The compound described by Mg2Si3 crystallizes in the triclinic P-1 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 6-coordinate geometry to one Si(1), two equivalent Si(2), two equivalent Si(3), and three equivalent Si(6) atoms. In the second Mg site, Mg(2) is bonded in a 8-coordinate geometry to one Si(6), two equivalent Si(2), and five equivalent Si(1) atoms. In the third Mg site, Mg(3) is bonded in a 7-coordinate geometry to one Mg(4), two equivalent Si(5), two equivalent Si(6), and three equivalent Si(3) atoms. In the fourth Mg site, Mg(4) is bonded in a 12-coordinate geometry to one Mg(3), one Mg(4), two equivalent Si(3), three equivalent Si(5), and five equivalent Si(4) 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), five equivalent Mg(2), one Si(1), and two equivalent Si(2) atoms. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Si(1), and two equivalent Si(6) atoms. In the third Si site, Si(3) is bonded in a 10-coordinate geometry to two equivalent Mg(1), two equivalent Mg(4), three equivalent Mg(3), one Si(6), and two equivalent Si(5) atoms. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to five equivalent Mg(4), two equivalent Si(4), and two equivalent Si(5) atoms. In the fifth Si site, Si(5) is bonded in a 9-coordinate geometry to two equivalent Mg(3), three equivalent Mg(4), two equivalent Si(3), and two equivalent Si(4) atoms. In the sixth Si site, Si(6) is bonded in a 9-coordinate geometry to one Mg(2), two equivalent Mg(3), three equivalent Mg(1), one Si(3), and two equivalent Si(2) atoms. is represented by the CIF card [CIF]
data_Mg2Si3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.263
_cell_length_b   3.557
_cell_length_c   20.363
_cell_angle_alpha   89.963
_cell_angle_beta   80.007
_cell_angle_gamma   109.043
_symmetry_Int_Tables_number   1
_cell_volume   354.251
_cell_formula_units_Z   4
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  0.113  0.354  0.813  1.0
  Mg  Mg1  1  0.887  0.245  0.187  1.0
  Mg  Mg2  1  0.757  0.680  0.943  1.0
  Mg  Mg3  1  0.243  0.920  0.057  1.0
  Mg  Mg4  1  0.453  0.530  0.285  1.0
  Mg  Mg5  1  0.547  0.070  0.715  1.0
  Mg  Mg6  1  0.147  0.375  0.426  1.0
  Mg  Mg7  1  0.853  0.224  0.574  1.0
  Si  Si8  1  0.190  0.398  0.949  1.0
  Si  Si9  1  0.810  0.202  0.051  1.0
  Si  Si10  1  0.441  0.021  0.876  1.0
  Si  Si11  1  0.560  0.580  0.124  1.0
  Si  Si12  1  0.982  0.793  0.313  1.0
  Si  Si13  1  0.018  0.807  0.687  1.0
  Si  Si14  1  0.658  0.626  0.465  1.0
  Si  Si15  1  0.342  0.973  0.535  1.0
  Si  Si16  1  0.665  0.137  0.372  1.0
  Si  Si17  1  0.335  0.463  0.628  1.0
  Si  Si18  1  0.706  0.649  0.802  1.0
  Si  Si19  1  0.294  0.951  0.198  1.0
[/CIF]
.
The compound described by Mg2Si3 crystallizes in the triclinic P-1 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 6-coordinate geometry to one Si(1), two equivalent Si(2), two equivalent Si(3), and three equivalent Si(6) atoms. In the second Mg site, Mg(2) is bonded in a 8-coordinate geometry to one Si(6), two equivalent Si(2), and five equivalent Si(1) atoms. In the third Mg site, Mg(3) is bonded in a 7-coordinate geometry to one Mg(4), two equivalent Si(5), two equivalent Si(6), and three equivalent Si(3) atoms. In the fourth Mg site, Mg(4) is bonded in a 12-coordinate geometry to one Mg(3), one Mg(4), two equivalent Si(3), three equivalent Si(5), and five equivalent Si(4) 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), five equivalent Mg(2), one Si(1), and two equivalent Si(2) atoms. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Si(1), and two equivalent Si(6) atoms. In the third Si site, Si(3) is bonded in a 10-coordinate geometry to two equivalent Mg(1), two equivalent Mg(4), three equivalent Mg(3), one Si(6), and two equivalent Si(5) atoms. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to five equivalent Mg(4), two equivalent Si(4), and two equivalent Si(5) atoms. In the fifth Si site, Si(5) is bonded in a 9-coordinate geometry to two equivalent Mg(3), three equivalent Mg(4), two equivalent Si(3), and two equivalent Si(4) atoms. In the sixth Si site, Si(6) is bonded in a 9-coordinate geometry to one Mg(2), two equivalent Mg(3), three equivalent Mg(1), one Si(3), and two equivalent Si(2) atoms. is represented by the CIF card [CIF]
data_Mg2Si3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.263
_cell_length_b   3.557
_cell_length_c   20.363
_cell_angle_alpha   89.963
_cell_angle_beta   80.007
_cell_angle_gamma   109.043
_symmetry_Int_Tables_number   1
_cell_volume   354.251
_cell_formula_units_Z   4
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  0.113  0.354  0.813  1.0
  Mg  Mg1  1  0.887  0.245  0.187  1.0
  Mg  Mg2  1  0.757  0.680  0.943  1.0
  Mg  Mg3  1  0.243  0.920  0.057  1.0
  Mg  Mg4  1  0.453  0.530  0.285  1.0
  Mg  Mg5  1  0.547  0.070  0.715  1.0
  Mg  Mg6  1  0.147  0.375  0.426  1.0
  Mg  Mg7  1  0.853  0.224  0.574  1.0
  Si  Si8  1  0.190  0.398  0.949  1.0
  Si  Si9  1  0.810  0.202  0.051  1.0
  Si  Si10  1  0.441  0.021  0.876  1.0
  Si  Si11  1  0.560  0.580  0.124  1.0
  Si  Si12  1  0.982  0.793  0.313  1.0
  Si  Si13  1  0.018  0.807  0.687  1.0
  Si  Si14  1  0.658  0.626  0.465  1.0
  Si  Si15  1  0.342  0.973  0.535  1.0
  Si  Si16  1  0.665  0.137  0.372  1.0
  Si  Si17  1  0.335  0.463  0.628  1.0
  Si  Si18  1  0.706  0.649  0.802  1.0
  Si  Si19  1  0.294  0.951  0.198  1.0
[/CIF]
.