KTlF4 crystallizes in the trigonal P3_1 space group. There are two inequivalent K sites. In the first K site, K(1) is bonded to one F(2), one F(4), one F(5), one F(7), two equivalent F(3), and two equivalent F(6) atoms to form distorted KF8 hexagonal bipyramids that share  a cornercorner with one Tl(1)F7 pentagonal bipyramid, edges with two equivalent K(1)F8 hexagonal bipyramids, edges with three equivalent Tl(1)F7 pentagonal bipyramids, and edges with three equivalent Tl(2)F7 pentagonal bipyramids. In the second K site, K(2) is bonded in a 8-coordinate geometry to one F(1), one F(3), one F(5), one F(7), two equivalent F(4), and two equivalent F(8) atoms. There are two inequivalent Tl sites. In the first Tl site, Tl(1) is bonded to one F(1), one F(3), one F(4), one F(5), one F(6), one F(7), and one F(8) atom to form distorted TlF7 pentagonal bipyramids that share  a cornercorner with one K(1)F8 hexagonal bipyramid, corners with three equivalent Tl(2)F7 pentagonal bipyramids, edges with three equivalent K(1)F8 hexagonal bipyramids, and  an edgeedge with one Tl(2)F7 pentagonal bipyramid. In the second Tl site, Tl(2) is bonded to one F(1), one F(5), one F(6), one F(7), one F(8), and two equivalent F(2) atoms to form TlF7 pentagonal bipyramids that share corners with two equivalent Tl(2)F7 pentagonal bipyramids, corners with three equivalent Tl(1)F7 pentagonal bipyramids, edges with three equivalent K(1)F8 hexagonal bipyramids, and  an edgeedge with one Tl(1)F7 pentagonal bipyramid. There are eight inequivalent F sites. In the first F site, F(8) is bonded to two equivalent K(2), one Tl(1), and one Tl(2) atom to form distorted FK2Tl2 tetrahedra that share  a cornercorner with one F(4)K3Tl tetrahedra, corners with two equivalent F(8)K2Tl2 tetrahedra, corners with three equivalent F(3)K3Tl tetrahedra, corners with four equivalent F(7)K2Tl2 trigonal pyramids,  an edgeedge with one F(6)K2Tl2 tetrahedra, edges with two equivalent F(4)K3Tl tetrahedra, and edges with two equivalent F(5)K2Tl2 trigonal pyramids. In the second F site, F(1) is bonded in a 3-coordinate geometry to one K(2), one Tl(1), and one Tl(2) atom. In the third F site, F(2) is bonded in a distorted trigonal non-coplanar geometry to one K(1) and two equivalent Tl(2) atoms. In the fourth F site, F(3) is bonded to one K(2), two equivalent K(1), and one Tl(1) atom to form FK3Tl tetrahedra that share  a cornercorner with one F(6)K2Tl2 tetrahedra, corners with two equivalent F(3)K3Tl tetrahedra, corners with three equivalent F(8)K2Tl2 tetrahedra, corners with three equivalent F(4)K3Tl tetrahedra, corners with four equivalent F(7)K2Tl2 trigonal pyramids,  an edgeedge with one F(4)K3Tl tetrahedra, edges with two equivalent F(6)K2Tl2 tetrahedra, and edges with two equivalent F(5)K2Tl2 trigonal pyramids. In the fifth F site, F(4) is bonded to one K(1), two equivalent K(2), and one Tl(1) atom to form distorted FK3Tl tetrahedra that share  a cornercorner with one F(8)K2Tl2 tetrahedra, corners with two equivalent F(4)K3Tl tetrahedra, corners with three equivalent F(6)K2Tl2 tetrahedra, corners with three equivalent F(3)K3Tl tetrahedra, corners with four equivalent F(5)K2Tl2 trigonal pyramids,  an edgeedge with one F(3)K3Tl tetrahedra, edges with two equivalent F(8)K2Tl2 tetrahedra, and edges with two equivalent F(7)K2Tl2 trigonal pyramids. In the sixth F site, F(5) is bonded to one K(1), one K(2), one Tl(1), and one Tl(2) atom to form distorted FK2Tl2 trigonal pyramids that share corners with four equivalent F(6)K2Tl2 tetrahedra, corners with four equivalent F(4)K3Tl tetrahedra, corners with four equivalent F(7)K2Tl2 trigonal pyramids, edges with two equivalent F(8)K2Tl2 tetrahedra, and edges with two equivalent F(3)K3Tl tetrahedra. In the seventh F site, F(6) is bonded to two equivalent K(1), one Tl(1), and one Tl(2) atom to form FK2Tl2 tetrahedra that share  a cornercorner with one F(3)K3Tl tetrahedra, corners with two equivalent F(6)K2Tl2 tetrahedra, corners with three equivalent F(4)K3Tl tetrahedra, corners with four equivalent F(5)K2Tl2 trigonal pyramids,  an edgeedge with one F(8)K2Tl2 tetrahedra, edges with two equivalent F(3)K3Tl tetrahedra, and edges with two equivalent F(7)K2Tl2 trigonal pyramids. In the eighth F site, F(7) is bonded to one K(1), one K(2), one Tl(1), and one Tl(2) atom to form distorted FK2Tl2 trigonal pyramids that share corners with four equivalent F(8)K2Tl2 tetrahedra, corners with four equivalent F(3)K3Tl tetrahedra, corners with four equivalent F(5)K2Tl2 trigonal pyramids, edges with two equivalent F(6)K2Tl2 tetrahedra, and edges with two equivalent F(4)K3Tl tetrahedra.
KTlF4 crystallizes in the trigonal P3_1 space group. There are two inequivalent K sites. In the first K site, K(1) is bonded to one F(2), one F(4), one F(5), one F(7), two equivalent F(3), and two equivalent F(6) atoms to form distorted KF8 hexagonal bipyramids that share  a cornercorner with one Tl(1)F7 pentagonal bipyramid, edges with two equivalent K(1)F8 hexagonal bipyramids, edges with three equivalent Tl(1)F7 pentagonal bipyramids, and edges with three equivalent Tl(2)F7 pentagonal bipyramids. The K(1)-F(2) bond length is 2.79 Å. The K(1)-F(4) bond length is 2.60 Å. The K(1)-F(5) bond length is 2.87 Å. The K(1)-F(7) bond length is 2.82 Å. There is one shorter (2.55 Å) and one longer (2.61 Å) K(1)-F(3) bond length. There is one shorter (2.58 Å) and one longer (2.84 Å) K(1)-F(6) bond length. In the second K site, K(2) is bonded in a 8-coordinate geometry to one F(1), one F(3), one F(5), one F(7), two equivalent F(4), and two equivalent F(8) atoms. The K(2)-F(1) bond length is 3.01 Å. The K(2)-F(3) bond length is 2.63 Å. The K(2)-F(5) bond length is 2.91 Å. The K(2)-F(7) bond length is 2.80 Å. There is one shorter (2.64 Å) and one longer (2.66 Å) K(2)-F(4) bond length. There is one shorter (2.59 Å) and one longer (2.88 Å) K(2)-F(8) bond length. There are two inequivalent Tl sites. In the first Tl site, Tl(1) is bonded to one F(1), one F(3), one F(4), one F(5), one F(6), one F(7), and one F(8) atom to form distorted TlF7 pentagonal bipyramids that share  a cornercorner with one K(1)F8 hexagonal bipyramid, corners with three equivalent Tl(2)F7 pentagonal bipyramids, edges with three equivalent K(1)F8 hexagonal bipyramids, and  an edgeedge with one Tl(2)F7 pentagonal bipyramid. The Tl(1)-F(1) bond length is 2.22 Å. The Tl(1)-F(3) bond length is 2.11 Å. The Tl(1)-F(4) bond length is 2.11 Å. The Tl(1)-F(5) bond length is 2.31 Å. The Tl(1)-F(6) bond length is 2.24 Å. The Tl(1)-F(7) bond length is 2.35 Å. The Tl(1)-F(8) bond length is 2.30 Å. In the second Tl site, Tl(2) is bonded to one F(1), one F(5), one F(6), one F(7), one F(8), and two equivalent F(2) atoms to form TlF7 pentagonal bipyramids that share corners with two equivalent Tl(2)F7 pentagonal bipyramids, corners with three equivalent Tl(1)F7 pentagonal bipyramids, edges with three equivalent K(1)F8 hexagonal bipyramids, and  an edgeedge with one Tl(1)F7 pentagonal bipyramid. The Tl(2)-F(1) bond length is 2.18 Å. The Tl(2)-F(5) bond length is 2.20 Å. The Tl(2)-F(6) bond length is 2.26 Å. The Tl(2)-F(7) bond length is 2.20 Å. The Tl(2)-F(8) bond length is 2.26 Å. There is one shorter (2.25 Å) and one longer (2.30 Å) Tl(2)-F(2) bond length. There are eight inequivalent F sites. In the first F site, F(8) is bonded to two equivalent K(2), one Tl(1), and one Tl(2) atom to form distorted FK2Tl2 tetrahedra that share  a cornercorner with one F(4)K3Tl tetrahedra, corners with two equivalent F(8)K2Tl2 tetrahedra, corners with three equivalent F(3)K3Tl tetrahedra, corners with four equivalent F(7)K2Tl2 trigonal pyramids,  an edgeedge with one F(6)K2Tl2 tetrahedra, edges with two equivalent F(4)K3Tl tetrahedra, and edges with two equivalent F(5)K2Tl2 trigonal pyramids. In the second F site, F(1) is bonded in a 3-coordinate geometry to one K(2), one Tl(1), and one Tl(2) atom. In the third F site, F(2) is bonded in a distorted trigonal non-coplanar geometry to one K(1) and two equivalent Tl(2) atoms. In the fourth F site, F(3) is bonded to one K(2), two equivalent K(1), and one Tl(1) atom to form FK3Tl tetrahedra that share  a cornercorner with one F(6)K2Tl2 tetrahedra, corners with two equivalent F(3)K3Tl tetrahedra, corners with three equivalent F(8)K2Tl2 tetrahedra, corners with three equivalent F(4)K3Tl tetrahedra, corners with four equivalent F(7)K2Tl2 trigonal pyramids,  an edgeedge with one F(4)K3Tl tetrahedra, edges with two equivalent F(6)K2Tl2 tetrahedra, and edges with two equivalent F(5)K2Tl2 trigonal pyramids. In the fifth F site, F(4) is bonded to one K(1), two equivalent K(2), and one Tl(1) atom to form distorted FK3Tl tetrahedra that share  a cornercorner with one F(8)K2Tl2 tetrahedra, corners with two equivalent F(4)K3Tl tetrahedra, corners with three equivalent F(6)K2Tl2 tetrahedra, corners with three equivalent F(3)K3Tl tetrahedra, corners with four equivalent F(5)K2Tl2 trigonal pyramids,  an edgeedge with one F(3)K3Tl tetrahedra, edges with two equivalent F(8)K2Tl2 tetrahedra, and edges with two equivalent F(7)K2Tl2 trigonal pyramids. In the sixth F site, F(5) is bonded to one K(1), one K(2), one Tl(1), and one Tl(2) atom to form distorted FK2Tl2 trigonal pyramids that share corners with four equivalent F(6)K2Tl2 tetrahedra, corners with four equivalent F(4)K3Tl tetrahedra, corners with four equivalent F(7)K2Tl2 trigonal pyramids, edges with two equivalent F(8)K2Tl2 tetrahedra, and edges with two equivalent F(3)K3Tl tetrahedra. In the seventh F site, F(6) is bonded to two equivalent K(1), one Tl(1), and one Tl(2) atom to form FK2Tl2 tetrahedra that share  a cornercorner with one F(3)K3Tl tetrahedra, corners with two equivalent F(6)K2Tl2 tetrahedra, corners with three equivalent F(4)K3Tl tetrahedra, corners with four equivalent F(5)K2Tl2 trigonal pyramids,  an edgeedge with one F(8)K2Tl2 tetrahedra, edges with two equivalent F(3)K3Tl tetrahedra, and edges with two equivalent F(7)K2Tl2 trigonal pyramids. In the eighth F site, F(7) is bonded to one K(1), one K(2), one Tl(1), and one Tl(2) atom to form distorted FK2Tl2 trigonal pyramids that share corners with four equivalent F(8)K2Tl2 tetrahedra, corners with four equivalent F(3)K3Tl tetrahedra, corners with four equivalent F(5)K2Tl2 trigonal pyramids, edges with two equivalent F(6)K2Tl2 tetrahedra, and edges with two equivalent F(4)K3Tl tetrahedra.