The crystal structure described by Mg2Si crystallizes in the triclinic P1 space group. There are eight inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 5-coordinate geometry to one Mg(2), one Mg(3), one Mg(4), two equivalent Mg(8), one Si(1), one Si(3), one Si(4), and two equivalent Si(2) atoms. In the second Mg site, Mg(2) is bonded in a 12-coordinate geometry to one Mg(1), one Mg(4), one Mg(5), one Mg(6), one Mg(8), two equivalent Mg(7), one Si(4), two equivalent Si(1), and two equivalent Si(3) atoms. In the third Mg site, Mg(3) is bonded in a 12-coordinate geometry to one Mg(1), one Mg(4), one Mg(6), one Mg(7), one Mg(8), two equivalent Mg(5), one Si(1), two equivalent Si(2), and two equivalent Si(4) atoms. In the fourth Mg site, Mg(4) is bonded in a 12-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(5), one Mg(6), two equivalent Mg(7), one Si(3), two equivalent Si(2), and two equivalent Si(4) atoms. In the fifth Mg site, Mg(5) is bonded in a 5-coordinate geometry to one Mg(2), one Mg(4), one Mg(8), two equivalent Mg(3), one Si(2), one Si(3), one Si(4), and two equivalent Si(1) atoms. In the sixth Mg site, Mg(6) is bonded to one Mg(2), one Mg(3), one Mg(4), one Mg(8), two equivalent Mg(7), one Si(1), one Si(2), two equivalent Si(3), and two equivalent Si(4) atoms to form distorted MgMg6Si6 cuboctahedra that share corners with two equivalent Mg(6)Mg6Si6 cuboctahedra, edges with two equivalent Mg(6)Mg6Si6 cuboctahedra, edges with two equivalent Mg(7)Mg8Si4 cuboctahedra, and faces with two equivalent Mg(7)Mg8Si4 cuboctahedra. In the seventh Mg site, Mg(7) is bonded to one Mg(3), one Mg(8), two equivalent Mg(2), two equivalent Mg(4), two equivalent Mg(6), one Si(1), one Si(2), one Si(3), and one Si(4) atom to form distorted MgMg8Si4 cuboctahedra that share corners with two equivalent Mg(7)Mg8Si4 cuboctahedra, edges with two equivalent Mg(6)Mg6Si6 cuboctahedra, edges with two equivalent Mg(7)Mg8Si4 cuboctahedra, and faces with two equivalent Mg(6)Mg6Si6 cuboctahedra. In the eighth Mg site, Mg(8) is bonded in a 12-coordinate geometry to one Mg(2), one Mg(3), one Mg(5), one Mg(6), one Mg(7), two equivalent Mg(1), one Si(2), two equivalent Si(1), and two equivalent Si(3) atoms. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 10-coordinate geometry to one Mg(1), one Mg(3), one Mg(6), one Mg(7), two equivalent Mg(2), two equivalent Mg(5), two equivalent Mg(8), and one Si(2) atom. In the second Si site, Si(2) is bonded in a 11-coordinate geometry to one Mg(5), one Mg(6), one Mg(7), one Mg(8), two equivalent Mg(1), two equivalent Mg(3), two equivalent Mg(4), and one Si(1) atom. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(4), one Mg(5), one Mg(7), two equivalent Mg(2), two equivalent Mg(6), and two equivalent Mg(8) atoms. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(2), one Mg(5), one Mg(7), two equivalent Mg(3), two equivalent Mg(4), and two equivalent Mg(6) atoms. is represented by the CIF card [CIF]
data_Mg2Si
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.303
_cell_length_b   6.147
_cell_length_c   7.635
_cell_angle_alpha   79.697
_cell_angle_beta   82.495
_cell_angle_gamma   105.919
_symmetry_Int_Tables_number   1
_cell_volume   231.194
_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  0.652  0.201  0.085  1.0
  Mg  Mg1  1  0.667  0.851  0.426  1.0
  Mg  Mg2  1  0.179  0.630  0.917  1.0
  Mg  Mg3  1  0.665  0.066  0.740  1.0
  Mg  Mg4  1  0.681  0.716  0.081  1.0
  Mg  Mg5  1  0.167  0.458  0.584  1.0
  Mg  Mg6  1  0.166  0.958  0.584  1.0
  Mg  Mg7  1  0.155  0.286  0.250  1.0
  Si  Si8  1  0.170  0.794  0.241  1.0
  Si  Si9  1  0.163  0.122  0.927  1.0
  Si  Si10  1  0.687  0.389  0.405  1.0
  Si  Si11  1  0.648  0.530  0.761  1.0
[/CIF]
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The crystal structure described by Mg2Si crystallizes in the triclinic P1 space group. There are eight inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 5-coordinate geometry to one Mg(2), one Mg(3), one Mg(4), two equivalent Mg(8), one Si(1), one Si(3), one Si(4), and two equivalent Si(2) atoms. In the second Mg site, Mg(2) is bonded in a 12-coordinate geometry to one Mg(1), one Mg(4), one Mg(5), one Mg(6), one Mg(8), two equivalent Mg(7), one Si(4), two equivalent Si(1), and two equivalent Si(3) atoms. In the third Mg site, Mg(3) is bonded in a 12-coordinate geometry to one Mg(1), one Mg(4), one Mg(6), one Mg(7), one Mg(8), two equivalent Mg(5), one Si(1), two equivalent Si(2), and two equivalent Si(4) atoms. In the fourth Mg site, Mg(4) is bonded in a 12-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(5), one Mg(6), two equivalent Mg(7), one Si(3), two equivalent Si(2), and two equivalent Si(4) atoms. In the fifth Mg site, Mg(5) is bonded in a 5-coordinate geometry to one Mg(2), one Mg(4), one Mg(8), two equivalent Mg(3), one Si(2), one Si(3), one Si(4), and two equivalent Si(1) atoms. In the sixth Mg site, Mg(6) is bonded to one Mg(2), one Mg(3), one Mg(4), one Mg(8), two equivalent Mg(7), one Si(1), one Si(2), two equivalent Si(3), and two equivalent Si(4) atoms to form distorted MgMg6Si6 cuboctahedra that share corners with two equivalent Mg(6)Mg6Si6 cuboctahedra, edges with two equivalent Mg(6)Mg6Si6 cuboctahedra, edges with two equivalent Mg(7)Mg8Si4 cuboctahedra, and faces with two equivalent Mg(7)Mg8Si4 cuboctahedra. In the seventh Mg site, Mg(7) is bonded to one Mg(3), one Mg(8), two equivalent Mg(2), two equivalent Mg(4), two equivalent Mg(6), one Si(1), one Si(2), one Si(3), and one Si(4) atom to form distorted MgMg8Si4 cuboctahedra that share corners with two equivalent Mg(7)Mg8Si4 cuboctahedra, edges with two equivalent Mg(6)Mg6Si6 cuboctahedra, edges with two equivalent Mg(7)Mg8Si4 cuboctahedra, and faces with two equivalent Mg(6)Mg6Si6 cuboctahedra. In the eighth Mg site, Mg(8) is bonded in a 12-coordinate geometry to one Mg(2), one Mg(3), one Mg(5), one Mg(6), one Mg(7), two equivalent Mg(1), one Si(2), two equivalent Si(1), and two equivalent Si(3) atoms. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 10-coordinate geometry to one Mg(1), one Mg(3), one Mg(6), one Mg(7), two equivalent Mg(2), two equivalent Mg(5), two equivalent Mg(8), and one Si(2) atom. In the second Si site, Si(2) is bonded in a 11-coordinate geometry to one Mg(5), one Mg(6), one Mg(7), one Mg(8), two equivalent Mg(1), two equivalent Mg(3), two equivalent Mg(4), and one Si(1) atom. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(4), one Mg(5), one Mg(7), two equivalent Mg(2), two equivalent Mg(6), and two equivalent Mg(8) atoms. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(2), one Mg(5), one Mg(7), two equivalent Mg(3), two equivalent Mg(4), and two equivalent Mg(6) atoms. is represented by the CIF card [CIF]
data_Mg2Si
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.303
_cell_length_b   6.147
_cell_length_c   7.635
_cell_angle_alpha   79.697
_cell_angle_beta   82.495
_cell_angle_gamma   105.919
_symmetry_Int_Tables_number   1
_cell_volume   231.194
_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  0.652  0.201  0.085  1.0
  Mg  Mg1  1  0.667  0.851  0.426  1.0
  Mg  Mg2  1  0.179  0.630  0.917  1.0
  Mg  Mg3  1  0.665  0.066  0.740  1.0
  Mg  Mg4  1  0.681  0.716  0.081  1.0
  Mg  Mg5  1  0.167  0.458  0.584  1.0
  Mg  Mg6  1  0.166  0.958  0.584  1.0
  Mg  Mg7  1  0.155  0.286  0.250  1.0
  Si  Si8  1  0.170  0.794  0.241  1.0
  Si  Si9  1  0.163  0.122  0.927  1.0
  Si  Si10  1  0.687  0.389  0.405  1.0
  Si  Si11  1  0.648  0.530  0.761  1.0
[/CIF]
.