data_MgMnSi2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   2.72
_cell_length_b   2.72
_cell_length_c   7.88
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   MgMnSi2
_chemical_formula_sum   'Mg1 Mn1 Si2'
_cell_volume   58.2
_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  0.04  1.0
  Mn  Mn1  1  0.36  0.36  0.13  1.0
  Si  Si2  1  0.0  0.0  0.7  1.0
  Si  Si3  1  0.36  0.36  0.82  1.0

data_MgMnSi2
_symmetry_space_group_name_H-M   Cm
_cell_length_a   3.84
_cell_length_b   3.84
_cell_length_c   7.88
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   MgMnSi2
_chemical_formula_sum   'Mg2 Mn2 Si4'
_cell_volume   116.4
_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  0.04  1.0
  Mn  Mn1  2  0.36  0.0  0.13  1.0
  Si  Si2  2  0.0  0.0  0.7  1.0
  Si  Si3  2  0.36  0.0  0.82  1.0

Mg Mn Si Si
MgMnSi2 crystallizes in the monoclinic Cm space group. The structure is zero-dimensional and consists of two MgMnSi2 clusters. Mg(1) is bonded in a 1-coordinate geometry to one Mn(1) and one Si(2) atom. The Mg(1)-Mn(1) bond length is 1.56 Å. The Mg(1)-Si(2) bond length is 2.24 Å. Mn(1) is bonded in a 1-coordinate geometry to one Mg(1) atom. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 1-coordinate geometry to one Si(2) atom. The Si(1)-Si(2) bond length is 1.66 Å. In the second Si site, Si(2) is bonded in a 2-coordinate geometry to one Mg(1) and one Si(1) atom.