data_Ca2FeSe
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.46
_cell_length_b   6.46
_cell_length_c   6.46
_cell_angle_alpha   146.03
_cell_angle_beta   138.97
_cell_angle_gamma   54.29
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Ca2FeSe
_chemical_formula_sum   'Ca2 Fe1 Se1'
_cell_volume   98.26
_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
  Ca  Ca0  1  0.0  0.0  0.37  1.0
  Ca  Ca1  1  0.89  0.0  0.01  1.0
  Fe  Fe2  1  0.0  0.0  0.29  1.0
  Se  Se3  1  0.0  0.26  0.32  1.0

data_Ca2FeSe
_symmetry_space_group_name_H-M   P1
_cell_length_a   3.77
_cell_length_b   4.53
_cell_length_c   6.46
_cell_angle_alpha   110.52
_cell_angle_beta   106.99
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Ca2FeSe
_chemical_formula_sum   'Ca2 Fe1 Se1'
_cell_volume   98.26
_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
  Ca  Ca0  1  0.63  0.63  0.63  1.0
  Ca  Ca1  1  0.88  0.99  0.88  1.0
  Fe  Fe2  1  0.71  0.71  0.71  1.0
  Se  Se3  1  0.68  0.94  0.94  1.0

Ca Ca Fe Se
Ca2FeSe crystallizes in the triclinic P1 space group. The structure is zero-dimensional and consists of one Ca2FeSe cluster. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a single-bond geometry to one Fe(1) atom. The Ca(1)-Fe(1) bond length is 0.55 Å. In the second Ca site, Ca(2) is bonded in a 2-coordinate geometry to one Fe(1) and one Se(1) atom. The Ca(2)-Fe(1) bond length is 1.34 Å. The Ca(2)-Se(1) bond length is 1.02 Å. Fe(1) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(2), and one Se(1) atom. The Fe(1)-Se(1) bond length is 1.53 Å. Se(1) is bonded in a distorted single-bond geometry to one Ca(2) and one Fe(1) atom.