data_Rb3Al
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.18
_cell_length_b   7.18
_cell_length_c   7.18
_cell_angle_alpha   128.51
_cell_angle_beta   128.51
_cell_angle_gamma   75.81
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Rb3Al
_chemical_formula_sum   'Rb3 Al1'
_cell_volume   220.18
_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
  Rb  Rb0  1  0.0  0.12  0.83  1.0
  Rb  Rb1  1  0.12  0.0  0.83  1.0
  Rb  Rb2  1  0.0  0.0  0.66  1.0
  Al  Al3  1  0.0  0.0  0.0  1.0

data_Rb3Al
_symmetry_space_group_name_H-M   Cm
_cell_length_a   8.82
_cell_length_b   8.82
_cell_length_c   7.18
_cell_angle_alpha   90.0
_cell_angle_beta   127.9
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   Rb3Al
_chemical_formula_sum   'Rb6 Al2'
_cell_volume   440.36
_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
  Rb  Rb0  4  0.44  0.44  0.71  1.0
  Rb  Rb1  2  0.0  0.0  0.66  1.0
  Al  Al2  2  0.0  0.0  0.0  1.0

Rb Rb Rb Al
Rb Rb Rb Al 0 2 o o o 0 1 o o o 0 3 o o + 1 2 o o o 1 3 o o + 
Rb3Al is Copper structured and crystallizes in the monoclinic Cm space group. The structure is zero-dimensional and consists of two Rb3Al clusters. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 3-coordinate geometry to one Rb(1), one Rb(2), and one Al(1) atom. The Rb(1)-Rb(1) bond length is 1.04 Å. The Rb(1)-Rb(2) bond length is 0.95 Å. The Rb(1)-Al(1) bond length is 1.86 Å. In the second Rb site, Rb(2) is bonded in a 2-coordinate geometry to two equivalent Rb(1) atoms. Al(1) is bonded in a 2-coordinate geometry to two equivalent Rb(1) atoms.