The material structure described by Si19Te8 crystallizes in the trigonal R3c space group. There are seven inequivalent Si sites. In the first Si site, Si(1) is bonded to one Si(3), one Si(5), one Si(6), one Te(1), and one Te(2) atom to form SiSi3Te2 trigonal bipyramids that share  a cornercorner with one Si(5)Si4 tetrahedra, corners with two equivalent Si(3)Si3Te tetrahedra, corners with three equivalent Si(4)Si3Te tetrahedra,  a cornercorner with one Si(2)Si3Te2 trigonal bipyramid,  a cornercorner with one Si(6)Si3Te2 trigonal bipyramid, and corners with two equivalent Si(7)Si3Te trigonal pyramids. In the second Si site, Si(2) is bonded to three equivalent Si(3), one Te(3), and one Te(4) atom to form distorted SiSi3Te2 trigonal bipyramids that share corners with three equivalent Si(5)Si4 tetrahedra, corners with three equivalent Si(1)Si3Te2 trigonal bipyramids, corners with three equivalent Si(6)Si3Te2 trigonal bipyramids, and corners with three equivalent Si(7)Si3Te trigonal pyramids. In the third Si site, Si(3) is bonded to one Si(1), one Si(2), one Si(5), and one Te(2) atom to form distorted SiSi3Te tetrahedra that share  a cornercorner with one Si(4)Si3Te tetrahedra,  a cornercorner with one Si(5)Si4 tetrahedra,  a cornercorner with one Te(3)Si4 tetrahedra, corners with two equivalent Si(3)Si3Te tetrahedra,  a cornercorner with one Si(6)Si3Te2 trigonal bipyramid, corners with two equivalent Si(1)Si3Te2 trigonal bipyramids, and  a cornercorner with one Si(7)Si3Te trigonal pyramid. In the fourth Si site, Si(4) is bonded to one Si(5), one Si(6), one Si(7), and one Te(1) atom to form distorted SiSi3Te tetrahedra that share  a cornercorner with one Si(3)Si3Te tetrahedra,  a cornercorner with one Si(5)Si4 tetrahedra,  a cornercorner with one Te(3)Si4 tetrahedra, corners with two equivalent Si(6)Si3Te2 trigonal bipyramids, corners with three equivalent Si(1)Si3Te2 trigonal bipyramids, and corners with two equivalent Si(7)Si3Te trigonal pyramids. In the fifth Si site, Si(5) is bonded to one Si(1), one Si(3), one Si(4), and one Si(7) atom to form SiSi4 tetrahedra that share  a cornercorner with one Si(3)Si3Te tetrahedra,  a cornercorner with one Si(4)Si3Te tetrahedra,  a cornercorner with one Te(3)Si4 tetrahedra,  a cornercorner with one Si(1)Si3Te2 trigonal bipyramid,  a cornercorner with one Si(2)Si3Te2 trigonal bipyramid, corners with three equivalent Si(6)Si3Te2 trigonal bipyramids, and  a cornercorner with one Si(7)Si3Te trigonal pyramid. In the sixth Si site, Si(6) is bonded to one Si(1), one Si(4), one Si(7), one Te(1), and one Te(4) atom to form distorted SiSi3Te2 trigonal bipyramids that share  a cornercorner with one Si(3)Si3Te tetrahedra,  a cornercorner with one Te(3)Si4 tetrahedra, corners with two equivalent Si(4)Si3Te tetrahedra, corners with three equivalent Si(5)Si4 tetrahedra,  a cornercorner with one Si(1)Si3Te2 trigonal bipyramid,  a cornercorner with one Si(2)Si3Te2 trigonal bipyramid, corners with two equivalent Si(6)Si3Te2 trigonal bipyramids, and  a cornercorner with one Si(7)Si3Te trigonal pyramid. In the seventh Si site, Si(7) is bonded to one Si(4), one Si(5), one Si(6), and one Te(3) atom to form distorted SiSi3Te trigonal pyramids that share  a cornercorner with one Si(3)Si3Te tetrahedra,  a cornercorner with one Si(5)Si4 tetrahedra, corners with two equivalent Si(4)Si3Te tetrahedra,  a cornercorner with one Si(2)Si3Te2 trigonal bipyramid,  a cornercorner with one Si(6)Si3Te2 trigonal bipyramid, corners with two equivalent Si(1)Si3Te2 trigonal bipyramids, and corners with two equivalent Si(7)Si3Te trigonal pyramids. There are four inequivalent Te sites. In the first Te site, Te(4) is bonded in a 4-coordinate geometry to one Si(2) and three equivalent Si(6) atoms. In the second Te site, Te(1) is bonded in a trigonal non-coplanar geometry to one Si(1), one Si(4), and one Si(6) atom. In the third Te site, Te(3) is bonded to one Si(2) and three equivalent Si(7) atoms to form distorted TeSi4 tetrahedra that share corners with three equivalent Si(3)Si3Te tetrahedra, corners with three equivalent Si(4)Si3Te tetrahedra, corners with three equivalent Si(5)Si4 tetrahedra, and corners with three equivalent Si(6)Si3Te2 trigonal bipyramids. In the fourth Te site, Te(2) is bonded in a distorted bent 120 degrees geometry to one Si(1) and one Si(3) atom. is represented by the CIF card [CIF]
data_Si19Te8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   10.556
_cell_length_b   10.556
_cell_length_c   10.556
_cell_angle_alpha   89.644
_cell_angle_beta   89.644
_cell_angle_gamma   89.644
_symmetry_Int_Tables_number   1
_cell_volume   1176.028
_cell_formula_units_Z   2
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
  Si  Si0  1  0.530  0.618  0.169  1.0
  Si  Si1  1  0.618  0.169  0.530  1.0
  Si  Si2  1  0.169  0.530  0.618  1.0
  Si  Si3  1  0.669  0.118  0.030  1.0
  Si  Si4  1  0.857  0.857  0.857  1.0
  Si  Si5  1  0.357  0.357  0.357  1.0
  Si  Si6  1  0.118  0.030  0.669  1.0
  Si  Si7  1  0.030  0.669  0.118  1.0
  Si  Si8  1  0.426  0.418  0.150  1.0
  Si  Si9  1  0.418  0.150  0.426  1.0
  Si  Si10  1  0.150  0.426  0.418  1.0
  Si  Si11  1  0.650  0.918  0.926  1.0
  Si  Si12  1  0.918  0.926  0.650  1.0
  Si  Si13  1  0.926  0.650  0.918  1.0
  Si  Si14  1  0.504  0.389  0.818  1.0
  Si  Si15  1  0.389  0.818  0.504  1.0
  Si  Si16  1  0.818  0.504  0.389  1.0
  Si  Si17  1  0.318  0.889  0.004  1.0
  Si  Si18  1  0.992  0.503  0.758  1.0
  Si  Si19  1  0.758  0.992  0.503  1.0
  Si  Si20  1  0.503  0.758  0.992  1.0
  Si  Si21  1  0.003  0.492  0.258  1.0
  Si  Si22  1  0.258  0.003  0.492  1.0
  Si  Si23  1  0.492  0.258  0.003  1.0
  Si  Si24  1  0.165  0.174  0.831  1.0
  Si  Si25  1  0.831  0.165  0.174  1.0
  Si  Si26  1  0.174  0.831  0.165  1.0
  Si  Si27  1  0.674  0.665  0.331  1.0
  Si  Si28  1  0.331  0.674  0.665  1.0
  Si  Si29  1  0.665  0.331  0.674  1.0
  Si  Si30  1  0.980  0.319  0.114  1.0
  Si  Si31  1  0.114  0.980  0.319  1.0
  Si  Si32  1  0.319  0.114  0.980  1.0
  Si  Si33  1  0.819  0.480  0.614  1.0
  Si  Si34  1  0.614  0.819  0.480  1.0
  Si  Si35  1  0.480  0.614  0.819  1.0
  Si  Si36  1  0.004  0.318  0.889  1.0
  Si  Si37  1  0.889  0.004  0.318  1.0
  Te  Te38  1  0.309  0.317  0.683  1.0
  Te  Te39  1  0.317  0.683  0.309  1.0
  Te  Te40  1  0.683  0.309  0.317  1.0
  Te  Te41  1  0.183  0.817  0.809  1.0
  Te  Te42  1  0.817  0.809  0.183  1.0
  Te  Te43  1  0.809  0.183  0.817  1.0
  Te  Te44  1  0.005  0.247  0.509  1.0
  Te  Te45  1  0.247  0.509  0.005  1.0
  Te  Te46  1  0.509  0.005  0.247  1.0
  Te  Te47  1  0.009  0.747  0.505  1.0
  Te  Te48  1  0.747  0.505  0.009  1.0
  Te  Te49  1  0.505  0.009  0.747  1.0
  Te  Te50  1  0.688  0.688  0.688  1.0
  Te  Te51  1  0.188  0.188  0.188  1.0
  Te  Te52  1  0.500  0.500  0.500  1.0
  Te  Te53  1  0.000  0.000  0.000  1.0
[/CIF]
.
The material structure described by Si19Te8 crystallizes in the trigonal R3c space group. There are seven inequivalent Si sites. In the first Si site, Si(1) is bonded to one Si(3), one Si(5), one Si(6), one Te(1), and one Te(2) atom to form SiSi3Te2 trigonal bipyramids that share  a cornercorner with one Si(5)Si4 tetrahedra, corners with two equivalent Si(3)Si3Te tetrahedra, corners with three equivalent Si(4)Si3Te tetrahedra,  a cornercorner with one Si(2)Si3Te2 trigonal bipyramid,  a cornercorner with one Si(6)Si3Te2 trigonal bipyramid, and corners with two equivalent Si(7)Si3Te trigonal pyramids. In the second Si site, Si(2) is bonded to three equivalent Si(3), one Te(3), and one Te(4) atom to form distorted SiSi3Te2 trigonal bipyramids that share corners with three equivalent Si(5)Si4 tetrahedra, corners with three equivalent Si(1)Si3Te2 trigonal bipyramids, corners with three equivalent Si(6)Si3Te2 trigonal bipyramids, and corners with three equivalent Si(7)Si3Te trigonal pyramids. In the third Si site, Si(3) is bonded to one Si(1), one Si(2), one Si(5), and one Te(2) atom to form distorted SiSi3Te tetrahedra that share  a cornercorner with one Si(4)Si3Te tetrahedra,  a cornercorner with one Si(5)Si4 tetrahedra,  a cornercorner with one Te(3)Si4 tetrahedra, corners with two equivalent Si(3)Si3Te tetrahedra,  a cornercorner with one Si(6)Si3Te2 trigonal bipyramid, corners with two equivalent Si(1)Si3Te2 trigonal bipyramids, and  a cornercorner with one Si(7)Si3Te trigonal pyramid. In the fourth Si site, Si(4) is bonded to one Si(5), one Si(6), one Si(7), and one Te(1) atom to form distorted SiSi3Te tetrahedra that share  a cornercorner with one Si(3)Si3Te tetrahedra,  a cornercorner with one Si(5)Si4 tetrahedra,  a cornercorner with one Te(3)Si4 tetrahedra, corners with two equivalent Si(6)Si3Te2 trigonal bipyramids, corners with three equivalent Si(1)Si3Te2 trigonal bipyramids, and corners with two equivalent Si(7)Si3Te trigonal pyramids. In the fifth Si site, Si(5) is bonded to one Si(1), one Si(3), one Si(4), and one Si(7) atom to form SiSi4 tetrahedra that share  a cornercorner with one Si(3)Si3Te tetrahedra,  a cornercorner with one Si(4)Si3Te tetrahedra,  a cornercorner with one Te(3)Si4 tetrahedra,  a cornercorner with one Si(1)Si3Te2 trigonal bipyramid,  a cornercorner with one Si(2)Si3Te2 trigonal bipyramid, corners with three equivalent Si(6)Si3Te2 trigonal bipyramids, and  a cornercorner with one Si(7)Si3Te trigonal pyramid. In the sixth Si site, Si(6) is bonded to one Si(1), one Si(4), one Si(7), one Te(1), and one Te(4) atom to form distorted SiSi3Te2 trigonal bipyramids that share  a cornercorner with one Si(3)Si3Te tetrahedra,  a cornercorner with one Te(3)Si4 tetrahedra, corners with two equivalent Si(4)Si3Te tetrahedra, corners with three equivalent Si(5)Si4 tetrahedra,  a cornercorner with one Si(1)Si3Te2 trigonal bipyramid,  a cornercorner with one Si(2)Si3Te2 trigonal bipyramid, corners with two equivalent Si(6)Si3Te2 trigonal bipyramids, and  a cornercorner with one Si(7)Si3Te trigonal pyramid. In the seventh Si site, Si(7) is bonded to one Si(4), one Si(5), one Si(6), and one Te(3) atom to form distorted SiSi3Te trigonal pyramids that share  a cornercorner with one Si(3)Si3Te tetrahedra,  a cornercorner with one Si(5)Si4 tetrahedra, corners with two equivalent Si(4)Si3Te tetrahedra,  a cornercorner with one Si(2)Si3Te2 trigonal bipyramid,  a cornercorner with one Si(6)Si3Te2 trigonal bipyramid, corners with two equivalent Si(1)Si3Te2 trigonal bipyramids, and corners with two equivalent Si(7)Si3Te trigonal pyramids. There are four inequivalent Te sites. In the first Te site, Te(4) is bonded in a 4-coordinate geometry to one Si(2) and three equivalent Si(6) atoms. In the second Te site, Te(1) is bonded in a trigonal non-coplanar geometry to one Si(1), one Si(4), and one Si(6) atom. In the third Te site, Te(3) is bonded to one Si(2) and three equivalent Si(7) atoms to form distorted TeSi4 tetrahedra that share corners with three equivalent Si(3)Si3Te tetrahedra, corners with three equivalent Si(4)Si3Te tetrahedra, corners with three equivalent Si(5)Si4 tetrahedra, and corners with three equivalent Si(6)Si3Te2 trigonal bipyramids. In the fourth Te site, Te(2) is bonded in a distorted bent 120 degrees geometry to one Si(1) and one Si(3) atom. is represented by the CIF card [CIF]
data_Si19Te8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   10.556
_cell_length_b   10.556
_cell_length_c   10.556
_cell_angle_alpha   89.644
_cell_angle_beta   89.644
_cell_angle_gamma   89.644
_symmetry_Int_Tables_number   1
_cell_volume   1176.028
_cell_formula_units_Z   2
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
  Si  Si0  1  0.530  0.618  0.169  1.0
  Si  Si1  1  0.618  0.169  0.530  1.0
  Si  Si2  1  0.169  0.530  0.618  1.0
  Si  Si3  1  0.669  0.118  0.030  1.0
  Si  Si4  1  0.857  0.857  0.857  1.0
  Si  Si5  1  0.357  0.357  0.357  1.0
  Si  Si6  1  0.118  0.030  0.669  1.0
  Si  Si7  1  0.030  0.669  0.118  1.0
  Si  Si8  1  0.426  0.418  0.150  1.0
  Si  Si9  1  0.418  0.150  0.426  1.0
  Si  Si10  1  0.150  0.426  0.418  1.0
  Si  Si11  1  0.650  0.918  0.926  1.0
  Si  Si12  1  0.918  0.926  0.650  1.0
  Si  Si13  1  0.926  0.650  0.918  1.0
  Si  Si14  1  0.504  0.389  0.818  1.0
  Si  Si15  1  0.389  0.818  0.504  1.0
  Si  Si16  1  0.818  0.504  0.389  1.0
  Si  Si17  1  0.318  0.889  0.004  1.0
  Si  Si18  1  0.992  0.503  0.758  1.0
  Si  Si19  1  0.758  0.992  0.503  1.0
  Si  Si20  1  0.503  0.758  0.992  1.0
  Si  Si21  1  0.003  0.492  0.258  1.0
  Si  Si22  1  0.258  0.003  0.492  1.0
  Si  Si23  1  0.492  0.258  0.003  1.0
  Si  Si24  1  0.165  0.174  0.831  1.0
  Si  Si25  1  0.831  0.165  0.174  1.0
  Si  Si26  1  0.174  0.831  0.165  1.0
  Si  Si27  1  0.674  0.665  0.331  1.0
  Si  Si28  1  0.331  0.674  0.665  1.0
  Si  Si29  1  0.665  0.331  0.674  1.0
  Si  Si30  1  0.980  0.319  0.114  1.0
  Si  Si31  1  0.114  0.980  0.319  1.0
  Si  Si32  1  0.319  0.114  0.980  1.0
  Si  Si33  1  0.819  0.480  0.614  1.0
  Si  Si34  1  0.614  0.819  0.480  1.0
  Si  Si35  1  0.480  0.614  0.819  1.0
  Si  Si36  1  0.004  0.318  0.889  1.0
  Si  Si37  1  0.889  0.004  0.318  1.0
  Te  Te38  1  0.309  0.317  0.683  1.0
  Te  Te39  1  0.317  0.683  0.309  1.0
  Te  Te40  1  0.683  0.309  0.317  1.0
  Te  Te41  1  0.183  0.817  0.809  1.0
  Te  Te42  1  0.817  0.809  0.183  1.0
  Te  Te43  1  0.809  0.183  0.817  1.0
  Te  Te44  1  0.005  0.247  0.509  1.0
  Te  Te45  1  0.247  0.509  0.005  1.0
  Te  Te46  1  0.509  0.005  0.247  1.0
  Te  Te47  1  0.009  0.747  0.505  1.0
  Te  Te48  1  0.747  0.505  0.009  1.0
  Te  Te49  1  0.505  0.009  0.747  1.0
  Te  Te50  1  0.688  0.688  0.688  1.0
  Te  Te51  1  0.188  0.188  0.188  1.0
  Te  Te52  1  0.500  0.500  0.500  1.0
  Te  Te53  1  0.000  0.000  0.000  1.0
[/CIF]
.