data_GaSi2Se
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.28
_cell_length_b   3.28
_cell_length_c   6.54
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   GaSi2Se
_chemical_formula_sum   'Ga1 Si2 Se1'
_cell_volume   70.27
_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
  Ga  Ga0  1  0.0  0.0  0.0  1.0
  Si  Si2  1  0.64  0.64  0.9  1.0
  Si  Si3  1  0.64  0.64  0.64  1.0
  Se  Se1  1  0.0  0.0  0.27  1.0

data_GaSi2Se
_symmetry_space_group_name_H-M   Cm
_cell_length_a   4.63
_cell_length_b   4.63
_cell_length_c   6.54
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   GaSi2Se
_chemical_formula_sum   'Ga2 Si4 Se2'
_cell_volume   140.54
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  'x, -y, z'
  3  'x+1/2, y+1/2, z'
  4  'x+1/2, -y+1/2, 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
  Ga  Ga0  2  0.0  0.0  0.0  1.0
  Si  Si1  2  0.14  0.5  0.64  1.0
  Si  Si2  2  0.14  0.5  0.9  1.0
  Se  Se3  2  0.0  0.0  0.27  1.0

Ga Si Si Se
Ga Si Si Se 0 1 - - - 0 3 o o o 1 2 o o o 
GaSi2Se crystallizes in the monoclinic Cm space group. Ga(1) is bonded in a 2-coordinate geometry to three equivalent Si(1) and one Se(1) atom. There is one shorter (1.80 Å) and two longer (2.49 Å) Ga(1)-Si(1) bond lengths. The Ga(1)-Se(1) bond length is 1.77 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 4-coordinate geometry to three equivalent Ga(1) and one Si(2) atom. The Si(1)-Si(2) bond length is 1.69 Å. In the second Si site, Si(2) is bonded in a bent 150 degrees geometry to one Si(1) and one Se(1) atom. The Si(2)-Se(1) bond length is 2.95 Å. Se(1) is bonded in a single-bond geometry to one Ga(1) and one Si(2) atom.