Ca2TiAlSi2O9F crystallizes in the triclinic P1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(6), one O(7), and one F(1) atom. In the second Ca site, Ca(2) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(8), and one O(9) atom. Ti(1) is bonded to one O(2), one O(4), one O(5), one O(7), one O(9), and one F(1) atom to form TiO5F octahedra that share corners with two equivalent Al(1)O5F octahedra, corners with two equivalent Si(1)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 38°. Al(1) is bonded to one O(1), one O(3), one O(6), one O(8), one O(9), and one F(1) atom to form AlO5F octahedra that share corners with two equivalent Ti(1)O5F octahedra, corners with two equivalent Si(1)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 38°. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(2), one O(3), one O(5), and one O(8) atom to form SiO4 tetrahedra that share corners with two equivalent Ti(1)O5F octahedra and corners with two equivalent Al(1)O5F octahedra. The corner-sharing octahedral tilt angles range from 38-56°. In the second Si site, Si(2) is bonded to one O(1), one O(4), one O(6), and one O(7) atom to form SiO4 tetrahedra that share corners with two equivalent Ti(1)O5F octahedra and corners with two equivalent Al(1)O5F octahedra. The corner-sharing octahedral tilt angles range from 30-51°. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Al(1), and one Si(2) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Ti(1), and one Si(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Al(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Ti(1), and one Si(2) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Ca(2), one Ti(1), and one Si(1) atom. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to one Ca(1), one Al(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted T-shaped geometry to one Ca(1), one Ti(1), and one Si(2) atom. In the eighth O site, O(8) is bonded in a distorted T-shaped geometry to one Ca(2), one Al(1), and one Si(1) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Ca(2), one Ti(1), and one Al(1) atom. F(1) is bonded in a distorted trigonal planar geometry to one Ca(1), one Ti(1), and one Al(1) atom.
Ca2TiAlSi2O9F crystallizes in the triclinic P1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(6), one O(7), and one F(1) atom. The Ca(1)-O(1) bond length is 2.40 Å. The Ca(1)-O(2) bond length is 2.66 Å. The Ca(1)-O(3) bond length is 2.63 Å. The Ca(1)-O(4) bond length is 2.44 Å. The Ca(1)-O(6) bond length is 2.37 Å. The Ca(1)-O(7) bond length is 2.40 Å. The Ca(1)-F(1) bond length is 2.29 Å. In the second Ca site, Ca(2) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(8), and one O(9) atom. The Ca(2)-O(1) bond length is 2.64 Å. The Ca(2)-O(2) bond length is 2.45 Å. The Ca(2)-O(3) bond length is 2.41 Å. The Ca(2)-O(4) bond length is 2.68 Å. The Ca(2)-O(5) bond length is 2.41 Å. The Ca(2)-O(8) bond length is 2.37 Å. The Ca(2)-O(9) bond length is 2.29 Å. Ti(1) is bonded to one O(2), one O(4), one O(5), one O(7), one O(9), and one F(1) atom to form TiO5F octahedra that share corners with two equivalent Al(1)O5F octahedra, corners with two equivalent Si(1)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 38°. The Ti(1)-O(2) bond length is 2.02 Å. The Ti(1)-O(4) bond length is 2.01 Å. The Ti(1)-O(5) bond length is 1.98 Å. The Ti(1)-O(7) bond length is 1.98 Å. The Ti(1)-O(9) bond length is 1.74 Å. The Ti(1)-F(1) bond length is 2.13 Å. Al(1) is bonded to one O(1), one O(3), one O(6), one O(8), one O(9), and one F(1) atom to form AlO5F octahedra that share corners with two equivalent Ti(1)O5F octahedra, corners with two equivalent Si(1)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 38°. The Al(1)-O(1) bond length is 1.95 Å. The Al(1)-O(3) bond length is 1.97 Å. The Al(1)-O(6) bond length is 1.92 Å. The Al(1)-O(8) bond length is 1.92 Å. The Al(1)-O(9) bond length is 1.84 Å. The Al(1)-F(1) bond length is 1.85 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(2), one O(3), one O(5), and one O(8) atom to form SiO4 tetrahedra that share corners with two equivalent Ti(1)O5F octahedra and corners with two equivalent Al(1)O5F octahedra. The corner-sharing octahedral tilt angles range from 38-56°. The Si(1)-O(2) bond length is 1.67 Å. The Si(1)-O(3) bond length is 1.65 Å. The Si(1)-O(5) bond length is 1.67 Å. The Si(1)-O(8) bond length is 1.64 Å. In the second Si site, Si(2) is bonded to one O(1), one O(4), one O(6), and one O(7) atom to form SiO4 tetrahedra that share corners with two equivalent Ti(1)O5F octahedra and corners with two equivalent Al(1)O5F octahedra. The corner-sharing octahedral tilt angles range from 30-51°. The Si(2)-O(1) bond length is 1.65 Å. The Si(2)-O(4) bond length is 1.66 Å. The Si(2)-O(6) bond length is 1.64 Å. The Si(2)-O(7) bond length is 1.66 Å. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Al(1), and one Si(2) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Ti(1), and one Si(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Al(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Ti(1), and one Si(2) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Ca(2), one Ti(1), and one Si(1) atom. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to one Ca(1), one Al(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted T-shaped geometry to one Ca(1), one Ti(1), and one Si(2) atom. In the eighth O site, O(8) is bonded in a distorted T-shaped geometry to one Ca(2), one Al(1), and one Si(1) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Ca(2), one Ti(1), and one Al(1) atom. F(1) is bonded in a distorted trigonal planar geometry to one Ca(1), one Ti(1), and one Al(1) atom.