The compound described by Pr2PbSi2S8 crystallizes in the monoclinic Cc space group. There are two inequivalent Pr sites. In the first Pr site, Pr(1) is bonded in a 8-coordinate geometry to one S(1), one S(2), one S(3), one S(6), one S(7), one S(8), and two equivalent S(4) atoms. In the second Pr site, Pr(2) is bonded in a 8-coordinate geometry to one S(3), one S(6), one S(7), one S(8), two equivalent S(2), and two equivalent S(5) atoms. Pb(1) is bonded in a 6-coordinate geometry to one S(5), one S(6), one S(7), one S(8), and two equivalent S(1) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a tetrahedral geometry to one S(1), one S(2), one S(3), and one S(7) atom. In the second Si site, Si(2) is bonded in a tetrahedral geometry to one S(4), one S(5), one S(6), and one S(8) atom. There are eight inequivalent S sites. In the first S site, S(7) is bonded in a 3-coordinate geometry to one Pr(1), one Pr(2), one Pb(1), and one Si(1) atom. In the second S site, S(8) is bonded in a 3-coordinate geometry to one Pr(1), one Pr(2), one Pb(1), and one Si(2) atom. In the third S site, S(1) is bonded in a distorted single-bond geometry to one Pr(1), two equivalent Pb(1), and one Si(1) atom. In the fourth S site, S(2) is bonded to one Pr(1), two equivalent Pr(2), and one Si(1) atom to form distorted SPr3Si trigonal pyramids that share corners with two equivalent S(5)Pr2SiPb trigonal pyramids, corners with two equivalent S(2)Pr3Si trigonal pyramids, and  an edgeedge with one S(5)Pr2SiPb trigonal pyramid. In the fifth S site, S(3) is bonded in a distorted T-shaped geometry to one Pr(1), one Pr(2), and one Si(1) atom. In the sixth S site, S(4) is bonded in a distorted T-shaped geometry to two equivalent Pr(1) and one Si(2) atom. In the seventh S site, S(5) is bonded to two equivalent Pr(2), one Pb(1), and one Si(2) atom to form distorted SPr2SiPb trigonal pyramids that share corners with two equivalent S(5)Pr2SiPb trigonal pyramids, corners with two equivalent S(2)Pr3Si trigonal pyramids, and  an edgeedge with one S(2)Pr3Si trigonal pyramid. In the eighth S site, S(6) is bonded in a 4-coordinate geometry to one Pr(1), one Pr(2), one Pb(1), and one Si(2) atom. is represented by the CIF file [CIF]
data_Pr2Si2PbS8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.082
_cell_length_b   9.082
_cell_length_c   10.282
_cell_angle_alpha   65.243
_cell_angle_beta   65.243
_cell_angle_gamma   60.295
_symmetry_Int_Tables_number   1
_cell_volume   644.448
_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
  Pr  Pr0  1  0.061  0.252  0.748  1.0
  Pr  Pr1  1  0.440  0.557  0.753  1.0
  Pr  Pr2  1  0.252  0.061  0.248  1.0
  Pr  Pr3  1  0.557  0.440  0.253  1.0
  Si  Si4  1  0.652  0.170  0.021  1.0
  Si  Si5  1  0.170  0.652  0.521  1.0
  Si  Si6  1  0.333  0.846  0.978  1.0
  Si  Si7  1  0.846  0.333  0.478  1.0
  Pb  Pb8  1  0.750  0.929  0.750  1.0
  Pb  Pb9  1  0.929  0.750  0.250  1.0
  S  S10  1  0.885  0.976  0.927  1.0
  S  S11  1  0.713  0.397  0.946  1.0
  S  S12  1  0.439  0.226  0.947  1.0
  S  S13  1  0.397  0.713  0.446  1.0
  S  S14  1  0.976  0.885  0.427  1.0
  S  S15  1  0.226  0.439  0.447  1.0
  S  S16  1  0.111  0.067  0.046  1.0
  S  S17  1  0.281  0.613  0.065  1.0
  S  S18  1  0.534  0.790  0.069  1.0
  S  S19  1  0.613  0.281  0.565  1.0
  S  S20  1  0.067  0.111  0.546  1.0
  S  S21  1  0.790  0.534  0.569  1.0
  S  S22  1  0.568  0.098  0.258  1.0
  S  S23  1  0.098  0.568  0.758  1.0
  S  S24  1  0.401  0.912  0.742  1.0
  S  S25  1  0.912  0.401  0.242  1.0
[/CIF]
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The compound described by Pr2PbSi2S8 crystallizes in the monoclinic Cc space group. There are two inequivalent Pr sites. In the first Pr site, Pr(1) is bonded in a 8-coordinate geometry to one S(1), one S(2), one S(3), one S(6), one S(7), one S(8), and two equivalent S(4) atoms. In the second Pr site, Pr(2) is bonded in a 8-coordinate geometry to one S(3), one S(6), one S(7), one S(8), two equivalent S(2), and two equivalent S(5) atoms. Pb(1) is bonded in a 6-coordinate geometry to one S(5), one S(6), one S(7), one S(8), and two equivalent S(1) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a tetrahedral geometry to one S(1), one S(2), one S(3), and one S(7) atom. In the second Si site, Si(2) is bonded in a tetrahedral geometry to one S(4), one S(5), one S(6), and one S(8) atom. There are eight inequivalent S sites. In the first S site, S(7) is bonded in a 3-coordinate geometry to one Pr(1), one Pr(2), one Pb(1), and one Si(1) atom. In the second S site, S(8) is bonded in a 3-coordinate geometry to one Pr(1), one Pr(2), one Pb(1), and one Si(2) atom. In the third S site, S(1) is bonded in a distorted single-bond geometry to one Pr(1), two equivalent Pb(1), and one Si(1) atom. In the fourth S site, S(2) is bonded to one Pr(1), two equivalent Pr(2), and one Si(1) atom to form distorted SPr3Si trigonal pyramids that share corners with two equivalent S(5)Pr2SiPb trigonal pyramids, corners with two equivalent S(2)Pr3Si trigonal pyramids, and  an edgeedge with one S(5)Pr2SiPb trigonal pyramid. In the fifth S site, S(3) is bonded in a distorted T-shaped geometry to one Pr(1), one Pr(2), and one Si(1) atom. In the sixth S site, S(4) is bonded in a distorted T-shaped geometry to two equivalent Pr(1) and one Si(2) atom. In the seventh S site, S(5) is bonded to two equivalent Pr(2), one Pb(1), and one Si(2) atom to form distorted SPr2SiPb trigonal pyramids that share corners with two equivalent S(5)Pr2SiPb trigonal pyramids, corners with two equivalent S(2)Pr3Si trigonal pyramids, and  an edgeedge with one S(2)Pr3Si trigonal pyramid. In the eighth S site, S(6) is bonded in a 4-coordinate geometry to one Pr(1), one Pr(2), one Pb(1), and one Si(2) atom. is represented by the CIF file [CIF]
data_Pr2Si2PbS8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.082
_cell_length_b   9.082
_cell_length_c   10.282
_cell_angle_alpha   65.243
_cell_angle_beta   65.243
_cell_angle_gamma   60.295
_symmetry_Int_Tables_number   1
_cell_volume   644.448
_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
  Pr  Pr0  1  0.061  0.252  0.748  1.0
  Pr  Pr1  1  0.440  0.557  0.753  1.0
  Pr  Pr2  1  0.252  0.061  0.248  1.0
  Pr  Pr3  1  0.557  0.440  0.253  1.0
  Si  Si4  1  0.652  0.170  0.021  1.0
  Si  Si5  1  0.170  0.652  0.521  1.0
  Si  Si6  1  0.333  0.846  0.978  1.0
  Si  Si7  1  0.846  0.333  0.478  1.0
  Pb  Pb8  1  0.750  0.929  0.750  1.0
  Pb  Pb9  1  0.929  0.750  0.250  1.0
  S  S10  1  0.885  0.976  0.927  1.0
  S  S11  1  0.713  0.397  0.946  1.0
  S  S12  1  0.439  0.226  0.947  1.0
  S  S13  1  0.397  0.713  0.446  1.0
  S  S14  1  0.976  0.885  0.427  1.0
  S  S15  1  0.226  0.439  0.447  1.0
  S  S16  1  0.111  0.067  0.046  1.0
  S  S17  1  0.281  0.613  0.065  1.0
  S  S18  1  0.534  0.790  0.069  1.0
  S  S19  1  0.613  0.281  0.565  1.0
  S  S20  1  0.067  0.111  0.546  1.0
  S  S21  1  0.790  0.534  0.569  1.0
  S  S22  1  0.568  0.098  0.258  1.0
  S  S23  1  0.098  0.568  0.758  1.0
  S  S24  1  0.401  0.912  0.742  1.0
  S  S25  1  0.912  0.401  0.242  1.0
[/CIF]
.