K3Al4P2O8F9 crystallizes in the monoclinic P2_1/m space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 7-coordinate geometry to one O(1), one O(3), one O(4), one F(3), one F(6), and two equivalent F(2) atoms. In the second K site, K(2) is bonded in a 9-coordinate geometry to two equivalent O(1), two equivalent O(2), one F(1), one F(4), one F(5), and two equivalent F(2) atoms. There are three inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(2), one O(4), one F(2), one F(3), one F(4), and one F(6) atom to form AlO2F4 octahedra that share  a cornercorner with one Al(1)O2F4 octahedra,  a cornercorner with one Al(2)O2F4 octahedra,  a cornercorner with one Al(3)O2F4 octahedra, and corners with two equivalent P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 33-35°. In the second Al site, Al(2) is bonded to two equivalent O(1), one F(1), one F(5), and two equivalent F(3) atoms to form AlO2F4 octahedra that share corners with two equivalent Al(1)O2F4 octahedra, corners with two equivalent Al(3)O2F4 octahedra, and corners with two equivalent P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 35-50°. In the third Al site, Al(3) is bonded to two equivalent O(3), one F(1), one F(5), and two equivalent F(6) atoms to form AlO2F4 octahedra that share corners with two equivalent Al(1)O2F4 octahedra, corners with two equivalent Al(2)O2F4 octahedra, and corners with two equivalent P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 35-50°. P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share  a cornercorner with one Al(2)O2F4 octahedra,  a cornercorner with one Al(3)O2F4 octahedra, and corners with two equivalent Al(1)O2F4 octahedra. The corner-sharing octahedral tilt angles range from 40-45°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one K(1), one K(2), one Al(2), and one P(1) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one K(2), one Al(1), and one P(1) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one K(1), one Al(3), and one P(1) atom. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to one K(1), one Al(1), and one P(1) atom. There are six inequivalent F sites. In the first F site, F(1) is bonded in a distorted bent 150 degrees geometry to one K(2), one Al(2), and one Al(3) atom. In the second F site, F(2) is bonded in a distorted single-bond geometry to one K(2), two equivalent K(1), and one Al(1) atom. In the third F site, F(3) is bonded in a bent 150 degrees geometry to one K(1), one Al(1), and one Al(2) atom. In the fourth F site, F(4) is bonded in a bent 150 degrees geometry to one K(2) and two equivalent Al(1) atoms. In the fifth F site, F(5) is bonded in a distorted trigonal planar geometry to one K(2), one Al(2), and one Al(3) atom. In the sixth F site, F(6) is bonded in a bent 150 degrees geometry to one K(1), one Al(1), and one Al(3) atom.
K3Al4P2O8F9 crystallizes in the monoclinic P2_1/m space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 7-coordinate geometry to one O(1), one O(3), one O(4), one F(3), one F(6), and two equivalent F(2) atoms. The K(1)-O(1) bond length is 2.99 Å. The K(1)-O(3) bond length is 2.88 Å. The K(1)-O(4) bond length is 2.99 Å. The K(1)-F(3) bond length is 3.19 Å. The K(1)-F(6) bond length is 3.27 Å. There is one shorter (2.69 Å) and one longer (2.90 Å) K(1)-F(2) bond length. In the second K site, K(2) is bonded in a 9-coordinate geometry to two equivalent O(1), two equivalent O(2), one F(1), one F(4), one F(5), and two equivalent F(2) atoms. Both K(2)-O(1) bond lengths are 2.82 Å. Both K(2)-O(2) bond lengths are 3.17 Å. The K(2)-F(1) bond length is 3.11 Å. The K(2)-F(4) bond length is 2.93 Å. The K(2)-F(5) bond length is 2.81 Å. Both K(2)-F(2) bond lengths are 2.74 Å. There are three inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(2), one O(4), one F(2), one F(3), one F(4), and one F(6) atom to form AlO2F4 octahedra that share  a cornercorner with one Al(1)O2F4 octahedra,  a cornercorner with one Al(2)O2F4 octahedra,  a cornercorner with one Al(3)O2F4 octahedra, and corners with two equivalent P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 33-35°. The Al(1)-O(2) bond length is 1.86 Å. The Al(1)-O(4) bond length is 1.86 Å. The Al(1)-F(2) bond length is 1.79 Å. The Al(1)-F(3) bond length is 1.91 Å. The Al(1)-F(4) bond length is 1.87 Å. The Al(1)-F(6) bond length is 1.89 Å. In the second Al site, Al(2) is bonded to two equivalent O(1), one F(1), one F(5), and two equivalent F(3) atoms to form AlO2F4 octahedra that share corners with two equivalent Al(1)O2F4 octahedra, corners with two equivalent Al(3)O2F4 octahedra, and corners with two equivalent P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 35-50°. Both Al(2)-O(1) bond lengths are 1.86 Å. The Al(2)-F(1) bond length is 1.83 Å. The Al(2)-F(5) bond length is 1.85 Å. Both Al(2)-F(3) bond lengths are 1.86 Å. In the third Al site, Al(3) is bonded to two equivalent O(3), one F(1), one F(5), and two equivalent F(6) atoms to form AlO2F4 octahedra that share corners with two equivalent Al(1)O2F4 octahedra, corners with two equivalent Al(2)O2F4 octahedra, and corners with two equivalent P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 35-50°. Both Al(3)-O(3) bond lengths are 1.83 Å. The Al(3)-F(1) bond length is 1.84 Å. The Al(3)-F(5) bond length is 1.86 Å. Both Al(3)-F(6) bond lengths are 1.87 Å. P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share  a cornercorner with one Al(2)O2F4 octahedra,  a cornercorner with one Al(3)O2F4 octahedra, and corners with two equivalent Al(1)O2F4 octahedra. The corner-sharing octahedral tilt angles range from 40-45°. The P(1)-O(1) bond length is 1.56 Å. The P(1)-O(2) bond length is 1.54 Å. The P(1)-O(3) bond length is 1.54 Å. The P(1)-O(4) bond length is 1.55 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one K(1), one K(2), one Al(2), and one P(1) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one K(2), one Al(1), and one P(1) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one K(1), one Al(3), and one P(1) atom. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to one K(1), one Al(1), and one P(1) atom. There are six inequivalent F sites. In the first F site, F(1) is bonded in a distorted bent 150 degrees geometry to one K(2), one Al(2), and one Al(3) atom. In the second F site, F(2) is bonded in a distorted single-bond geometry to one K(2), two equivalent K(1), and one Al(1) atom. In the third F site, F(3) is bonded in a bent 150 degrees geometry to one K(1), one Al(1), and one Al(2) atom. In the fourth F site, F(4) is bonded in a bent 150 degrees geometry to one K(2) and two equivalent Al(1) atoms. In the fifth F site, F(5) is bonded in a distorted trigonal planar geometry to one K(2), one Al(2), and one Al(3) atom. In the sixth F site, F(6) is bonded in a bent 150 degrees geometry to one K(1), one Al(1), and one Al(3) atom.