The crystal structure described by Nd2PbSi2Se8 crystallizes in the monoclinic Cc space group. There are two inequivalent Nd sites. In the first Nd site, Nd(1) is bonded in a 8-coordinate geometry to one Se(1), one Se(2), one Se(3), one Se(6), one Se(7), one Se(8), and two equivalent Se(4) atoms. In the second Nd site, Nd(2) is bonded in a 8-coordinate geometry to one Se(3), one Se(6), one Se(7), one Se(8), two equivalent Se(2), and two equivalent Se(5) atoms. Pb(1) is bonded in a 6-coordinate geometry to one Se(5), one Se(6), one Se(7), one Se(8), and two equivalent Se(1) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a tetrahedral geometry to one Se(1), one Se(2), one Se(3), and one Se(7) atom. In the second Si site, Si(2) is bonded in a tetrahedral geometry to one Se(4), one Se(5), one Se(6), and one Se(8) atom. There are eight inequivalent Se sites. In the first Se site, Se(7) is bonded in a 3-coordinate geometry to one Nd(1), one Nd(2), one Pb(1), and one Si(1) atom. In the second Se site, Se(8) is bonded in a 3-coordinate geometry to one Nd(1), one Nd(2), one Pb(1), and one Si(2) atom. In the third Se site, Se(1) is bonded in a distorted single-bond geometry to one Nd(1), two equivalent Pb(1), and one Si(1) atom. In the fourth Se site, Se(2) is bonded to one Nd(1), two equivalent Nd(2), and one Si(1) atom to form distorted SeNd3Si trigonal pyramids that share corners with two equivalent Se(5)Nd2SiPb trigonal pyramids, corners with two equivalent Se(2)Nd3Si trigonal pyramids, and  an edgeedge with one Se(5)Nd2SiPb trigonal pyramid. In the fifth Se site, Se(3) is bonded in a distorted T-shaped geometry to one Nd(1), one Nd(2), and one Si(1) atom. In the sixth Se site, Se(4) is bonded in a T-shaped geometry to two equivalent Nd(1) and one Si(2) atom. In the seventh Se site, Se(5) is bonded to two equivalent Nd(2), one Pb(1), and one Si(2) atom to form distorted SeNd2SiPb trigonal pyramids that share corners with two equivalent Se(5)Nd2SiPb trigonal pyramids, corners with two equivalent Se(2)Nd3Si trigonal pyramids, and  an edgeedge with one Se(2)Nd3Si trigonal pyramid. In the eighth Se site, Se(6) is bonded in a 4-coordinate geometry to one Nd(1), one Nd(2), one Pb(1), and one Si(2) atom. is represented by the CIF file [CIF]
data_Nd2Si2PbSe8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.439
_cell_length_b   9.439
_cell_length_c   10.749
_cell_angle_alpha   65.075
_cell_angle_beta   65.075
_cell_angle_gamma   60.166
_symmetry_Int_Tables_number   1
_cell_volume   725.522
_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
  Nd  Nd0  1  0.250  0.437  0.251  1.0
  Nd  Nd1  1  0.942  0.062  0.247  1.0
  Nd  Nd2  1  0.437  0.250  0.751  1.0
  Nd  Nd3  1  0.062  0.942  0.747  1.0
  Si  Si4  1  0.334  0.845  0.979  1.0
  Si  Si5  1  0.845  0.334  0.479  1.0
  Si  Si6  1  0.656  0.164  0.022  1.0
  Si  Si7  1  0.164  0.656  0.522  1.0
  Pb  Pb8  1  0.572  0.750  0.250  1.0
  Pb  Pb9  1  0.750  0.572  0.750  1.0
  Se  Se10  1  0.537  0.603  0.073  1.0
  Se  Se11  1  0.097  0.784  0.057  1.0
  Se  Se12  1  0.275  0.067  0.054  1.0
  Se  Se13  1  0.784  0.097  0.557  1.0
  Se  Se14  1  0.603  0.537  0.573  1.0
  Se  Se15  1  0.067  0.275  0.554  1.0
  Se  Se16  1  0.429  0.396  0.951  1.0
  Se  Se17  1  0.897  0.217  0.936  1.0
  Se  Se18  1  0.714  0.955  0.930  1.0
  Se  Se19  1  0.217  0.897  0.436  1.0
  Se  Se20  1  0.396  0.429  0.451  1.0
  Se  Se21  1  0.955  0.714  0.430  1.0
  Se  Se22  1  0.408  0.934  0.734  1.0
  Se  Se23  1  0.934  0.408  0.234  1.0
  Se  Se24  1  0.582  0.094  0.267  1.0
  Se  Se25  1  0.094  0.582  0.767  1.0
[/CIF]
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The crystal structure described by Nd2PbSi2Se8 crystallizes in the monoclinic Cc space group. There are two inequivalent Nd sites. In the first Nd site, Nd(1) is bonded in a 8-coordinate geometry to one Se(1), one Se(2), one Se(3), one Se(6), one Se(7), one Se(8), and two equivalent Se(4) atoms. In the second Nd site, Nd(2) is bonded in a 8-coordinate geometry to one Se(3), one Se(6), one Se(7), one Se(8), two equivalent Se(2), and two equivalent Se(5) atoms. Pb(1) is bonded in a 6-coordinate geometry to one Se(5), one Se(6), one Se(7), one Se(8), and two equivalent Se(1) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a tetrahedral geometry to one Se(1), one Se(2), one Se(3), and one Se(7) atom. In the second Si site, Si(2) is bonded in a tetrahedral geometry to one Se(4), one Se(5), one Se(6), and one Se(8) atom. There are eight inequivalent Se sites. In the first Se site, Se(7) is bonded in a 3-coordinate geometry to one Nd(1), one Nd(2), one Pb(1), and one Si(1) atom. In the second Se site, Se(8) is bonded in a 3-coordinate geometry to one Nd(1), one Nd(2), one Pb(1), and one Si(2) atom. In the third Se site, Se(1) is bonded in a distorted single-bond geometry to one Nd(1), two equivalent Pb(1), and one Si(1) atom. In the fourth Se site, Se(2) is bonded to one Nd(1), two equivalent Nd(2), and one Si(1) atom to form distorted SeNd3Si trigonal pyramids that share corners with two equivalent Se(5)Nd2SiPb trigonal pyramids, corners with two equivalent Se(2)Nd3Si trigonal pyramids, and  an edgeedge with one Se(5)Nd2SiPb trigonal pyramid. In the fifth Se site, Se(3) is bonded in a distorted T-shaped geometry to one Nd(1), one Nd(2), and one Si(1) atom. In the sixth Se site, Se(4) is bonded in a T-shaped geometry to two equivalent Nd(1) and one Si(2) atom. In the seventh Se site, Se(5) is bonded to two equivalent Nd(2), one Pb(1), and one Si(2) atom to form distorted SeNd2SiPb trigonal pyramids that share corners with two equivalent Se(5)Nd2SiPb trigonal pyramids, corners with two equivalent Se(2)Nd3Si trigonal pyramids, and  an edgeedge with one Se(2)Nd3Si trigonal pyramid. In the eighth Se site, Se(6) is bonded in a 4-coordinate geometry to one Nd(1), one Nd(2), one Pb(1), and one Si(2) atom. is represented by the CIF file [CIF]
data_Nd2Si2PbSe8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.439
_cell_length_b   9.439
_cell_length_c   10.749
_cell_angle_alpha   65.075
_cell_angle_beta   65.075
_cell_angle_gamma   60.166
_symmetry_Int_Tables_number   1
_cell_volume   725.522
_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
  Nd  Nd0  1  0.250  0.437  0.251  1.0
  Nd  Nd1  1  0.942  0.062  0.247  1.0
  Nd  Nd2  1  0.437  0.250  0.751  1.0
  Nd  Nd3  1  0.062  0.942  0.747  1.0
  Si  Si4  1  0.334  0.845  0.979  1.0
  Si  Si5  1  0.845  0.334  0.479  1.0
  Si  Si6  1  0.656  0.164  0.022  1.0
  Si  Si7  1  0.164  0.656  0.522  1.0
  Pb  Pb8  1  0.572  0.750  0.250  1.0
  Pb  Pb9  1  0.750  0.572  0.750  1.0
  Se  Se10  1  0.537  0.603  0.073  1.0
  Se  Se11  1  0.097  0.784  0.057  1.0
  Se  Se12  1  0.275  0.067  0.054  1.0
  Se  Se13  1  0.784  0.097  0.557  1.0
  Se  Se14  1  0.603  0.537  0.573  1.0
  Se  Se15  1  0.067  0.275  0.554  1.0
  Se  Se16  1  0.429  0.396  0.951  1.0
  Se  Se17  1  0.897  0.217  0.936  1.0
  Se  Se18  1  0.714  0.955  0.930  1.0
  Se  Se19  1  0.217  0.897  0.436  1.0
  Se  Se20  1  0.396  0.429  0.451  1.0
  Se  Se21  1  0.955  0.714  0.430  1.0
  Se  Se22  1  0.408  0.934  0.734  1.0
  Se  Se23  1  0.934  0.408  0.234  1.0
  Se  Se24  1  0.582  0.094  0.267  1.0
  Se  Se25  1  0.094  0.582  0.767  1.0
[/CIF]
.