The crystal structure described by Ba2FeSe3 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 7-coordinate geometry to two equivalent Se(1), two equivalent Se(3), and three equivalent Se(2) atoms. In the second Ba site, Ba(2) is bonded to two equivalent Se(2), two equivalent Se(3), and three equivalent Se(1) atoms to form distorted BaSe7 pentagonal bipyramids that share corners with two equivalent Ba(2)Se7 pentagonal bipyramids,  a cornercorner with one Fe(1)Se4 tetrahedra, edges with four equivalent Ba(2)Se7 pentagonal bipyramids, and edges with four equivalent Fe(1)Se4 tetrahedra. Fe(1) is bonded to one Se(1), one Se(2), and two equivalent Se(3) atoms to form FeSe4 tetrahedra that share  a cornercorner with one Ba(2)Se7 pentagonal bipyramid, corners with two equivalent Fe(1)Se4 tetrahedra, and edges with four equivalent Ba(2)Se7 pentagonal bipyramids. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Ba(1), three equivalent Ba(2), and one Fe(1) atom to form distorted SeBa5Fe octahedra that share corners with eight equivalent Se(2)Ba5Fe octahedra, corners with five equivalent Se(3)Ba4Fe2 pentagonal pyramids,  an edgeedge with one Se(2)Ba5Fe octahedra, edges with four equivalent Se(1)Ba5Fe octahedra, edges with two equivalent Se(3)Ba4Fe2 pentagonal pyramids,  a faceface with one Se(2)Ba5Fe octahedra, and  a faceface with one Se(3)Ba4Fe2 pentagonal pyramid. The corner-sharing octahedral tilt angles range from 25-57°. In the second Se site, Se(2) is bonded to two equivalent Ba(2), three equivalent Ba(1), and one Fe(1) atom to form distorted SeBa5Fe octahedra that share corners with eight equivalent Se(1)Ba5Fe octahedra, corners with two equivalent Se(3)Ba4Fe2 pentagonal pyramids,  an edgeedge with one Se(1)Ba5Fe octahedra, edges with four equivalent Se(2)Ba5Fe octahedra, edges with five equivalent Se(3)Ba4Fe2 pentagonal pyramids, and  a faceface with one Se(1)Ba5Fe octahedra. The corner-sharing octahedral tilt angles range from 25-57°. In the third Se site, Se(3) is bonded to two equivalent Ba(1), two equivalent Ba(2), and two equivalent Fe(1) atoms to form distorted SeBa4Fe2 pentagonal pyramids that share corners with two equivalent Se(2)Ba5Fe octahedra, corners with five equivalent Se(1)Ba5Fe octahedra, corners with two equivalent Se(3)Ba4Fe2 pentagonal pyramids, edges with two equivalent Se(1)Ba5Fe octahedra, edges with five equivalent Se(2)Ba5Fe octahedra, edges with two equivalent Se(3)Ba4Fe2 pentagonal pyramids, and  a faceface with one Se(1)Ba5Fe octahedra. The corner-sharing octahedral tilt angles range from 16-60°. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ba2FeSe3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.454
_cell_length_b   12.686
_cell_length_c   12.974
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   733.163
_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  0.250  0.324  0.981  1.0
  Ba  Ba1  1  0.250  0.824  0.519  1.0
  Ba  Ba2  1  0.750  0.676  0.019  1.0
  Ba  Ba3  1  0.750  0.176  0.481  1.0
  Ba  Ba4  1  0.250  0.988  0.175  1.0
  Ba  Ba5  1  0.250  0.488  0.325  1.0
  Ba  Ba6  1  0.750  0.012  0.825  1.0
  Ba  Ba7  1  0.750  0.512  0.675  1.0
  Fe  Fe8  1  0.250  0.245  0.699  1.0
  Fe  Fe9  1  0.250  0.745  0.801  1.0
  Fe  Fe10  1  0.750  0.755  0.301  1.0
  Fe  Fe11  1  0.750  0.255  0.199  1.0
  Se  Se12  1  0.250  0.366  0.554  1.0
  Se  Se13  1  0.250  0.866  0.946  1.0
  Se  Se14  1  0.750  0.634  0.446  1.0
  Se  Se15  1  0.750  0.134  0.054  1.0
  Se  Se16  1  0.250  0.062  0.641  1.0
  Se  Se17  1  0.250  0.562  0.859  1.0
  Se  Se18  1  0.750  0.938  0.359  1.0
  Se  Se19  1  0.750  0.438  0.141  1.0
  Se  Se20  1  0.250  0.725  0.211  1.0
  Se  Se21  1  0.250  0.225  0.289  1.0
  Se  Se22  1  0.750  0.275  0.789  1.0
  Se  Se23  1  0.750  0.775  0.711  1.0
[/CIF]
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The crystal structure described by Ba2FeSe3 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 7-coordinate geometry to two equivalent Se(1), two equivalent Se(3), and three equivalent Se(2) atoms. In the second Ba site, Ba(2) is bonded to two equivalent Se(2), two equivalent Se(3), and three equivalent Se(1) atoms to form distorted BaSe7 pentagonal bipyramids that share corners with two equivalent Ba(2)Se7 pentagonal bipyramids,  a cornercorner with one Fe(1)Se4 tetrahedra, edges with four equivalent Ba(2)Se7 pentagonal bipyramids, and edges with four equivalent Fe(1)Se4 tetrahedra. Fe(1) is bonded to one Se(1), one Se(2), and two equivalent Se(3) atoms to form FeSe4 tetrahedra that share  a cornercorner with one Ba(2)Se7 pentagonal bipyramid, corners with two equivalent Fe(1)Se4 tetrahedra, and edges with four equivalent Ba(2)Se7 pentagonal bipyramids. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Ba(1), three equivalent Ba(2), and one Fe(1) atom to form distorted SeBa5Fe octahedra that share corners with eight equivalent Se(2)Ba5Fe octahedra, corners with five equivalent Se(3)Ba4Fe2 pentagonal pyramids,  an edgeedge with one Se(2)Ba5Fe octahedra, edges with four equivalent Se(1)Ba5Fe octahedra, edges with two equivalent Se(3)Ba4Fe2 pentagonal pyramids,  a faceface with one Se(2)Ba5Fe octahedra, and  a faceface with one Se(3)Ba4Fe2 pentagonal pyramid. The corner-sharing octahedral tilt angles range from 25-57°. In the second Se site, Se(2) is bonded to two equivalent Ba(2), three equivalent Ba(1), and one Fe(1) atom to form distorted SeBa5Fe octahedra that share corners with eight equivalent Se(1)Ba5Fe octahedra, corners with two equivalent Se(3)Ba4Fe2 pentagonal pyramids,  an edgeedge with one Se(1)Ba5Fe octahedra, edges with four equivalent Se(2)Ba5Fe octahedra, edges with five equivalent Se(3)Ba4Fe2 pentagonal pyramids, and  a faceface with one Se(1)Ba5Fe octahedra. The corner-sharing octahedral tilt angles range from 25-57°. In the third Se site, Se(3) is bonded to two equivalent Ba(1), two equivalent Ba(2), and two equivalent Fe(1) atoms to form distorted SeBa4Fe2 pentagonal pyramids that share corners with two equivalent Se(2)Ba5Fe octahedra, corners with five equivalent Se(1)Ba5Fe octahedra, corners with two equivalent Se(3)Ba4Fe2 pentagonal pyramids, edges with two equivalent Se(1)Ba5Fe octahedra, edges with five equivalent Se(2)Ba5Fe octahedra, edges with two equivalent Se(3)Ba4Fe2 pentagonal pyramids, and  a faceface with one Se(1)Ba5Fe octahedra. The corner-sharing octahedral tilt angles range from 16-60°. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ba2FeSe3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.454
_cell_length_b   12.686
_cell_length_c   12.974
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   733.163
_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  0.250  0.324  0.981  1.0
  Ba  Ba1  1  0.250  0.824  0.519  1.0
  Ba  Ba2  1  0.750  0.676  0.019  1.0
  Ba  Ba3  1  0.750  0.176  0.481  1.0
  Ba  Ba4  1  0.250  0.988  0.175  1.0
  Ba  Ba5  1  0.250  0.488  0.325  1.0
  Ba  Ba6  1  0.750  0.012  0.825  1.0
  Ba  Ba7  1  0.750  0.512  0.675  1.0
  Fe  Fe8  1  0.250  0.245  0.699  1.0
  Fe  Fe9  1  0.250  0.745  0.801  1.0
  Fe  Fe10  1  0.750  0.755  0.301  1.0
  Fe  Fe11  1  0.750  0.255  0.199  1.0
  Se  Se12  1  0.250  0.366  0.554  1.0
  Se  Se13  1  0.250  0.866  0.946  1.0
  Se  Se14  1  0.750  0.634  0.446  1.0
  Se  Se15  1  0.750  0.134  0.054  1.0
  Se  Se16  1  0.250  0.062  0.641  1.0
  Se  Se17  1  0.250  0.562  0.859  1.0
  Se  Se18  1  0.750  0.938  0.359  1.0
  Se  Se19  1  0.750  0.438  0.141  1.0
  Se  Se20  1  0.250  0.725  0.211  1.0
  Se  Se21  1  0.250  0.225  0.289  1.0
  Se  Se22  1  0.750  0.275  0.789  1.0
  Se  Se23  1  0.750  0.775  0.711  1.0
[/CIF]
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