The compound described by Mg3Si2 crystallizes in the triclinic P-1 space group. There are seven inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 5-coordinate geometry to one Si(2), two equivalent Si(1), and two equivalent Si(3) atoms. In the second Mg site, Mg(2) is bonded in a 5-coordinate geometry to one Si(2), one Si(3), and three equivalent Si(1) atoms. In the third Mg site, Mg(3) is bonded in a distorted square co-planar geometry to two equivalent Si(1) and two equivalent Si(3) atoms. In the fourth Mg site, Mg(4) is bonded in a distorted rectangular see-saw-like geometry to one Si(1), one Si(2), one Si(3), and one Si(4) atom. In the fifth Mg site, Mg(5) is bonded in a 5-coordinate geometry to one Si(3), two equivalent Si(2), and three equivalent Si(4) atoms. In the sixth Mg site, Mg(6) is bonded in a 6-coordinate geometry to one Si(3), two equivalent Si(2), and three equivalent Si(4) atoms. In the seventh Mg site, Mg(7) is bonded in a 4-coordinate geometry to two equivalent Si(2) 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(3), one Mg(4), two equivalent Mg(1), three equivalent Mg(2), and one Si(1) atom. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(2), one Mg(4), one Mg(7), two equivalent Mg(5), two equivalent Mg(6), and one Si(3) atom. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to one Mg(2), one Mg(3), one Mg(4), one Mg(5), one Mg(6), two equivalent Mg(1), and one Si(2) atom. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to one Mg(4), one Mg(7), three equivalent Mg(5), three equivalent Mg(6), and one Si(4) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg3Si2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.087
_cell_length_b   5.659
_cell_length_c   13.750
_cell_angle_alpha   97.401
_cell_angle_beta   98.256
_cell_angle_gamma   92.048
_symmetry_Int_Tables_number   1
_cell_volume   387.890
_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  0.412  0.895  0.868  1.0
  Mg  Mg1  1  0.071  0.417  0.876  1.0
  Mg  Mg2  1  0.000  0.000  0.000  1.0
  Mg  Mg3  1  0.531  0.382  0.752  1.0
  Mg  Mg4  1  0.962  0.521  0.625  1.0
  Mg  Mg5  1  0.588  0.105  0.132  1.0
  Mg  Mg6  1  0.479  0.103  0.376  1.0
  Mg  Mg7  1  0.038  0.479  0.375  1.0
  Mg  Mg8  1  0.000  0.000  0.500  1.0
  Mg  Mg9  1  0.469  0.618  0.248  1.0
  Mg  Mg10  1  0.929  0.583  0.124  1.0
  Mg  Mg11  1  0.521  0.897  0.624  1.0
  Si  Si12  1  0.406  0.664  0.048  1.0
  Si  Si13  1  0.070  0.070  0.698  1.0
  Si  Si14  1  0.594  0.336  0.952  1.0
  Si  Si15  1  0.874  0.810  0.797  1.0
  Si  Si16  1  0.402  0.371  0.550  1.0
  Si  Si17  1  0.126  0.190  0.203  1.0
  Si  Si18  1  0.598  0.629  0.450  1.0
  Si  Si19  1  0.930  0.930  0.302  1.0
[/CIF]
.
The compound described by Mg3Si2 crystallizes in the triclinic P-1 space group. There are seven inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 5-coordinate geometry to one Si(2), two equivalent Si(1), and two equivalent Si(3) atoms. In the second Mg site, Mg(2) is bonded in a 5-coordinate geometry to one Si(2), one Si(3), and three equivalent Si(1) atoms. In the third Mg site, Mg(3) is bonded in a distorted square co-planar geometry to two equivalent Si(1) and two equivalent Si(3) atoms. In the fourth Mg site, Mg(4) is bonded in a distorted rectangular see-saw-like geometry to one Si(1), one Si(2), one Si(3), and one Si(4) atom. In the fifth Mg site, Mg(5) is bonded in a 5-coordinate geometry to one Si(3), two equivalent Si(2), and three equivalent Si(4) atoms. In the sixth Mg site, Mg(6) is bonded in a 6-coordinate geometry to one Si(3), two equivalent Si(2), and three equivalent Si(4) atoms. In the seventh Mg site, Mg(7) is bonded in a 4-coordinate geometry to two equivalent Si(2) 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(3), one Mg(4), two equivalent Mg(1), three equivalent Mg(2), and one Si(1) atom. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(2), one Mg(4), one Mg(7), two equivalent Mg(5), two equivalent Mg(6), and one Si(3) atom. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to one Mg(2), one Mg(3), one Mg(4), one Mg(5), one Mg(6), two equivalent Mg(1), and one Si(2) atom. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to one Mg(4), one Mg(7), three equivalent Mg(5), three equivalent Mg(6), and one Si(4) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg3Si2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.087
_cell_length_b   5.659
_cell_length_c   13.750
_cell_angle_alpha   97.401
_cell_angle_beta   98.256
_cell_angle_gamma   92.048
_symmetry_Int_Tables_number   1
_cell_volume   387.890
_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  0.412  0.895  0.868  1.0
  Mg  Mg1  1  0.071  0.417  0.876  1.0
  Mg  Mg2  1  0.000  0.000  0.000  1.0
  Mg  Mg3  1  0.531  0.382  0.752  1.0
  Mg  Mg4  1  0.962  0.521  0.625  1.0
  Mg  Mg5  1  0.588  0.105  0.132  1.0
  Mg  Mg6  1  0.479  0.103  0.376  1.0
  Mg  Mg7  1  0.038  0.479  0.375  1.0
  Mg  Mg8  1  0.000  0.000  0.500  1.0
  Mg  Mg9  1  0.469  0.618  0.248  1.0
  Mg  Mg10  1  0.929  0.583  0.124  1.0
  Mg  Mg11  1  0.521  0.897  0.624  1.0
  Si  Si12  1  0.406  0.664  0.048  1.0
  Si  Si13  1  0.070  0.070  0.698  1.0
  Si  Si14  1  0.594  0.336  0.952  1.0
  Si  Si15  1  0.874  0.810  0.797  1.0
  Si  Si16  1  0.402  0.371  0.550  1.0
  Si  Si17  1  0.126  0.190  0.203  1.0
  Si  Si18  1  0.598  0.629  0.450  1.0
  Si  Si19  1  0.930  0.930  0.302  1.0
[/CIF]
.