data_NaCaCr2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.24
_cell_length_b   5.24
_cell_length_c   5.24
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   NaCaCr2
_chemical_formula_sum   'Na1 Ca1 Cr2'
_cell_volume   101.61
_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  Na3  1  0.0  0.0  0.0  1.0
  Ca  Ca0  1  0.85  0.85  0.85  1.0
  Cr  Cr1  1  0.56  0.56  0.56  1.0
  Cr  Cr2  1  0.7  0.7  0.7  1.0

data_NaCaCr2
_symmetry_space_group_name_H-M   R3m
_cell_length_a   5.24
_cell_length_b   5.24
_cell_length_c   12.83
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   NaCaCr2
_chemical_formula_sum   'Na3 Ca3 Cr6'
_cell_volume   304.83
_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
  Ca  Ca1  3  0.0  0.0  0.15  1.0
  Cr  Cr2  3  0.0  0.0  0.3  1.0
  Cr  Cr3  3  0.0  0.0  0.44  1.0

Na Ca Cr Cr
Na Ca Cr Cr 0 1 - - - 1 3 o o o 2 3 o o o 
NaCaCr2 crystallizes in the trigonal R3m space group. Na(1) is bonded in a 4-coordinate geometry to one Ca(1) and three equivalent Cr(2) atoms. The Na(1)-Ca(1) bond length is 1.90 Å. All Na(1)-Cr(2) bond lengths are 3.06 Å. Ca(1) is bonded in a 5-coordinate geometry to one Na(1), one Cr(2), and three equivalent Cr(1) atoms. The Ca(1)-Cr(2) bond length is 1.90 Å. All Ca(1)-Cr(1) bond lengths are 3.06 Å. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to three equivalent Ca(1) and one Cr(2) atom to form distorted corner-sharing CrCa3Cr trigonal pyramids. The Cr(1)-Cr(2) bond length is 1.90 Å. In the second Cr site, Cr(2) is bonded in a distorted single-bond geometry to three equivalent Na(1), one Ca(1), and one Cr(1) atom.