data_Na2GeSe
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.03
_cell_length_b   5.03
_cell_length_c   5.03
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Na2GeSe
_chemical_formula_sum   'Na2 Ge1 Se1'
_cell_volume   90.09
_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  Na1  1  0.78  0.78  0.78  1.0
  Na  Na2  1  0.34  0.34  0.34  1.0
  Ge  Ge0  1  0.0  0.0  0.0  1.0
  Se  Se3  1  0.56  0.56  0.56  1.0

data_Na2GeSe
_symmetry_space_group_name_H-M   R3m
_cell_length_a   5.03
_cell_length_b   5.03
_cell_length_c   12.33
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   Na2GeSe
_chemical_formula_sum   'Na6 Ge3 Se3'
_cell_volume   270.28
_cell_formula_units_Z   3
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  '-y, x-y, z'
  3  '-x+y, -x, z'
  4  '-y, -x, z'
  5  '-x+y, y, z'
  6  'x, x-y, z'
  7  'x+1/3, y+2/3, z+2/3'
  8  '-y+1/3, x-y+2/3, z+2/3'
  9  '-x+y+1/3, -x+2/3, z+2/3'
  10  '-y+1/3, -x+2/3, z+2/3'
  11  '-x+y+1/3, y+2/3, z+2/3'
  12  'x+1/3, x-y+2/3, z+2/3'
  13  'x+2/3, y+1/3, z+1/3'
  14  '-y+2/3, x-y+1/3, z+1/3'
  15  '-x+y+2/3, -x+1/3, z+1/3'
  16  '-y+2/3, -x+1/3, z+1/3'
  17  '-x+y+2/3, y+1/3, z+1/3'
  18  'x+2/3, x-y+1/3, z+1/3'
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  3  0.0  0.0  0.22  1.0
  Na  Na1  3  0.0  0.0  0.66  1.0
  Ge  Ge2  3  0.0  0.0  0.0  1.0
  Se  Se3  3  0.0  0.0  0.44  1.0

Na Na Ge Se
Na2GeSe is Heusler structured and crystallizes in the trigonal R3m space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 8-coordinate geometry to four equivalent Ge(1) and four equivalent Se(1) atoms. There is one shorter (2.72 Å) and three longer (3.22 Å) Na(1)-Ge(1) bond lengths. There is one shorter (2.72 Å) and three longer (3.22 Å) Na(1)-Se(1) bond lengths. In the second Na site, Na(2) is bonded in a 7-coordinate geometry to three equivalent Ge(1) and four equivalent Se(1) atoms. All Na(2)-Ge(1) bond lengths are 2.91 Å. There is one shorter (2.72 Å) and three longer (3.22 Å) Na(2)-Se(1) bond lengths. Ge(1) is bonded in a 7-coordinate geometry to three equivalent Na(2) and four equivalent Na(1) atoms. Se(1) is bonded in a distorted body-centered cubic geometry to four equivalent Na(1) and four equivalent Na(2) atoms.