The compound described by Ca2TiAlSi2O9F crystallizes in the triclinic P-1 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(3), one O(4), one O(5), one O(9), two equivalent O(2), 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(5), one O(7), one O(8), one O(9), and two equivalent O(6) atoms. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to two equivalent O(6), two equivalent O(7), and two equivalent O(8) atoms to form TiO6 octahedra that share corners with two equivalent Ti(2)O6 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°. In the second Ti site, Ti(2) is bonded to two equivalent O(3), two equivalent O(7), and two equivalent O(9) atoms to form TiO6 octahedra that share corners with two equivalent Ti(1)O6 octahedra and corners with four equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 38°. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent F(1) atoms to form AlO4F2 octahedra that share corners with two equivalent Al(2)O4F2 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 37°. In the second Al site, Al(2) is bonded to two equivalent O(1), two equivalent O(5), and two equivalent F(1) atoms to form AlO4F2 octahedra that share corners with two equivalent Al(1)O4F2 octahedra and corners with four equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 37°. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(5), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Ti(1)O6 octahedra,  a cornercorner with one Al(1)O4F2 octahedra, and corners with two equivalent Al(2)O4F2 octahedra. The corner-sharing octahedral tilt angles range from 34-52°. In the second Si site, Si(2) is bonded to one O(3), one O(4), one O(6), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Ti(1)O6 octahedra,  a cornercorner with one Al(1)O4F2 octahedra, and corners with two equivalent Ti(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 37-53°. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to one Ca(2), one Al(2), and one Si(1) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Ca(1), one Al(1), and one Si(1) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Ca(1), one Ti(2), and one Si(2) atom. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to one Ca(1), one Al(1), and one Si(2) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Al(2), and one Si(1) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to two equivalent Ca(2), one Ti(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Ca(2), one Ti(1), and one Ti(2) atom. In the eighth O site, O(8) is bonded in a distorted T-shaped geometry to one Ca(2), one Ti(1), and one Si(1) atom. In the ninth O site, O(9) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Ti(2), and one Si(2) atom. F(1) is bonded in a distorted trigonal planar geometry to one Ca(1), one Al(1), and one Al(2) atom. is represented by the CIF card [CIF]
data_Ca2TiAlSi2O9F
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.445
_cell_length_b   7.091
_cell_length_c   10.419
_cell_angle_alpha   106.501
_cell_angle_beta   94.111
_cell_angle_gamma   104.580
_symmetry_Int_Tables_number   1
_cell_volume   368.825
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
loop_
 _atom_site_type_symbol
 _atom_site_label
 _atom_site_symmetry_multiplicity
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_occupancy
  Ca  Ca0  1  0.998  0.584  0.835  1.0
  Ca  Ca1  1  0.504  0.084  0.332  1.0
  Ca  Ca2  1  0.002  0.416  0.165  1.0
  Ca  Ca3  1  0.496  0.916  0.668  1.0
  Ti  Ti4  1  0.000  0.000  0.500  1.0
  Ti  Ti5  1  0.000  0.500  0.500  1.0
  Al  Al6  1  0.500  0.500  0.000  1.0
  Al  Al7  1  0.500  0.000  0.000  1.0
  Si  Si8  1  0.027  0.093  0.848  1.0
  Si  Si9  1  0.524  0.590  0.335  1.0
  Si  Si10  1  0.973  0.907  0.152  1.0
  Si  Si11  1  0.476  0.410  0.665  1.0
  O  O12  1  0.251  0.021  0.117  1.0
  O  O13  1  0.146  0.335  0.948  1.0
  O  O14  1  0.746  0.537  0.628  1.0
  O  O15  1  0.441  0.591  0.181  1.0
  O  O16  1  0.239  0.962  0.852  1.0
  O  O17  1  0.628  0.826  0.441  1.0
  O  O18  1  0.761  0.038  0.148  1.0
  O  O19  1  0.559  0.409  0.819  1.0
  O  O20  1  0.893  0.216  0.467  1.0
  O  O21  1  0.944  0.095  0.692  1.0
  O  O22  1  0.733  0.459  0.340  1.0
  O  O23  1  0.854  0.665  0.052  1.0
  O  O24  1  0.267  0.541  0.660  1.0
  O  O25  1  0.056  0.905  0.308  1.0
  O  O26  1  0.749  0.979  0.883  1.0
  O  O27  1  0.107  0.784  0.533  1.0
  O  O28  1  0.372  0.174  0.559  1.0
  O  O29  1  0.254  0.463  0.372  1.0
  F  F30  1  0.400  0.715  0.964  1.0
  F  F31  1  0.600  0.285  0.036  1.0
[/CIF]
.
The compound described by Ca2TiAlSi2O9F crystallizes in the triclinic P-1 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(3), one O(4), one O(5), one O(9), two equivalent O(2), 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(5), one O(7), one O(8), one O(9), and two equivalent O(6) atoms. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to two equivalent O(6), two equivalent O(7), and two equivalent O(8) atoms to form TiO6 octahedra that share corners with two equivalent Ti(2)O6 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°. In the second Ti site, Ti(2) is bonded to two equivalent O(3), two equivalent O(7), and two equivalent O(9) atoms to form TiO6 octahedra that share corners with two equivalent Ti(1)O6 octahedra and corners with four equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 38°. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent F(1) atoms to form AlO4F2 octahedra that share corners with two equivalent Al(2)O4F2 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 37°. In the second Al site, Al(2) is bonded to two equivalent O(1), two equivalent O(5), and two equivalent F(1) atoms to form AlO4F2 octahedra that share corners with two equivalent Al(1)O4F2 octahedra and corners with four equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 37°. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(5), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Ti(1)O6 octahedra,  a cornercorner with one Al(1)O4F2 octahedra, and corners with two equivalent Al(2)O4F2 octahedra. The corner-sharing octahedral tilt angles range from 34-52°. In the second Si site, Si(2) is bonded to one O(3), one O(4), one O(6), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Ti(1)O6 octahedra,  a cornercorner with one Al(1)O4F2 octahedra, and corners with two equivalent Ti(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 37-53°. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to one Ca(2), one Al(2), and one Si(1) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Ca(1), one Al(1), and one Si(1) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Ca(1), one Ti(2), and one Si(2) atom. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to one Ca(1), one Al(1), and one Si(2) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Al(2), and one Si(1) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to two equivalent Ca(2), one Ti(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Ca(2), one Ti(1), and one Ti(2) atom. In the eighth O site, O(8) is bonded in a distorted T-shaped geometry to one Ca(2), one Ti(1), and one Si(1) atom. In the ninth O site, O(9) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Ti(2), and one Si(2) atom. F(1) is bonded in a distorted trigonal planar geometry to one Ca(1), one Al(1), and one Al(2) atom. is represented by the CIF card [CIF]
data_Ca2TiAlSi2O9F
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.445
_cell_length_b   7.091
_cell_length_c   10.419
_cell_angle_alpha   106.501
_cell_angle_beta   94.111
_cell_angle_gamma   104.580
_symmetry_Int_Tables_number   1
_cell_volume   368.825
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
loop_
 _atom_site_type_symbol
 _atom_site_label
 _atom_site_symmetry_multiplicity
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_occupancy
  Ca  Ca0  1  0.998  0.584  0.835  1.0
  Ca  Ca1  1  0.504  0.084  0.332  1.0
  Ca  Ca2  1  0.002  0.416  0.165  1.0
  Ca  Ca3  1  0.496  0.916  0.668  1.0
  Ti  Ti4  1  0.000  0.000  0.500  1.0
  Ti  Ti5  1  0.000  0.500  0.500  1.0
  Al  Al6  1  0.500  0.500  0.000  1.0
  Al  Al7  1  0.500  0.000  0.000  1.0
  Si  Si8  1  0.027  0.093  0.848  1.0
  Si  Si9  1  0.524  0.590  0.335  1.0
  Si  Si10  1  0.973  0.907  0.152  1.0
  Si  Si11  1  0.476  0.410  0.665  1.0
  O  O12  1  0.251  0.021  0.117  1.0
  O  O13  1  0.146  0.335  0.948  1.0
  O  O14  1  0.746  0.537  0.628  1.0
  O  O15  1  0.441  0.591  0.181  1.0
  O  O16  1  0.239  0.962  0.852  1.0
  O  O17  1  0.628  0.826  0.441  1.0
  O  O18  1  0.761  0.038  0.148  1.0
  O  O19  1  0.559  0.409  0.819  1.0
  O  O20  1  0.893  0.216  0.467  1.0
  O  O21  1  0.944  0.095  0.692  1.0
  O  O22  1  0.733  0.459  0.340  1.0
  O  O23  1  0.854  0.665  0.052  1.0
  O  O24  1  0.267  0.541  0.660  1.0
  O  O25  1  0.056  0.905  0.308  1.0
  O  O26  1  0.749  0.979  0.883  1.0
  O  O27  1  0.107  0.784  0.533  1.0
  O  O28  1  0.372  0.174  0.559  1.0
  O  O29  1  0.254  0.463  0.372  1.0
  F  F30  1  0.400  0.715  0.964  1.0
  F  F31  1  0.600  0.285  0.036  1.0
[/CIF]
.