data_RbUNb2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.09
_cell_length_b   5.09
_cell_length_c   5.09
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   RbUNb2
_chemical_formula_sum   'Rb1 U1 Nb2'
_cell_volume   93.24
_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  Rb2  1  0.0  0.0  0.0  1.0
  U  U3  1  0.6  0.6  0.6  1.0
  Nb  Nb0  1  0.4  0.4  0.4  1.0
  Nb  Nb1  1  0.8  0.8  0.8  1.0

data_RbUNb2
_symmetry_space_group_name_H-M   R3m
_cell_length_a   5.09
_cell_length_b   5.09
_cell_length_c   12.47
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   RbUNb2
_chemical_formula_sum   'Rb3 U3 Nb6'
_cell_volume   279.73
_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
  U  U1  3  0.0  0.0  0.4  1.0
  Nb  Nb2  3  0.0  0.0  0.2  1.0
  Nb  Nb3  3  0.0  0.0  0.6  1.0

Rb U Nb Nb
RbUNb2 crystallizes in the trigonal R3m space group. Rb(1) is bonded in a 10-coordinate geometry to three equivalent U(1), three equivalent Nb(1), and four equivalent Nb(2) atoms. All Rb(1)-U(1) bond lengths are 3.06 Å. All Rb(1)-Nb(1) bond lengths are 3.05 Å. There is one shorter (2.50 Å) and three longer (3.37 Å) Rb(1)-Nb(2) bond lengths. U(1) is bonded in a 5-coordinate geometry to three equivalent Rb(1), one Nb(1), and one Nb(2) atom. The U(1)-Nb(1) bond length is 2.50 Å. The U(1)-Nb(2) bond length is 2.50 Å. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to three equivalent Rb(1) and one U(1) atom to form distorted corner-sharing NbRb3U tetrahedra. In the second Nb site, Nb(2) is bonded in a distorted linear geometry to four equivalent Rb(1) and one U(1) atom.