The crystal structure described by MgSi2 crystallizes in the monoclinic Cm space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 7-coordinate geometry to one Si(1), one Si(3), two equivalent Si(2), and three equivalent Si(5) atoms. In the second Mg site, Mg(2) is bonded in a 9-coordinate geometry to one Si(5), one Si(7), two equivalent Si(2), two equivalent Si(6), and three equivalent Si(1) atoms. In the third Mg site, Mg(3) is bonded in a 8-coordinate geometry to one Si(3), two equivalent Si(6), two equivalent Si(7), two equivalent Si(8), and three equivalent Si(4) atoms. In the fourth Mg site, Mg(4) is bonded in a 6-coordinate geometry to one Si(4), two equivalent Si(8), and three equivalent Si(3) atoms. There are eight inequivalent Si sites. In the first Si site, Si(1) is bonded in a 10-coordinate geometry to one Mg(1), three equivalent Mg(2), two equivalent Si(2), two equivalent Si(6), and two equivalent Si(7) atoms. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Si(1), and two equivalent Si(5) atoms. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(3), three equivalent Mg(4), two equivalent Si(5), and two equivalent Si(8) atoms. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to one Mg(4), three equivalent Mg(3), one Si(6), two equivalent Si(7), and two equivalent Si(8) atoms. In the fifth Si site, Si(5) is bonded in a 8-coordinate geometry to one Mg(2), three equivalent Mg(1), two equivalent Si(2), and two equivalent Si(3) atoms. In the sixth Si site, Si(6) is bonded in a 8-coordinate geometry to two equivalent Mg(2), two equivalent Mg(3), one Si(4), one Si(7), and two equivalent Si(1) atoms. In the seventh Si site, Si(7) is bonded in a 8-coordinate geometry to one Mg(2), two equivalent Mg(3), one Si(6), two equivalent Si(1), and two equivalent Si(4) atoms. In the eighth Si site, Si(8) is bonded in a distorted body-centered cubic geometry to two equivalent Mg(3), two equivalent Mg(4), two equivalent Si(3), and two equivalent Si(4) atoms. is represented by the CIF file [CIF]
data_MgSi2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.340
_cell_length_b   5.340
_cell_length_c   11.800
_cell_angle_alpha   76.783
_cell_angle_beta   76.783
_cell_angle_gamma   39.037
_symmetry_Int_Tables_number   1
_cell_volume   205.611
_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  0.847  0.847  0.127  1.0
  Mg  Mg1  1  0.512  0.512  0.936  1.0
  Mg  Mg2  1  0.784  0.784  0.576  1.0
  Mg  Mg3  1  0.211  0.211  0.352  1.0
  Si  Si4  1  0.803  0.803  0.890  1.0
  Si  Si5  1  0.183  0.183  0.033  1.0
  Si  Si6  1  0.939  0.939  0.327  1.0
  Si  Si7  1  0.057  0.057  0.608  1.0
  Si  Si8  1  0.552  0.552  0.182  1.0
  Si  Si9  1  0.180  0.180  0.775  1.0
  Si  Si10  1  0.427  0.427  0.732  1.0
  Si  Si11  1  0.498  0.498  0.461  1.0
[/CIF]
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The crystal structure described by MgSi2 crystallizes in the monoclinic Cm space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 7-coordinate geometry to one Si(1), one Si(3), two equivalent Si(2), and three equivalent Si(5) atoms. In the second Mg site, Mg(2) is bonded in a 9-coordinate geometry to one Si(5), one Si(7), two equivalent Si(2), two equivalent Si(6), and three equivalent Si(1) atoms. In the third Mg site, Mg(3) is bonded in a 8-coordinate geometry to one Si(3), two equivalent Si(6), two equivalent Si(7), two equivalent Si(8), and three equivalent Si(4) atoms. In the fourth Mg site, Mg(4) is bonded in a 6-coordinate geometry to one Si(4), two equivalent Si(8), and three equivalent Si(3) atoms. There are eight inequivalent Si sites. In the first Si site, Si(1) is bonded in a 10-coordinate geometry to one Mg(1), three equivalent Mg(2), two equivalent Si(2), two equivalent Si(6), and two equivalent Si(7) atoms. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Si(1), and two equivalent Si(5) atoms. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(3), three equivalent Mg(4), two equivalent Si(5), and two equivalent Si(8) atoms. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to one Mg(4), three equivalent Mg(3), one Si(6), two equivalent Si(7), and two equivalent Si(8) atoms. In the fifth Si site, Si(5) is bonded in a 8-coordinate geometry to one Mg(2), three equivalent Mg(1), two equivalent Si(2), and two equivalent Si(3) atoms. In the sixth Si site, Si(6) is bonded in a 8-coordinate geometry to two equivalent Mg(2), two equivalent Mg(3), one Si(4), one Si(7), and two equivalent Si(1) atoms. In the seventh Si site, Si(7) is bonded in a 8-coordinate geometry to one Mg(2), two equivalent Mg(3), one Si(6), two equivalent Si(1), and two equivalent Si(4) atoms. In the eighth Si site, Si(8) is bonded in a distorted body-centered cubic geometry to two equivalent Mg(3), two equivalent Mg(4), two equivalent Si(3), and two equivalent Si(4) atoms. is represented by the CIF file [CIF]
data_MgSi2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.340
_cell_length_b   5.340
_cell_length_c   11.800
_cell_angle_alpha   76.783
_cell_angle_beta   76.783
_cell_angle_gamma   39.037
_symmetry_Int_Tables_number   1
_cell_volume   205.611
_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  0.847  0.847  0.127  1.0
  Mg  Mg1  1  0.512  0.512  0.936  1.0
  Mg  Mg2  1  0.784  0.784  0.576  1.0
  Mg  Mg3  1  0.211  0.211  0.352  1.0
  Si  Si4  1  0.803  0.803  0.890  1.0
  Si  Si5  1  0.183  0.183  0.033  1.0
  Si  Si6  1  0.939  0.939  0.327  1.0
  Si  Si7  1  0.057  0.057  0.608  1.0
  Si  Si8  1  0.552  0.552  0.182  1.0
  Si  Si9  1  0.180  0.180  0.775  1.0
  Si  Si10  1  0.427  0.427  0.732  1.0
  Si  Si11  1  0.498  0.498  0.461  1.0
[/CIF]
.