The material 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 9-coordinate geometry to two equivalent Si(1), two equivalent Si(3), two equivalent Si(5), and three equivalent Si(2) atoms. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to one Si(5), one Si(7), two equivalent Si(1), three equivalent Si(4), and three equivalent Si(6) atoms. In the third Mg site, Mg(3) is bonded in a 7-coordinate geometry to two equivalent Si(4), two equivalent Si(8), and three equivalent Si(7) atoms. In the fourth Mg site, Mg(4) is bonded in a 8-coordinate geometry to one Si(2), one Si(7), three equivalent Si(3), and three equivalent Si(8) atoms. There are eight inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), one Si(2), one Si(5), and two equivalent Si(6) atoms. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Mg(4), three equivalent Mg(1), one Si(1), two equivalent Si(3), and two equivalent Si(5) atoms. In the third Si site, Si(3) is bonded in a distorted q6 geometry to two equivalent Mg(1), three equivalent Mg(4), two equivalent Si(2), and two equivalent Si(8) atoms. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to two equivalent Mg(3), three equivalent Mg(2), two equivalent Si(6), and two equivalent Si(7) atoms. In the fifth Si site, Si(5) is bonded in a 8-coordinate geometry to one Mg(2), two equivalent Mg(1), one Si(1), two equivalent Si(2), and two equivalent Si(6) atoms. In the sixth Si site, Si(6) is bonded in a 9-coordinate geometry to three equivalent Mg(2), two equivalent Si(1), two equivalent Si(4), and two equivalent Si(5) atoms. In the seventh Si site, Si(7) is bonded in a 9-coordinate geometry to one Mg(2), one Mg(4), three equivalent Mg(3), two equivalent Si(4), and two equivalent Si(8) atoms. In the eighth Si site, Si(8) is bonded in a distorted q6 geometry to two equivalent Mg(3), three equivalent Mg(4), two equivalent Si(3), and two equivalent Si(7) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_MgSi2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.229
_cell_length_b   5.229
_cell_length_c   12.247
_cell_angle_alpha   72.821
_cell_angle_beta   72.821
_cell_angle_gamma   39.746
_symmetry_Int_Tables_number   1
_cell_volume   203.240
_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  0.609  0.609  0.163  1.0
  Mg  Mg1  1  0.957  0.957  0.801  1.0
  Mg  Mg2  1  0.640  0.640  0.585  1.0
  Mg  Mg3  1  0.127  0.127  0.373  1.0
  Si  Si4  1  0.266  0.266  0.971  1.0
  Si  Si5  1  0.336  0.336  0.156  1.0
  Si  Si6  1  0.867  0.867  0.295  1.0
  Si  Si7  1  0.269  0.269  0.724  1.0
  Si  Si8  1  0.989  0.989  0.017  1.0
  Si  Si9  1  0.645  0.645  0.882  1.0
  Si  Si10  1  0.916  0.916  0.584  1.0
  Si  Si11  1  0.385  0.385  0.448  1.0
[/CIF]
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The material 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 9-coordinate geometry to two equivalent Si(1), two equivalent Si(3), two equivalent Si(5), and three equivalent Si(2) atoms. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to one Si(5), one Si(7), two equivalent Si(1), three equivalent Si(4), and three equivalent Si(6) atoms. In the third Mg site, Mg(3) is bonded in a 7-coordinate geometry to two equivalent Si(4), two equivalent Si(8), and three equivalent Si(7) atoms. In the fourth Mg site, Mg(4) is bonded in a 8-coordinate geometry to one Si(2), one Si(7), three equivalent Si(3), and three equivalent Si(8) atoms. There are eight inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), one Si(2), one Si(5), and two equivalent Si(6) atoms. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Mg(4), three equivalent Mg(1), one Si(1), two equivalent Si(3), and two equivalent Si(5) atoms. In the third Si site, Si(3) is bonded in a distorted q6 geometry to two equivalent Mg(1), three equivalent Mg(4), two equivalent Si(2), and two equivalent Si(8) atoms. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to two equivalent Mg(3), three equivalent Mg(2), two equivalent Si(6), and two equivalent Si(7) atoms. In the fifth Si site, Si(5) is bonded in a 8-coordinate geometry to one Mg(2), two equivalent Mg(1), one Si(1), two equivalent Si(2), and two equivalent Si(6) atoms. In the sixth Si site, Si(6) is bonded in a 9-coordinate geometry to three equivalent Mg(2), two equivalent Si(1), two equivalent Si(4), and two equivalent Si(5) atoms. In the seventh Si site, Si(7) is bonded in a 9-coordinate geometry to one Mg(2), one Mg(4), three equivalent Mg(3), two equivalent Si(4), and two equivalent Si(8) atoms. In the eighth Si site, Si(8) is bonded in a distorted q6 geometry to two equivalent Mg(3), three equivalent Mg(4), two equivalent Si(3), and two equivalent Si(7) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_MgSi2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.229
_cell_length_b   5.229
_cell_length_c   12.247
_cell_angle_alpha   72.821
_cell_angle_beta   72.821
_cell_angle_gamma   39.746
_symmetry_Int_Tables_number   1
_cell_volume   203.240
_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  0.609  0.609  0.163  1.0
  Mg  Mg1  1  0.957  0.957  0.801  1.0
  Mg  Mg2  1  0.640  0.640  0.585  1.0
  Mg  Mg3  1  0.127  0.127  0.373  1.0
  Si  Si4  1  0.266  0.266  0.971  1.0
  Si  Si5  1  0.336  0.336  0.156  1.0
  Si  Si6  1  0.867  0.867  0.295  1.0
  Si  Si7  1  0.269  0.269  0.724  1.0
  Si  Si8  1  0.989  0.989  0.017  1.0
  Si  Si9  1  0.645  0.645  0.882  1.0
  Si  Si10  1  0.916  0.916  0.584  1.0
  Si  Si11  1  0.385  0.385  0.448  1.0
[/CIF]
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