geometry to one K(2), one K(3), one K(5), two equivalent K(4), and one Ti(2) atom. In the third O site, O(3) is bonded in a 6-coordinate geometry to one K(2), one K(3), one K(4), one K(5), one K(6), and one Ti(2) atom. In the fourth O site, O(4) is bonded in a 6-coordinate geometry to one K(1), one K(2), one K(4), one K(5), one K(6), and one Ti(1) atom. In the fifth O site, O(5) is bonded in a 1-coordinate geometry to one K(1), one K(2), one K(5), two equivalent K(6), and one Ti(1) atom. In the sixth O site, O(6) is bonded in a distorted linear geometry to one K(1), one K(3), one K(4), one K(6), one Ti(1), and one Ti(2) atom. In the seventh O site, O(7) is bonded in a 1-coordinate geometry to one K(1), one K(3), one K(4), one K(5), and one Ti(2) atom.