data_Na2Al
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.28
_cell_length_b   8.28
_cell_length_c   8.28
_cell_angle_alpha   158.38
_cell_angle_beta   158.38
_cell_angle_gamma   30.76
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Na2Al
_chemical_formula_sum   'Na2 Al1'
_cell_volume   76.95
_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  Na1  1  0.0  0.0  0.39  1.0
  Na  Na2  1  0.0  0.0  0.58  1.0
  Al  Al0  1  0.0  0.0  0.0  1.0

data_Na2Al
_symmetry_space_group_name_H-M   Cm
_cell_length_a   4.39
_cell_length_b   4.39
_cell_length_c   8.28
_cell_angle_alpha   90.0
_cell_angle_beta   105.38
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   Na2Al
_chemical_formula_sum   'Na4 Al2'
_cell_volume   153.91
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  'x, -y, z'
  3  'x+1/2, y+1/2, z'
  4  'x+1/2, -y+1/2, 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  Na0  2  0.0  0.0  0.42  1.0
  Na  Na1  2  0.0  0.0  0.61  1.0
  Al  Al2  2  0.0  0.0  0.0  1.0

Na Na Al
Na2Al crystallizes in the monoclinic Cm space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a distorted linear geometry to one Na(2) and one Al(1) atom. The Na(1)-Na(2) bond length is 1.58 Å. The Na(1)-Al(1) bond length is 3.19 Å. In the second Na site, Na(2) is bonded in a distorted single-bond geometry to one Na(1) and one Al(1) atom. The Na(2)-Al(1) bond length is 3.51 Å. Al(1) is bonded in a 6-coordinate geometry to one Na(1), one Na(2), and four equivalent Al(1) atoms. All Al(1)-Al(1) bond lengths are 3.11 Å.