The material structure described by Mg2Si crystallizes in the monoclinic P2_1 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 4-coordinate geometry to two equivalent Si(1) and two equivalent Si(2) atoms. In the second Mg site, Mg(2) is bonded in a 4-coordinate geometry to two equivalent Si(1) and two equivalent Si(2) atoms. In the third Mg site, Mg(3) is bonded to two equivalent Si(1) and two equivalent Si(2) atoms to form corner-sharing MgSi4 tetrahedra. In the fourth Mg site, Mg(4) is bonded in a distorted bent 120 degrees geometry to one Si(1) and one Si(2) atom. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to one Mg(4), two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), and one Si(2) atom. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to one Mg(4), two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), and one Si(1) atom. is represented by the CIF file [CIF]
data_Mg2Si
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.964
_cell_length_b   6.031
_cell_length_c   7.631
_cell_angle_alpha   66.959
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   252.573
_cell_formula_units_Z   4
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  0.172  0.817  0.855  1.0
  Mg  Mg1  1  0.708  0.582  0.434  1.0
  Mg  Mg2  1  0.208  0.418  0.566  1.0
  Mg  Mg3  1  0.676  0.753  0.003  1.0
  Mg  Mg4  1  0.672  0.183  0.145  1.0
  Mg  Mg5  1  0.591  0.985  0.581  1.0
  Mg  Mg6  1  0.091  0.015  0.419  1.0
  Mg  Mg7  1  0.176  0.247  0.997  1.0
  Si  Si8  1  0.824  0.210  0.778  1.0
  Si  Si9  1  0.029  0.499  0.205  1.0
  Si  Si10  1  0.529  0.501  0.795  1.0
  Si  Si11  1  0.324  0.790  0.222  1.0
[/CIF]
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The material structure described by Mg2Si crystallizes in the monoclinic P2_1 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 4-coordinate geometry to two equivalent Si(1) and two equivalent Si(2) atoms. In the second Mg site, Mg(2) is bonded in a 4-coordinate geometry to two equivalent Si(1) and two equivalent Si(2) atoms. In the third Mg site, Mg(3) is bonded to two equivalent Si(1) and two equivalent Si(2) atoms to form corner-sharing MgSi4 tetrahedra. In the fourth Mg site, Mg(4) is bonded in a distorted bent 120 degrees geometry to one Si(1) and one Si(2) atom. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to one Mg(4), two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), and one Si(2) atom. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to one Mg(4), two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), and one Si(1) atom. is represented by the CIF file [CIF]
data_Mg2Si
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.964
_cell_length_b   6.031
_cell_length_c   7.631
_cell_angle_alpha   66.959
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   252.573
_cell_formula_units_Z   4
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  0.172  0.817  0.855  1.0
  Mg  Mg1  1  0.708  0.582  0.434  1.0
  Mg  Mg2  1  0.208  0.418  0.566  1.0
  Mg  Mg3  1  0.676  0.753  0.003  1.0
  Mg  Mg4  1  0.672  0.183  0.145  1.0
  Mg  Mg5  1  0.591  0.985  0.581  1.0
  Mg  Mg6  1  0.091  0.015  0.419  1.0
  Mg  Mg7  1  0.176  0.247  0.997  1.0
  Si  Si8  1  0.824  0.210  0.778  1.0
  Si  Si9  1  0.029  0.499  0.205  1.0
  Si  Si10  1  0.529  0.501  0.795  1.0
  Si  Si11  1  0.324  0.790  0.222  1.0
[/CIF]
.