data_NaEr2Al
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.21
_cell_length_b   5.21
_cell_length_c   5.21
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   NaEr2Al
_chemical_formula_sum   'Na1 Er2 Al1'
_cell_volume   100.15
_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
  Er  Er1  1  0.53  0.53  0.53  1.0
  Er  Er2  1  0.84  0.84  0.84  1.0
  Al  Al0  1  0.69  0.69  0.69  1.0

data_NaEr2Al
_symmetry_space_group_name_H-M   R3m
_cell_length_a   5.21
_cell_length_b   5.21
_cell_length_c   12.77
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   NaEr2Al
_chemical_formula_sum   'Na3 Er6 Al3'
_cell_volume   300.44
_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
  Er  Er1  3  0.0  0.0  0.16  1.0
  Er  Er2  3  0.0  0.0  0.47  1.0
  Al  Al3  3  0.0  0.0  0.31  1.0

Na Er Er Al
NaEr2Al crystallizes in the trigonal R3m space group. Na(1) is bonded to one Er(2) and three equivalent Al(1) atoms to form distorted NaErAl3 trigonal pyramids that share  a cornercorner with one Al(1)Na3Er2 trigonal bipyramid and corners with six equivalent Na(1)ErAl3 trigonal pyramids. The Na(1)-Er(2) bond length is 2.01 Å. All Na(1)-Al(1) bond lengths are 3.02 Å. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a single-bond geometry to one Al(1) atom. The Er(1)-Al(1) bond length is 2.01 Å. In the second Er site, Er(2) is bonded in a linear geometry to one Na(1) and one Al(1) atom. The Er(2)-Al(1) bond length is 2.01 Å. Al(1) is bonded to three equivalent Na(1), one Er(1), and one Er(2) atom to form distorted AlNa3Er2 trigonal bipyramids that share corners with six equivalent Al(1)Na3Er2 trigonal bipyramids and  a cornercorner with one Na(1)ErAl3 trigonal pyramid.