The compound described by Ti2FeSe4 crystallizes in the trigonal P-3m1 space group. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one Se(1), one Se(2), two equivalent Se(3), and two equivalent Se(4) atoms to form TiSe6 octahedra that share corners with two equivalent Fe(1)Se6 octahedra, corners with four equivalent Fe(2)Se6 octahedra, edges with two equivalent Ti(2)Se6 octahedra, edges with four equivalent Ti(1)Se6 octahedra, and  a faceface with one Fe(2)Se6 octahedra. The corner-sharing octahedral tilt angles range from 48-50°. In the second Ti site, Ti(2) is bonded to three equivalent Se(3) and three equivalent Se(4) atoms to form TiSe6 octahedra that share corners with six equivalent Fe(2)Se6 octahedra, edges with six equivalent Ti(1)Se6 octahedra, and  a faceface with one Fe(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 47°. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to six equivalent Se(3) atoms to form FeSe6 octahedra that share corners with twelve equivalent Ti(1)Se6 octahedra and faces with two equivalent Ti(2)Se6 octahedra. The corner-sharing octahedral tilt angles are 50°. In the second Fe site, Fe(2) is bonded to two equivalent Se(1) and four equivalent Se(4) atoms to form FeSe6 octahedra that share corners with four equivalent Ti(2)Se6 octahedra, corners with eight equivalent Ti(1)Se6 octahedra, edges with four equivalent Fe(2)Se6 octahedra, and faces with two equivalent Ti(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 47-50°. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to three equivalent Ti(1) and three equivalent Fe(2) atoms to form distorted SeTi3Fe3 pentagonal pyramids that share corners with three equivalent Se(1)Ti3Fe3 pentagonal pyramids and edges with nine equivalent Se(4)Ti3Fe2 square pyramids. In the second Se site, Se(2) is bonded in a distorted T-shaped geometry to three equivalent Ti(1) atoms. In the third Se site, Se(3) is bonded in a rectangular see-saw-like geometry to one Ti(2), two equivalent Ti(1), and one Fe(1) atom. In the fourth Se site, Se(4) is bonded to one Ti(2), two equivalent Ti(1), and two equivalent Fe(2) atoms to form distorted SeTi3Fe2 square pyramids that share corners with six equivalent Se(4)Ti3Fe2 square pyramids, edges with three equivalent Se(1)Ti3Fe3 pentagonal pyramids, and edges with two equivalent Se(4)Ti3Fe2 square pyramids. is represented by the CIF card [CIF]
data_Ti2FeSe4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.190
_cell_length_b   7.190
_cell_length_c   12.140
_cell_angle_alpha   90.000
_cell_angle_beta   89.998
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   543.507
_cell_formula_units_Z   4
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
  Ti  Ti0  1  0.018  0.509  0.248  1.0
  Ti  Ti1  1  0.491  0.509  0.248  1.0
  Ti  Ti2  1  0.491  0.982  0.248  1.0
  Ti  Ti3  1  0.982  0.491  0.752  1.0
  Ti  Ti4  1  0.509  0.491  0.752  1.0
  Ti  Ti5  1  0.509  0.018  0.752  1.0
  Ti  Ti6  1  1.000  1.000  0.250  1.0
  Ti  Ti7  1  0.000  0.000  0.750  1.0
  Fe  Fe8  1  0.000  0.000  0.000  1.0
  Fe  Fe9  1  0.500  0.500  0.500  1.0
  Fe  Fe10  1  0.500  0.000  0.500  1.0
  Fe  Fe11  1  0.000  0.500  0.500  1.0
  Se  Se12  1  0.333  0.667  0.626  1.0
  Se  Se13  1  0.667  0.333  0.374  1.0
  Se  Se14  1  0.334  0.667  0.116  1.0
  Se  Se15  1  0.666  0.333  0.884  1.0
  Se  Se16  1  0.666  0.833  0.876  1.0
  Se  Se17  1  0.167  0.833  0.876  1.0
  Se  Se18  1  0.167  0.334  0.876  1.0
  Se  Se19  1  0.334  0.167  0.124  1.0
  Se  Se20  1  0.833  0.167  0.124  1.0
  Se  Se21  1  0.833  0.666  0.124  1.0
  Se  Se22  1  0.670  0.835  0.382  1.0
  Se  Se23  1  0.165  0.835  0.382  1.0
  Se  Se24  1  0.165  0.330  0.382  1.0
  Se  Se25  1  0.330  0.165  0.618  1.0
  Se  Se26  1  0.835  0.165  0.618  1.0
  Se  Se27  1  0.835  0.670  0.618  1.0
[/CIF]
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The compound described by Ti2FeSe4 crystallizes in the trigonal P-3m1 space group. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one Se(1), one Se(2), two equivalent Se(3), and two equivalent Se(4) atoms to form TiSe6 octahedra that share corners with two equivalent Fe(1)Se6 octahedra, corners with four equivalent Fe(2)Se6 octahedra, edges with two equivalent Ti(2)Se6 octahedra, edges with four equivalent Ti(1)Se6 octahedra, and  a faceface with one Fe(2)Se6 octahedra. The corner-sharing octahedral tilt angles range from 48-50°. In the second Ti site, Ti(2) is bonded to three equivalent Se(3) and three equivalent Se(4) atoms to form TiSe6 octahedra that share corners with six equivalent Fe(2)Se6 octahedra, edges with six equivalent Ti(1)Se6 octahedra, and  a faceface with one Fe(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 47°. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to six equivalent Se(3) atoms to form FeSe6 octahedra that share corners with twelve equivalent Ti(1)Se6 octahedra and faces with two equivalent Ti(2)Se6 octahedra. The corner-sharing octahedral tilt angles are 50°. In the second Fe site, Fe(2) is bonded to two equivalent Se(1) and four equivalent Se(4) atoms to form FeSe6 octahedra that share corners with four equivalent Ti(2)Se6 octahedra, corners with eight equivalent Ti(1)Se6 octahedra, edges with four equivalent Fe(2)Se6 octahedra, and faces with two equivalent Ti(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 47-50°. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to three equivalent Ti(1) and three equivalent Fe(2) atoms to form distorted SeTi3Fe3 pentagonal pyramids that share corners with three equivalent Se(1)Ti3Fe3 pentagonal pyramids and edges with nine equivalent Se(4)Ti3Fe2 square pyramids. In the second Se site, Se(2) is bonded in a distorted T-shaped geometry to three equivalent Ti(1) atoms. In the third Se site, Se(3) is bonded in a rectangular see-saw-like geometry to one Ti(2), two equivalent Ti(1), and one Fe(1) atom. In the fourth Se site, Se(4) is bonded to one Ti(2), two equivalent Ti(1), and two equivalent Fe(2) atoms to form distorted SeTi3Fe2 square pyramids that share corners with six equivalent Se(4)Ti3Fe2 square pyramids, edges with three equivalent Se(1)Ti3Fe3 pentagonal pyramids, and edges with two equivalent Se(4)Ti3Fe2 square pyramids. is represented by the CIF card [CIF]
data_Ti2FeSe4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.190
_cell_length_b   7.190
_cell_length_c   12.140
_cell_angle_alpha   90.000
_cell_angle_beta   89.998
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   543.507
_cell_formula_units_Z   4
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
  Ti  Ti0  1  0.018  0.509  0.248  1.0
  Ti  Ti1  1  0.491  0.509  0.248  1.0
  Ti  Ti2  1  0.491  0.982  0.248  1.0
  Ti  Ti3  1  0.982  0.491  0.752  1.0
  Ti  Ti4  1  0.509  0.491  0.752  1.0
  Ti  Ti5  1  0.509  0.018  0.752  1.0
  Ti  Ti6  1  1.000  1.000  0.250  1.0
  Ti  Ti7  1  0.000  0.000  0.750  1.0
  Fe  Fe8  1  0.000  0.000  0.000  1.0
  Fe  Fe9  1  0.500  0.500  0.500  1.0
  Fe  Fe10  1  0.500  0.000  0.500  1.0
  Fe  Fe11  1  0.000  0.500  0.500  1.0
  Se  Se12  1  0.333  0.667  0.626  1.0
  Se  Se13  1  0.667  0.333  0.374  1.0
  Se  Se14  1  0.334  0.667  0.116  1.0
  Se  Se15  1  0.666  0.333  0.884  1.0
  Se  Se16  1  0.666  0.833  0.876  1.0
  Se  Se17  1  0.167  0.833  0.876  1.0
  Se  Se18  1  0.167  0.334  0.876  1.0
  Se  Se19  1  0.334  0.167  0.124  1.0
  Se  Se20  1  0.833  0.167  0.124  1.0
  Se  Se21  1  0.833  0.666  0.124  1.0
  Se  Se22  1  0.670  0.835  0.382  1.0
  Se  Se23  1  0.165  0.835  0.382  1.0
  Se  Se24  1  0.165  0.330  0.382  1.0
  Se  Se25  1  0.330  0.165  0.618  1.0
  Se  Se26  1  0.835  0.165  0.618  1.0
  Se  Se27  1  0.835  0.670  0.618  1.0
[/CIF]
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