data_MgSe2Cl
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.64
_cell_length_b   6.64
_cell_length_c   6.64
_cell_angle_alpha   146.62
_cell_angle_beta   146.62
_cell_angle_gamma   47.93
_symmetry_Int_Tables_number   1
_chemical_formula_structural   MgSe2Cl
_chemical_formula_sum   'Mg1 Se2 Cl1'
_cell_volume   88.37
_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  Mg1  1  0.0  0.0  0.0  1.0
  Se  Se2  1  0.91  0.0  0.04  1.0
  Se  Se3  1  0.0  0.91  0.04  1.0
  Cl  Cl0  1  0.0  0.0  0.07  1.0

data_MgSe2Cl
_symmetry_space_group_name_H-M   Cm
_cell_length_a   5.4
_cell_length_b   5.4
_cell_length_c   6.64
_cell_angle_alpha   90.0
_cell_angle_beta   113.96
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   MgSe2Cl
_chemical_formula_sum   'Mg2 Se4 Cl2'
_cell_volume   176.74
_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
  Mg  Mg0  2  0.0  0.0  0.0  1.0
  Se  Se1  4  0.45  0.45  0.87  1.0
  Cl  Cl2  2  0.0  0.0  0.93  1.0

Mg Se Se Cl
MgSe2Cl is Indium-like structured and crystallizes in the monoclinic Cm space group. The structure is zero-dimensional and consists of two MgSe2Cl clusters. Mg(1) is bonded in a single-bond geometry to one Cl(1) atom. The Mg(1)-Cl(1) bond length is 0.47 Å. Se(1) is bonded in a single-bond geometry to one Cl(1) atom. The Se(1)-Cl(1) bond length is 0.44 Å. Cl(1) is bonded in a 3-coordinate geometry to one Mg(1) and two equivalent Se(1) atoms.