data_MgCu2Si
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.18
_cell_length_b   3.18
_cell_length_c   5.6
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   MgCu2Si
_chemical_formula_sum   'Mg1 Cu2 Si1'
_cell_volume   56.77
_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
  Cu  Cu0  1  0.59  0.59  0.07  1.0
  Cu  Cu1  1  0.59  0.59  0.54  1.0
  Si  Si3  1  0.0  0.0  0.8  1.0

data_MgCu2Si
_symmetry_space_group_name_H-M   Cm
_cell_length_a   4.5
_cell_length_b   4.5
_cell_length_c   5.6
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   MgCu2Si
_chemical_formula_sum   'Mg2 Cu4 Si2'
_cell_volume   113.54
_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
  Mg  Mg0  2  0.0  0.0  0.0  1.0
  Si  Si1  2  0.0  0.0  0.8  1.0
  Cu  Cu2  2  0.09  0.5  0.07  1.0
  Cu  Cu3  2  0.09  0.5  0.54  1.0

Mg Cu Cu Si
Mg Cu Cu Si 0 3 o o - 0 1 o - o 0 1 - o o 0 1 - - o 0 2 - - - 1 3 + + - 1 2 o o o 1 2 o o - 2 3 o o o 2 3 o + o 2 3 + o o 2 3 + + o 2 2 + o o 2 2 o + o 
MgCu2Si crystallizes in the monoclinic Cm space group. Mg(1) is bonded in a distorted single-bond geometry to three equivalent Cu(1) and one Si(1) atom. There is one shorter (1.88 Å) and two longer (2.32 Å) Mg(1)-Cu(1) bond lengths. The Mg(1)-Si(1) bond length is 1.11 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 3-coordinate geometry to three equivalent Mg(1) and one Cu(2) atom. The Cu(1)-Cu(2) bond length is 2.65 Å. In the second Cu site, Cu(2) is bonded in a 4-coordinate geometry to one Cu(1) and three equivalent Si(1) atoms. There is one shorter (2.36 Å) and two longer (2.72 Å) Cu(2)-Si(1) bond lengths. Si(1) is bonded in a single-bond geometry to one Mg(1) and three equivalent Cu(2) atoms.