data_RbSi3As
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.11
_cell_length_b   5.11
_cell_length_c   5.11
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   RbSi3As
_chemical_formula_sum   'Rb1 Si3 As1'
_cell_volume   133.67
_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  Rb4  1  0.56  0.56  0.56  1.0
  Si  Si1  1  0.0  0.56  0.0  1.0
  Si  Si2  1  0.0  0.0  0.56  1.0
  Si  Si3  1  0.56  0.0  0.0  1.0
  As  As0  1  0.0  0.0  0.0  1.0

data_RbSi3As
_symmetry_space_group_name_H-M   R3m
_cell_length_a   7.23
_cell_length_b   7.23
_cell_length_c   8.86
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   RbSi3As
_chemical_formula_sum   'Rb3 Si9 As3'
_cell_volume   401.0
_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
  Rb  Rb0  3  0.0  0.0  0.56  1.0
  Si  Si1  9  0.04  0.52  0.52  1.0
  As  As2  3  0.0  0.0  0.0  1.0

Rb Si Si Si As
RbSi3As crystallizes in the trigonal R3m space group. Rb(1) is bonded in a 9-coordinate geometry to nine equivalent Si(1) atoms. There are three shorter (3.21 Å) and six longer (3.64 Å) Rb(1)-Si(1) bond lengths. Si(1) is bonded in a 1-coordinate geometry to three equivalent Rb(1) and two equivalent As(1) atoms. There is one shorter (2.27 Å) and one longer (2.85 Å) Si(1)-As(1) bond length. As(1) is bonded to six equivalent Si(1) atoms to form corner-sharing AsSi6 octahedra. The corner-sharing octahedra are not tilted.