The crystal structure described by MgSi crystallizes in the triclinic P1 space group. There are six inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 5-coordinate geometry to one Si(1), two equivalent Si(3), and two equivalent Si(4) atoms. In the second Mg site, Mg(2) is bonded in a 5-coordinate geometry to one Si(5), two equivalent Si(3), and two equivalent Si(4) atoms. In the third Mg site, Mg(3) is bonded in a 6-coordinate geometry to one Si(1), one Si(4), one Si(6), two equivalent Si(2), and two equivalent Si(5) atoms. In the fourth Mg site, Mg(4) is bonded in a 6-coordinate geometry to one Si(2), one Si(3), one Si(5), two equivalent Si(1), and two equivalent Si(6) atoms. In the fifth Mg site, Mg(5) is bonded to one Si(2), one Si(3), and two equivalent Si(4) atoms to form distorted MgSi4 tetrahedra that share  a cornercorner with one Si(6)Mg4Si3 pentagonal bipyramid, corners with two equivalent Mg(5)Si4 tetrahedra, and edges with two equivalent Mg(6)Si4 tetrahedra. In the sixth Mg site, Mg(6) is bonded to one Si(4), one Si(6), and two equivalent Si(3) atoms to form distorted MgSi4 tetrahedra that share  a cornercorner with one Si(2)Mg4Si3 pentagonal bipyramid, corners with two equivalent Mg(6)Si4 tetrahedra, and edges with two equivalent Mg(5)Si4 tetrahedra. There are six inequivalent Si sites. In the first Si site, Si(1) is bonded in a 7-coordinate geometry to one Mg(1), one Mg(3), two equivalent Mg(4), one Si(5), and two equivalent Si(6) atoms. In the second Si site, Si(2) is bonded to one Mg(4), one Mg(5), two equivalent Mg(3), one Si(6), and two equivalent Si(5) atoms to form distorted SiMg4Si3 pentagonal bipyramids that share  a cornercorner with one Mg(6)Si4 tetrahedra, edges with two equivalent Si(2)Mg4Si3 pentagonal bipyramids, and edges with two equivalent Si(6)Mg4Si3 pentagonal bipyramids. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to one Mg(4), one Mg(5), two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(6), and one Si(4) atom. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to one Mg(3), one Mg(6), two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(5), and one Si(3) atom. In the fifth Si site, Si(5) is bonded in a 7-coordinate geometry to one Mg(2), one Mg(4), two equivalent Mg(3), one Si(1), and two equivalent Si(2) atoms. In the sixth Si site, Si(6) is bonded to one Mg(3), one Mg(6), two equivalent Mg(4), one Si(2), and two equivalent Si(1) atoms to form distorted SiMg4Si3 pentagonal bipyramids that share  a cornercorner with one Mg(5)Si4 tetrahedra, edges with two equivalent Si(2)Mg4Si3 pentagonal bipyramids, and edges with two equivalent Si(6)Mg4Si3 pentagonal bipyramids. is represented by the CIF file [CIF]
data_MgSi
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.894
_cell_length_b   6.198
_cell_length_c   10.159
_cell_angle_alpha   94.537
_cell_angle_beta   96.498
_cell_angle_gamma   107.187
_symmetry_Int_Tables_number   1
_cell_volume   231.083
_cell_formula_units_Z   6
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  0.579  0.083  0.855  1.0
  Mg  Mg1  1  0.588  0.927  0.142  1.0
  Mg  Mg2  1  0.306  0.239  0.338  1.0
  Mg  Mg3  1  0.858  0.757  0.663  1.0
  Mg  Mg4  1  0.867  0.497  0.139  1.0
  Mg  Mg5  1  0.304  0.513  0.865  1.0
  Si  Si6  1  0.588  0.127  0.594  1.0
  Si  Si7  1  0.987  0.599  0.410  1.0
  Si  Si8  1  0.972  0.806  0.949  1.0
  Si  Si9  1  0.198  0.203  0.051  1.0
  Si  Si10  1  0.574  0.860  0.400  1.0
  Si  Si11  1  0.180  0.389  0.595  1.0
[/CIF]
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The crystal structure described by MgSi crystallizes in the triclinic P1 space group. There are six inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 5-coordinate geometry to one Si(1), two equivalent Si(3), and two equivalent Si(4) atoms. In the second Mg site, Mg(2) is bonded in a 5-coordinate geometry to one Si(5), two equivalent Si(3), and two equivalent Si(4) atoms. In the third Mg site, Mg(3) is bonded in a 6-coordinate geometry to one Si(1), one Si(4), one Si(6), two equivalent Si(2), and two equivalent Si(5) atoms. In the fourth Mg site, Mg(4) is bonded in a 6-coordinate geometry to one Si(2), one Si(3), one Si(5), two equivalent Si(1), and two equivalent Si(6) atoms. In the fifth Mg site, Mg(5) is bonded to one Si(2), one Si(3), and two equivalent Si(4) atoms to form distorted MgSi4 tetrahedra that share  a cornercorner with one Si(6)Mg4Si3 pentagonal bipyramid, corners with two equivalent Mg(5)Si4 tetrahedra, and edges with two equivalent Mg(6)Si4 tetrahedra. In the sixth Mg site, Mg(6) is bonded to one Si(4), one Si(6), and two equivalent Si(3) atoms to form distorted MgSi4 tetrahedra that share  a cornercorner with one Si(2)Mg4Si3 pentagonal bipyramid, corners with two equivalent Mg(6)Si4 tetrahedra, and edges with two equivalent Mg(5)Si4 tetrahedra. There are six inequivalent Si sites. In the first Si site, Si(1) is bonded in a 7-coordinate geometry to one Mg(1), one Mg(3), two equivalent Mg(4), one Si(5), and two equivalent Si(6) atoms. In the second Si site, Si(2) is bonded to one Mg(4), one Mg(5), two equivalent Mg(3), one Si(6), and two equivalent Si(5) atoms to form distorted SiMg4Si3 pentagonal bipyramids that share  a cornercorner with one Mg(6)Si4 tetrahedra, edges with two equivalent Si(2)Mg4Si3 pentagonal bipyramids, and edges with two equivalent Si(6)Mg4Si3 pentagonal bipyramids. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to one Mg(4), one Mg(5), two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(6), and one Si(4) atom. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to one Mg(3), one Mg(6), two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(5), and one Si(3) atom. In the fifth Si site, Si(5) is bonded in a 7-coordinate geometry to one Mg(2), one Mg(4), two equivalent Mg(3), one Si(1), and two equivalent Si(2) atoms. In the sixth Si site, Si(6) is bonded to one Mg(3), one Mg(6), two equivalent Mg(4), one Si(2), and two equivalent Si(1) atoms to form distorted SiMg4Si3 pentagonal bipyramids that share  a cornercorner with one Mg(5)Si4 tetrahedra, edges with two equivalent Si(2)Mg4Si3 pentagonal bipyramids, and edges with two equivalent Si(6)Mg4Si3 pentagonal bipyramids. is represented by the CIF file [CIF]
data_MgSi
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.894
_cell_length_b   6.198
_cell_length_c   10.159
_cell_angle_alpha   94.537
_cell_angle_beta   96.498
_cell_angle_gamma   107.187
_symmetry_Int_Tables_number   1
_cell_volume   231.083
_cell_formula_units_Z   6
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  0.579  0.083  0.855  1.0
  Mg  Mg1  1  0.588  0.927  0.142  1.0
  Mg  Mg2  1  0.306  0.239  0.338  1.0
  Mg  Mg3  1  0.858  0.757  0.663  1.0
  Mg  Mg4  1  0.867  0.497  0.139  1.0
  Mg  Mg5  1  0.304  0.513  0.865  1.0
  Si  Si6  1  0.588  0.127  0.594  1.0
  Si  Si7  1  0.987  0.599  0.410  1.0
  Si  Si8  1  0.972  0.806  0.949  1.0
  Si  Si9  1  0.198  0.203  0.051  1.0
  Si  Si10  1  0.574  0.860  0.400  1.0
  Si  Si11  1  0.180  0.389  0.595  1.0
[/CIF]
.