The compound described by MgSi2 crystallizes in the triclinic P1 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 6-coordinate geometry to three equivalent Si(2) and three equivalent Si(5) atoms. In the second Mg site, Mg(2) is bonded in a 8-coordinate geometry to two equivalent Si(6), three equivalent Si(1), and three equivalent Si(2) atoms. In the third Mg site, Mg(3) is bonded in a 10-coordinate geometry to one Si(1), one Si(3), two equivalent Si(6), two equivalent Si(8), three equivalent Si(4), and three equivalent Si(7) atoms. In the fourth Mg site, Mg(4) is bonded in a 8-coordinate geometry to two equivalent Si(8), three equivalent Si(3), and three equivalent Si(5) atoms. There are eight inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to one Mg(3), three equivalent Mg(2), two equivalent Si(7), and three equivalent Si(6) atoms. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to three equivalent Mg(1), three equivalent Mg(2), and two equivalent Si(5) atoms. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to one Mg(3), three equivalent Mg(4), two equivalent Si(4), and three equivalent Si(8) atoms. In the fourth Si site, Si(4) is bonded in a 8-coordinate geometry to three equivalent Mg(3), two equivalent Si(3), and three equivalent Si(8) atoms. In the fifth Si site, Si(5) is bonded in a 8-coordinate geometry to three equivalent Mg(1), three equivalent Mg(4), and two equivalent Si(2) atoms. In the sixth Si site, Si(6) is bonded in a 10-coordinate geometry to two equivalent Mg(2), two equivalent Mg(3), three equivalent Si(1), and three equivalent Si(7) atoms. In the seventh Si site, Si(7) is bonded in a 8-coordinate geometry to three equivalent Mg(3), two equivalent Si(1), and three equivalent Si(6) atoms. In the eighth Si site, Si(8) is bonded in a 10-coordinate geometry to two equivalent Mg(3), two equivalent Mg(4), three equivalent Si(3), and three equivalent Si(4) atoms. is represented by the CIF file [CIF]
data_MgSi2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.613
_cell_length_b   3.574
_cell_length_c   14.399
_cell_angle_alpha   91.003
_cell_angle_beta   72.592
_cell_angle_gamma   70.017
_symmetry_Int_Tables_number   1
_cell_volume   211.023
_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  0.499  0.833  0.875  1.0
  Mg  Mg1  1  0.136  0.511  0.054  1.0
  Mg  Mg2  1  0.501  0.834  0.375  1.0
  Mg  Mg3  1  0.863  0.156  0.696  1.0
  Si  Si4  1  0.450  0.841  0.163  1.0
  Si  Si5  1  0.871  0.149  0.936  1.0
  Si  Si6  1  0.550  0.826  0.587  1.0
  Si  Si7  1  0.851  0.183  0.469  1.0
  Si  Si8  1  0.128  0.518  0.814  1.0
  Si  Si9  1  0.794  0.187  0.215  1.0
  Si  Si10  1  0.150  0.484  0.281  1.0
  Si  Si11  1  0.206  0.479  0.536  1.0
[/CIF]
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The compound described by MgSi2 crystallizes in the triclinic P1 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 6-coordinate geometry to three equivalent Si(2) and three equivalent Si(5) atoms. In the second Mg site, Mg(2) is bonded in a 8-coordinate geometry to two equivalent Si(6), three equivalent Si(1), and three equivalent Si(2) atoms. In the third Mg site, Mg(3) is bonded in a 10-coordinate geometry to one Si(1), one Si(3), two equivalent Si(6), two equivalent Si(8), three equivalent Si(4), and three equivalent Si(7) atoms. In the fourth Mg site, Mg(4) is bonded in a 8-coordinate geometry to two equivalent Si(8), three equivalent Si(3), and three equivalent Si(5) atoms. There are eight inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to one Mg(3), three equivalent Mg(2), two equivalent Si(7), and three equivalent Si(6) atoms. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to three equivalent Mg(1), three equivalent Mg(2), and two equivalent Si(5) atoms. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to one Mg(3), three equivalent Mg(4), two equivalent Si(4), and three equivalent Si(8) atoms. In the fourth Si site, Si(4) is bonded in a 8-coordinate geometry to three equivalent Mg(3), two equivalent Si(3), and three equivalent Si(8) atoms. In the fifth Si site, Si(5) is bonded in a 8-coordinate geometry to three equivalent Mg(1), three equivalent Mg(4), and two equivalent Si(2) atoms. In the sixth Si site, Si(6) is bonded in a 10-coordinate geometry to two equivalent Mg(2), two equivalent Mg(3), three equivalent Si(1), and three equivalent Si(7) atoms. In the seventh Si site, Si(7) is bonded in a 8-coordinate geometry to three equivalent Mg(3), two equivalent Si(1), and three equivalent Si(6) atoms. In the eighth Si site, Si(8) is bonded in a 10-coordinate geometry to two equivalent Mg(3), two equivalent Mg(4), three equivalent Si(3), and three equivalent Si(4) atoms. is represented by the CIF file [CIF]
data_MgSi2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.613
_cell_length_b   3.574
_cell_length_c   14.399
_cell_angle_alpha   91.003
_cell_angle_beta   72.592
_cell_angle_gamma   70.017
_symmetry_Int_Tables_number   1
_cell_volume   211.023
_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  0.499  0.833  0.875  1.0
  Mg  Mg1  1  0.136  0.511  0.054  1.0
  Mg  Mg2  1  0.501  0.834  0.375  1.0
  Mg  Mg3  1  0.863  0.156  0.696  1.0
  Si  Si4  1  0.450  0.841  0.163  1.0
  Si  Si5  1  0.871  0.149  0.936  1.0
  Si  Si6  1  0.550  0.826  0.587  1.0
  Si  Si7  1  0.851  0.183  0.469  1.0
  Si  Si8  1  0.128  0.518  0.814  1.0
  Si  Si9  1  0.794  0.187  0.215  1.0
  Si  Si10  1  0.150  0.484  0.281  1.0
  Si  Si11  1  0.206  0.479  0.536  1.0
[/CIF]
.