K2HfF6 crystallizes in the monoclinic Pm space group. There are twelve inequivalent K sites. In the first K site, K(1) is bonded in a 3-coordinate geometry to one F(24) and two equivalent F(4) atoms. In the second K site, K(2) is bonded in a 7-coordinate geometry to one F(14), two equivalent F(1), two equivalent F(11), and two equivalent F(5) atoms. In the third K site, K(3) is bonded in a 2-coordinate geometry to one F(20) and one F(7) atom. In the fourth K site, K(4) is bonded in a 3-coordinate geometry to one F(7) and two equivalent F(4) atoms. In the fifth K site, K(5) is bonded in a 9-coordinate geometry to one F(19), two equivalent F(10), two equivalent F(12), two equivalent F(3), and two equivalent F(9) atoms. In the sixth K site, K(6) is bonded in a 5-coordinate geometry to one F(23), two equivalent F(3), and two equivalent F(4) atoms. In the seventh K site, K(7) is bonded to one F(12), one F(24), two equivalent F(10), two equivalent F(16), two equivalent F(19), two equivalent F(21), and two equivalent F(9) atoms to form distorted KF12 cuboctahedra that share corners with two equivalent K(7)F12 cuboctahedra, corners with two equivalent K(11)F5 square pyramids,  a faceface with one Hf(3)F6 octahedra,  a faceface with one Hf(6)F6 octahedra, and faces with two equivalent Hf(5)F6 octahedra. In the eighth K site, K(8) is bonded in a 4-coordinate geometry to one F(14), one F(23), and two equivalent F(16) atoms. In the ninth K site, K(9) is bonded in a 5-coordinate geometry to one F(6), two equivalent F(16), and two equivalent F(4) atoms. In the tenth K site, K(10) is bonded in a 9-coordinate geometry to one F(18), two equivalent F(14), two equivalent F(17), two equivalent F(5), and two equivalent F(9) atoms. In the eleventh K site, K(11) is bonded to one F(20), two equivalent F(15), and two equivalent F(21) atoms to form distorted KF5 square pyramids that share corners with two equivalent K(7)F12 cuboctahedra, corners with two equivalent Hf(1)F6 octahedra, and corners with two equivalent Hf(6)F6 octahedra. The corner-sharing octahedral tilt angles range from 56-59°. In the twelfth K site, K(12) is bonded in a 9-coordinate geometry to one F(13), two equivalent F(10), two equivalent F(15), two equivalent F(17), and two equivalent F(21) atoms. There are six inequivalent Hf sites. In the first Hf site, Hf(1) is bonded to one F(22), one F(23), two equivalent F(15), and two equivalent F(2) atoms to form HfF6 octahedra that share  a cornercorner with one Hf(6)F6 octahedra, corners with two equivalent Hf(2)F6 octahedra, and corners with two equivalent K(11)F5 square pyramids. The corner-sharing octahedral tilt angles range from 4-11°. In the second Hf site, Hf(2) is bonded to one F(6), one F(8), two equivalent F(11), and two equivalent F(2) atoms to form distorted corner-sharing HfF6 octahedra. The corner-sharing octahedral tilt angles are 11°. In the third Hf site, Hf(3) is bonded to one F(12), one F(13), two equivalent F(10), and two equivalent F(3) atoms to form HfF6 octahedra that share  a cornercorner with one Hf(4)F6 octahedra and  a faceface with one K(7)F12 cuboctahedra. The corner-sharing octahedral tilt angles are 1°. In the fourth Hf site, Hf(4) is bonded to one F(13), one F(14), two equivalent F(17), and two equivalent F(5) atoms to form corner-sharing HfF6 octahedra. The corner-sharing octahedral tilt angles are 1°. In the fifth Hf site, Hf(5) is bonded to one F(18), one F(19), two equivalent F(16), and two equivalent F(9) atoms to form HfF6 octahedra that share faces with two equivalent K(7)F12 cuboctahedra. In the sixth Hf site, Hf(6) is bonded to one F(22), one F(24), two equivalent F(1), and two equivalent F(21) atoms to form HfF6 octahedra that share  a cornercorner with one Hf(1)F6 octahedra, corners with two equivalent K(11)F5 square pyramids, and  a faceface with one K(7)F12 cuboctahedra. The corner-sharing octahedral tilt angles are 4°. There are twenty-four inequivalent F sites. In the first F site, F(1) is bonded in a distorted single-bond geometry to one K(2) and one Hf(6) atom. In the second F site, F(2) is bonded in a linear geometry to one Hf(1) and one Hf(2) atom. In the third F site, F(3) is bonded in a distorted single-bond geometry to one K(5), one K(6), and one Hf(3) atom. In the fourth F site, F(4) is bonded in a rectangular see-saw-like geometry to one K(1), one K(4), one K(6), and one K(9) atom. In the fifth F site, F(5) is bonded in a distorted single-bond geometry to one K(10), one K(2), and one Hf(4) atom. In the sixth F site, F(6) is bonded in a distorted single-bond geometry to one K(9) and one Hf(2) atom. In the seventh F site, F(7) is bonded in a linear geometry to one K(3) and one K(4) atom. In the eighth F site, F(8) is bonded in a single-bond geometry to one Hf(2) atom. In the ninth F site, F(9) is bonded in a distorted single-bond geometry to one K(10), one K(5), one K(7), and one Hf(5) atom. In the tenth F site, F(10) is bonded in a 1-coordinate geometry to one K(12), one K(5), one K(7), and one Hf(3) atom. In the eleventh F site, F(11) is bonded in a distorted single-bond geometry to one K(2) and one Hf(2) atom. In the twelfth F site, F(12) is bonded in a distorted single-bond geometry to one K(7), two equivalent K(5), and one Hf(3) atom. In the thirteenth F site, F(13) is bonded in a distorted linear geometry to one K(12), one Hf(3), and one Hf(4) atom. In the fourteenth F site, F(14) is bonded in a distorted single-bond geometry to one K(2), one K(8), two equivalent K(10), and one Hf(4) atom. In the fifteenth F site, F(15) is bonded in a distorted single-bond geometry to one K(11), one K(12), and one Hf(1) atom. In the sixteenth F site, F(16) is bonded in a 4-coordinate geometry to one K(7), one K(8), one K(9), and one Hf(5) atom. In the seventeenth F site, F(17) is bonded in a distorted single-bond geometry to one K(10), one K(12), and one Hf(4) atom. In the eighteenth F site, F(18) is bonded in a distorted water-like geometry to one K(10) and one Hf(5) atom. In the nineteenth F site, F(19) is bonded in a distorted water-like geometry to one K(5), two equivalent K(7), and one Hf(5) atom. In the twentieth F site, F(20) is bonded in a distorted linear geometry to one K(11) and one K(3) atom. In the twenty-first F site, F(21) is bonded in a 2-coordinate geometry to one K(11), one K(12), one K(7), and one Hf(6) atom. In the twenty-second F site, F(22) is bonded in a linear geometry to one Hf(1) and one Hf(6) atom. In the twenty-third F site, F(23) is bonded in a distorted single-bond geometry to one K(6), one K(8), and one Hf(1) atom. In the twenty-fourth F site, F(24) is bonded in a distorted single-bond geometry to one K(1), one K(7), and one Hf(6) atom.
K2HfF6 crystallizes in the monoclinic Pm space group. There are twelve inequivalent K sites. In the first K site, K(1) is bonded in a 3-coordinate geometry to one F(24) and two equivalent F(4) atoms. The K(1)-F(24) bond length is 2.81 Å. Both K(1)-F(4) bond lengths are 2.51 Å. In the second K site, K(2) is bonded in a 7-coordinate geometry to one F(14), two equivalent F(1), two equivalent F(11), and two equivalent F(5) atoms. The K(2)-F(14) bond length is 3.09 Å. Both K(2)-F(1) bond lengths are 2.83 Å. Both K(2)-F(11) bond lengths are 3.03 Å. Both K(2)-F(5) bond lengths are 2.74 Å. In the third K site, K(3) is bonded in a 2-coordinate geometry to one F(20) and one F(7) atom. The K(3)-F(20) bond length is 2.53 Å. The K(3)-F(7) bond length is 2.45 Å. In the fourth K site, K(4) is bonded in a 3-coordinate geometry to one F(7) and two equivalent F(4) atoms. The K(4)-F(7) bond length is 2.39 Å. Both K(4)-F(4) bond lengths are 2.54 Å. In the fifth K site, K(5) is bonded in a 9-coordinate geometry to one F(19), two equivalent F(10), two equivalent F(12), two equivalent F(3), and two equivalent F(9) atoms. The K(5)-F(19) bond length is 2.65 Å. Both K(5)-F(10) bond lengths are 2.78 Å. Both K(5)-F(12) bond lengths are 3.27 Å. Both K(5)-F(3) bond lengths are 3.17 Å. Both K(5)-F(9) bond lengths are 3.27 Å. In the sixth K site, K(6) is bonded in a 5-coordinate geometry to one F(23), two equivalent F(3), and two equivalent F(4) atoms. The K(6)-F(23) bond length is 2.72 Å. Both K(6)-F(3) bond lengths are 2.88 Å. Both K(6)-F(4) bond lengths are 2.46 Å. In the seventh K site, K(7) is bonded to one F(12), one F(24), two equivalent F(10), two equivalent F(16), two equivalent F(19), two equivalent F(21), and two equivalent F(9) atoms to form distorted KF12 cuboctahedra that share corners with two equivalent K(7)F12 cuboctahedra, corners with two equivalent K(11)F5 square pyramids,  a faceface with one Hf(3)F6 octahedra,  a faceface with one Hf(6)F6 octahedra, and faces with two equivalent Hf(5)F6 octahedra. The K(7)-F(12) bond length is 3.09 Å. The K(7)-F(24) bond length is 3.21 Å. Both K(7)-F(10) bond lengths are 3.31 Å. Both K(7)-F(16) bond lengths are 3.04 Å. Both K(7)-F(19) bond lengths are 3.24 Å. Both K(7)-F(21) bond lengths are 3.14 Å. Both K(7)-F(9) bond lengths are 2.97 Å. In the eighth K site, K(8) is bonded in a 4-coordinate geometry to one F(14), one F(23), and two equivalent F(16) atoms. The K(8)-F(14) bond length is 2.89 Å. The K(8)-F(23) bond length is 3.08 Å. Both K(8)-F(16) bond lengths are 2.77 Å. In the ninth K site, K(9) is bonded in a 5-coordinate geometry to one F(6), two equivalent F(16), and two equivalent F(4) atoms. The K(9)-F(6) bond length is 2.86 Å. Both K(9)-F(16) bond lengths are 3.11 Å. Both K(9)-F(4) bond lengths are 2.44 Å. In the tenth K site, K(10) is bonded in a 9-coordinate geometry to one F(18), two equivalent F(14), two equivalent F(17), two equivalent F(5), and two equivalent F(9) atoms. The K(10)-F(18) bond length is 2.67 Å. Both K(10)-F(14) bond lengths are 3.25 Å. Both K(10)-F(17) bond lengths are 2.94 Å. Both K(10)-F(5) bond lengths are 2.83 Å. Both K(10)-F(9) bond lengths are 3.21 Å. In the eleventh K site, K(11) is bonded to one F(20), two equivalent F(15), and two equivalent F(21) atoms to form distorted KF5 square pyramids that share corners with two equivalent K(7)F12 cuboctahedra, corners with two equivalent Hf(1)F6 octahedra, and corners with two equivalent Hf(6)F6 octahedra. The corner-sharing octahedral tilt angles range from 56-59°. The K(11)-F(20) bond length is 2.37 Å. Both K(11)-F(15) bond lengths are 2.82 Å. Both K(11)-F(21) bond lengths are 2.58 Å. In the twelfth K site, K(12) is bonded in a 9-coordinate geometry to one F(13), two equivalent F(10), two equivalent F(15), two equivalent F(17), and two equivalent F(21) atoms. The K(12)-F(13) bond length is 2.96 Å. Both K(12)-F(10) bond lengths are 2.84 Å. Both K(12)-F(15) bond lengths are 2.90 Å. Both K(12)-F(17) bond lengths are 3.14 Å. Both K(12)-F(21) bond lengths are 3.13 Å. There are six inequivalent Hf sites. In the first Hf site, Hf(1) is bonded to one F(22), one F(23), two equivalent F(15), and two equivalent F(2) atoms to form HfF6 octahedra that share  a cornercorner with one Hf(6)F6 octahedra, corners with two equivalent Hf(2)F6 octahedra, and corners with two equivalent K(11)F5 square pyramids. The corner-sharing octahedral tilt angles range from 4-11°. The Hf(1)-F(22) bond length is 2.03 Å. The Hf(1)-F(23) bond length is 1.95 Å. Both Hf(1)-F(15) bond lengths are 1.94 Å. Both Hf(1)-F(2) bond lengths are 2.08 Å. In the second Hf site, Hf(2) is bonded to one F(6), one F(8), two equivalent F(11), and two equivalent F(2) atoms to form distorted corner-sharing HfF6 octahedra. The corner-sharing octahedral tilt angles are 11°. The Hf(2)-F(6) bond length is 1.96 Å. The Hf(2)-F(8) bond length is 1.93 Å. Both Hf(2)-F(11) bond lengths are 1.94 Å. Both Hf(2)-F(2) bond lengths are 2.26 Å. In the third Hf site, Hf(3) is bonded to one F(12), one F(13), two equivalent F(10), and two equivalent F(3) atoms to form HfF6 octahedra that share  a cornercorner with one Hf(4)F6 octahedra and  a faceface with one K(7)F12 cuboctahedra. The corner-sharing octahedral tilt angles are 1°. The Hf(3)-F(12) bond length is 1.95 Å. The Hf(3)-F(13) bond length is 2.24 Å. Both Hf(3)-F(10) bond lengths are 2.00 Å. Both Hf(3)-F(3) bond lengths are 1.98 Å. In the fourth Hf site, Hf(4) is bonded to one F(13), one F(14), two equivalent F(17), and two equivalent F(5) atoms to form corner-sharing HfF6 octahedra. The corner-sharing octahedral tilt angles are 1°. The Hf(4)-F(13) bond length is 2.20 Å. The Hf(4)-F(14) bond length is 1.96 Å. Both Hf(4)-F(17) bond lengths are 1.98 Å. Both Hf(4)-F(5) bond lengths are 1.99 Å. In the fifth Hf site, Hf(5) is bonded to one F(18), one F(19), two equivalent F(16), and two equivalent F(9) atoms to form HfF6 octahedra that share faces with two equivalent K(7)F12 cuboctahedra. The Hf(5)-F(18) bond length is 2.01 Å. The Hf(5)-F(19) bond length is 1.99 Å. Both Hf(5)-F(16) bond lengths are 2.00 Å. Both Hf(5)-F(9) bond lengths are 2.02 Å. In the sixth Hf site, Hf(6) is bonded to one F(22), one F(24), two equivalent F(1), and two equivalent F(21) atoms to form HfF6 octahedra that share  a cornercorner with one Hf(1)F6 octahedra, corners with two equivalent K(11)F5 square pyramids, and  a faceface with one K(7)F12 cuboctahedra. The corner-sharing octahedral tilt angles are 4°. The Hf(6)-F(22) bond length is 2.23 Å. The Hf(6)-F(24) bond length is 1.94 Å. Both Hf(6)-F(1) bond lengths are 1.98 Å. Both Hf(6)-F(21) bond lengths are 2.00 Å. There are twenty-four inequivalent F sites. In the first F site, F(1) is bonded in a distorted single-bond geometry to one K(2) and one Hf(6) atom. In the second F site, F(2) is bonded in a linear geometry to one Hf(1) and one Hf(2) atom. In the third F site, F(3) is bonded in a distorted single-bond geometry to one K(5), one K(6), and one Hf(3) atom. In the fourth F site, F(4) is bonded in a rectangular see-saw-like geometry to one K(1), one K(4), one K(6), and one K(9) atom. In the fifth F site, F(5) is bonded in a distorted single-bond geometry to one K(10), one K(2), and one Hf(4) atom. In the sixth F site, F(6) is bonded in a distorted single-bond geometry to one K(9) and one Hf(2) atom. In the seventh F site, F(7) is bonded in a linear geometry to one K(3) and one K(4) atom. In the eighth F site, F(8) is bonded in a single-bond geometry to one Hf(2) atom. In the ninth F site, F(9) is bonded in a distorted single-bond geometry to one K(10), one K(5), one K(7), and one Hf(5) atom. In the tenth F site, F(10) is bonded in a 1-coordinate geometry to one K(12), one K(5), one K(7), and one Hf(3) atom. In the eleventh F site, F(11) is bonded in a distorted single-bond geometry to one K(2) and one Hf(2) atom. In the twelfth F site, F(12) is bonded in a distorted single-bond geometry to one K(7), two equivalent K(5), and one Hf(3) atom. In the thirteenth F site, F(13) is bonded in a distorted linear geometry to one K(12), one Hf(3), and one Hf(4) atom. In the fourteenth F site, F(14) is bonded in a distorted single-bond geometry to one K(2), one K(8), two equivalent K(10), and one Hf(4) atom. In the fifteenth F site, F(15) is bonded in a distorted single-bond geometry to one K(11), one K(12), and one Hf(1) atom. In the sixteenth F site, F(16) is bonded in a 4-coordinate geometry to one K(7), one K(8), one K(9), and one Hf(5) atom. In the seventeenth F site, F(17) is bonded in a distorted single-bond geometry to one K(10), one K(12), and one Hf(4) atom. In the eighteenth F site, F(18) is bonded in a distorted water-like geometry to one K(10) and one Hf(5) atom. In the nineteenth F site, F(19) is bonded in a distorted water-like geometry to one K(5), two equivalent K(7), and one Hf(5) atom. In the twentieth F site, F(20) is bonded in a distorted linear geometry to one K(11) and one K(3) atom. In the twenty-first F site, F(21) is bonded in a 2-coordinate geometry to one K(11), one K(12), one K(7), and one Hf(6) atom. In the twenty-second F site, F(22) is bonded in a linear geometry to one Hf(1) and one Hf(6) atom. In the twenty-third F site, F(23) is bonded in a distorted single-bond geometry to one K(6), one K(8), and one Hf(1) atom. In the twenty-fourth F site, F(24) is bonded in a distorted single-bond geometry to one K(1), one K(7), and one Hf(6) atom.