data_MgCuSi2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.87
_cell_length_b   3.87
_cell_length_c   3.97
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   MgCuSi2
_chemical_formula_sum   'Mg1 Cu1 Si2'
_cell_volume   59.39
_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
  Cu  Cu0  1  0.93  0.93  0.0  1.0
  Si  Si2  1  0.0  0.93  0.99  1.0
  Si  Si3  1  0.93  0.0  0.99  1.0

data_MgCuSi2
_symmetry_space_group_name_H-M   Cm
_cell_length_a   5.47
_cell_length_b   5.47
_cell_length_c   3.97
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   MgCuSi2
_chemical_formula_sum   'Mg2 Cu2 Si4'
_cell_volume   118.78
_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  4  0.47  0.47  0.99  1.0
  Cu  Cu2  2  0.43  0.5  0.0  1.0

Mg Cu Si Si
Mg Cu Si Si 0 3 - o - 0 2 o - - 1 2 + o - 1 3 o + - 
MgCuSi2 is alpha Po structured and crystallizes in the monoclinic Cm space group. The structure is zero-dimensional and consists of two MgCuSi2 clusters. Mg(1) is bonded in an L-shaped geometry to two equivalent Si(1) atoms. Both Mg(1)-Si(1) bond lengths are 0.26 Å. Cu(1) is bonded in a distorted L-shaped geometry to two equivalent Si(1) atoms. Both Cu(1)-Si(1) bond lengths are 0.26 Å. Si(1) is bonded in a distorted single-bond geometry to one Mg(1) and one Cu(1) atom.