The crystal structure described by Mg4Si7 crystallizes in the triclinic P-1 space group. There are five inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a distorted square co-planar geometry to four equivalent Si(1) atoms. In the second Mg site, Mg(2) is bonded in a square co-planar geometry to two equivalent Si(3) and two equivalent Si(5) atoms. In the third Mg site, Mg(3) is bonded in a 5-coordinate geometry to one Si(4), one Si(7), two equivalent Si(3), and two equivalent Si(5) atoms. In the fourth Mg site, Mg(4) is bonded in a 6-coordinate geometry to one Si(1), one Si(2), one Si(4), one Si(5), and two equivalent Si(6) atoms. In the fifth Mg site, Mg(5) is bonded in a 7-coordinate geometry to two equivalent Si(5), two equivalent Si(7), and three equivalent Si(3) atoms. There are seven inequivalent Si sites. In the first Si site, Si(1) is bonded in a 6-coordinate geometry to one Mg(4), two equivalent Mg(1), one Si(4), and two equivalent Si(2) atoms. In the second Si site, Si(2) is bonded in a 5-coordinate geometry to one Mg(4), one Si(2), one Si(6), and two equivalent Si(1) atoms. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to one Mg(2), two equivalent Mg(3), three equivalent Mg(5), one Si(3), and one Si(7) atom. In the fourth Si site, Si(4) is bonded to one Mg(3), one Mg(4), one Si(1), one Si(6), and two equivalent Si(7) atoms to form distorted corner-sharing SiMg2Si4 pentagonal pyramids. In the fifth Si site, Si(5) is bonded in a 8-coordinate geometry to one Mg(2), one Mg(4), two equivalent Mg(3), two equivalent Mg(5), one Si(6), and one Si(7) atom. In the sixth Si site, Si(6) is bonded in a 5-coordinate geometry to two equivalent Mg(4), one Si(2), one Si(4), and one Si(5) atom. In the seventh Si site, Si(7) is bonded in a 7-coordinate geometry to one Mg(3), two equivalent Mg(5), one Si(3), one Si(5), and two equivalent Si(4) atoms. is represented by the CIF file [CIF]
data_Mg4Si7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.241
_cell_length_b   6.759
_cell_length_c   14.793
_cell_angle_alpha   81.410
_cell_angle_beta   81.780
_cell_angle_gamma   85.879
_symmetry_Int_Tables_number   1
_cell_volume   414.402
_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  0.000  0.000  0.000  1.0
  Mg  Mg1  1  0.000  0.000  0.500  1.0
  Mg  Mg2  1  0.591  0.881  0.351  1.0
  Mg  Mg3  1  0.409  0.119  0.649  1.0
  Mg  Mg4  1  0.635  0.978  0.838  1.0
  Mg  Mg5  1  0.365  0.022  0.162  1.0
  Mg  Mg6  1  0.520  0.328  0.423  1.0
  Mg  Mg7  1  0.480  0.672  0.577  1.0
  Si  Si8  1  0.543  0.280  0.940  1.0
  Si  Si9  1  0.457  0.720  0.060  1.0
  Si  Si10  1  0.177  0.429  0.054  1.0
  Si  Si11  1  0.823  0.571  0.946  1.0
  Si  Si12  1  0.932  0.356  0.555  1.0
  Si  Si13  1  0.068  0.644  0.445  1.0
  Si  Si14  1  0.603  0.619  0.214  1.0
  Si  Si15  1  0.397  0.381  0.786  1.0
  Si  Si16  1  0.929  0.827  0.682  1.0
  Si  Si17  1  0.071  0.173  0.318  1.0
  Si  Si18  1  0.807  0.275  0.179  1.0
  Si  Si19  1  0.193  0.725  0.821  1.0
  Si  Si20  1  0.911  0.467  0.703  1.0
  Si  Si21  1  0.089  0.533  0.297  1.0
[/CIF]
.
The crystal structure described by Mg4Si7 crystallizes in the triclinic P-1 space group. There are five inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a distorted square co-planar geometry to four equivalent Si(1) atoms. In the second Mg site, Mg(2) is bonded in a square co-planar geometry to two equivalent Si(3) and two equivalent Si(5) atoms. In the third Mg site, Mg(3) is bonded in a 5-coordinate geometry to one Si(4), one Si(7), two equivalent Si(3), and two equivalent Si(5) atoms. In the fourth Mg site, Mg(4) is bonded in a 6-coordinate geometry to one Si(1), one Si(2), one Si(4), one Si(5), and two equivalent Si(6) atoms. In the fifth Mg site, Mg(5) is bonded in a 7-coordinate geometry to two equivalent Si(5), two equivalent Si(7), and three equivalent Si(3) atoms. There are seven inequivalent Si sites. In the first Si site, Si(1) is bonded in a 6-coordinate geometry to one Mg(4), two equivalent Mg(1), one Si(4), and two equivalent Si(2) atoms. In the second Si site, Si(2) is bonded in a 5-coordinate geometry to one Mg(4), one Si(2), one Si(6), and two equivalent Si(1) atoms. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to one Mg(2), two equivalent Mg(3), three equivalent Mg(5), one Si(3), and one Si(7) atom. In the fourth Si site, Si(4) is bonded to one Mg(3), one Mg(4), one Si(1), one Si(6), and two equivalent Si(7) atoms to form distorted corner-sharing SiMg2Si4 pentagonal pyramids. In the fifth Si site, Si(5) is bonded in a 8-coordinate geometry to one Mg(2), one Mg(4), two equivalent Mg(3), two equivalent Mg(5), one Si(6), and one Si(7) atom. In the sixth Si site, Si(6) is bonded in a 5-coordinate geometry to two equivalent Mg(4), one Si(2), one Si(4), and one Si(5) atom. In the seventh Si site, Si(7) is bonded in a 7-coordinate geometry to one Mg(3), two equivalent Mg(5), one Si(3), one Si(5), and two equivalent Si(4) atoms. is represented by the CIF file [CIF]
data_Mg4Si7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.241
_cell_length_b   6.759
_cell_length_c   14.793
_cell_angle_alpha   81.410
_cell_angle_beta   81.780
_cell_angle_gamma   85.879
_symmetry_Int_Tables_number   1
_cell_volume   414.402
_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  0.000  0.000  0.000  1.0
  Mg  Mg1  1  0.000  0.000  0.500  1.0
  Mg  Mg2  1  0.591  0.881  0.351  1.0
  Mg  Mg3  1  0.409  0.119  0.649  1.0
  Mg  Mg4  1  0.635  0.978  0.838  1.0
  Mg  Mg5  1  0.365  0.022  0.162  1.0
  Mg  Mg6  1  0.520  0.328  0.423  1.0
  Mg  Mg7  1  0.480  0.672  0.577  1.0
  Si  Si8  1  0.543  0.280  0.940  1.0
  Si  Si9  1  0.457  0.720  0.060  1.0
  Si  Si10  1  0.177  0.429  0.054  1.0
  Si  Si11  1  0.823  0.571  0.946  1.0
  Si  Si12  1  0.932  0.356  0.555  1.0
  Si  Si13  1  0.068  0.644  0.445  1.0
  Si  Si14  1  0.603  0.619  0.214  1.0
  Si  Si15  1  0.397  0.381  0.786  1.0
  Si  Si16  1  0.929  0.827  0.682  1.0
  Si  Si17  1  0.071  0.173  0.318  1.0
  Si  Si18  1  0.807  0.275  0.179  1.0
  Si  Si19  1  0.193  0.725  0.821  1.0
  Si  Si20  1  0.911  0.467  0.703  1.0
  Si  Si21  1  0.089  0.533  0.297  1.0
[/CIF]
.