The structure described by Be17Ta2 crystallizes in the trigonal R-3m space group. There are four inequivalent Be sites. In the first Be site, Be(1) is bonded in a 14-coordinate geometry to one Be(1), three equivalent Be(2), three equivalent Be(4), six equivalent Be(3), and one Ta(1) atom. In the second Be site, Be(2) is bonded to two equivalent Be(1), four equivalent Be(3), four equivalent Be(4), and two equivalent Ta(1) atoms to form distorted BeTa2Be10 cuboctahedra that share corners with four equivalent Be(2)Ta2Be10 cuboctahedra, corners with eight equivalent Be(3)Ta2Be10 cuboctahedra, corners with ten equivalent Be(4)Ta3Be9 cuboctahedra, edges with four equivalent Be(3)Ta2Be10 cuboctahedra, edges with six equivalent Be(4)Ta3Be9 cuboctahedra, faces with four equivalent Be(2)Ta2Be10 cuboctahedra, faces with six equivalent Be(4)Ta3Be9 cuboctahedra, and faces with eight equivalent Be(3)Ta2Be10 cuboctahedra. In the third Be site, Be(3) is bonded to two equivalent Be(1), two equivalent Be(2), two equivalent Be(3), four equivalent Be(4), and two equivalent Ta(1) atoms to form distorted BeTa2Be10 cuboctahedra that share corners with four equivalent Be(2)Ta2Be10 cuboctahedra, corners with eight equivalent Be(4)Ta3Be9 cuboctahedra, corners with twelve equivalent Be(3)Ta2Be10 cuboctahedra,  an edgeedge with one Be(3)Ta2Be10 cuboctahedra, edges with two equivalent Be(2)Ta2Be10 cuboctahedra, edges with two equivalent Be(4)Ta3Be9 cuboctahedra, faces with four equivalent Be(2)Ta2Be10 cuboctahedra, faces with seven equivalent Be(3)Ta2Be10 cuboctahedra, and faces with ten equivalent Be(4)Ta3Be9 cuboctahedra. In the fourth Be site, Be(4) is bonded to one Be(1), two equivalent Be(2), two equivalent Be(4), four equivalent Be(3), and three equivalent Ta(1) atoms to form distorted BeTa3Be9 cuboctahedra that share corners with five equivalent Be(2)Ta2Be10 cuboctahedra, corners with eight equivalent Be(3)Ta2Be10 cuboctahedra, corners with ten equivalent Be(4)Ta3Be9 cuboctahedra, edges with two equivalent Be(3)Ta2Be10 cuboctahedra, edges with three equivalent Be(2)Ta2Be10 cuboctahedra, edges with five equivalent Be(4)Ta3Be9 cuboctahedra, faces with three equivalent Be(2)Ta2Be10 cuboctahedra, faces with seven equivalent Be(4)Ta3Be9 cuboctahedra, and faces with ten equivalent Be(3)Ta2Be10 cuboctahedra. Ta(1) is bonded in a 19-coordinate geometry to one Be(1), three equivalent Be(2), six equivalent Be(3), and nine equivalent Be(4) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ta2Be17
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.546
_cell_length_b   5.546
_cell_length_c   5.546
_cell_angle_alpha   83.073
_cell_angle_beta   83.073
_cell_angle_gamma   83.073
_symmetry_Int_Tables_number   1
_cell_volume   167.111
_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
  Ta  Ta0  1  0.840  0.840  0.840  1.0
  Ta  Ta1  1  0.160  0.160  0.160  1.0
  Be  Be2  1  0.599  0.599  0.599  1.0
  Be  Be3  1  0.401  0.401  0.401  1.0
  Be  Be4  1  0.500  0.500  0.000  1.0
  Be  Be5  1  0.500  0.000  0.500  1.0
  Be  Be6  1  0.000  0.500  0.500  1.0
  Be  Be7  1  0.500  0.204  0.796  1.0
  Be  Be8  1  0.204  0.796  0.500  1.0
  Be  Be9  1  0.796  0.500  0.204  1.0
  Be  Be10  1  0.500  0.796  0.204  1.0
  Be  Be11  1  0.796  0.204  0.500  1.0
  Be  Be12  1  0.204  0.500  0.796  1.0
  Be  Be13  1  0.339  0.847  0.847  1.0
  Be  Be14  1  0.847  0.847  0.339  1.0
  Be  Be15  1  0.847  0.339  0.847  1.0
  Be  Be16  1  0.661  0.153  0.153  1.0
  Be  Be17  1  0.153  0.153  0.661  1.0
  Be  Be18  1  0.153  0.661  0.153  1.0
[/CIF]
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The structure described by Be17Ta2 crystallizes in the trigonal R-3m space group. There are four inequivalent Be sites. In the first Be site, Be(1) is bonded in a 14-coordinate geometry to one Be(1), three equivalent Be(2), three equivalent Be(4), six equivalent Be(3), and one Ta(1) atom. In the second Be site, Be(2) is bonded to two equivalent Be(1), four equivalent Be(3), four equivalent Be(4), and two equivalent Ta(1) atoms to form distorted BeTa2Be10 cuboctahedra that share corners with four equivalent Be(2)Ta2Be10 cuboctahedra, corners with eight equivalent Be(3)Ta2Be10 cuboctahedra, corners with ten equivalent Be(4)Ta3Be9 cuboctahedra, edges with four equivalent Be(3)Ta2Be10 cuboctahedra, edges with six equivalent Be(4)Ta3Be9 cuboctahedra, faces with four equivalent Be(2)Ta2Be10 cuboctahedra, faces with six equivalent Be(4)Ta3Be9 cuboctahedra, and faces with eight equivalent Be(3)Ta2Be10 cuboctahedra. In the third Be site, Be(3) is bonded to two equivalent Be(1), two equivalent Be(2), two equivalent Be(3), four equivalent Be(4), and two equivalent Ta(1) atoms to form distorted BeTa2Be10 cuboctahedra that share corners with four equivalent Be(2)Ta2Be10 cuboctahedra, corners with eight equivalent Be(4)Ta3Be9 cuboctahedra, corners with twelve equivalent Be(3)Ta2Be10 cuboctahedra,  an edgeedge with one Be(3)Ta2Be10 cuboctahedra, edges with two equivalent Be(2)Ta2Be10 cuboctahedra, edges with two equivalent Be(4)Ta3Be9 cuboctahedra, faces with four equivalent Be(2)Ta2Be10 cuboctahedra, faces with seven equivalent Be(3)Ta2Be10 cuboctahedra, and faces with ten equivalent Be(4)Ta3Be9 cuboctahedra. In the fourth Be site, Be(4) is bonded to one Be(1), two equivalent Be(2), two equivalent Be(4), four equivalent Be(3), and three equivalent Ta(1) atoms to form distorted BeTa3Be9 cuboctahedra that share corners with five equivalent Be(2)Ta2Be10 cuboctahedra, corners with eight equivalent Be(3)Ta2Be10 cuboctahedra, corners with ten equivalent Be(4)Ta3Be9 cuboctahedra, edges with two equivalent Be(3)Ta2Be10 cuboctahedra, edges with three equivalent Be(2)Ta2Be10 cuboctahedra, edges with five equivalent Be(4)Ta3Be9 cuboctahedra, faces with three equivalent Be(2)Ta2Be10 cuboctahedra, faces with seven equivalent Be(4)Ta3Be9 cuboctahedra, and faces with ten equivalent Be(3)Ta2Be10 cuboctahedra. Ta(1) is bonded in a 19-coordinate geometry to one Be(1), three equivalent Be(2), six equivalent Be(3), and nine equivalent Be(4) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ta2Be17
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.546
_cell_length_b   5.546
_cell_length_c   5.546
_cell_angle_alpha   83.073
_cell_angle_beta   83.073
_cell_angle_gamma   83.073
_symmetry_Int_Tables_number   1
_cell_volume   167.111
_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
  Ta  Ta0  1  0.840  0.840  0.840  1.0
  Ta  Ta1  1  0.160  0.160  0.160  1.0
  Be  Be2  1  0.599  0.599  0.599  1.0
  Be  Be3  1  0.401  0.401  0.401  1.0
  Be  Be4  1  0.500  0.500  0.000  1.0
  Be  Be5  1  0.500  0.000  0.500  1.0
  Be  Be6  1  0.000  0.500  0.500  1.0
  Be  Be7  1  0.500  0.204  0.796  1.0
  Be  Be8  1  0.204  0.796  0.500  1.0
  Be  Be9  1  0.796  0.500  0.204  1.0
  Be  Be10  1  0.500  0.796  0.204  1.0
  Be  Be11  1  0.796  0.204  0.500  1.0
  Be  Be12  1  0.204  0.500  0.796  1.0
  Be  Be13  1  0.339  0.847  0.847  1.0
  Be  Be14  1  0.847  0.847  0.339  1.0
  Be  Be15  1  0.847  0.339  0.847  1.0
  Be  Be16  1  0.661  0.153  0.153  1.0
  Be  Be17  1  0.153  0.153  0.661  1.0
  Be  Be18  1  0.153  0.661  0.153  1.0
[/CIF]
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