data_Zn3Si4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.05
_cell_length_b   5.05
_cell_length_c   5.05
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Zn3Si4
_chemical_formula_sum   'Zn3 Si4'
_cell_volume   128.97
_cell_formula_units_Z   1
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
  Zn  Zn4  1  0.0  0.53  0.0  1.0
  Zn  Zn5  1  0.0  0.0  0.53  1.0
  Zn  Zn6  1  0.53  0.0  0.0  1.0
  Si  Si0  1  0.0  0.0  0.0  1.0
  Si  Si1  1  0.0  0.53  0.53  1.0
  Si  Si2  1  0.53  0.0  0.53  1.0
  Si  Si3  1  0.53  0.53  0.0  1.0

data_Zn3Si4
_symmetry_space_group_name_H-M   R3m
_cell_length_a   7.15
_cell_length_b   7.15
_cell_length_c   8.75
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   Zn3Si4
_chemical_formula_sum   'Zn9 Si12'
_cell_volume   386.9
_cell_formula_units_Z   3
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  '-y, x-y, z'
  3  '-x+y, -x, z'
  4  '-y, -x, z'
  5  '-x+y, y, z'
  6  'x, x-y, z'
  7  'x+1/3, y+2/3, z+2/3'
  8  '-y+1/3, x-y+2/3, z+2/3'
  9  '-x+y+1/3, -x+2/3, z+2/3'
  10  '-y+1/3, -x+2/3, z+2/3'
  11  '-x+y+1/3, y+2/3, z+2/3'
  12  'x+1/3, x-y+2/3, z+2/3'
  13  'x+2/3, y+1/3, z+1/3'
  14  '-y+2/3, x-y+1/3, z+1/3'
  15  '-x+y+2/3, -x+1/3, z+1/3'
  16  '-y+2/3, -x+1/3, z+1/3'
  17  '-x+y+2/3, y+1/3, z+1/3'
  18  'x+2/3, x-y+1/3, z+1/3'
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
  Zn  Zn0  9  0.02  0.51  0.51  1.0
  Si  Si1  9  0.18  0.82  0.35  1.0
  Si  Si2  3  0.0  0.0  -0.0  1.0

Zn Zn Zn Si Si Si Si
Zn Zn Zn Si Si Si Si 0 6 - o o 0 6 o o o 0 3 o o o 0 3 o + o 0 4 o o - 0 4 o o o 1 5 - o o 1 5 o o o 1 4 o - o 1 4 o o o 1 3 o o o 1 3 o o + 2 3 o o o 2 3 + o o 2 6 o - o 2 6 o o o 2 5 o o - 2 5 o o o 
Zn3Si4 crystallizes in the trigonal R3m space group. Zn(1) is bonded to two equivalent Si(1) and four equivalent Si(2) atoms to form a mixture of corner and edge-sharing ZnSi6 octahedra. The corner-sharing octahedra are not tilted. There is one shorter (2.39 Å) and one longer (2.66 Å) Zn(1)-Si(1) bond length. There are two shorter (2.39 Å) and two longer (2.66 Å) Zn(1)-Si(2) bond lengths. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to six equivalent Zn(1) atoms to form corner-sharing SiZn6 octahedra. The corner-sharing octahedra are not tilted. In the second Si site, Si(2) is bonded in a square co-planar geometry to four equivalent Zn(1) atoms.