The material structure described by Si3N4 is Hausmannite-like structured and crystallizes in the orthorhombic Pnma space group. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one N(1), one N(3), and two equivalent N(2) atoms to form a mixture of corner and edge-sharing SiN4 tetrahedra. The corner-sharing octahedral tilt angles range from 62-66°. In the second Si site, Si(2) is bonded to one N(1), one N(3), and four equivalent N(2) atoms to form SiN6 octahedra that share corners with four equivalent Si(2)N6 octahedra, corners with four equivalent Si(3)N6 octahedra, corners with four equivalent Si(1)N4 tetrahedra, edges with two equivalent Si(3)N6 octahedra, and  an edgeedge with one Si(1)N4 tetrahedra. The corner-sharing octahedral tilt angles range from 49-54°. In the third Si site, Si(3) is bonded to two equivalent N(1), two equivalent N(2), and two equivalent N(3) atoms to form SiN6 octahedra that share corners with four equivalent Si(2)N6 octahedra, corners with two equivalent Si(1)N4 tetrahedra, edges with two equivalent Si(2)N6 octahedra, edges with two equivalent Si(3)N6 octahedra, and edges with two equivalent Si(1)N4 tetrahedra. The corner-sharing octahedral tilt angles range from 50-54°. There are three inequivalent N sites. In the first N site, N(1) is bonded to one Si(1), one Si(2), and two equivalent Si(3) atoms to form corner-sharing NSi4 tetrahedra. In the second N site, N(2) is bonded in a rectangular see-saw-like geometry to one Si(1), one Si(3), and two equivalent Si(2) atoms. In the third N site, N(3) is bonded in a rectangular see-saw-like geometry to one Si(1), one Si(2), and two equivalent Si(3) atoms. is represented by the CIF file [CIF]
data_Si3N4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.576
_cell_length_b   5.578
_cell_length_c   9.524
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   243.074
_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
  Si  Si0  1  0.560  0.750  0.092  1.0
  Si  Si1  1  0.060  0.250  0.408  1.0
  Si  Si2  1  0.491  0.750  0.774  1.0
  Si  Si3  1  0.440  0.250  0.908  1.0
  Si  Si4  1  0.009  0.750  0.274  1.0
  Si  Si5  1  0.940  0.750  0.592  1.0
  Si  Si6  1  0.991  0.250  0.726  1.0
  Si  Si7  1  0.500  0.000  0.500  1.0
  Si  Si8  1  0.000  0.000  0.000  1.0
  Si  Si9  1  0.509  0.250  0.226  1.0
  Si  Si10  1  0.000  0.500  0.000  1.0
  Si  Si11  1  0.500  0.500  0.500  1.0
  N  N12  1  0.312  0.750  0.592  1.0
  N  N13  1  0.188  0.750  0.092  1.0
  N  N14  1  0.242  0.005  0.337  1.0
  N  N15  1  0.243  0.250  0.571  1.0
  N  N16  1  0.758  0.505  0.663  1.0
  N  N17  1  0.758  0.995  0.663  1.0
  N  N18  1  0.742  0.505  0.163  1.0
  N  N19  1  0.757  0.750  0.429  1.0
  N  N20  1  0.258  0.495  0.837  1.0
  N  N21  1  0.742  0.995  0.163  1.0
  N  N22  1  0.257  0.250  0.071  1.0
  N  N23  1  0.258  0.005  0.837  1.0
  N  N24  1  0.688  0.250  0.408  1.0
  N  N25  1  0.743  0.750  0.929  1.0
  N  N26  1  0.242  0.495  0.337  1.0
  N  N27  1  0.812  0.250  0.908  1.0
[/CIF]
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The material structure described by Si3N4 is Hausmannite-like structured and crystallizes in the orthorhombic Pnma space group. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one N(1), one N(3), and two equivalent N(2) atoms to form a mixture of corner and edge-sharing SiN4 tetrahedra. The corner-sharing octahedral tilt angles range from 62-66°. In the second Si site, Si(2) is bonded to one N(1), one N(3), and four equivalent N(2) atoms to form SiN6 octahedra that share corners with four equivalent Si(2)N6 octahedra, corners with four equivalent Si(3)N6 octahedra, corners with four equivalent Si(1)N4 tetrahedra, edges with two equivalent Si(3)N6 octahedra, and  an edgeedge with one Si(1)N4 tetrahedra. The corner-sharing octahedral tilt angles range from 49-54°. In the third Si site, Si(3) is bonded to two equivalent N(1), two equivalent N(2), and two equivalent N(3) atoms to form SiN6 octahedra that share corners with four equivalent Si(2)N6 octahedra, corners with two equivalent Si(1)N4 tetrahedra, edges with two equivalent Si(2)N6 octahedra, edges with two equivalent Si(3)N6 octahedra, and edges with two equivalent Si(1)N4 tetrahedra. The corner-sharing octahedral tilt angles range from 50-54°. There are three inequivalent N sites. In the first N site, N(1) is bonded to one Si(1), one Si(2), and two equivalent Si(3) atoms to form corner-sharing NSi4 tetrahedra. In the second N site, N(2) is bonded in a rectangular see-saw-like geometry to one Si(1), one Si(3), and two equivalent Si(2) atoms. In the third N site, N(3) is bonded in a rectangular see-saw-like geometry to one Si(1), one Si(2), and two equivalent Si(3) atoms. is represented by the CIF file [CIF]
data_Si3N4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.576
_cell_length_b   5.578
_cell_length_c   9.524
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   243.074
_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
  Si  Si0  1  0.560  0.750  0.092  1.0
  Si  Si1  1  0.060  0.250  0.408  1.0
  Si  Si2  1  0.491  0.750  0.774  1.0
  Si  Si3  1  0.440  0.250  0.908  1.0
  Si  Si4  1  0.009  0.750  0.274  1.0
  Si  Si5  1  0.940  0.750  0.592  1.0
  Si  Si6  1  0.991  0.250  0.726  1.0
  Si  Si7  1  0.500  0.000  0.500  1.0
  Si  Si8  1  0.000  0.000  0.000  1.0
  Si  Si9  1  0.509  0.250  0.226  1.0
  Si  Si10  1  0.000  0.500  0.000  1.0
  Si  Si11  1  0.500  0.500  0.500  1.0
  N  N12  1  0.312  0.750  0.592  1.0
  N  N13  1  0.188  0.750  0.092  1.0
  N  N14  1  0.242  0.005  0.337  1.0
  N  N15  1  0.243  0.250  0.571  1.0
  N  N16  1  0.758  0.505  0.663  1.0
  N  N17  1  0.758  0.995  0.663  1.0
  N  N18  1  0.742  0.505  0.163  1.0
  N  N19  1  0.757  0.750  0.429  1.0
  N  N20  1  0.258  0.495  0.837  1.0
  N  N21  1  0.742  0.995  0.163  1.0
  N  N22  1  0.257  0.250  0.071  1.0
  N  N23  1  0.258  0.005  0.837  1.0
  N  N24  1  0.688  0.250  0.408  1.0
  N  N25  1  0.743  0.750  0.929  1.0
  N  N26  1  0.242  0.495  0.337  1.0
  N  N27  1  0.812  0.250  0.908  1.0
[/CIF]
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