data_MgB2Se
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.73
_cell_length_b   3.2
_cell_length_c   4.69
_cell_angle_alpha   90.0
_cell_angle_beta   93.11
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   MgB2Se
_chemical_formula_sum   'Mg1 B2 Se1'
_cell_volume   55.87
_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
  Mg  Mg2  1  0.0  0.0  0.0  1.0
  B  B0  1  0.86  0.6  0.78  1.0
  B  B1  1  0.61  0.6  0.91  1.0
  Se  Se3  1  0.74  0.0  0.34  1.0

data_MgB2Se
_symmetry_space_group_name_H-M   P1
_cell_length_a   3.2
_cell_length_b   3.73
_cell_length_c   4.69
_cell_angle_alpha   93.11
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   MgB2Se
_chemical_formula_sum   'Mg1 B2 Se1'
_cell_volume   55.87
_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
  Mg  Mg0  1  0.0  0.0  0.0  1.0
  B  B1  1  0.4  0.14  0.22  1.0
  B  B2  1  0.4  0.39  0.09  1.0
  Se  Se3  1  0.0  0.26  0.66  1.0

Mg B B Se
Mg B B Se 0 2 - - - 0 1 - - - 0 3 - o o 1 2 o o o 
MgB2Se crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 2-coordinate geometry to two equivalent B(1), three equivalent B(2), and one Se(1) atom. There is one shorter (1.73 Å) and one longer (2.24 Å) Mg(1)-B(1) bond length. There are a spread of Mg(1)-B(2) bond distances ranging from 1.95-2.68 Å. The Mg(1)-Se(1) bond length is 1.94 Å. There are two inequivalent B sites. In the first B site, B(1) is bonded in a 4-coordinate geometry to two equivalent Mg(1), one B(2), and one Se(1) atom. The B(1)-B(2) bond length is 1.14 Å. The B(1)-Se(1) bond length is 2.42 Å. In the second B site, B(2) is bonded in a 5-coordinate geometry to three equivalent Mg(1), one B(1), and one Se(1) atom. The B(2)-Se(1) bond length is 2.42 Å. Se(1) is bonded in a 1-coordinate geometry to one Mg(1), one B(1), and one B(2) atom.