The material described by Mg7Si4 crystallizes in the monoclinic Pm space group. There are fourteen inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 4-coordinate geometry to two equivalent Mg(10), one Si(3), one Si(7), and two equivalent Si(6) atoms. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to one Mg(13), two equivalent Mg(3), two equivalent Mg(4), two equivalent Mg(7), two equivalent Mg(8), and one Si(4) atom. In the third Mg site, Mg(3) is bonded in a 3-coordinate geometry to two equivalent Mg(2), one Si(5), and two equivalent Si(4) atoms. In the fourth Mg site, Mg(4) is bonded in a 3-coordinate geometry to two equivalent Mg(2), one Si(2), and two equivalent Si(3) atoms. In the fifth Mg site, Mg(5) is bonded in a 5-coordinate geometry to two equivalent Mg(10), one Si(3), two equivalent Si(2), and two equivalent Si(6) atoms. In the sixth Mg site, Mg(6) is bonded in a 2-coordinate geometry to one Si(4), one Si(8), and two equivalent Si(5) atoms. In the seventh Mg site, Mg(7) is bonded in a 4-coordinate geometry to two equivalent Mg(2), two equivalent Si(4), and two equivalent Si(8) atoms. In the eighth Mg site, Mg(8) is bonded in a 2-coordinate geometry to two equivalent Mg(2) and two equivalent Si(7) atoms. In the ninth Mg site, Mg(9) is bonded in a distorted bent 120 degrees geometry to one Si(5) and one Si(6) atom. In the tenth Mg site, Mg(10) is bonded in a 10-coordinate geometry to two equivalent Mg(1), two equivalent Mg(11), two equivalent Mg(12), two equivalent Mg(5), one Si(1), and one Si(2) atom. In the eleventh Mg site, Mg(11) is bonded in a 4-coordinate geometry to two equivalent Mg(10), two equivalent Si(1), and two equivalent Si(5) atoms. In the twelfth Mg site, Mg(12) is bonded in a 3-coordinate geometry to two equivalent Mg(10), one Si(8), and two equivalent Si(1) atoms. In the thirteenth Mg site, Mg(13) is bonded in a distorted single-bond geometry to one Mg(2), one Si(7), and two equivalent Si(2) atoms. In the fourteenth Mg site, Mg(14) is bonded in a distorted single-bond geometry to one Si(8) atom. There are eight inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to one Mg(10), two equivalent Mg(11), two equivalent Mg(12), one Si(5), and two equivalent Si(8) atoms. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to one Mg(10), one Mg(4), two equivalent Mg(13), two equivalent Mg(5), and two equivalent Si(7) atoms. In the third Si site, Si(3) is bonded in a 7-coordinate geometry to one Mg(1), one Mg(5), two equivalent Mg(4), one Si(7), and two equivalent Si(6) atoms. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to one Mg(2), one Mg(6), two equivalent Mg(3), two equivalent Mg(7), one Si(8), and two equivalent Si(5) atoms. In the fifth Si site, Si(5) is bonded in a 9-coordinate geometry to one Mg(3), one Mg(9), two equivalent Mg(11), two equivalent Mg(6), one Si(1), and two equivalent Si(4) atoms. In the sixth Si site, Si(6) is bonded in a 7-coordinate geometry to one Mg(9), two equivalent Mg(1), two equivalent Mg(5), and two equivalent Si(3) atoms. In the seventh Si site, Si(7) is bonded in a 7-coordinate geometry to one Mg(1), one Mg(13), two equivalent Mg(8), one Si(3), and two equivalent Si(2) atoms. In the eighth Si site, Si(8) is bonded in a 8-coordinate geometry to one Mg(12), one Mg(14), one Mg(6), two equivalent Mg(7), one Si(4), and two equivalent Si(1) atoms. is represented by the CIF card [CIF]
data_Mg7Si4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.550
_cell_length_b   8.513
_cell_length_c   14.828
_cell_angle_alpha   87.740
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   447.737
_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  0.500  0.132  0.886  1.0
  Mg  Mg1  1  0.500  0.504  0.507  1.0
  Mg  Mg2  1  0.000  0.347  0.371  1.0
  Mg  Mg3  1  0.000  0.595  0.664  1.0
  Mg  Mg4  1  0.500  0.667  0.825  1.0
  Mg  Mg5  1  0.500  0.222  0.219  1.0
  Mg  Mg6  1  0.000  0.760  0.413  1.0
  Mg  Mg7  1  0.000  0.212  0.571  1.0
  Mg  Mg8  1  0.000  0.273  0.039  1.0
  Mg  Mg9  1  0.000  0.846  0.948  1.0
  Mg  Mg10  1  0.500  0.571  0.034  1.0
  Mg  Mg11  1  0.500  0.986  0.083  1.0
  Mg  Mg12  1  0.500  0.867  0.583  1.0
  Mg  Mg13  1  0.500  0.060  0.406  1.0
  Si  Si14  1  0.000  0.770  0.156  1.0
  Si  Si15  1  0.000  0.917  0.753  1.0
  Si  Si16  1  0.500  0.366  0.745  1.0
  Si  Si17  1  0.500  0.566  0.295  1.0
  Si  Si18  1  0.000  0.485  0.187  1.0
  Si  Si19  1  0.000  0.408  0.854  1.0
  Si  Si20  1  0.500  0.090  0.707  1.0
  Si  Si21  1  0.500  0.858  0.258  1.0
[/CIF]
.
The material described by Mg7Si4 crystallizes in the monoclinic Pm space group. There are fourteen inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 4-coordinate geometry to two equivalent Mg(10), one Si(3), one Si(7), and two equivalent Si(6) atoms. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to one Mg(13), two equivalent Mg(3), two equivalent Mg(4), two equivalent Mg(7), two equivalent Mg(8), and one Si(4) atom. In the third Mg site, Mg(3) is bonded in a 3-coordinate geometry to two equivalent Mg(2), one Si(5), and two equivalent Si(4) atoms. In the fourth Mg site, Mg(4) is bonded in a 3-coordinate geometry to two equivalent Mg(2), one Si(2), and two equivalent Si(3) atoms. In the fifth Mg site, Mg(5) is bonded in a 5-coordinate geometry to two equivalent Mg(10), one Si(3), two equivalent Si(2), and two equivalent Si(6) atoms. In the sixth Mg site, Mg(6) is bonded in a 2-coordinate geometry to one Si(4), one Si(8), and two equivalent Si(5) atoms. In the seventh Mg site, Mg(7) is bonded in a 4-coordinate geometry to two equivalent Mg(2), two equivalent Si(4), and two equivalent Si(8) atoms. In the eighth Mg site, Mg(8) is bonded in a 2-coordinate geometry to two equivalent Mg(2) and two equivalent Si(7) atoms. In the ninth Mg site, Mg(9) is bonded in a distorted bent 120 degrees geometry to one Si(5) and one Si(6) atom. In the tenth Mg site, Mg(10) is bonded in a 10-coordinate geometry to two equivalent Mg(1), two equivalent Mg(11), two equivalent Mg(12), two equivalent Mg(5), one Si(1), and one Si(2) atom. In the eleventh Mg site, Mg(11) is bonded in a 4-coordinate geometry to two equivalent Mg(10), two equivalent Si(1), and two equivalent Si(5) atoms. In the twelfth Mg site, Mg(12) is bonded in a 3-coordinate geometry to two equivalent Mg(10), one Si(8), and two equivalent Si(1) atoms. In the thirteenth Mg site, Mg(13) is bonded in a distorted single-bond geometry to one Mg(2), one Si(7), and two equivalent Si(2) atoms. In the fourteenth Mg site, Mg(14) is bonded in a distorted single-bond geometry to one Si(8) atom. There are eight inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to one Mg(10), two equivalent Mg(11), two equivalent Mg(12), one Si(5), and two equivalent Si(8) atoms. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to one Mg(10), one Mg(4), two equivalent Mg(13), two equivalent Mg(5), and two equivalent Si(7) atoms. In the third Si site, Si(3) is bonded in a 7-coordinate geometry to one Mg(1), one Mg(5), two equivalent Mg(4), one Si(7), and two equivalent Si(6) atoms. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to one Mg(2), one Mg(6), two equivalent Mg(3), two equivalent Mg(7), one Si(8), and two equivalent Si(5) atoms. In the fifth Si site, Si(5) is bonded in a 9-coordinate geometry to one Mg(3), one Mg(9), two equivalent Mg(11), two equivalent Mg(6), one Si(1), and two equivalent Si(4) atoms. In the sixth Si site, Si(6) is bonded in a 7-coordinate geometry to one Mg(9), two equivalent Mg(1), two equivalent Mg(5), and two equivalent Si(3) atoms. In the seventh Si site, Si(7) is bonded in a 7-coordinate geometry to one Mg(1), one Mg(13), two equivalent Mg(8), one Si(3), and two equivalent Si(2) atoms. In the eighth Si site, Si(8) is bonded in a 8-coordinate geometry to one Mg(12), one Mg(14), one Mg(6), two equivalent Mg(7), one Si(4), and two equivalent Si(1) atoms. is represented by the CIF card [CIF]
data_Mg7Si4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.550
_cell_length_b   8.513
_cell_length_c   14.828
_cell_angle_alpha   87.740
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   447.737
_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  0.500  0.132  0.886  1.0
  Mg  Mg1  1  0.500  0.504  0.507  1.0
  Mg  Mg2  1  0.000  0.347  0.371  1.0
  Mg  Mg3  1  0.000  0.595  0.664  1.0
  Mg  Mg4  1  0.500  0.667  0.825  1.0
  Mg  Mg5  1  0.500  0.222  0.219  1.0
  Mg  Mg6  1  0.000  0.760  0.413  1.0
  Mg  Mg7  1  0.000  0.212  0.571  1.0
  Mg  Mg8  1  0.000  0.273  0.039  1.0
  Mg  Mg9  1  0.000  0.846  0.948  1.0
  Mg  Mg10  1  0.500  0.571  0.034  1.0
  Mg  Mg11  1  0.500  0.986  0.083  1.0
  Mg  Mg12  1  0.500  0.867  0.583  1.0
  Mg  Mg13  1  0.500  0.060  0.406  1.0
  Si  Si14  1  0.000  0.770  0.156  1.0
  Si  Si15  1  0.000  0.917  0.753  1.0
  Si  Si16  1  0.500  0.366  0.745  1.0
  Si  Si17  1  0.500  0.566  0.295  1.0
  Si  Si18  1  0.000  0.485  0.187  1.0
  Si  Si19  1  0.000  0.408  0.854  1.0
  Si  Si20  1  0.500  0.090  0.707  1.0
  Si  Si21  1  0.500  0.858  0.258  1.0
[/CIF]
.