data_RbBe3Nb
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.92
_cell_length_b   4.92
_cell_length_c   4.92
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   RbBe3Nb
_chemical_formula_sum   'Rb1 Be3 Nb1'
_cell_volume   118.89
_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  0.0  0.0  0.0  1.0
  Be  Be0  1  0.46  0.0  0.46  1.0
  Be  Be1  1  0.46  0.46  0.0  1.0
  Be  Be2  1  0.0  0.46  0.46  1.0
  Nb  Nb3  1  0.46  0.46  0.46  1.0

data_RbBe3Nb
_symmetry_space_group_name_H-M   R3m
_cell_length_a   6.95
_cell_length_b   6.95
_cell_length_c   8.52
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   RbBe3Nb
_chemical_formula_sum   'Rb3 Be9 Nb3'
_cell_volume   356.66
_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  0.0  1.0
  Be  Be1  9  0.03  0.51  0.97  1.0
  Nb  Nb2  3  0.0  0.0  0.46  1.0

Rb Be Be Be Nb
RbBe3Nb is (Cubic) Perovskite structured and crystallizes in the trigonal R3m space group. Rb(1) is bonded to twelve equivalent Be(1) atoms to form RbBe12 cuboctahedra that share corners with twelve equivalent Rb(1)Be12 cuboctahedra, faces with six equivalent Rb(1)Be12 cuboctahedra, and faces with eight equivalent Nb(1)Be6 octahedra. There are a spread of Rb(1)-Be(1) bond distances ranging from 3.19-3.77 Å. Be(1) is bonded to four equivalent Rb(1) and two equivalent Nb(1) atoms to form a mixture of distorted edge, corner, and face-sharing BeRb4Nb2 octahedra. The corner-sharing octahedral tilt angles range from 0-63°. There is one shorter (2.25 Å) and one longer (2.66 Å) Be(1)-Nb(1) bond length. Nb(1) is bonded to six equivalent Be(1) atoms to form NbBe6 octahedra that share corners with six equivalent Nb(1)Be6 octahedra and faces with eight equivalent Rb(1)Be12 cuboctahedra. The corner-sharing octahedra are not tilted.