The material structure described by MgSi2 crystallizes in the monoclinic C2/m space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 10-coordinate geometry to two equivalent Si(3), four equivalent Si(1), and four equivalent Si(2) atoms. In the second Mg site, Mg(2) is bonded in a 9-coordinate geometry to two equivalent Si(1), two equivalent Si(2), two equivalent Si(3), and three equivalent Si(4) atoms. In the third Mg site, Mg(3) is bonded to two equivalent Si(1) and four equivalent Si(4) atoms to form distorted MgSi6 octahedra that share edges with four equivalent Si(3)Mg3Si4 hexagonal pyramids and edges with two equivalent Mg(3)Si6 octahedra. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 7-coordinate geometry to one Mg(3), two equivalent Mg(1), two equivalent Mg(2), and two equivalent Si(3) atoms. In the second Si site, Si(2) is bonded in a 7-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), one Si(3), and two equivalent Si(2) atoms. In the third Si site, Si(3) is bonded to one Mg(1), two equivalent Mg(2), one Si(2), one Si(4), and two equivalent Si(1) atoms to form distorted SiMg3Si4 hexagonal pyramids that share  a cornercorner with one Si(3)Mg3Si4 hexagonal pyramid, edges with two equivalent Si(3)Mg3Si4 hexagonal pyramids, and edges with two equivalent Mg(3)Si6 octahedra. In the fourth Si site, Si(4) is bonded in a 8-coordinate geometry to two equivalent Mg(3), three equivalent Mg(2), one Si(3), and two equivalent Si(4) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_MgSi2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.941
_cell_length_b   5.941
_cell_length_c   10.374
_cell_angle_alpha   89.931
_cell_angle_beta   89.931
_cell_angle_gamma   36.382
_symmetry_Int_Tables_number   1
_cell_volume   217.151
_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  0.000  0.000  0.500  1.0
  Mg  Mg1  1  0.163  0.163  0.784  1.0
  Mg  Mg2  1  0.500  0.500  0.000  1.0
  Mg  Mg3  1  0.837  0.837  0.216  1.0
  Si  Si4  1  0.494  0.494  0.714  1.0
  Si  Si5  1  0.289  0.289  0.439  1.0
  Si  Si6  1  0.141  0.141  0.266  1.0
  Si  Si7  1  0.809  0.809  0.957  1.0
  Si  Si8  1  0.711  0.711  0.561  1.0
  Si  Si9  1  0.859  0.859  0.734  1.0
  Si  Si10  1  0.191  0.191  0.043  1.0
  Si  Si11  1  0.506  0.506  0.286  1.0
[/CIF]
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The material structure described by MgSi2 crystallizes in the monoclinic C2/m space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 10-coordinate geometry to two equivalent Si(3), four equivalent Si(1), and four equivalent Si(2) atoms. In the second Mg site, Mg(2) is bonded in a 9-coordinate geometry to two equivalent Si(1), two equivalent Si(2), two equivalent Si(3), and three equivalent Si(4) atoms. In the third Mg site, Mg(3) is bonded to two equivalent Si(1) and four equivalent Si(4) atoms to form distorted MgSi6 octahedra that share edges with four equivalent Si(3)Mg3Si4 hexagonal pyramids and edges with two equivalent Mg(3)Si6 octahedra. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 7-coordinate geometry to one Mg(3), two equivalent Mg(1), two equivalent Mg(2), and two equivalent Si(3) atoms. In the second Si site, Si(2) is bonded in a 7-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), one Si(3), and two equivalent Si(2) atoms. In the third Si site, Si(3) is bonded to one Mg(1), two equivalent Mg(2), one Si(2), one Si(4), and two equivalent Si(1) atoms to form distorted SiMg3Si4 hexagonal pyramids that share  a cornercorner with one Si(3)Mg3Si4 hexagonal pyramid, edges with two equivalent Si(3)Mg3Si4 hexagonal pyramids, and edges with two equivalent Mg(3)Si6 octahedra. In the fourth Si site, Si(4) is bonded in a 8-coordinate geometry to two equivalent Mg(3), three equivalent Mg(2), one Si(3), and two equivalent Si(4) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_MgSi2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.941
_cell_length_b   5.941
_cell_length_c   10.374
_cell_angle_alpha   89.931
_cell_angle_beta   89.931
_cell_angle_gamma   36.382
_symmetry_Int_Tables_number   1
_cell_volume   217.151
_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  0.000  0.000  0.500  1.0
  Mg  Mg1  1  0.163  0.163  0.784  1.0
  Mg  Mg2  1  0.500  0.500  0.000  1.0
  Mg  Mg3  1  0.837  0.837  0.216  1.0
  Si  Si4  1  0.494  0.494  0.714  1.0
  Si  Si5  1  0.289  0.289  0.439  1.0
  Si  Si6  1  0.141  0.141  0.266  1.0
  Si  Si7  1  0.809  0.809  0.957  1.0
  Si  Si8  1  0.711  0.711  0.561  1.0
  Si  Si9  1  0.859  0.859  0.734  1.0
  Si  Si10  1  0.191  0.191  0.043  1.0
  Si  Si11  1  0.506  0.506  0.286  1.0
[/CIF]
.