data_Na2AlCr
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.97
_cell_length_b   4.97
_cell_length_c   4.97
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Na2AlCr
_chemical_formula_sum   'Na2 Al1 Cr1'
_cell_volume   87.05
_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
  Na  Na2  1  0.0  0.0  0.0  1.0
  Na  Na3  1  0.28  0.28  0.28  1.0
  Al  Al0  1  0.52  0.52  0.52  1.0
  Cr  Cr1  1  0.76  0.76  0.76  1.0

data_Na2AlCr
_symmetry_space_group_name_H-M   R3m
_cell_length_a   4.97
_cell_length_b   4.97
_cell_length_c   12.19
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   Na2AlCr
_chemical_formula_sum   'Na6 Al3 Cr3'
_cell_volume   261.16
_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
  Na  Na0  3  0.0  0.0  0.0  1.0
  Na  Na1  3  0.0  0.0  0.72  1.0
  Al  Al2  3  0.0  0.0  0.48  1.0
  Cr  Cr3  3  0.0  0.0  0.24  1.0

Na Na Al Cr
Na2CrAl crystallizes in the trigonal R3m space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to four equivalent Cr(1) and three equivalent Al(1) atoms to form a mixture of distorted edge and corner-sharing NaAl3Cr4 tetrahedra. There is one shorter (2.94 Å) and three longer (3.08 Å) Na(1)-Cr(1) bond lengths. All Na(1)-Al(1) bond lengths are 3.40 Å. In the second Na site, Na(2) is bonded in a 4-coordinate geometry to six equivalent Cr(1) and four equivalent Al(1) atoms. There are three shorter (3.40 Å) and three longer (3.65 Å) Na(2)-Cr(1) bond lengths. There is one shorter (2.94 Å) and three longer (3.08 Å) Na(2)-Al(1) bond lengths. Cr(1) is bonded in a 14-coordinate geometry to four equivalent Na(1), six equivalent Na(2), and four equivalent Al(1) atoms. There is one shorter (2.94 Å) and three longer (3.08 Å) Cr(1)-Al(1) bond lengths. Al(1) is bonded in a 11-coordinate geometry to three equivalent Na(1), four equivalent Na(2), and four equivalent Cr(1) atoms.