The compound 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(4), one Mg(7), one Si(5), one Si(6), and two equivalent Si(2) atoms. In the second Mg site, Mg(2) is bonded in a 1-coordinate geometry to one Mg(6), one Si(4), and one Si(6) atom. In the third Mg site, Mg(3) is bonded in a 4-coordinate geometry to one Mg(8), one Si(1), one Si(2), and one Si(3) atom. In the fourth Mg site, Mg(4) is bonded in a single-bond geometry to one Mg(1), one Mg(8), and one Si(1) atom. In the fifth Mg site, Mg(5) is bonded in a 4-coordinate geometry to one Mg(6), one Mg(8), one Si(1), one Si(4), and one Si(5) atom. In the sixth Mg site, Mg(6) is bonded in a 6-coordinate geometry to one Mg(2), one Mg(5), one Si(3), one Si(5), and two equivalent Si(4) atoms. In the seventh Mg site, Mg(7) is bonded in a 2-coordinate geometry to one Mg(1), one Mg(8), and one Si(6) atom. In the eighth Mg site, Mg(8) is bonded in a 7-coordinate geometry to one Mg(3), one Mg(4), one Mg(5), one Mg(7), one Si(5), and two equivalent Si(1) atoms. There are six inequivalent Si sites. In the first Si site, Si(1) is bonded in a 1-coordinate geometry to one Mg(3), one Mg(4), one Mg(5), and two equivalent Mg(8) atoms. In the second Si site, Si(2) is bonded in a 4-coordinate geometry to one Mg(3), two equivalent Mg(1), and one Si(6) atom. In the third Si site, Si(3) is bonded in a 3-coordinate geometry to one Mg(3), one Mg(6), and one Si(4) atom. In the fourth Si site, Si(4) is bonded in a 4-coordinate geometry to one Mg(2), one Mg(5), two equivalent Mg(6), one Si(3), and one Si(5) atom. In the fifth Si site, Si(5) is bonded in a 5-coordinate geometry to one Mg(1), one Mg(5), one Mg(6), one Mg(8), and one Si(4) atom. In the sixth Si site, Si(6) is bonded in a 4-coordinate geometry to one Mg(1), one Mg(2), one Mg(7), and one Si(2) atom. is represented by the CIF file [CIF]
data_Mg4Si3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.603
_cell_length_b   7.540
_cell_length_c   7.631
_cell_angle_alpha   116.579
_cell_angle_beta   89.933
_cell_angle_gamma   111.260
_symmetry_Int_Tables_number   1
_cell_volume   263.632
_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  0.816  0.494  0.683  1.0
  Mg  Mg1  1  0.504  0.005  0.952  1.0
  Mg  Mg2  1  0.118  0.067  0.555  1.0
  Mg  Mg3  1  0.626  0.047  0.588  1.0
  Mg  Mg4  1  0.422  0.534  0.285  1.0
  Mg  Mg5  1  0.491  0.282  0.119  1.0
  Mg  Mg6  1  0.904  0.691  0.970  1.0
  Mg  Mg7  1  0.148  0.840  0.323  1.0
  Si  Si8  1  0.683  0.896  0.353  1.0
  Si  Si9  1  0.288  0.432  0.678  1.0
  Si  Si10  1  0.028  0.110  0.904  1.0
  Si  Si11  1  0.967  0.233  0.125  1.0
  Si  Si12  1  0.926  0.438  0.377  1.0
  Si  Si13  1  0.328  0.680  0.838  1.0
[/CIF]
.
The compound 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(4), one Mg(7), one Si(5), one Si(6), and two equivalent Si(2) atoms. In the second Mg site, Mg(2) is bonded in a 1-coordinate geometry to one Mg(6), one Si(4), and one Si(6) atom. In the third Mg site, Mg(3) is bonded in a 4-coordinate geometry to one Mg(8), one Si(1), one Si(2), and one Si(3) atom. In the fourth Mg site, Mg(4) is bonded in a single-bond geometry to one Mg(1), one Mg(8), and one Si(1) atom. In the fifth Mg site, Mg(5) is bonded in a 4-coordinate geometry to one Mg(6), one Mg(8), one Si(1), one Si(4), and one Si(5) atom. In the sixth Mg site, Mg(6) is bonded in a 6-coordinate geometry to one Mg(2), one Mg(5), one Si(3), one Si(5), and two equivalent Si(4) atoms. In the seventh Mg site, Mg(7) is bonded in a 2-coordinate geometry to one Mg(1), one Mg(8), and one Si(6) atom. In the eighth Mg site, Mg(8) is bonded in a 7-coordinate geometry to one Mg(3), one Mg(4), one Mg(5), one Mg(7), one Si(5), and two equivalent Si(1) atoms. There are six inequivalent Si sites. In the first Si site, Si(1) is bonded in a 1-coordinate geometry to one Mg(3), one Mg(4), one Mg(5), and two equivalent Mg(8) atoms. In the second Si site, Si(2) is bonded in a 4-coordinate geometry to one Mg(3), two equivalent Mg(1), and one Si(6) atom. In the third Si site, Si(3) is bonded in a 3-coordinate geometry to one Mg(3), one Mg(6), and one Si(4) atom. In the fourth Si site, Si(4) is bonded in a 4-coordinate geometry to one Mg(2), one Mg(5), two equivalent Mg(6), one Si(3), and one Si(5) atom. In the fifth Si site, Si(5) is bonded in a 5-coordinate geometry to one Mg(1), one Mg(5), one Mg(6), one Mg(8), and one Si(4) atom. In the sixth Si site, Si(6) is bonded in a 4-coordinate geometry to one Mg(1), one Mg(2), one Mg(7), and one Si(2) atom. is represented by the CIF file [CIF]
data_Mg4Si3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.603
_cell_length_b   7.540
_cell_length_c   7.631
_cell_angle_alpha   116.579
_cell_angle_beta   89.933
_cell_angle_gamma   111.260
_symmetry_Int_Tables_number   1
_cell_volume   263.632
_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  0.816  0.494  0.683  1.0
  Mg  Mg1  1  0.504  0.005  0.952  1.0
  Mg  Mg2  1  0.118  0.067  0.555  1.0
  Mg  Mg3  1  0.626  0.047  0.588  1.0
  Mg  Mg4  1  0.422  0.534  0.285  1.0
  Mg  Mg5  1  0.491  0.282  0.119  1.0
  Mg  Mg6  1  0.904  0.691  0.970  1.0
  Mg  Mg7  1  0.148  0.840  0.323  1.0
  Si  Si8  1  0.683  0.896  0.353  1.0
  Si  Si9  1  0.288  0.432  0.678  1.0
  Si  Si10  1  0.028  0.110  0.904  1.0
  Si  Si11  1  0.967  0.233  0.125  1.0
  Si  Si12  1  0.926  0.438  0.377  1.0
  Si  Si13  1  0.328  0.680  0.838  1.0
[/CIF]
.