data_BeB2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.1
_cell_length_b   3.1
_cell_length_c   3.1
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   BeB2
_chemical_formula_sum   'Be1 B2'
_cell_volume   21.05
_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
  Be  Be2  1  0.0  0.0  0.0  1.0
  B  B0  1  0.29  0.29  0.29  1.0
  B  B1  1  0.1  0.1  0.1  1.0

data_BeB2
_symmetry_space_group_name_H-M   R3m
_cell_length_a   3.1
_cell_length_b   3.1
_cell_length_c   7.59
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   BeB2
_chemical_formula_sum   'Be3 B6'
_cell_volume   63.15
_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
  Be  Be0  3  0.0  0.0  0.0  1.0
  B  B1  3  0.0  0.0  0.71  1.0
  B  B2  3  0.0  0.0  0.9  1.0

Be B B
BeB2 crystallizes in the trigonal R3m space group. Be(1) is bonded in a single-bond geometry to one B(2) and three equivalent B(1) atoms. The Be(1)-B(2) bond length is 0.73 Å. All Be(1)-B(1) bond lengths are 1.82 Å. There are two inequivalent B sites. In the first B site, B(1) is bonded to three equivalent Be(1) and one B(2) atom to form distorted corner-sharing BBe3B tetrahedra. The B(1)-B(2) bond length is 1.45 Å. In the second B site, B(2) is bonded in a single-bond geometry to one Be(1) and one B(1) atom.