The compound described by Ta4AlN3 is MAX Phase-like structured and crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to three equivalent N(1) and three equivalent N(2) atoms to form a mixture of distorted corner and edge-sharing TaN6 pentagonal pyramids. In the second Ta site, Ta(2) is bonded in a 3-coordinate geometry to three equivalent Al(1) and three equivalent N(2) atoms. Al(1) is bonded to six equivalent Ta(2) and six equivalent Al(1) atoms to form distorted AlTa6Al6 cuboctahedra that share corners with six equivalent Al(1)Ta6Al6 cuboctahedra, corners with six equivalent N(2)Ta6 octahedra, edges with six equivalent Al(1)Ta6Al6 cuboctahedra, edges with six equivalent N(2)Ta6 octahedra, and faces with six equivalent Al(1)Ta6Al6 cuboctahedra. The corner-sharing octahedral tilt angles are 13°. There are two inequivalent N sites. In the first N site, N(1) is bonded to six equivalent Ta(1) atoms to form a mixture of face, corner, and edge-sharing NTa6 octahedra. The corner-sharing octahedral tilt angles are 46°. In the second N site, N(2) is bonded to three equivalent Ta(1) and three equivalent Ta(2) atoms to form NTa6 octahedra that share corners with three equivalent Al(1)Ta6Al6 cuboctahedra, corners with six equivalent N(1)Ta6 octahedra, edges with three equivalent Al(1)Ta6Al6 cuboctahedra, edges with six equivalent N(2)Ta6 octahedra, and  a faceface with one N(1)Ta6 octahedra. The corner-sharing octahedral tilt angles are 46°. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ta4AlN3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   2.975
_cell_length_b   2.975
_cell_length_c   25.781
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   197.647
_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
  Ta  Ta0  1  0.333  0.667  0.445  1.0
  Ta  Ta1  1  0.667  0.333  0.555  1.0
  Ta  Ta2  1  0.667  0.333  0.945  1.0
  Ta  Ta3  1  0.333  0.667  0.055  1.0
  Ta  Ta4  1  0.333  0.667  0.836  1.0
  Ta  Ta5  1  0.667  0.333  0.164  1.0
  Ta  Ta6  1  0.667  0.333  0.336  1.0
  Ta  Ta7  1  0.333  0.667  0.664  1.0
  Al  Al8  1  0.333  0.667  0.250  1.0
  Al  Al9  1  0.667  0.333  0.750  1.0
  N  N10  1  0.000  0.000  0.500  1.0
  N  N11  1  0.000  0.000  0.000  1.0
  N  N12  1  0.000  0.000  0.391  1.0
  N  N13  1  0.000  0.000  0.609  1.0
  N  N14  1  0.000  0.000  0.891  1.0
  N  N15  1  0.000  0.000  0.109  1.0
[/CIF]
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The compound described by Ta4AlN3 is MAX Phase-like structured and crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to three equivalent N(1) and three equivalent N(2) atoms to form a mixture of distorted corner and edge-sharing TaN6 pentagonal pyramids. In the second Ta site, Ta(2) is bonded in a 3-coordinate geometry to three equivalent Al(1) and three equivalent N(2) atoms. Al(1) is bonded to six equivalent Ta(2) and six equivalent Al(1) atoms to form distorted AlTa6Al6 cuboctahedra that share corners with six equivalent Al(1)Ta6Al6 cuboctahedra, corners with six equivalent N(2)Ta6 octahedra, edges with six equivalent Al(1)Ta6Al6 cuboctahedra, edges with six equivalent N(2)Ta6 octahedra, and faces with six equivalent Al(1)Ta6Al6 cuboctahedra. The corner-sharing octahedral tilt angles are 13°. There are two inequivalent N sites. In the first N site, N(1) is bonded to six equivalent Ta(1) atoms to form a mixture of face, corner, and edge-sharing NTa6 octahedra. The corner-sharing octahedral tilt angles are 46°. In the second N site, N(2) is bonded to three equivalent Ta(1) and three equivalent Ta(2) atoms to form NTa6 octahedra that share corners with three equivalent Al(1)Ta6Al6 cuboctahedra, corners with six equivalent N(1)Ta6 octahedra, edges with three equivalent Al(1)Ta6Al6 cuboctahedra, edges with six equivalent N(2)Ta6 octahedra, and  a faceface with one N(1)Ta6 octahedra. The corner-sharing octahedral tilt angles are 46°. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ta4AlN3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   2.975
_cell_length_b   2.975
_cell_length_c   25.781
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   197.647
_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
  Ta  Ta0  1  0.333  0.667  0.445  1.0
  Ta  Ta1  1  0.667  0.333  0.555  1.0
  Ta  Ta2  1  0.667  0.333  0.945  1.0
  Ta  Ta3  1  0.333  0.667  0.055  1.0
  Ta  Ta4  1  0.333  0.667  0.836  1.0
  Ta  Ta5  1  0.667  0.333  0.164  1.0
  Ta  Ta6  1  0.667  0.333  0.336  1.0
  Ta  Ta7  1  0.333  0.667  0.664  1.0
  Al  Al8  1  0.333  0.667  0.250  1.0
  Al  Al9  1  0.667  0.333  0.750  1.0
  N  N10  1  0.000  0.000  0.500  1.0
  N  N11  1  0.000  0.000  0.000  1.0
  N  N12  1  0.000  0.000  0.391  1.0
  N  N13  1  0.000  0.000  0.609  1.0
  N  N14  1  0.000  0.000  0.891  1.0
  N  N15  1  0.000  0.000  0.109  1.0
[/CIF]
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