The crystal structure described by Al4SiC4 is Aluminum carbonitride-like structured and crystallizes in the hexagonal P6_3mc space group. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded in a 4-coordinate geometry to one C(1) and three equivalent C(2) atoms. In the second Al site, Al(2) is bonded to one C(3) and three equivalent C(1) atoms to form a mixture of edge and corner-sharing AlC4 tetrahedra. In the third Al site, Al(3) is bonded to one C(1) and three equivalent C(3) atoms to form a mixture of distorted edge and corner-sharing AlC4 trigonal pyramids. In the fourth Al site, Al(4) is bonded to one C(3) 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(4)C4 tetrahedra, and corners with three equivalent Al(3)C4 trigonal pyramids. Si(1) is bonded to one C(4) and three equivalent C(2) atoms to form distorted SiC4 tetrahedra that share corners with three equivalent Al(4)C4 tetrahedra and corners with six equivalent Si(1)C4 tetrahedra. There are four inequivalent C sites. In the first C site, C(1) is bonded in a 5-coordinate geometry to one Al(1), one Al(3), and three equivalent Al(2) atoms. In the second C site, C(2) is bonded to three equivalent Al(1) and three equivalent Si(1) atoms to form CAl3Si3 octahedra that share corners with three equivalent C(4)Al3Si tetrahedra and edges with six equivalent C(2)Al3Si3 octahedra. In the third C site, C(3) is bonded to one Al(2), one Al(4), and three equivalent Al(3) atoms to form CAl5 trigonal bipyramids that share corners with three equivalent C(4)Al3Si tetrahedra and corners with six equivalent C(3)Al5 trigonal bipyramids. In the fourth C site, C(4) is bonded to three equivalent Al(4) and one Si(1) atom to form CAl3Si tetrahedra that share corners with three equivalent C(2)Al3Si3 octahedra, corners with six equivalent C(4)Al3Si tetrahedra, and corners with three equivalent C(3)Al5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 64°. is represented by the CIF file [CIF]
data_Al4SiC4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.326
_cell_length_b   3.326
_cell_length_c   21.956
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   210.322
_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
  Al  Al0  1  0.333  0.667  0.449  1.0
  Al  Al1  1  0.667  0.333  0.949  1.0
  Al  Al2  1  0.000  0.000  0.342  1.0
  Al  Al3  1  0.000  0.000  0.842  1.0
  Al  Al4  1  0.333  0.667  0.254  1.0
  Al  Al5  1  0.667  0.333  0.754  1.0
  Al  Al6  1  0.000  0.000  0.155  1.0
  Al  Al7  1  0.000  0.000  0.655  1.0
  Si  Si8  1  0.333  0.667  0.047  1.0
  Si  Si9  1  0.667  0.333  0.547  1.0
  C  C10  1  0.333  0.667  0.363  1.0
  C  C11  1  0.667  0.333  0.863  1.0
  C  C12  1  0.000  0.000  0.504  1.0
  C  C13  1  0.000  0.000  0.004  1.0
  C  C14  1  0.000  0.000  0.247  1.0
  C  C15  1  0.000  0.000  0.747  1.0
  C  C16  1  0.333  0.667  0.127  1.0
  C  C17  1  0.667  0.333  0.627  1.0
[/CIF]
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The crystal structure described by Al4SiC4 is Aluminum carbonitride-like structured and crystallizes in the hexagonal P6_3mc space group. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded in a 4-coordinate geometry to one C(1) and three equivalent C(2) atoms. In the second Al site, Al(2) is bonded to one C(3) and three equivalent C(1) atoms to form a mixture of edge and corner-sharing AlC4 tetrahedra. In the third Al site, Al(3) is bonded to one C(1) and three equivalent C(3) atoms to form a mixture of distorted edge and corner-sharing AlC4 trigonal pyramids. In the fourth Al site, Al(4) is bonded to one C(3) 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(4)C4 tetrahedra, and corners with three equivalent Al(3)C4 trigonal pyramids. Si(1) is bonded to one C(4) and three equivalent C(2) atoms to form distorted SiC4 tetrahedra that share corners with three equivalent Al(4)C4 tetrahedra and corners with six equivalent Si(1)C4 tetrahedra. There are four inequivalent C sites. In the first C site, C(1) is bonded in a 5-coordinate geometry to one Al(1), one Al(3), and three equivalent Al(2) atoms. In the second C site, C(2) is bonded to three equivalent Al(1) and three equivalent Si(1) atoms to form CAl3Si3 octahedra that share corners with three equivalent C(4)Al3Si tetrahedra and edges with six equivalent C(2)Al3Si3 octahedra. In the third C site, C(3) is bonded to one Al(2), one Al(4), and three equivalent Al(3) atoms to form CAl5 trigonal bipyramids that share corners with three equivalent C(4)Al3Si tetrahedra and corners with six equivalent C(3)Al5 trigonal bipyramids. In the fourth C site, C(4) is bonded to three equivalent Al(4) and one Si(1) atom to form CAl3Si tetrahedra that share corners with three equivalent C(2)Al3Si3 octahedra, corners with six equivalent C(4)Al3Si tetrahedra, and corners with three equivalent C(3)Al5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 64°. is represented by the CIF file [CIF]
data_Al4SiC4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.326
_cell_length_b   3.326
_cell_length_c   21.956
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   210.322
_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
  Al  Al0  1  0.333  0.667  0.449  1.0
  Al  Al1  1  0.667  0.333  0.949  1.0
  Al  Al2  1  0.000  0.000  0.342  1.0
  Al  Al3  1  0.000  0.000  0.842  1.0
  Al  Al4  1  0.333  0.667  0.254  1.0
  Al  Al5  1  0.667  0.333  0.754  1.0
  Al  Al6  1  0.000  0.000  0.155  1.0
  Al  Al7  1  0.000  0.000  0.655  1.0
  Si  Si8  1  0.333  0.667  0.047  1.0
  Si  Si9  1  0.667  0.333  0.547  1.0
  C  C10  1  0.333  0.667  0.363  1.0
  C  C11  1  0.667  0.333  0.863  1.0
  C  C12  1  0.000  0.000  0.504  1.0
  C  C13  1  0.000  0.000  0.004  1.0
  C  C14  1  0.000  0.000  0.247  1.0
  C  C15  1  0.000  0.000  0.747  1.0
  C  C16  1  0.333  0.667  0.127  1.0
  C  C17  1  0.667  0.333  0.627  1.0
[/CIF]
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