The material 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 7-coordinate geometry to one Si(1), two equivalent Si(2), two equivalent Si(3), and two equivalent Si(4) atoms. In the second Mg site, Mg(2) is bonded in a 6-coordinate geometry to two equivalent Si(2) and four equivalent Si(4) atoms. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 5-coordinate geometry to one Mg(1), one Si(1), one Si(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(1), and two equivalent Si(4) atoms. In the third Si site, Si(3) is bonded in a 5-coordinate geometry to two equivalent Mg(1), one Si(3), and two equivalent Si(1) atoms. In the fourth Si site, Si(4) is bonded in a 8-coordinate geometry to two equivalent Mg(1), four equivalent Mg(2), and two equivalent Si(2) atoms. is represented by the CIF card [CIF]
data_MgSi2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   12.069
_cell_length_b   12.069
_cell_length_c   5.329
_cell_angle_alpha   82.962
_cell_angle_beta   82.962
_cell_angle_gamma   17.678
_symmetry_Int_Tables_number   1
_cell_volume   233.900
_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  0.388  0.388  0.934  1.0
  Mg  Mg1  1  0.612  0.612  0.066  1.0
  Mg  Mg2  1  0.220  0.220  0.762  1.0
  Mg  Mg3  1  0.780  0.780  0.238  1.0
  Si  Si4  1  0.543  0.543  0.602  1.0
  Si  Si5  1  0.457  0.457  0.398  1.0
  Si  Si6  1  0.351  0.351  0.472  1.0
  Si  Si7  1  0.649  0.649  0.528  1.0
  Si  Si8  1  0.956  0.956  0.128  1.0
  Si  Si9  1  0.044  0.044  0.872  1.0
  Si  Si10  1  0.186  0.186  0.274  1.0
  Si  Si11  1  0.814  0.814  0.726  1.0
[/CIF]
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The material 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 7-coordinate geometry to one Si(1), two equivalent Si(2), two equivalent Si(3), and two equivalent Si(4) atoms. In the second Mg site, Mg(2) is bonded in a 6-coordinate geometry to two equivalent Si(2) and four equivalent Si(4) atoms. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 5-coordinate geometry to one Mg(1), one Si(1), one Si(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(1), and two equivalent Si(4) atoms. In the third Si site, Si(3) is bonded in a 5-coordinate geometry to two equivalent Mg(1), one Si(3), and two equivalent Si(1) atoms. In the fourth Si site, Si(4) is bonded in a 8-coordinate geometry to two equivalent Mg(1), four equivalent Mg(2), and two equivalent Si(2) atoms. is represented by the CIF card [CIF]
data_MgSi2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   12.069
_cell_length_b   12.069
_cell_length_c   5.329
_cell_angle_alpha   82.962
_cell_angle_beta   82.962
_cell_angle_gamma   17.678
_symmetry_Int_Tables_number   1
_cell_volume   233.900
_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  0.388  0.388  0.934  1.0
  Mg  Mg1  1  0.612  0.612  0.066  1.0
  Mg  Mg2  1  0.220  0.220  0.762  1.0
  Mg  Mg3  1  0.780  0.780  0.238  1.0
  Si  Si4  1  0.543  0.543  0.602  1.0
  Si  Si5  1  0.457  0.457  0.398  1.0
  Si  Si6  1  0.351  0.351  0.472  1.0
  Si  Si7  1  0.649  0.649  0.528  1.0
  Si  Si8  1  0.956  0.956  0.128  1.0
  Si  Si9  1  0.044  0.044  0.872  1.0
  Si  Si10  1  0.186  0.186  0.274  1.0
  Si  Si11  1  0.814  0.814  0.726  1.0
[/CIF]
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