The structure described by MgSi2 crystallizes in the monoclinic C2/m space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 10-coordinate geometry to one Si(1), four equivalent Si(4), and five equivalent Si(2) atoms. In the second Mg site, Mg(2) is bonded in a 8-coordinate geometry to one Si(2), three equivalent Si(1), and four equivalent Si(3) atoms. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 7-coordinate geometry to one Mg(1), three equivalent Mg(2), one Si(1), and two equivalent Si(3) atoms. In the second Si site, Si(2) is bonded in a 10-coordinate geometry to one Mg(2), five equivalent Mg(1), one Si(2), and three equivalent Si(4) atoms. In the third Si site, Si(3) is bonded to four equivalent Mg(2), one Si(4), and two equivalent Si(1) atoms to form a mixture of distorted corner and edge-sharing SiMg4Si3 pentagonal bipyramids. In the fourth Si site, Si(4) is bonded to four equivalent Mg(1), one Si(3), and three equivalent Si(2) atoms to form a mixture of distorted face, corner, and edge-sharing SiMg4Si4 hexagonal bipyramids. is represented by the CIF file [CIF]
data_MgSi2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.315
_cell_length_b   5.315
_cell_length_c   10.155
_cell_angle_alpha   80.310
_cell_angle_beta   80.310
_cell_angle_gamma   49.794
_symmetry_Int_Tables_number   1
_cell_volume   215.262
_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  0.553  0.553  0.646  1.0
  Mg  Mg1  1  0.892  0.892  0.858  1.0
  Mg  Mg2  1  0.108  0.108  0.142  1.0
  Mg  Mg3  1  0.447  0.447  0.354  1.0
  Si  Si4  1  0.589  0.589  0.904  1.0
  Si  Si5  1  0.876  0.876  0.570  1.0
  Si  Si6  1  0.124  0.124  0.430  1.0
  Si  Si7  1  0.810  0.810  0.143  1.0
  Si  Si8  1  0.259  0.259  0.618  1.0
  Si  Si9  1  0.190  0.190  0.857  1.0
  Si  Si10  1  0.411  0.411  0.096  1.0
  Si  Si11  1  0.741  0.741  0.382  1.0
[/CIF]
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The structure described by MgSi2 crystallizes in the monoclinic C2/m space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 10-coordinate geometry to one Si(1), four equivalent Si(4), and five equivalent Si(2) atoms. In the second Mg site, Mg(2) is bonded in a 8-coordinate geometry to one Si(2), three equivalent Si(1), and four equivalent Si(3) atoms. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 7-coordinate geometry to one Mg(1), three equivalent Mg(2), one Si(1), and two equivalent Si(3) atoms. In the second Si site, Si(2) is bonded in a 10-coordinate geometry to one Mg(2), five equivalent Mg(1), one Si(2), and three equivalent Si(4) atoms. In the third Si site, Si(3) is bonded to four equivalent Mg(2), one Si(4), and two equivalent Si(1) atoms to form a mixture of distorted corner and edge-sharing SiMg4Si3 pentagonal bipyramids. In the fourth Si site, Si(4) is bonded to four equivalent Mg(1), one Si(3), and three equivalent Si(2) atoms to form a mixture of distorted face, corner, and edge-sharing SiMg4Si4 hexagonal bipyramids. is represented by the CIF file [CIF]
data_MgSi2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.315
_cell_length_b   5.315
_cell_length_c   10.155
_cell_angle_alpha   80.310
_cell_angle_beta   80.310
_cell_angle_gamma   49.794
_symmetry_Int_Tables_number   1
_cell_volume   215.262
_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  0.553  0.553  0.646  1.0
  Mg  Mg1  1  0.892  0.892  0.858  1.0
  Mg  Mg2  1  0.108  0.108  0.142  1.0
  Mg  Mg3  1  0.447  0.447  0.354  1.0
  Si  Si4  1  0.589  0.589  0.904  1.0
  Si  Si5  1  0.876  0.876  0.570  1.0
  Si  Si6  1  0.124  0.124  0.430  1.0
  Si  Si7  1  0.810  0.810  0.143  1.0
  Si  Si8  1  0.259  0.259  0.618  1.0
  Si  Si9  1  0.190  0.190  0.857  1.0
  Si  Si10  1  0.411  0.411  0.096  1.0
  Si  Si11  1  0.741  0.741  0.382  1.0
[/CIF]
.