The compound described by Ba2SnSe5 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 9-coordinate geometry to one Se(4), one Se(5), two equivalent Se(2), two equivalent Se(3), and three equivalent Se(1) atoms. In the second Ba site, Ba(2) is bonded in a 9-coordinate geometry to one Se(1), one Se(4), two equivalent Se(2), two equivalent Se(3), and three equivalent Se(5) atoms. Sn(1) is bonded to one Se(1), one Se(2), one Se(3), and one Se(4) atom to form SnSe4 tetrahedra that share  a cornercorner with one Se(5)Ba4Se trigonal bipyramid. There are five inequivalent Se sites. In the first Se site, Se(1) is bonded to one Ba(2), three equivalent Ba(1), and one Sn(1) atom to form distorted SeBa4Sn trigonal bipyramids that share corners with two equivalent Se(5)Ba4Se trigonal bipyramids, corners with three equivalent Se(3)Ba4Sn trigonal bipyramids, corners with four equivalent Se(1)Ba4Sn trigonal bipyramids,  an edgeedge with one Se(1)Ba4Sn trigonal bipyramid, edges with two equivalent Se(5)Ba4Se trigonal bipyramids, and edges with three equivalent Se(3)Ba4Sn trigonal bipyramids. In the second Se site, Se(2) is bonded in a 5-coordinate geometry to two equivalent Ba(1), two equivalent Ba(2), and one Sn(1) atom. In the third Se site, Se(3) is bonded to two equivalent Ba(1), two equivalent Ba(2), and one Sn(1) atom to form distorted SeBa4Sn trigonal bipyramids that share corners with three equivalent Se(1)Ba4Sn trigonal bipyramids, corners with four equivalent Se(5)Ba4Se trigonal bipyramids, corners with four equivalent Se(3)Ba4Sn trigonal bipyramids, edges with two equivalent Se(5)Ba4Se trigonal bipyramids, and edges with three equivalent Se(1)Ba4Sn trigonal bipyramids. In the fourth Se site, Se(4) is bonded in a distorted rectangular see-saw-like geometry to one Ba(1), one Ba(2), one Sn(1), and one Se(5) atom. In the fifth Se site, Se(5) is bonded to one Ba(1), three equivalent Ba(2), and one Se(4) atom to form distorted SeBa4Se trigonal bipyramids that share  a cornercorner with one Sn(1)Se4 tetrahedra, corners with two equivalent Se(1)Ba4Sn trigonal bipyramids, corners with four equivalent Se(5)Ba4Se trigonal bipyramids, corners with four equivalent Se(3)Ba4Sn trigonal bipyramids,  an edgeedge with one Se(5)Ba4Se trigonal bipyramid, edges with two equivalent Se(1)Ba4Sn trigonal bipyramids, and edges with two equivalent Se(3)Ba4Sn trigonal bipyramids. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ba2SnSe5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.006
_cell_length_b   9.527
_cell_length_c   12.566
_cell_angle_alpha   68.870
_cell_angle_beta   90.000
_cell_angle_gamma   89.999
_symmetry_Int_Tables_number   1
_cell_volume   1005.709
_cell_formula_units_Z   4
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
  Ba  Ba0  1  0.137  0.744  0.175  1.0
  Ba  Ba1  1  0.637  0.756  0.325  1.0
  Ba  Ba2  1  0.863  0.256  0.825  1.0
  Ba  Ba3  1  0.363  0.244  0.675  1.0
  Ba  Ba4  1  0.626  0.308  0.155  1.0
  Ba  Ba5  1  0.126  0.192  0.345  1.0
  Ba  Ba6  1  0.374  0.692  0.845  1.0
  Ba  Ba7  1  0.874  0.808  0.655  1.0
  Sn  Sn8  1  0.793  0.355  0.483  1.0
  Sn  Sn9  1  0.294  0.145  0.017  1.0
  Sn  Sn10  1  0.206  0.645  0.517  1.0
  Sn  Sn11  1  0.706  0.855  0.983  1.0
  Se  Se12  1  0.321  0.499  0.405  1.0
  Se  Se13  1  0.821  0.001  0.095  1.0
  Se  Se14  1  0.678  0.501  0.595  1.0
  Se  Se15  1  0.179  0.999  0.905  1.0
  Se  Se16  1  0.510  0.682  0.104  1.0
  Se  Se17  1  0.010  0.818  0.396  1.0
  Se  Se18  1  0.490  0.318  0.896  1.0
  Se  Se19  1  0.990  0.182  0.604  1.0
  Se  Se20  1  0.872  0.486  0.278  1.0
  Se  Se21  1  0.372  0.014  0.222  1.0
  Se  Se22  1  0.128  0.514  0.722  1.0
  Se  Se23  1  0.628  0.986  0.778  1.0
  Se  Se24  1  0.577  0.197  0.443  1.0
  Se  Se25  1  0.077  0.303  0.057  1.0
  Se  Se26  1  0.423  0.803  0.557  1.0
  Se  Se27  1  0.923  0.697  0.943  1.0
  Se  Se28  1  0.761  0.041  0.402  1.0
  Se  Se29  1  0.261  0.459  0.098  1.0
  Se  Se30  1  0.239  0.959  0.598  1.0
  Se  Se31  1  0.739  0.541  0.902  1.0
[/CIF]
.
The compound described by Ba2SnSe5 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 9-coordinate geometry to one Se(4), one Se(5), two equivalent Se(2), two equivalent Se(3), and three equivalent Se(1) atoms. In the second Ba site, Ba(2) is bonded in a 9-coordinate geometry to one Se(1), one Se(4), two equivalent Se(2), two equivalent Se(3), and three equivalent Se(5) atoms. Sn(1) is bonded to one Se(1), one Se(2), one Se(3), and one Se(4) atom to form SnSe4 tetrahedra that share  a cornercorner with one Se(5)Ba4Se trigonal bipyramid. There are five inequivalent Se sites. In the first Se site, Se(1) is bonded to one Ba(2), three equivalent Ba(1), and one Sn(1) atom to form distorted SeBa4Sn trigonal bipyramids that share corners with two equivalent Se(5)Ba4Se trigonal bipyramids, corners with three equivalent Se(3)Ba4Sn trigonal bipyramids, corners with four equivalent Se(1)Ba4Sn trigonal bipyramids,  an edgeedge with one Se(1)Ba4Sn trigonal bipyramid, edges with two equivalent Se(5)Ba4Se trigonal bipyramids, and edges with three equivalent Se(3)Ba4Sn trigonal bipyramids. In the second Se site, Se(2) is bonded in a 5-coordinate geometry to two equivalent Ba(1), two equivalent Ba(2), and one Sn(1) atom. In the third Se site, Se(3) is bonded to two equivalent Ba(1), two equivalent Ba(2), and one Sn(1) atom to form distorted SeBa4Sn trigonal bipyramids that share corners with three equivalent Se(1)Ba4Sn trigonal bipyramids, corners with four equivalent Se(5)Ba4Se trigonal bipyramids, corners with four equivalent Se(3)Ba4Sn trigonal bipyramids, edges with two equivalent Se(5)Ba4Se trigonal bipyramids, and edges with three equivalent Se(1)Ba4Sn trigonal bipyramids. In the fourth Se site, Se(4) is bonded in a distorted rectangular see-saw-like geometry to one Ba(1), one Ba(2), one Sn(1), and one Se(5) atom. In the fifth Se site, Se(5) is bonded to one Ba(1), three equivalent Ba(2), and one Se(4) atom to form distorted SeBa4Se trigonal bipyramids that share  a cornercorner with one Sn(1)Se4 tetrahedra, corners with two equivalent Se(1)Ba4Sn trigonal bipyramids, corners with four equivalent Se(5)Ba4Se trigonal bipyramids, corners with four equivalent Se(3)Ba4Sn trigonal bipyramids,  an edgeedge with one Se(5)Ba4Se trigonal bipyramid, edges with two equivalent Se(1)Ba4Sn trigonal bipyramids, and edges with two equivalent Se(3)Ba4Sn trigonal bipyramids. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ba2SnSe5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.006
_cell_length_b   9.527
_cell_length_c   12.566
_cell_angle_alpha   68.870
_cell_angle_beta   90.000
_cell_angle_gamma   89.999
_symmetry_Int_Tables_number   1
_cell_volume   1005.709
_cell_formula_units_Z   4
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
  Ba  Ba0  1  0.137  0.744  0.175  1.0
  Ba  Ba1  1  0.637  0.756  0.325  1.0
  Ba  Ba2  1  0.863  0.256  0.825  1.0
  Ba  Ba3  1  0.363  0.244  0.675  1.0
  Ba  Ba4  1  0.626  0.308  0.155  1.0
  Ba  Ba5  1  0.126  0.192  0.345  1.0
  Ba  Ba6  1  0.374  0.692  0.845  1.0
  Ba  Ba7  1  0.874  0.808  0.655  1.0
  Sn  Sn8  1  0.793  0.355  0.483  1.0
  Sn  Sn9  1  0.294  0.145  0.017  1.0
  Sn  Sn10  1  0.206  0.645  0.517  1.0
  Sn  Sn11  1  0.706  0.855  0.983  1.0
  Se  Se12  1  0.321  0.499  0.405  1.0
  Se  Se13  1  0.821  0.001  0.095  1.0
  Se  Se14  1  0.678  0.501  0.595  1.0
  Se  Se15  1  0.179  0.999  0.905  1.0
  Se  Se16  1  0.510  0.682  0.104  1.0
  Se  Se17  1  0.010  0.818  0.396  1.0
  Se  Se18  1  0.490  0.318  0.896  1.0
  Se  Se19  1  0.990  0.182  0.604  1.0
  Se  Se20  1  0.872  0.486  0.278  1.0
  Se  Se21  1  0.372  0.014  0.222  1.0
  Se  Se22  1  0.128  0.514  0.722  1.0
  Se  Se23  1  0.628  0.986  0.778  1.0
  Se  Se24  1  0.577  0.197  0.443  1.0
  Se  Se25  1  0.077  0.303  0.057  1.0
  Se  Se26  1  0.423  0.803  0.557  1.0
  Se  Se27  1  0.923  0.697  0.943  1.0
  Se  Se28  1  0.761  0.041  0.402  1.0
  Se  Se29  1  0.261  0.459  0.098  1.0
  Se  Se30  1  0.239  0.959  0.598  1.0
  Se  Se31  1  0.739  0.541  0.902  1.0
[/CIF]
.