data_Ba2AlSi
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.68
_cell_length_b   3.81
_cell_length_c   9.81
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Ba2AlSi
_chemical_formula_sum   'Ba2 Al1 Si1'
_cell_volume   137.56
_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
  Ba  Ba1  1  0.84  0.9  0.01  1.0
  Ba  Ba2  1  0.0  0.0  0.31  1.0
  Al  Al0  1  0.0  0.0  0.6  1.0
  Si  Si3  1  0.84  0.9  0.61  1.0

data_Ba2AlSi
_symmetry_space_group_name_H-M   P1
_cell_length_a   3.68
_cell_length_b   3.81
_cell_length_c   9.81
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Ba2AlSi
_chemical_formula_sum   'Ba2 Al1 Si1'
_cell_volume   137.56
_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
  Ba  Ba0  1  0.0  0.0  0.31  1.0
  Ba  Ba1  1  0.84  0.9  0.01  1.0
  Al  Al2  1  0.0  0.0  0.6  1.0
  Si  Si3  1  0.84  0.9  0.61  1.0

Ba Ba Al Si
Ba Ba Al Si 0 0 + o o 0 0 o + o 0 2 + + - 0 3 o o - 0 1 + + o 1 3 - - o 1 2 o o o 2 3 - - o 
Ba2AlSi crystallizes in the triclinic P1 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 6-coordinate geometry to one Ba(2), four equivalent Ba(1), and one Si(1) atom. The Ba(1)-Ba(2) bond length is 3.05 Å. There are two shorter (3.68 Å) and two longer (3.81 Å) Ba(1)-Ba(1) bond lengths. The Ba(1)-Si(1) bond length is 3.92 Å. In the second Ba site, Ba(2) is bonded in a distorted single-bond geometry to one Ba(1) and one Al(1) atom. The Ba(2)-Al(1) bond length is 2.83 Å. Al(1) is bonded in a single-bond geometry to one Ba(2) and one Si(1) atom. The Al(1)-Si(1) bond length is 0.70 Å. Si(1) is bonded in a single-bond geometry to one Ba(1) and one Al(1) atom.