The material 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 12-coordinate geometry to one Mg(2), one Mg(3), one Mg(4), one Mg(5), one Mg(6), one Mg(7), one Mg(8), one Si(1), one Si(2), one Si(4), and two equivalent Si(3) atoms. In the second Mg site, Mg(2) is bonded in a distorted T-shaped geometry to one Mg(1), one Mg(5), one Mg(7), one Si(1), one Si(2), one Si(3), and one Si(4) atom. In the third Mg site, Mg(3) is bonded in a 4-coordinate geometry to one Mg(1), one Mg(5), one Mg(7), one Si(1), one Si(2), one Si(3), and one Si(4) atom. In the fourth Mg site, Mg(4) is bonded in a 2-coordinate geometry to one Mg(1), one Mg(5), two equivalent Mg(7), one Si(2), and one Si(4) atom. In the fifth Mg site, Mg(5) is bonded in a 12-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(4), one Mg(6), one Mg(7), one Mg(8), one Si(1), one Si(3), one Si(4), and two equivalent Si(2) atoms. In the sixth Mg site, Mg(6) is bonded in a 4-coordinate geometry to one Mg(1), one Mg(5), one Mg(7), one Si(1), one Si(2), one Si(3), and one Si(4) atom. In the seventh Mg site, Mg(7) is bonded in a 12-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(5), one Mg(6), one Mg(8), two equivalent Mg(4), one Si(1), one Si(2), one Si(3), and one Si(4) atom. In the eighth Mg site, Mg(8) is bonded in a 4-coordinate geometry to one Mg(1), one Mg(5), one Mg(7), one Si(1), one Si(2), one Si(3), and two equivalent Si(4) atoms. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(5), one Mg(6), one Mg(7), one Mg(8), and one Si(3) atom. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(4), one Mg(6), one Mg(7), one Mg(8), and two equivalent Mg(5) atoms. In the third Si site, Si(3) is bonded in a 10-coordinate geometry to one Mg(2), one Mg(3), one Mg(5), one Mg(6), one Mg(7), one Mg(8), two equivalent Mg(1), one Si(1), and one Si(4) atom. In the fourth Si site, Si(4) is bonded in a 10-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(4), one Mg(5), one Mg(6), one Mg(7), two equivalent Mg(8), and one Si(3) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg2Si
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.035
_cell_length_b   6.648
_cell_length_c   6.766
_cell_angle_alpha   97.600
_cell_angle_beta   112.040
_cell_angle_gamma   105.825
_symmetry_Int_Tables_number   1
_cell_volume   233.567
_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  0.026  0.827  0.908  1.0
  Mg  Mg1  1  0.796  0.174  0.726  1.0
  Mg  Mg2  1  0.300  0.169  0.754  1.0
  Mg  Mg3  1  0.793  0.511  0.119  1.0
  Mg  Mg4  1  0.298  0.839  0.421  1.0
  Mg  Mg5  1  0.547  0.492  0.564  1.0
  Mg  Mg6  1  0.295  0.510  0.085  1.0
  Mg  Mg7  1  0.995  0.155  0.256  1.0
  Si  Si8  1  0.117  0.533  0.636  1.0
  Si  Si9  1  0.820  0.824  0.448  1.0
  Si  Si10  1  0.523  0.846  0.887  1.0
  Si  Si11  1  0.490  0.122  0.197  1.0
[/CIF]
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The material 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 12-coordinate geometry to one Mg(2), one Mg(3), one Mg(4), one Mg(5), one Mg(6), one Mg(7), one Mg(8), one Si(1), one Si(2), one Si(4), and two equivalent Si(3) atoms. In the second Mg site, Mg(2) is bonded in a distorted T-shaped geometry to one Mg(1), one Mg(5), one Mg(7), one Si(1), one Si(2), one Si(3), and one Si(4) atom. In the third Mg site, Mg(3) is bonded in a 4-coordinate geometry to one Mg(1), one Mg(5), one Mg(7), one Si(1), one Si(2), one Si(3), and one Si(4) atom. In the fourth Mg site, Mg(4) is bonded in a 2-coordinate geometry to one Mg(1), one Mg(5), two equivalent Mg(7), one Si(2), and one Si(4) atom. In the fifth Mg site, Mg(5) is bonded in a 12-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(4), one Mg(6), one Mg(7), one Mg(8), one Si(1), one Si(3), one Si(4), and two equivalent Si(2) atoms. In the sixth Mg site, Mg(6) is bonded in a 4-coordinate geometry to one Mg(1), one Mg(5), one Mg(7), one Si(1), one Si(2), one Si(3), and one Si(4) atom. In the seventh Mg site, Mg(7) is bonded in a 12-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(5), one Mg(6), one Mg(8), two equivalent Mg(4), one Si(1), one Si(2), one Si(3), and one Si(4) atom. In the eighth Mg site, Mg(8) is bonded in a 4-coordinate geometry to one Mg(1), one Mg(5), one Mg(7), one Si(1), one Si(2), one Si(3), and two equivalent Si(4) atoms. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(5), one Mg(6), one Mg(7), one Mg(8), and one Si(3) atom. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(4), one Mg(6), one Mg(7), one Mg(8), and two equivalent Mg(5) atoms. In the third Si site, Si(3) is bonded in a 10-coordinate geometry to one Mg(2), one Mg(3), one Mg(5), one Mg(6), one Mg(7), one Mg(8), two equivalent Mg(1), one Si(1), and one Si(4) atom. In the fourth Si site, Si(4) is bonded in a 10-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(4), one Mg(5), one Mg(6), one Mg(7), two equivalent Mg(8), and one Si(3) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg2Si
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.035
_cell_length_b   6.648
_cell_length_c   6.766
_cell_angle_alpha   97.600
_cell_angle_beta   112.040
_cell_angle_gamma   105.825
_symmetry_Int_Tables_number   1
_cell_volume   233.567
_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  0.026  0.827  0.908  1.0
  Mg  Mg1  1  0.796  0.174  0.726  1.0
  Mg  Mg2  1  0.300  0.169  0.754  1.0
  Mg  Mg3  1  0.793  0.511  0.119  1.0
  Mg  Mg4  1  0.298  0.839  0.421  1.0
  Mg  Mg5  1  0.547  0.492  0.564  1.0
  Mg  Mg6  1  0.295  0.510  0.085  1.0
  Mg  Mg7  1  0.995  0.155  0.256  1.0
  Si  Si8  1  0.117  0.533  0.636  1.0
  Si  Si9  1  0.820  0.824  0.448  1.0
  Si  Si10  1  0.523  0.846  0.887  1.0
  Si  Si11  1  0.490  0.122  0.197  1.0
[/CIF]
.