The compound described by Ta3Ni8Si crystallizes in the trigonal P3m1 space group. There are three inequivalent Ta sites. In the first Ta site, Ta(1) is bonded in a 15-coordinate geometry to three equivalent Ni(1), three equivalent Ni(3), six equivalent Ni(4), and three equivalent Si(1) atoms. In the second Ta site, Ta(2) is bonded in a 12-coordinate geometry to three equivalent Ni(2), three equivalent Ni(3), and six equivalent Ni(4) atoms. In the third Ta site, Ta(3) is bonded in a 13-coordinate geometry to three equivalent Ni(2), three equivalent Ni(4), six equivalent Ni(3), and one Si(1) atom. There are four inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to three equivalent Ta(1), three equivalent Ni(3), three equivalent Ni(4), and three equivalent Si(1) atoms to form NiTa3Si3Ni6 cuboctahedra that share corners with six equivalent Ni(3)Ta4Si2Ni6 cuboctahedra, corners with six equivalent Ni(4)Ta5SiNi6 cuboctahedra, edges with six equivalent Ni(1)Ta3Si3Ni6 cuboctahedra, faces with two equivalent Ni(2)Ta6Ni6 cuboctahedra, faces with nine equivalent Ni(3)Ta4Si2Ni6 cuboctahedra, and faces with nine equivalent Ni(4)Ta5SiNi6 cuboctahedra. In the second Ni site, Ni(2) is bonded to three equivalent Ta(2), three equivalent Ta(3), three equivalent Ni(3), and three equivalent Ni(4) atoms to form NiTa6Ni6 cuboctahedra that share corners with six equivalent Ni(3)Ta4Si2Ni6 cuboctahedra, corners with six equivalent Ni(4)Ta5SiNi6 cuboctahedra, edges with six equivalent Ni(2)Ta6Ni6 cuboctahedra, faces with two equivalent Ni(1)Ta3Si3Ni6 cuboctahedra, faces with nine equivalent Ni(3)Ta4Si2Ni6 cuboctahedra, and faces with nine equivalent Ni(4)Ta5SiNi6 cuboctahedra. In the third Ni site, Ni(3) is bonded to one Ta(1), one Ta(2), two equivalent Ta(3), one Ni(1), one Ni(2), four equivalent Ni(3), and two equivalent Si(1) atoms to form distorted NiTa4Si2Ni6 cuboctahedra that share corners with two equivalent Ni(1)Ta3Si3Ni6 cuboctahedra, corners with two equivalent Ni(2)Ta6Ni6 cuboctahedra, corners with four equivalent Ni(3)Ta4Si2Ni6 cuboctahedra, corners with ten equivalent Ni(4)Ta5SiNi6 cuboctahedra, edges with two equivalent Ni(3)Ta4Si2Ni6 cuboctahedra, edges with four equivalent Ni(4)Ta5SiNi6 cuboctahedra, faces with three equivalent Ni(1)Ta3Si3Ni6 cuboctahedra, faces with three equivalent Ni(2)Ta6Ni6 cuboctahedra, faces with four equivalent Ni(4)Ta5SiNi6 cuboctahedra, and faces with eight equivalent Ni(3)Ta4Si2Ni6 cuboctahedra. In the fourth Ni site, Ni(4) is bonded to one Ta(3), two equivalent Ta(1), two equivalent Ta(2), one Ni(1), one Ni(2), four equivalent Ni(4), and one Si(1) atom to form NiTa5SiNi6 cuboctahedra that share corners with two equivalent Ni(1)Ta3Si3Ni6 cuboctahedra, corners with two equivalent Ni(2)Ta6Ni6 cuboctahedra, corners with four equivalent Ni(4)Ta5SiNi6 cuboctahedra, corners with ten equivalent Ni(3)Ta4Si2Ni6 cuboctahedra, edges with two equivalent Ni(4)Ta5SiNi6 cuboctahedra, edges with four equivalent Ni(3)Ta4Si2Ni6 cuboctahedra, faces with three equivalent Ni(1)Ta3Si3Ni6 cuboctahedra, faces with three equivalent Ni(2)Ta6Ni6 cuboctahedra, faces with four equivalent Ni(3)Ta4Si2Ni6 cuboctahedra, and faces with eight equivalent Ni(4)Ta5SiNi6 cuboctahedra. Si(1) is bonded in a 16-coordinate geometry to one Ta(3), three equivalent Ta(1), three equivalent Ni(1), three equivalent Ni(4), and six equivalent Ni(3) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ta3SiNi8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.767
_cell_length_b   4.767
_cell_length_c   7.677
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   151.090
_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  0.667  0.333  0.448  1.0
  Ta  Ta1  1  0.667  0.333  0.066  1.0
  Ta  Ta2  1  0.000  0.000  0.916  1.0
  Si  Si3  1  0.000  0.000  0.537  1.0
  Ni  Ni4  1  0.333  0.667  0.505  1.0
  Ni  Ni5  1  0.333  0.667  0.006  1.0
  Ni  Ni6  1  0.503  0.005  0.755  1.0
  Ni  Ni7  1  0.503  0.497  0.755  1.0
  Ni  Ni8  1  0.995  0.497  0.755  1.0
  Ni  Ni9  1  0.163  0.326  0.253  1.0
  Ni  Ni10  1  0.163  0.837  0.253  1.0
  Ni  Ni11  1  0.674  0.837  0.253  1.0
[/CIF]
.
The compound described by Ta3Ni8Si crystallizes in the trigonal P3m1 space group. There are three inequivalent Ta sites. In the first Ta site, Ta(1) is bonded in a 15-coordinate geometry to three equivalent Ni(1), three equivalent Ni(3), six equivalent Ni(4), and three equivalent Si(1) atoms. In the second Ta site, Ta(2) is bonded in a 12-coordinate geometry to three equivalent Ni(2), three equivalent Ni(3), and six equivalent Ni(4) atoms. In the third Ta site, Ta(3) is bonded in a 13-coordinate geometry to three equivalent Ni(2), three equivalent Ni(4), six equivalent Ni(3), and one Si(1) atom. There are four inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to three equivalent Ta(1), three equivalent Ni(3), three equivalent Ni(4), and three equivalent Si(1) atoms to form NiTa3Si3Ni6 cuboctahedra that share corners with six equivalent Ni(3)Ta4Si2Ni6 cuboctahedra, corners with six equivalent Ni(4)Ta5SiNi6 cuboctahedra, edges with six equivalent Ni(1)Ta3Si3Ni6 cuboctahedra, faces with two equivalent Ni(2)Ta6Ni6 cuboctahedra, faces with nine equivalent Ni(3)Ta4Si2Ni6 cuboctahedra, and faces with nine equivalent Ni(4)Ta5SiNi6 cuboctahedra. In the second Ni site, Ni(2) is bonded to three equivalent Ta(2), three equivalent Ta(3), three equivalent Ni(3), and three equivalent Ni(4) atoms to form NiTa6Ni6 cuboctahedra that share corners with six equivalent Ni(3)Ta4Si2Ni6 cuboctahedra, corners with six equivalent Ni(4)Ta5SiNi6 cuboctahedra, edges with six equivalent Ni(2)Ta6Ni6 cuboctahedra, faces with two equivalent Ni(1)Ta3Si3Ni6 cuboctahedra, faces with nine equivalent Ni(3)Ta4Si2Ni6 cuboctahedra, and faces with nine equivalent Ni(4)Ta5SiNi6 cuboctahedra. In the third Ni site, Ni(3) is bonded to one Ta(1), one Ta(2), two equivalent Ta(3), one Ni(1), one Ni(2), four equivalent Ni(3), and two equivalent Si(1) atoms to form distorted NiTa4Si2Ni6 cuboctahedra that share corners with two equivalent Ni(1)Ta3Si3Ni6 cuboctahedra, corners with two equivalent Ni(2)Ta6Ni6 cuboctahedra, corners with four equivalent Ni(3)Ta4Si2Ni6 cuboctahedra, corners with ten equivalent Ni(4)Ta5SiNi6 cuboctahedra, edges with two equivalent Ni(3)Ta4Si2Ni6 cuboctahedra, edges with four equivalent Ni(4)Ta5SiNi6 cuboctahedra, faces with three equivalent Ni(1)Ta3Si3Ni6 cuboctahedra, faces with three equivalent Ni(2)Ta6Ni6 cuboctahedra, faces with four equivalent Ni(4)Ta5SiNi6 cuboctahedra, and faces with eight equivalent Ni(3)Ta4Si2Ni6 cuboctahedra. In the fourth Ni site, Ni(4) is bonded to one Ta(3), two equivalent Ta(1), two equivalent Ta(2), one Ni(1), one Ni(2), four equivalent Ni(4), and one Si(1) atom to form NiTa5SiNi6 cuboctahedra that share corners with two equivalent Ni(1)Ta3Si3Ni6 cuboctahedra, corners with two equivalent Ni(2)Ta6Ni6 cuboctahedra, corners with four equivalent Ni(4)Ta5SiNi6 cuboctahedra, corners with ten equivalent Ni(3)Ta4Si2Ni6 cuboctahedra, edges with two equivalent Ni(4)Ta5SiNi6 cuboctahedra, edges with four equivalent Ni(3)Ta4Si2Ni6 cuboctahedra, faces with three equivalent Ni(1)Ta3Si3Ni6 cuboctahedra, faces with three equivalent Ni(2)Ta6Ni6 cuboctahedra, faces with four equivalent Ni(3)Ta4Si2Ni6 cuboctahedra, and faces with eight equivalent Ni(4)Ta5SiNi6 cuboctahedra. Si(1) is bonded in a 16-coordinate geometry to one Ta(3), three equivalent Ta(1), three equivalent Ni(1), three equivalent Ni(4), and six equivalent Ni(3) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ta3SiNi8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.767
_cell_length_b   4.767
_cell_length_c   7.677
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   151.090
_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  0.667  0.333  0.448  1.0
  Ta  Ta1  1  0.667  0.333  0.066  1.0
  Ta  Ta2  1  0.000  0.000  0.916  1.0
  Si  Si3  1  0.000  0.000  0.537  1.0
  Ni  Ni4  1  0.333  0.667  0.505  1.0
  Ni  Ni5  1  0.333  0.667  0.006  1.0
  Ni  Ni6  1  0.503  0.005  0.755  1.0
  Ni  Ni7  1  0.503  0.497  0.755  1.0
  Ni  Ni8  1  0.995  0.497  0.755  1.0
  Ni  Ni9  1  0.163  0.326  0.253  1.0
  Ni  Ni10  1  0.163  0.837  0.253  1.0
  Ni  Ni11  1  0.674  0.837  0.253  1.0
[/CIF]
.