The material described by Mg2Si crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 5-coordinate geometry to six equivalent Mg(2) and five equivalent Si(1) atoms. In the second Mg site, Mg(2) is bonded in a 14-coordinate geometry to two equivalent Mg(2), six equivalent Mg(1), and six equivalent Si(1) atoms. Si(1) is bonded in a 11-coordinate geometry to five equivalent Mg(1) and six equivalent Mg(2) atoms. is represented by the CIF file [CIF]
data_Mg2Si
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.586
_cell_length_b   4.586
_cell_length_c   6.132
_cell_angle_alpha   89.654
_cell_angle_beta   89.654
_cell_angle_gamma   118.763
_symmetry_Int_Tables_number   1
_cell_volume   113.059
_cell_formula_units_Z   2
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  0.664  0.836  0.750  1.0
  Mg  Mg1  1  0.000  0.500  0.500  1.0
  Mg  Mg2  1  0.336  0.164  0.250  1.0
  Mg  Mg3  1  1.000  0.500  1.000  1.0
  Si  Si4  1  0.328  0.172  0.750  1.0
  Si  Si5  1  0.672  0.828  0.250  1.0
[/CIF]
.
The material described by Mg2Si crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 5-coordinate geometry to six equivalent Mg(2) and five equivalent Si(1) atoms. In the second Mg site, Mg(2) is bonded in a 14-coordinate geometry to two equivalent Mg(2), six equivalent Mg(1), and six equivalent Si(1) atoms. Si(1) is bonded in a 11-coordinate geometry to five equivalent Mg(1) and six equivalent Mg(2) atoms. is represented by the CIF file [CIF]
data_Mg2Si
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.586
_cell_length_b   4.586
_cell_length_c   6.132
_cell_angle_alpha   89.654
_cell_angle_beta   89.654
_cell_angle_gamma   118.763
_symmetry_Int_Tables_number   1
_cell_volume   113.059
_cell_formula_units_Z   2
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  0.664  0.836  0.750  1.0
  Mg  Mg1  1  0.000  0.500  0.500  1.0
  Mg  Mg2  1  0.336  0.164  0.250  1.0
  Mg  Mg3  1  1.000  0.500  1.000  1.0
  Si  Si4  1  0.328  0.172  0.750  1.0
  Si  Si5  1  0.672  0.828  0.250  1.0
[/CIF]
.