The material described by Mg3Si4 crystallizes in the triclinic P1 space group. There are six inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one Mg(2), one Si(1), one Si(2), one Si(3), one Si(4), one Si(7), and one Si(8) atom to form distorted MgMgSi6 octahedra that share corners with three equivalent Si(1)Mg4Si3 pentagonal bipyramids. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to one Mg(1), one Mg(4), one Mg(6), one Si(1), one Si(3), one Si(5), one Si(7), one Si(8), and two equivalent Si(2) atoms. In the third Mg site, Mg(3) is bonded in a 7-coordinate geometry to one Si(1), one Si(2), one Si(3), one Si(4), one Si(5), one Si(7), and one Si(8) atom. In the fourth Mg site, Mg(4) is bonded in a 4-coordinate geometry to one Mg(2), one Si(1), one Si(2), one Si(3), one Si(6), one Si(7), and one Si(8) atom. In the fifth Mg site, Mg(5) is bonded in a 7-coordinate geometry to one Si(2), one Si(3), one Si(4), one Si(5), one Si(7), and two equivalent Si(6) atoms. In the sixth Mg site, Mg(6) is bonded in a 5-coordinate geometry to one Mg(2), one Si(2), one Si(3), one Si(4), one Si(5), one Si(7), and one Si(8) atom. There are eight inequivalent Si sites. In the first Si site, Si(1) is bonded to one Mg(1), one Mg(2), one Mg(3), one Mg(4), one Si(4), one Si(5), and one Si(7) atom to form distorted SiMg4Si3 pentagonal bipyramids that share corners with three equivalent Mg(1)MgSi6 octahedra. The corner-sharing octahedral tilt angles range from 37-123°. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(3), one Mg(4), one Mg(5), one Mg(6), two equivalent Mg(2), one Si(5), and one Si(8) atom. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(4), one Mg(5), one Mg(6), one Si(4), and one Si(6) atom. In the fourth Si site, Si(4) is bonded in a 7-coordinate geometry to one Mg(1), one Mg(3), one Mg(5), one Mg(6), one Si(1), one Si(3), and one Si(6) atom. In the fifth Si site, Si(5) is bonded in a 7-coordinate geometry to one Mg(2), one Mg(3), one Mg(5), one Mg(6), one Si(1), one Si(2), and one Si(6) atom. In the sixth Si site, Si(6) is bonded in a 7-coordinate geometry to one Mg(4), two equivalent Mg(5), one Si(3), one Si(4), one Si(5), and one Si(8) atom. In the seventh Si site, Si(7) is bonded in a 7-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(4), one Mg(5), one Mg(6), and one Si(1) atom. In the eighth Si site, Si(8) is bonded in a 7-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(4), one Mg(6), one Si(2), and one Si(6) atom. is represented by the CIF card [CIF]
data_Mg3Si4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.872
_cell_length_b   7.102
_cell_length_c   7.613
_cell_angle_alpha   111.879
_cell_angle_beta   111.140
_cell_angle_gamma   93.817
_symmetry_Int_Tables_number   1
_cell_volume   267.269
_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  0.731  0.493  0.057  1.0
  Mg  Mg1  1  0.328  0.785  0.066  1.0
  Mg  Mg2  1  0.744  0.293  0.380  1.0
  Mg  Mg3  1  0.735  0.670  0.756  1.0
  Mg  Mg4  1  0.934  0.950  0.534  1.0
  Mg  Mg5  1  0.166  0.210  0.066  1.0
  Si  Si6  1  0.284  0.451  0.690  1.0
  Si  Si7  1  0.898  0.937  0.157  1.0
  Si  Si8  1  0.510  0.623  0.356  1.0
  Si  Si9  1  0.146  0.595  0.435  1.0
  Si  Si10  1  0.323  0.156  0.429  1.0
  Si  Si11  1  0.440  0.929  0.591  1.0
  Si  Si12  1  0.957  0.349  0.778  1.0
  Si  Si13  1  0.558  0.060  0.961  1.0
[/CIF]
.
The material described by Mg3Si4 crystallizes in the triclinic P1 space group. There are six inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one Mg(2), one Si(1), one Si(2), one Si(3), one Si(4), one Si(7), and one Si(8) atom to form distorted MgMgSi6 octahedra that share corners with three equivalent Si(1)Mg4Si3 pentagonal bipyramids. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to one Mg(1), one Mg(4), one Mg(6), one Si(1), one Si(3), one Si(5), one Si(7), one Si(8), and two equivalent Si(2) atoms. In the third Mg site, Mg(3) is bonded in a 7-coordinate geometry to one Si(1), one Si(2), one Si(3), one Si(4), one Si(5), one Si(7), and one Si(8) atom. In the fourth Mg site, Mg(4) is bonded in a 4-coordinate geometry to one Mg(2), one Si(1), one Si(2), one Si(3), one Si(6), one Si(7), and one Si(8) atom. In the fifth Mg site, Mg(5) is bonded in a 7-coordinate geometry to one Si(2), one Si(3), one Si(4), one Si(5), one Si(7), and two equivalent Si(6) atoms. In the sixth Mg site, Mg(6) is bonded in a 5-coordinate geometry to one Mg(2), one Si(2), one Si(3), one Si(4), one Si(5), one Si(7), and one Si(8) atom. There are eight inequivalent Si sites. In the first Si site, Si(1) is bonded to one Mg(1), one Mg(2), one Mg(3), one Mg(4), one Si(4), one Si(5), and one Si(7) atom to form distorted SiMg4Si3 pentagonal bipyramids that share corners with three equivalent Mg(1)MgSi6 octahedra. The corner-sharing octahedral tilt angles range from 37-123°. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(3), one Mg(4), one Mg(5), one Mg(6), two equivalent Mg(2), one Si(5), and one Si(8) atom. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(4), one Mg(5), one Mg(6), one Si(4), and one Si(6) atom. In the fourth Si site, Si(4) is bonded in a 7-coordinate geometry to one Mg(1), one Mg(3), one Mg(5), one Mg(6), one Si(1), one Si(3), and one Si(6) atom. In the fifth Si site, Si(5) is bonded in a 7-coordinate geometry to one Mg(2), one Mg(3), one Mg(5), one Mg(6), one Si(1), one Si(2), and one Si(6) atom. In the sixth Si site, Si(6) is bonded in a 7-coordinate geometry to one Mg(4), two equivalent Mg(5), one Si(3), one Si(4), one Si(5), and one Si(8) atom. In the seventh Si site, Si(7) is bonded in a 7-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(4), one Mg(5), one Mg(6), and one Si(1) atom. In the eighth Si site, Si(8) is bonded in a 7-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(4), one Mg(6), one Si(2), and one Si(6) atom. is represented by the CIF card [CIF]
data_Mg3Si4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.872
_cell_length_b   7.102
_cell_length_c   7.613
_cell_angle_alpha   111.879
_cell_angle_beta   111.140
_cell_angle_gamma   93.817
_symmetry_Int_Tables_number   1
_cell_volume   267.269
_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  0.731  0.493  0.057  1.0
  Mg  Mg1  1  0.328  0.785  0.066  1.0
  Mg  Mg2  1  0.744  0.293  0.380  1.0
  Mg  Mg3  1  0.735  0.670  0.756  1.0
  Mg  Mg4  1  0.934  0.950  0.534  1.0
  Mg  Mg5  1  0.166  0.210  0.066  1.0
  Si  Si6  1  0.284  0.451  0.690  1.0
  Si  Si7  1  0.898  0.937  0.157  1.0
  Si  Si8  1  0.510  0.623  0.356  1.0
  Si  Si9  1  0.146  0.595  0.435  1.0
  Si  Si10  1  0.323  0.156  0.429  1.0
  Si  Si11  1  0.440  0.929  0.591  1.0
  Si  Si12  1  0.957  0.349  0.778  1.0
  Si  Si13  1  0.558  0.060  0.961  1.0
[/CIF]
.