The material described by Mg2Si crystallizes in the monoclinic C2/m space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(2), two equivalent Mg(3), two equivalent Si(1), two equivalent Si(2), and two equivalent Si(3) atoms to form distorted MgMg4Si6 cuboctahedra that share corners with two equivalent Mg(3)Mg8Si4 cuboctahedra, corners with four equivalent Mg(1)Mg4Si6 cuboctahedra, edges with two equivalent Mg(1)Mg4Si6 cuboctahedra, edges with four equivalent Mg(3)Mg8Si4 cuboctahedra, faces with two equivalent Mg(1)Mg4Si6 cuboctahedra, and faces with two equivalent Mg(3)Mg8Si4 cuboctahedra. In the second Mg site, Mg(2) is bonded in a 12-coordinate geometry to one Mg(1), three equivalent Mg(2), three equivalent Mg(3), one Si(2), one Si(3), and three equivalent Si(1) atoms. In the third Mg site, Mg(3) is bonded to two equivalent Mg(1), six equivalent Mg(2), one Si(2), and three equivalent Si(1) atoms to form distorted MgMg8Si4 cuboctahedra that share corners with two equivalent Mg(1)Mg4Si6 cuboctahedra, corners with nine equivalent Mg(3)Mg8Si4 cuboctahedra, edges with four equivalent Mg(1)Mg4Si6 cuboctahedra, faces with two equivalent Mg(1)Mg4Si6 cuboctahedra, and faces with three equivalent Mg(3)Mg8Si4 cuboctahedra. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 11-coordinate geometry to two equivalent Mg(1), three equivalent Mg(3), and six equivalent Mg(2) atoms. In the second Si site, Si(2) is bonded in a distorted q6 geometry to two equivalent Mg(3), four equivalent Mg(1), and four equivalent Mg(2) atoms. In the third Si site, Si(3) is bonded in a distorted body-centered cubic geometry to four equivalent Mg(1) and four equivalent Mg(2) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg2Si
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.903
_cell_length_b   5.903
_cell_length_c   7.266
_cell_angle_alpha   88.878
_cell_angle_beta   88.878
_cell_angle_gamma   62.664
_symmetry_Int_Tables_number   1
_cell_volume   224.835
_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  0.500  0.000  0.500  1.0
  Mg  Mg1  1  0.000  0.500  0.500  1.0
  Mg  Mg2  1  0.175  0.667  0.823  1.0
  Mg  Mg3  1  0.825  0.333  0.177  1.0
  Mg  Mg4  1  0.333  0.825  0.177  1.0
  Mg  Mg5  1  0.667  0.175  0.823  1.0
  Mg  Mg6  1  0.165  0.165  0.840  1.0
  Mg  Mg7  1  0.835  0.835  0.160  1.0
  Si  Si8  1  0.332  0.332  0.168  1.0
  Si  Si9  1  0.668  0.668  0.832  1.0
  Si  Si10  1  0.000  0.000  0.500  1.0
  Si  Si11  1  0.500  0.500  0.500  1.0
[/CIF]
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The material described by Mg2Si crystallizes in the monoclinic C2/m space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(2), two equivalent Mg(3), two equivalent Si(1), two equivalent Si(2), and two equivalent Si(3) atoms to form distorted MgMg4Si6 cuboctahedra that share corners with two equivalent Mg(3)Mg8Si4 cuboctahedra, corners with four equivalent Mg(1)Mg4Si6 cuboctahedra, edges with two equivalent Mg(1)Mg4Si6 cuboctahedra, edges with four equivalent Mg(3)Mg8Si4 cuboctahedra, faces with two equivalent Mg(1)Mg4Si6 cuboctahedra, and faces with two equivalent Mg(3)Mg8Si4 cuboctahedra. In the second Mg site, Mg(2) is bonded in a 12-coordinate geometry to one Mg(1), three equivalent Mg(2), three equivalent Mg(3), one Si(2), one Si(3), and three equivalent Si(1) atoms. In the third Mg site, Mg(3) is bonded to two equivalent Mg(1), six equivalent Mg(2), one Si(2), and three equivalent Si(1) atoms to form distorted MgMg8Si4 cuboctahedra that share corners with two equivalent Mg(1)Mg4Si6 cuboctahedra, corners with nine equivalent Mg(3)Mg8Si4 cuboctahedra, edges with four equivalent Mg(1)Mg4Si6 cuboctahedra, faces with two equivalent Mg(1)Mg4Si6 cuboctahedra, and faces with three equivalent Mg(3)Mg8Si4 cuboctahedra. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 11-coordinate geometry to two equivalent Mg(1), three equivalent Mg(3), and six equivalent Mg(2) atoms. In the second Si site, Si(2) is bonded in a distorted q6 geometry to two equivalent Mg(3), four equivalent Mg(1), and four equivalent Mg(2) atoms. In the third Si site, Si(3) is bonded in a distorted body-centered cubic geometry to four equivalent Mg(1) and four equivalent Mg(2) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg2Si
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.903
_cell_length_b   5.903
_cell_length_c   7.266
_cell_angle_alpha   88.878
_cell_angle_beta   88.878
_cell_angle_gamma   62.664
_symmetry_Int_Tables_number   1
_cell_volume   224.835
_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  0.500  0.000  0.500  1.0
  Mg  Mg1  1  0.000  0.500  0.500  1.0
  Mg  Mg2  1  0.175  0.667  0.823  1.0
  Mg  Mg3  1  0.825  0.333  0.177  1.0
  Mg  Mg4  1  0.333  0.825  0.177  1.0
  Mg  Mg5  1  0.667  0.175  0.823  1.0
  Mg  Mg6  1  0.165  0.165  0.840  1.0
  Mg  Mg7  1  0.835  0.835  0.160  1.0
  Si  Si8  1  0.332  0.332  0.168  1.0
  Si  Si9  1  0.668  0.668  0.832  1.0
  Si  Si10  1  0.000  0.000  0.500  1.0
  Si  Si11  1  0.500  0.500  0.500  1.0
[/CIF]
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