The structure described by Na2Ca5TiSi4(O8F)2 is Esseneite-derived structured and crystallizes in the triclinic P1 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to one O(10), one O(13), one O(14), one O(7), one O(8), one O(9), one F(1), and one F(2) atom to form distorted NaO6F2 hexagonal bipyramids that share edges with two equivalent Ti(1)O6 octahedra,  an edgeedge with one Si(1)O4 tetrahedra,  an edgeedge with one Si(2)O4 tetrahedra,  an edgeedge with one Si(3)O4 tetrahedra, and  an edgeedge with one Si(4)O4 tetrahedra. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to one O(11), one O(15), one O(16), one O(3), one O(5), and one F(1) atom. There are five inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 6-coordinate geometry to one O(1), one O(14), one O(2), one O(9), one F(1), and one F(2) atom. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to one O(1), one O(10), one O(13), one O(2), one F(1), and one F(2) atom. In the third Ca site, Ca(3) is bonded to one O(1), one O(11), one O(12), one O(15), one O(3), and one O(5) atom to form CaO6 octahedra that share  a cornercorner with one Ti(1)O6 octahedra,  a cornercorner with one Si(4)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra, and  an edgeedge with one Ca(4)O6 octahedra. The corner-sharing octahedral tilt angles are 52°. In the fourth Ca site, Ca(4) is bonded to one O(11), one O(12), one O(16), one O(2), one O(4), and one O(6) atom to form CaO6 octahedra that share  a cornercorner with one Ti(1)O6 octahedra,  a cornercorner with one Si(3)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Si(4)O4 tetrahedra, and  an edgeedge with one Ca(3)O6 octahedra. The corner-sharing octahedral tilt angles are 54°. In the fifth Ca site, Ca(5) is bonded in a 6-coordinate geometry to one O(12), one O(15), one O(16), one O(4), one O(6), and one F(2) atom. Ti(1) is bonded to one O(1), one O(10), one O(13), one O(14), one O(2), and one O(9) atom to form TiO6 octahedra that share  a cornercorner with one Ca(3)O6 octahedra,  a cornercorner with one Ca(4)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra, and edges with two equivalent Na(1)O6F2 hexagonal bipyramids. The corner-sharing octahedral tilt angles range from 52-54°. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(13), one O(15), one O(5), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Ti(1)O6 octahedra, corners with two equivalent Ca(3)O6 octahedra,  a cornercorner with one Si(3)O4 tetrahedra, and  an edgeedge with one Na(1)O6F2 hexagonal bipyramid. The corner-sharing octahedral tilt angles range from 35-52°. In the second Si site, Si(2) is bonded to one O(14), one O(16), one O(6), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Ti(1)O6 octahedra, corners with two equivalent Ca(4)O6 octahedra,  a cornercorner with one Si(4)O4 tetrahedra, and  an edgeedge with one Na(1)O6F2 hexagonal bipyramid. The corner-sharing octahedral tilt angles range from 36-51°. In the third Si site, Si(3) is bonded to one O(11), one O(3), one O(7), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Ca(4)O6 octahedra,  a cornercorner with one Ti(1)O6 octahedra, corners with two equivalent Ca(3)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  an edgeedge with one Na(1)O6F2 hexagonal bipyramid. The corner-sharing octahedral tilt angles range from 33-56°. In the fourth Si site, Si(4) is bonded to one O(10), one O(12), one O(4), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Ca(3)O6 octahedra,  a cornercorner with one Ti(1)O6 octahedra, corners with two equivalent Ca(4)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, and  an edgeedge with one Na(1)O6F2 hexagonal bipyramid. The corner-sharing octahedral tilt angles range from 34-58°. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1), one Ca(2), one Ca(3), and one Ti(1) atom to form distorted OCa3Ti tetrahedra that share  a cornercorner with one O(2)Ca3Ti tetrahedra, corners with two equivalent F(1)Na2Ca2 tetrahedra, corners with two equivalent F(2)NaCa3 tetrahedra,  a cornercorner with one O(11)NaCa2Si trigonal pyramid, and  an edgeedge with one O(2)Ca3Ti tetrahedra. In the second O site, O(2) is bonded to one Ca(1), one Ca(2), one Ca(4), and one Ti(1) atom to form distorted OCa3Ti tetrahedra that share  a cornercorner with one O(1)Ca3Ti tetrahedra,  a cornercorner with one O(16)NaCa2Si tetrahedra, corners with two equivalent F(1)Na2Ca2 tetrahedra, corners with two equivalent F(2)NaCa3 tetrahedra,  a cornercorner with one O(11)NaCa2Si trigonal pyramid, and  an edgeedge with one O(1)Ca3Ti tetrahedra. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Na(2), one Ca(3), and one Si(3) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Ca(4), one Ca(5), and one Si(4) atom. In the fifth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to one Na(2), one Ca(3), and one Si(1) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Ca(4), one Ca(5), and one Si(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Na(1), one Si(1), and one Si(3) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Na(1), one Si(2), and one Si(4) atom. In the ninth O site, O(9) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Ca(1), one Ti(1), and one Si(3) atom. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one Na(1), one Ca(2), one Ti(1), and one Si(4) atom. In the eleventh O site, O(11) is bonded to one Na(2), one Ca(3), one Ca(4), and one Si(3) atom to form distorted ONaCa2Si trigonal pyramids that share  a cornercorner with one O(1)Ca3Ti tetrahedra,  a cornercorner with one O(2)Ca3Ti tetrahedra,  a cornercorner with one F(1)Na2Ca2 tetrahedra, and  an edgeedge with one O(16)NaCa2Si tetrahedra. In the twelfth O site, O(12) is bonded in a 4-coordinate geometry to one Ca(3), one Ca(4), one Ca(5), and one Si(4) atom. In the thirteenth O site, O(13) is bonded in a 4-coordinate geometry to one Na(1), one Ca(2), one Ti(1), and one Si(1) atom. In the fourteenth O site, O(14) is bonded in a 4-coordinate geometry to one Na(1), one Ca(1), one Ti(1), and one Si(2) atom. In the fifteenth O site, O(15) is bonded in a 4-coordinate geometry to one Na(2), one Ca(3), one Ca(5), and one Si(1) atom. In the sixteenth O site, O(16) is bonded to one Na(2), one Ca(4), one Ca(5), and one Si(2) atom to form distorted ONaCa2Si tetrahedra that share  a cornercorner with one O(2)Ca3Ti tetrahedra,  a cornercorner with one F(1)Na2Ca2 tetrahedra,  a cornercorner with one F(2)NaCa3 tetrahedra, and  an edgeedge with one O(11)NaCa2Si trigonal pyramid. There are two inequivalent F sites. In the first F site, F(1) is bonded to one Na(1), one Na(2), one Ca(1), and one Ca(2) atom to form FNa2Ca2 tetrahedra that share  a cornercorner with one O(16)NaCa2Si tetrahedra,  a cornercorner with one F(2)NaCa3 tetrahedra, corners with two equivalent O(1)Ca3Ti tetrahedra, corners with two equivalent O(2)Ca3Ti tetrahedra,  a cornercorner with one O(11)NaCa2Si trigonal pyramid, and  an edgeedge with one F(2)NaCa3 tetrahedra. In the second F site, F(2) is bonded to one Na(1), one Ca(1), one Ca(2), and one Ca(5) atom to form FNaCa3 tetrahedra that share  a cornercorner with one O(16)NaCa2Si tetrahedra,  a cornercorner with one F(1)Na2Ca2 tetrahedra, corners with two equivalent O(1)Ca3Ti tetrahedra, corners with two equivalent O(2)Ca3Ti tetrahedra, and  an edgeedge with one F(1)Na2Ca2 tetrahedra. is represented by the CIF file [CIF]
data_Na2Ca5TiSi4(O8F)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.810
_cell_length_b   7.441
_cell_length_c   9.786
_cell_angle_alpha   101.057
_cell_angle_beta   101.430
_cell_angle_gamma   89.954
_symmetry_Int_Tables_number   1
_cell_volume   406.648
_cell_formula_units_Z   1
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
  Na  Na0  1  0.998  0.500  0.001  1.0
  Na  Na1  1  0.779  0.593  0.366  1.0
  Ca  Ca2  1  0.509  0.764  0.013  1.0
  Ca  Ca3  1  0.497  0.236  0.991  1.0
  Ca  Ca4  1  0.793  0.089  0.361  1.0
  Ca  Ca5  1  0.208  0.909  0.639  1.0
  Ca  Ca6  1  0.211  0.410  0.635  1.0
  Ti  Ti7  1  0.002  1.000  0.997  1.0
  Si  Si8  1  0.251  0.353  0.283  1.0
  Si  Si9  1  0.749  0.647  0.716  1.0
  Si  Si10  1  0.250  0.786  0.278  1.0
  Si  Si11  1  0.747  0.214  0.721  1.0
  O  O12  1  0.751  0.032  0.106  1.0
  O  O13  1  0.248  0.968  0.896  1.0
  O  O14  1  0.528  0.845  0.321  1.0
  O  O15  1  0.467  0.164  0.674  1.0
  O  O16  1  0.523  0.326  0.356  1.0
  O  O17  1  0.474  0.664  0.646  1.0
  O  O18  1  0.217  0.560  0.245  1.0
  O  O19  1  0.786  0.441  0.758  1.0
  O  O20  1  0.164  0.828  0.116  1.0
  O  O21  1  0.832  0.169  0.882  1.0
  O  O22  1  0.090  0.871  0.389  1.0
  O  O23  1  0.920  0.140  0.614  1.0
  O  O24  1  0.193  0.222  0.123  1.0
  O  O25  1  0.806  0.781  0.876  1.0
  O  O26  1  0.075  0.328  0.388  1.0
  O  O27  1  0.942  0.666  0.621  1.0
  F  F28  1  0.684  0.519  0.105  1.0
  F  F29  1  0.307  0.478  0.885  1.0
[/CIF]
.
The structure described by Na2Ca5TiSi4(O8F)2 is Esseneite-derived structured and crystallizes in the triclinic P1 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to one O(10), one O(13), one O(14), one O(7), one O(8), one O(9), one F(1), and one F(2) atom to form distorted NaO6F2 hexagonal bipyramids that share edges with two equivalent Ti(1)O6 octahedra,  an edgeedge with one Si(1)O4 tetrahedra,  an edgeedge with one Si(2)O4 tetrahedra,  an edgeedge with one Si(3)O4 tetrahedra, and  an edgeedge with one Si(4)O4 tetrahedra. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to one O(11), one O(15), one O(16), one O(3), one O(5), and one F(1) atom. There are five inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 6-coordinate geometry to one O(1), one O(14), one O(2), one O(9), one F(1), and one F(2) atom. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to one O(1), one O(10), one O(13), one O(2), one F(1), and one F(2) atom. In the third Ca site, Ca(3) is bonded to one O(1), one O(11), one O(12), one O(15), one O(3), and one O(5) atom to form CaO6 octahedra that share  a cornercorner with one Ti(1)O6 octahedra,  a cornercorner with one Si(4)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra, and  an edgeedge with one Ca(4)O6 octahedra. The corner-sharing octahedral tilt angles are 52°. In the fourth Ca site, Ca(4) is bonded to one O(11), one O(12), one O(16), one O(2), one O(4), and one O(6) atom to form CaO6 octahedra that share  a cornercorner with one Ti(1)O6 octahedra,  a cornercorner with one Si(3)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Si(4)O4 tetrahedra, and  an edgeedge with one Ca(3)O6 octahedra. The corner-sharing octahedral tilt angles are 54°. In the fifth Ca site, Ca(5) is bonded in a 6-coordinate geometry to one O(12), one O(15), one O(16), one O(4), one O(6), and one F(2) atom. Ti(1) is bonded to one O(1), one O(10), one O(13), one O(14), one O(2), and one O(9) atom to form TiO6 octahedra that share  a cornercorner with one Ca(3)O6 octahedra,  a cornercorner with one Ca(4)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra, and edges with two equivalent Na(1)O6F2 hexagonal bipyramids. The corner-sharing octahedral tilt angles range from 52-54°. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(13), one O(15), one O(5), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Ti(1)O6 octahedra, corners with two equivalent Ca(3)O6 octahedra,  a cornercorner with one Si(3)O4 tetrahedra, and  an edgeedge with one Na(1)O6F2 hexagonal bipyramid. The corner-sharing octahedral tilt angles range from 35-52°. In the second Si site, Si(2) is bonded to one O(14), one O(16), one O(6), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Ti(1)O6 octahedra, corners with two equivalent Ca(4)O6 octahedra,  a cornercorner with one Si(4)O4 tetrahedra, and  an edgeedge with one Na(1)O6F2 hexagonal bipyramid. The corner-sharing octahedral tilt angles range from 36-51°. In the third Si site, Si(3) is bonded to one O(11), one O(3), one O(7), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Ca(4)O6 octahedra,  a cornercorner with one Ti(1)O6 octahedra, corners with two equivalent Ca(3)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  an edgeedge with one Na(1)O6F2 hexagonal bipyramid. The corner-sharing octahedral tilt angles range from 33-56°. In the fourth Si site, Si(4) is bonded to one O(10), one O(12), one O(4), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Ca(3)O6 octahedra,  a cornercorner with one Ti(1)O6 octahedra, corners with two equivalent Ca(4)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, and  an edgeedge with one Na(1)O6F2 hexagonal bipyramid. The corner-sharing octahedral tilt angles range from 34-58°. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1), one Ca(2), one Ca(3), and one Ti(1) atom to form distorted OCa3Ti tetrahedra that share  a cornercorner with one O(2)Ca3Ti tetrahedra, corners with two equivalent F(1)Na2Ca2 tetrahedra, corners with two equivalent F(2)NaCa3 tetrahedra,  a cornercorner with one O(11)NaCa2Si trigonal pyramid, and  an edgeedge with one O(2)Ca3Ti tetrahedra. In the second O site, O(2) is bonded to one Ca(1), one Ca(2), one Ca(4), and one Ti(1) atom to form distorted OCa3Ti tetrahedra that share  a cornercorner with one O(1)Ca3Ti tetrahedra,  a cornercorner with one O(16)NaCa2Si tetrahedra, corners with two equivalent F(1)Na2Ca2 tetrahedra, corners with two equivalent F(2)NaCa3 tetrahedra,  a cornercorner with one O(11)NaCa2Si trigonal pyramid, and  an edgeedge with one O(1)Ca3Ti tetrahedra. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Na(2), one Ca(3), and one Si(3) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Ca(4), one Ca(5), and one Si(4) atom. In the fifth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to one Na(2), one Ca(3), and one Si(1) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Ca(4), one Ca(5), and one Si(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Na(1), one Si(1), and one Si(3) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Na(1), one Si(2), and one Si(4) atom. In the ninth O site, O(9) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Ca(1), one Ti(1), and one Si(3) atom. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one Na(1), one Ca(2), one Ti(1), and one Si(4) atom. In the eleventh O site, O(11) is bonded to one Na(2), one Ca(3), one Ca(4), and one Si(3) atom to form distorted ONaCa2Si trigonal pyramids that share  a cornercorner with one O(1)Ca3Ti tetrahedra,  a cornercorner with one O(2)Ca3Ti tetrahedra,  a cornercorner with one F(1)Na2Ca2 tetrahedra, and  an edgeedge with one O(16)NaCa2Si tetrahedra. In the twelfth O site, O(12) is bonded in a 4-coordinate geometry to one Ca(3), one Ca(4), one Ca(5), and one Si(4) atom. In the thirteenth O site, O(13) is bonded in a 4-coordinate geometry to one Na(1), one Ca(2), one Ti(1), and one Si(1) atom. In the fourteenth O site, O(14) is bonded in a 4-coordinate geometry to one Na(1), one Ca(1), one Ti(1), and one Si(2) atom. In the fifteenth O site, O(15) is bonded in a 4-coordinate geometry to one Na(2), one Ca(3), one Ca(5), and one Si(1) atom. In the sixteenth O site, O(16) is bonded to one Na(2), one Ca(4), one Ca(5), and one Si(2) atom to form distorted ONaCa2Si tetrahedra that share  a cornercorner with one O(2)Ca3Ti tetrahedra,  a cornercorner with one F(1)Na2Ca2 tetrahedra,  a cornercorner with one F(2)NaCa3 tetrahedra, and  an edgeedge with one O(11)NaCa2Si trigonal pyramid. There are two inequivalent F sites. In the first F site, F(1) is bonded to one Na(1), one Na(2), one Ca(1), and one Ca(2) atom to form FNa2Ca2 tetrahedra that share  a cornercorner with one O(16)NaCa2Si tetrahedra,  a cornercorner with one F(2)NaCa3 tetrahedra, corners with two equivalent O(1)Ca3Ti tetrahedra, corners with two equivalent O(2)Ca3Ti tetrahedra,  a cornercorner with one O(11)NaCa2Si trigonal pyramid, and  an edgeedge with one F(2)NaCa3 tetrahedra. In the second F site, F(2) is bonded to one Na(1), one Ca(1), one Ca(2), and one Ca(5) atom to form FNaCa3 tetrahedra that share  a cornercorner with one O(16)NaCa2Si tetrahedra,  a cornercorner with one F(1)Na2Ca2 tetrahedra, corners with two equivalent O(1)Ca3Ti tetrahedra, corners with two equivalent O(2)Ca3Ti tetrahedra, and  an edgeedge with one F(1)Na2Ca2 tetrahedra. is represented by the CIF file [CIF]
data_Na2Ca5TiSi4(O8F)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.810
_cell_length_b   7.441
_cell_length_c   9.786
_cell_angle_alpha   101.057
_cell_angle_beta   101.430
_cell_angle_gamma   89.954
_symmetry_Int_Tables_number   1
_cell_volume   406.648
_cell_formula_units_Z   1
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
  Na  Na0  1  0.998  0.500  0.001  1.0
  Na  Na1  1  0.779  0.593  0.366  1.0
  Ca  Ca2  1  0.509  0.764  0.013  1.0
  Ca  Ca3  1  0.497  0.236  0.991  1.0
  Ca  Ca4  1  0.793  0.089  0.361  1.0
  Ca  Ca5  1  0.208  0.909  0.639  1.0
  Ca  Ca6  1  0.211  0.410  0.635  1.0
  Ti  Ti7  1  0.002  1.000  0.997  1.0
  Si  Si8  1  0.251  0.353  0.283  1.0
  Si  Si9  1  0.749  0.647  0.716  1.0
  Si  Si10  1  0.250  0.786  0.278  1.0
  Si  Si11  1  0.747  0.214  0.721  1.0
  O  O12  1  0.751  0.032  0.106  1.0
  O  O13  1  0.248  0.968  0.896  1.0
  O  O14  1  0.528  0.845  0.321  1.0
  O  O15  1  0.467  0.164  0.674  1.0
  O  O16  1  0.523  0.326  0.356  1.0
  O  O17  1  0.474  0.664  0.646  1.0
  O  O18  1  0.217  0.560  0.245  1.0
  O  O19  1  0.786  0.441  0.758  1.0
  O  O20  1  0.164  0.828  0.116  1.0
  O  O21  1  0.832  0.169  0.882  1.0
  O  O22  1  0.090  0.871  0.389  1.0
  O  O23  1  0.920  0.140  0.614  1.0
  O  O24  1  0.193  0.222  0.123  1.0
  O  O25  1  0.806  0.781  0.876  1.0
  O  O26  1  0.075  0.328  0.388  1.0
  O  O27  1  0.942  0.666  0.621  1.0
  F  F28  1  0.684  0.519  0.105  1.0
  F  F29  1  0.307  0.478  0.885  1.0
[/CIF]
.