The crystal structure described by Mg4Si3 crystallizes in the triclinic P1 space group. There are eight inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 6-coordinate geometry to one Mg(2), two equivalent Mg(6), one Si(1), one Si(4), one Si(5), one Si(6), 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(3), one Mg(4), one Mg(5), one Mg(6), one Si(1), one Si(2), one Si(3), two equivalent Si(4), and two equivalent Si(5) atoms. In the third Mg site, Mg(3) is bonded in a 12-coordinate geometry to one Mg(2), one Mg(5), one Mg(7), one Mg(8), two equivalent Mg(4), one Si(1), one Si(4), one Si(5), one Si(6), and two equivalent Si(3) atoms. In the fourth Mg site, Mg(4) is bonded in a 5-coordinate geometry to one Mg(2), one Mg(6), two equivalent Mg(3), one Si(1), one Si(5), one Si(6), 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(3), two equivalent Mg(6), one Si(2), one Si(4), one Si(6), and two equivalent Si(5) atoms. In the sixth Mg site, Mg(6) is bonded to one Mg(2), one Mg(4), one Mg(7), one Mg(8), two equivalent Mg(1), two equivalent Mg(5), one Si(2), one Si(4), one Si(5), and one Si(6) atom to form distorted edge-sharing MgMg8Si4 cuboctahedra. In the seventh Mg site, Mg(7) is bonded in a 6-coordinate geometry to one Mg(3), one Mg(6), one Si(1), one Si(3), one Si(5), one Si(6), and two equivalent Si(2) atoms. In the eighth Mg site, Mg(8) is bonded in a 6-coordinate geometry to one Mg(3), one Mg(6), one Si(2), one Si(3), one Si(4), one Si(6), and two equivalent Si(1) atoms. There are six inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(4), one Mg(7), two equivalent Mg(8), one Si(2), and one Si(3) atom. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Mg(2), one Mg(5), one Mg(6), one Mg(8), two equivalent Mg(1), two equivalent Mg(7), and one Si(1) atom. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to one Mg(2), one Mg(7), one Mg(8), two equivalent Mg(3), one Si(1), one Si(4), and one Si(5) atom. In the fourth Si site, Si(4) is bonded in a 10-coordinate geometry to one Mg(1), one Mg(3), one Mg(5), one Mg(6), one Mg(8), two equivalent Mg(2), two equivalent Mg(4), and one Si(3) atom. In the fifth Si site, Si(5) is bonded in a 10-coordinate geometry to one Mg(1), one Mg(3), one Mg(4), one Mg(6), one Mg(7), two equivalent Mg(2), two equivalent Mg(5), and one Si(3) atom. In the sixth Si site, Si(6) is bonded in a 7-coordinate geometry to one Mg(1), one Mg(3), one Mg(4), one Mg(5), one Mg(6), one Mg(7), and one Mg(8) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg4Si3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.951
_cell_length_b   7.147
_cell_length_c   7.717
_cell_angle_alpha   88.810
_cell_angle_beta   93.916
_cell_angle_gamma   108.219
_symmetry_Int_Tables_number   1
_cell_volume   258.765
_cell_formula_units_Z   2
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  0.559  0.813  0.499  1.0
  Mg  Mg1  1  0.214  0.926  0.775  1.0
  Mg  Mg2  1  0.489  0.273  0.993  1.0
  Mg  Mg3  1  0.103  0.512  0.932  1.0
  Mg  Mg4  1  0.341  0.325  0.606  1.0
  Mg  Mg5  1  0.949  0.572  0.554  1.0
  Mg  Mg6  1  0.723  0.206  0.340  1.0
  Mg  Mg7  1  0.788  0.661  0.183  1.0
  Si  Si8  1  0.364  0.873  0.138  1.0
  Si  Si9  1  0.126  0.981  0.373  1.0
  Si  Si10  1  0.880  0.040  0.026  1.0
  Si  Si11  1  0.659  0.689  0.832  1.0
  Si  Si12  1  0.792  0.180  0.721  1.0
  Si  Si13  1  0.264  0.451  0.278  1.0
[/CIF]
.
The crystal structure described by Mg4Si3 crystallizes in the triclinic P1 space group. There are eight inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 6-coordinate geometry to one Mg(2), two equivalent Mg(6), one Si(1), one Si(4), one Si(5), one Si(6), 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(3), one Mg(4), one Mg(5), one Mg(6), one Si(1), one Si(2), one Si(3), two equivalent Si(4), and two equivalent Si(5) atoms. In the third Mg site, Mg(3) is bonded in a 12-coordinate geometry to one Mg(2), one Mg(5), one Mg(7), one Mg(8), two equivalent Mg(4), one Si(1), one Si(4), one Si(5), one Si(6), and two equivalent Si(3) atoms. In the fourth Mg site, Mg(4) is bonded in a 5-coordinate geometry to one Mg(2), one Mg(6), two equivalent Mg(3), one Si(1), one Si(5), one Si(6), 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(3), two equivalent Mg(6), one Si(2), one Si(4), one Si(6), and two equivalent Si(5) atoms. In the sixth Mg site, Mg(6) is bonded to one Mg(2), one Mg(4), one Mg(7), one Mg(8), two equivalent Mg(1), two equivalent Mg(5), one Si(2), one Si(4), one Si(5), and one Si(6) atom to form distorted edge-sharing MgMg8Si4 cuboctahedra. In the seventh Mg site, Mg(7) is bonded in a 6-coordinate geometry to one Mg(3), one Mg(6), one Si(1), one Si(3), one Si(5), one Si(6), and two equivalent Si(2) atoms. In the eighth Mg site, Mg(8) is bonded in a 6-coordinate geometry to one Mg(3), one Mg(6), one Si(2), one Si(3), one Si(4), one Si(6), and two equivalent Si(1) atoms. There are six inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(4), one Mg(7), two equivalent Mg(8), one Si(2), and one Si(3) atom. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Mg(2), one Mg(5), one Mg(6), one Mg(8), two equivalent Mg(1), two equivalent Mg(7), and one Si(1) atom. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to one Mg(2), one Mg(7), one Mg(8), two equivalent Mg(3), one Si(1), one Si(4), and one Si(5) atom. In the fourth Si site, Si(4) is bonded in a 10-coordinate geometry to one Mg(1), one Mg(3), one Mg(5), one Mg(6), one Mg(8), two equivalent Mg(2), two equivalent Mg(4), and one Si(3) atom. In the fifth Si site, Si(5) is bonded in a 10-coordinate geometry to one Mg(1), one Mg(3), one Mg(4), one Mg(6), one Mg(7), two equivalent Mg(2), two equivalent Mg(5), and one Si(3) atom. In the sixth Si site, Si(6) is bonded in a 7-coordinate geometry to one Mg(1), one Mg(3), one Mg(4), one Mg(5), one Mg(6), one Mg(7), and one Mg(8) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg4Si3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.951
_cell_length_b   7.147
_cell_length_c   7.717
_cell_angle_alpha   88.810
_cell_angle_beta   93.916
_cell_angle_gamma   108.219
_symmetry_Int_Tables_number   1
_cell_volume   258.765
_cell_formula_units_Z   2
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  0.559  0.813  0.499  1.0
  Mg  Mg1  1  0.214  0.926  0.775  1.0
  Mg  Mg2  1  0.489  0.273  0.993  1.0
  Mg  Mg3  1  0.103  0.512  0.932  1.0
  Mg  Mg4  1  0.341  0.325  0.606  1.0
  Mg  Mg5  1  0.949  0.572  0.554  1.0
  Mg  Mg6  1  0.723  0.206  0.340  1.0
  Mg  Mg7  1  0.788  0.661  0.183  1.0
  Si  Si8  1  0.364  0.873  0.138  1.0
  Si  Si9  1  0.126  0.981  0.373  1.0
  Si  Si10  1  0.880  0.040  0.026  1.0
  Si  Si11  1  0.659  0.689  0.832  1.0
  Si  Si12  1  0.792  0.180  0.721  1.0
  Si  Si13  1  0.264  0.451  0.278  1.0
[/CIF]
.