The crystal 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 5-coordinate geometry to two equivalent Si(3), three equivalent Si(1), three equivalent Si(2), and three equivalent Si(4) atoms. In the second Mg site, Mg(2) is bonded to two equivalent Si(2), four equivalent Si(4), and six equivalent Si(1) atoms to form a mixture of distorted edge and face-sharing MgSi12 cuboctahedra. In the third Mg site, Mg(3) is bonded in a 8-coordinate geometry to two equivalent Si(2) and six equivalent Si(3) atoms. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 11-coordinate geometry to three equivalent Mg(1), three equivalent Mg(2), one Si(2), two equivalent Si(1), and two equivalent Si(4) atoms. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Mg(2), one Mg(3), three equivalent Mg(1), one Si(1), one Si(3), and two equivalent Si(4) atoms. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to two equivalent Mg(1), three equivalent Mg(3), one Si(2), and two equivalent Si(3) atoms. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to two equivalent Mg(2), three equivalent Mg(1), two equivalent Si(1), and two equivalent Si(2) atoms. is represented by the CIF file [CIF]
data_MgSi2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.143
_cell_length_b   5.143
_cell_length_c   10.538
_cell_angle_alpha   72.261
_cell_angle_beta   72.261
_cell_angle_gamma   52.303
_symmetry_Int_Tables_number   1
_cell_volume   207.437
_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  0.426  0.426  0.737  1.0
  Mg  Mg1  1  0.500  0.500  0.000  1.0
  Mg  Mg2  1  0.574  0.574  0.263  1.0
  Mg  Mg3  1  0.000  0.000  0.500  1.0
  Si  Si4  1  0.821  0.821  0.972  1.0
  Si  Si5  1  0.729  0.729  0.743  1.0
  Si  Si6  1  0.310  0.310  0.480  1.0
  Si  Si7  1  0.271  0.271  0.257  1.0
  Si  Si8  1  0.106  0.106  0.823  1.0
  Si  Si9  1  0.179  0.179  0.028  1.0
  Si  Si10  1  0.894  0.894  0.177  1.0
  Si  Si11  1  0.690  0.690  0.520  1.0
[/CIF]
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The crystal 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 5-coordinate geometry to two equivalent Si(3), three equivalent Si(1), three equivalent Si(2), and three equivalent Si(4) atoms. In the second Mg site, Mg(2) is bonded to two equivalent Si(2), four equivalent Si(4), and six equivalent Si(1) atoms to form a mixture of distorted edge and face-sharing MgSi12 cuboctahedra. In the third Mg site, Mg(3) is bonded in a 8-coordinate geometry to two equivalent Si(2) and six equivalent Si(3) atoms. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 11-coordinate geometry to three equivalent Mg(1), three equivalent Mg(2), one Si(2), two equivalent Si(1), and two equivalent Si(4) atoms. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Mg(2), one Mg(3), three equivalent Mg(1), one Si(1), one Si(3), and two equivalent Si(4) atoms. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to two equivalent Mg(1), three equivalent Mg(3), one Si(2), and two equivalent Si(3) atoms. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to two equivalent Mg(2), three equivalent Mg(1), two equivalent Si(1), and two equivalent Si(2) atoms. is represented by the CIF file [CIF]
data_MgSi2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.143
_cell_length_b   5.143
_cell_length_c   10.538
_cell_angle_alpha   72.261
_cell_angle_beta   72.261
_cell_angle_gamma   52.303
_symmetry_Int_Tables_number   1
_cell_volume   207.437
_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  0.426  0.426  0.737  1.0
  Mg  Mg1  1  0.500  0.500  0.000  1.0
  Mg  Mg2  1  0.574  0.574  0.263  1.0
  Mg  Mg3  1  0.000  0.000  0.500  1.0
  Si  Si4  1  0.821  0.821  0.972  1.0
  Si  Si5  1  0.729  0.729  0.743  1.0
  Si  Si6  1  0.310  0.310  0.480  1.0
  Si  Si7  1  0.271  0.271  0.257  1.0
  Si  Si8  1  0.106  0.106  0.823  1.0
  Si  Si9  1  0.179  0.179  0.028  1.0
  Si  Si10  1  0.894  0.894  0.177  1.0
  Si  Si11  1  0.690  0.690  0.520  1.0
[/CIF]
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