The compound described by Al9SiC7N is Aluminum carbonitride-derived structured and crystallizes in the trigonal P3m1 space group. There are nine inequivalent Al sites. In the first Al site, Al(1) is bonded to one C(1) and three equivalent N(1) atoms to form AlCN3 tetrahedra that share corners with three equivalent Al(7)C3N tetrahedra, corners with six equivalent Al(1)CN3 tetrahedra,  a cornercorner with one Al(5)C4 trigonal pyramid, and corners with three equivalent Al(3)C4 trigonal pyramids. In the second Al site, Al(2) is bonded to one C(2) and three equivalent C(7) atoms to form a mixture of distorted edge and corner-sharing AlC4 tetrahedra. In the third Al site, Al(3) is bonded to one C(3) and three equivalent C(1) atoms to form distorted AlC4 trigonal pyramids that share  a cornercorner with one Al(9)C4 tetrahedra, corners with three equivalent Al(1)CN3 tetrahedra, corners with six equivalent Al(3)C4 trigonal pyramids, and edges with three equivalent Al(5)C4 trigonal pyramids. In the fourth Al site, Al(4) is bonded to one C(7) and three equivalent C(2) atoms to form a mixture of distorted edge and corner-sharing AlC4 trigonal pyramids. In the fifth Al site, Al(5) is bonded to one C(1) and three equivalent C(3) atoms to form distorted AlC4 trigonal pyramids that share  a cornercorner with one Al(1)CN3 tetrahedra, corners with three equivalent Al(9)C4 tetrahedra, corners with six equivalent Al(5)C4 trigonal pyramids, and edges with three equivalent Al(3)C4 trigonal pyramids. In the sixth Al site, Al(6) is bonded to one C(2) and three equivalent C(4) atoms to form AlC4 tetrahedra that share  a cornercorner with one Al(2)C4 tetrahedra, corners with three equivalent Si(1)C4 tetrahedra, corners with six equivalent Al(6)C4 tetrahedra, and corners with three equivalent Al(4)C4 trigonal pyramids. In the seventh Al site, Al(7) is bonded to three equivalent C(5) and one N(1) atom to form distorted AlC3N tetrahedra that share corners with three equivalent Al(1)CN3 tetrahedra, corners with three equivalent Si(1)C4 tetrahedra, corners with six equivalent Al(7)C3N tetrahedra, and edges with three equivalent Si(1)C4 tetrahedra. In the eighth Al site, Al(8) is bonded to one C(7) and three equivalent C(6) atoms to form a mixture of distorted edge and corner-sharing AlC4 tetrahedra. In the ninth Al site, Al(9) is bonded to one C(3) and three equivalent C(6) atoms to form a mixture of distorted edge and corner-sharing AlC4 tetrahedra. Si(1) is bonded to one C(4) and three equivalent C(5) atoms to form distorted SiC4 tetrahedra that share corners with three equivalent Al(7)C3N tetrahedra, corners with three equivalent Al(6)C4 tetrahedra, corners with six equivalent Si(1)C4 tetrahedra, and edges with three equivalent Al(7)C3N tetrahedra. There are seven inequivalent C sites. In the first C site, C(1) is bonded to one Al(1), one Al(5), and three equivalent Al(3) atoms to form distorted CAl5 trigonal bipyramids that share corners with three equivalent N(1)Al4 tetrahedra, corners with six equivalent C(1)Al5 trigonal bipyramids, and edges with three equivalent C(3)Al5 trigonal bipyramids. In the second C site, C(2) is bonded to one Al(2), one Al(6), and three equivalent Al(4) atoms to form CAl5 trigonal bipyramids that share corners with three equivalent C(4)Al3Si tetrahedra, corners with six equivalent C(2)Al5 trigonal bipyramids, and edges with three equivalent C(7)Al5 trigonal bipyramids. In the third C site, C(3) is bonded to one Al(3), one Al(9), and three equivalent Al(5) atoms to form distorted CAl5 trigonal bipyramids that share corners with three equivalent C(6)Al6 octahedra, corners with six equivalent C(3)Al5 trigonal bipyramids, and edges with three equivalent C(1)Al5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 62°. In the fourth C site, C(4) is bonded to three equivalent Al(6) and one Si(1) atom to form CAl3Si tetrahedra that share corners with three equivalent C(5)Al3Si3 octahedra, corners with six equivalent C(4)Al3Si tetrahedra, and corners with three equivalent C(2)Al5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 62°. In the fifth C site, C(5) is bonded to three equivalent Al(7) and three equivalent Si(1) atoms to form distorted CAl3Si3 octahedra that share corners with three equivalent C(4)Al3Si tetrahedra, corners with three equivalent N(1)Al4 tetrahedra, and edges with six equivalent C(5)Al3Si3 octahedra. In the sixth C site, C(6) is bonded to three equivalent Al(8) and three equivalent Al(9) atoms to form CAl6 octahedra that share corners with three equivalent C(3)Al5 trigonal bipyramids, corners with three equivalent C(7)Al5 trigonal bipyramids, and edges with six equivalent C(6)Al6 octahedra. In the seventh C site, C(7) is bonded to one Al(4), one Al(8), and three equivalent Al(2) atoms to form distorted CAl5 trigonal bipyramids that share corners with three equivalent C(6)Al6 octahedra, corners with six equivalent C(7)Al5 trigonal bipyramids, and edges with three equivalent C(2)Al5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 62°. N(1) is bonded to one Al(7) and three equivalent Al(1) atoms to form NAl4 tetrahedra that share corners with three equivalent C(5)Al3Si3 octahedra, corners with six equivalent N(1)Al4 tetrahedra, and corners with three equivalent C(1)Al5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 63°. is represented by the CIF file [CIF]
data_Al9SiC7N
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.325
_cell_length_b   3.325
_cell_length_c   21.805
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   208.724
_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
  Al  Al0  1  0.333  0.667  0.339  1.0
  Al  Al1  1  0.333  0.667  0.846  1.0
  Al  Al2  1  0.667  0.333  0.235  1.0
  Al  Al3  1  0.000  0.000  0.760  1.0
  Al  Al4  1  0.333  0.667  0.150  1.0
  Al  Al5  1  0.333  0.667  0.655  1.0
  Al  Al6  1  0.667  0.333  0.454  1.0
  Al  Al7  1  0.000  0.000  0.953  1.0
  Al  Al8  1  0.667  0.333  0.045  1.0
  Si  Si9  1  0.000  0.000  0.546  1.0
  C  C10  1  0.333  0.667  0.251  1.0
  C  C11  1  0.333  0.667  0.747  1.0
  C  C12  1  0.667  0.333  0.134  1.0
  C  C13  1  0.000  0.000  0.625  1.0
  C  C14  1  0.333  0.667  0.500  1.0
  C  C15  1  0.333  0.667  0.999  1.0
  C  C16  1  0.000  0.000  0.864  1.0
  N  N17  1  0.667  0.333  0.371  1.0
[/CIF]
.
The compound described by Al9SiC7N is Aluminum carbonitride-derived structured and crystallizes in the trigonal P3m1 space group. There are nine inequivalent Al sites. In the first Al site, Al(1) is bonded to one C(1) and three equivalent N(1) atoms to form AlCN3 tetrahedra that share corners with three equivalent Al(7)C3N tetrahedra, corners with six equivalent Al(1)CN3 tetrahedra,  a cornercorner with one Al(5)C4 trigonal pyramid, and corners with three equivalent Al(3)C4 trigonal pyramids. In the second Al site, Al(2) is bonded to one C(2) and three equivalent C(7) atoms to form a mixture of distorted edge and corner-sharing AlC4 tetrahedra. In the third Al site, Al(3) is bonded to one C(3) and three equivalent C(1) atoms to form distorted AlC4 trigonal pyramids that share  a cornercorner with one Al(9)C4 tetrahedra, corners with three equivalent Al(1)CN3 tetrahedra, corners with six equivalent Al(3)C4 trigonal pyramids, and edges with three equivalent Al(5)C4 trigonal pyramids. In the fourth Al site, Al(4) is bonded to one C(7) and three equivalent C(2) atoms to form a mixture of distorted edge and corner-sharing AlC4 trigonal pyramids. In the fifth Al site, Al(5) is bonded to one C(1) and three equivalent C(3) atoms to form distorted AlC4 trigonal pyramids that share  a cornercorner with one Al(1)CN3 tetrahedra, corners with three equivalent Al(9)C4 tetrahedra, corners with six equivalent Al(5)C4 trigonal pyramids, and edges with three equivalent Al(3)C4 trigonal pyramids. In the sixth Al site, Al(6) is bonded to one C(2) and three equivalent C(4) atoms to form AlC4 tetrahedra that share  a cornercorner with one Al(2)C4 tetrahedra, corners with three equivalent Si(1)C4 tetrahedra, corners with six equivalent Al(6)C4 tetrahedra, and corners with three equivalent Al(4)C4 trigonal pyramids. In the seventh Al site, Al(7) is bonded to three equivalent C(5) and one N(1) atom to form distorted AlC3N tetrahedra that share corners with three equivalent Al(1)CN3 tetrahedra, corners with three equivalent Si(1)C4 tetrahedra, corners with six equivalent Al(7)C3N tetrahedra, and edges with three equivalent Si(1)C4 tetrahedra. In the eighth Al site, Al(8) is bonded to one C(7) and three equivalent C(6) atoms to form a mixture of distorted edge and corner-sharing AlC4 tetrahedra. In the ninth Al site, Al(9) is bonded to one C(3) and three equivalent C(6) atoms to form a mixture of distorted edge and corner-sharing AlC4 tetrahedra. Si(1) is bonded to one C(4) and three equivalent C(5) atoms to form distorted SiC4 tetrahedra that share corners with three equivalent Al(7)C3N tetrahedra, corners with three equivalent Al(6)C4 tetrahedra, corners with six equivalent Si(1)C4 tetrahedra, and edges with three equivalent Al(7)C3N tetrahedra. There are seven inequivalent C sites. In the first C site, C(1) is bonded to one Al(1), one Al(5), and three equivalent Al(3) atoms to form distorted CAl5 trigonal bipyramids that share corners with three equivalent N(1)Al4 tetrahedra, corners with six equivalent C(1)Al5 trigonal bipyramids, and edges with three equivalent C(3)Al5 trigonal bipyramids. In the second C site, C(2) is bonded to one Al(2), one Al(6), and three equivalent Al(4) atoms to form CAl5 trigonal bipyramids that share corners with three equivalent C(4)Al3Si tetrahedra, corners with six equivalent C(2)Al5 trigonal bipyramids, and edges with three equivalent C(7)Al5 trigonal bipyramids. In the third C site, C(3) is bonded to one Al(3), one Al(9), and three equivalent Al(5) atoms to form distorted CAl5 trigonal bipyramids that share corners with three equivalent C(6)Al6 octahedra, corners with six equivalent C(3)Al5 trigonal bipyramids, and edges with three equivalent C(1)Al5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 62°. In the fourth C site, C(4) is bonded to three equivalent Al(6) and one Si(1) atom to form CAl3Si tetrahedra that share corners with three equivalent C(5)Al3Si3 octahedra, corners with six equivalent C(4)Al3Si tetrahedra, and corners with three equivalent C(2)Al5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 62°. In the fifth C site, C(5) is bonded to three equivalent Al(7) and three equivalent Si(1) atoms to form distorted CAl3Si3 octahedra that share corners with three equivalent C(4)Al3Si tetrahedra, corners with three equivalent N(1)Al4 tetrahedra, and edges with six equivalent C(5)Al3Si3 octahedra. In the sixth C site, C(6) is bonded to three equivalent Al(8) and three equivalent Al(9) atoms to form CAl6 octahedra that share corners with three equivalent C(3)Al5 trigonal bipyramids, corners with three equivalent C(7)Al5 trigonal bipyramids, and edges with six equivalent C(6)Al6 octahedra. In the seventh C site, C(7) is bonded to one Al(4), one Al(8), and three equivalent Al(2) atoms to form distorted CAl5 trigonal bipyramids that share corners with three equivalent C(6)Al6 octahedra, corners with six equivalent C(7)Al5 trigonal bipyramids, and edges with three equivalent C(2)Al5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 62°. N(1) is bonded to one Al(7) and three equivalent Al(1) atoms to form NAl4 tetrahedra that share corners with three equivalent C(5)Al3Si3 octahedra, corners with six equivalent N(1)Al4 tetrahedra, and corners with three equivalent C(1)Al5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 63°. is represented by the CIF file [CIF]
data_Al9SiC7N
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.325
_cell_length_b   3.325
_cell_length_c   21.805
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   208.724
_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
  Al  Al0  1  0.333  0.667  0.339  1.0
  Al  Al1  1  0.333  0.667  0.846  1.0
  Al  Al2  1  0.667  0.333  0.235  1.0
  Al  Al3  1  0.000  0.000  0.760  1.0
  Al  Al4  1  0.333  0.667  0.150  1.0
  Al  Al5  1  0.333  0.667  0.655  1.0
  Al  Al6  1  0.667  0.333  0.454  1.0
  Al  Al7  1  0.000  0.000  0.953  1.0
  Al  Al8  1  0.667  0.333  0.045  1.0
  Si  Si9  1  0.000  0.000  0.546  1.0
  C  C10  1  0.333  0.667  0.251  1.0
  C  C11  1  0.333  0.667  0.747  1.0
  C  C12  1  0.667  0.333  0.134  1.0
  C  C13  1  0.000  0.000  0.625  1.0
  C  C14  1  0.333  0.667  0.500  1.0
  C  C15  1  0.333  0.667  0.999  1.0
  C  C16  1  0.000  0.000  0.864  1.0
  N  N17  1  0.667  0.333  0.371  1.0
[/CIF]
.