The crystal structure described by CaU2Se5 crystallizes in the orthorhombic Pnma space group. Ca(1) is bonded to one Se(2), one Se(3), one Se(4), and four equivalent Se(1) atoms to form distorted edge-sharing CaSe7 pentagonal bipyramids. U(1) is bonded in a 8-coordinate geometry to two equivalent Se(1), two equivalent Se(2), two equivalent Se(3), and two equivalent Se(4) atoms. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Ca(1) and two equivalent U(1) atoms to form distorted SeCa2U2 tetrahedra that share corners with two equivalent Se(4)CaU4 square pyramids, corners with four equivalent Se(3)CaU4 square pyramids, corners with six equivalent Se(1)Ca2U2 tetrahedra, corners with two equivalent Se(2)CaU4 trigonal bipyramids,  an edgeedge with one Se(3)CaU4 square pyramid, edges with two equivalent Se(4)CaU4 square pyramids,  an edgeedge with one Se(1)Ca2U2 tetrahedra, and edges with two equivalent Se(2)CaU4 trigonal bipyramids. In the second Se site, Se(2) is bonded to one Ca(1) and four equivalent U(1) atoms to form distorted SeCaU4 trigonal bipyramids that share  a cornercorner with one Se(4)CaU4 square pyramid, corners with five equivalent Se(3)CaU4 square pyramids, corners with four equivalent Se(1)Ca2U2 tetrahedra, corners with four equivalent Se(2)CaU4 trigonal bipyramids, edges with two equivalent Se(3)CaU4 square pyramids, edges with four equivalent Se(4)CaU4 square pyramids, and edges with four equivalent Se(1)Ca2U2 tetrahedra. In the third Se site, Se(3) is bonded to one Ca(1) and four equivalent U(1) atoms to form SeCaU4 square pyramids that share corners with four equivalent Se(4)CaU4 square pyramids, corners with eight equivalent Se(1)Ca2U2 tetrahedra, corners with five equivalent Se(2)CaU4 trigonal bipyramids,  an edgeedge with one Se(4)CaU4 square pyramid, edges with two equivalent Se(3)CaU4 square pyramids, edges with two equivalent Se(1)Ca2U2 tetrahedra, edges with two equivalent Se(2)CaU4 trigonal bipyramids, and  a faceface with one Se(4)CaU4 square pyramid. In the fourth Se site, Se(4) is bonded to one Ca(1) and four equivalent U(1) atoms to form SeCaU4 square pyramids that share corners with four equivalent Se(3)CaU4 square pyramids, corners with four equivalent Se(4)CaU4 square pyramids, corners with four equivalent Se(1)Ca2U2 tetrahedra,  a cornercorner with one Se(2)CaU4 trigonal bipyramid,  an edgeedge with one Se(3)CaU4 square pyramid, edges with four equivalent Se(1)Ca2U2 tetrahedra, edges with four equivalent Se(2)CaU4 trigonal bipyramids, and  a faceface with one Se(3)CaU4 square pyramid. is represented by the Crystallographic Information File (CIF) [CIF]
data_CaU2Se5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.652
_cell_length_b   8.126
_cell_length_c   12.557
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   780.800
_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
  Ca  Ca0  1  0.423  0.750  0.007  1.0
  Ca  Ca1  1  0.077  0.750  0.507  1.0
  Ca  Ca2  1  0.577  0.250  0.993  1.0
  Ca  Ca3  1  0.923  0.250  0.493  1.0
  U  U4  1  0.991  0.999  0.181  1.0
  U  U5  1  0.509  0.501  0.681  1.0
  U  U6  1  0.009  0.499  0.819  1.0
  U  U7  1  0.491  0.001  0.319  1.0
  U  U8  1  0.009  0.001  0.819  1.0
  U  U9  1  0.491  0.499  0.319  1.0
  U  U10  1  0.991  0.501  0.181  1.0
  U  U11  1  0.509  0.999  0.681  1.0
  Se  Se12  1  0.663  0.544  0.887  1.0
  Se  Se13  1  0.837  0.956  0.387  1.0
  Se  Se14  1  0.337  0.044  0.113  1.0
  Se  Se15  1  0.163  0.456  0.613  1.0
  Se  Se16  1  0.337  0.456  0.113  1.0
  Se  Se17  1  0.163  0.044  0.613  1.0
  Se  Se18  1  0.663  0.956  0.887  1.0
  Se  Se19  1  0.837  0.544  0.387  1.0
  Se  Se20  1  0.680  0.750  0.184  1.0
  Se  Se21  1  0.820  0.750  0.684  1.0
  Se  Se22  1  0.320  0.250  0.816  1.0
  Se  Se23  1  0.180  0.250  0.316  1.0
  Se  Se24  1  0.024  0.750  0.003  1.0
  Se  Se25  1  0.476  0.750  0.503  1.0
  Se  Se26  1  0.976  0.250  0.997  1.0
  Se  Se27  1  0.524  0.250  0.497  1.0
  Se  Se28  1  0.291  0.750  0.788  1.0
  Se  Se29  1  0.209  0.750  0.288  1.0
  Se  Se30  1  0.709  0.250  0.212  1.0
  Se  Se31  1  0.791  0.250  0.712  1.0
[/CIF]
.
The crystal structure described by CaU2Se5 crystallizes in the orthorhombic Pnma space group. Ca(1) is bonded to one Se(2), one Se(3), one Se(4), and four equivalent Se(1) atoms to form distorted edge-sharing CaSe7 pentagonal bipyramids. U(1) is bonded in a 8-coordinate geometry to two equivalent Se(1), two equivalent Se(2), two equivalent Se(3), and two equivalent Se(4) atoms. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Ca(1) and two equivalent U(1) atoms to form distorted SeCa2U2 tetrahedra that share corners with two equivalent Se(4)CaU4 square pyramids, corners with four equivalent Se(3)CaU4 square pyramids, corners with six equivalent Se(1)Ca2U2 tetrahedra, corners with two equivalent Se(2)CaU4 trigonal bipyramids,  an edgeedge with one Se(3)CaU4 square pyramid, edges with two equivalent Se(4)CaU4 square pyramids,  an edgeedge with one Se(1)Ca2U2 tetrahedra, and edges with two equivalent Se(2)CaU4 trigonal bipyramids. In the second Se site, Se(2) is bonded to one Ca(1) and four equivalent U(1) atoms to form distorted SeCaU4 trigonal bipyramids that share  a cornercorner with one Se(4)CaU4 square pyramid, corners with five equivalent Se(3)CaU4 square pyramids, corners with four equivalent Se(1)Ca2U2 tetrahedra, corners with four equivalent Se(2)CaU4 trigonal bipyramids, edges with two equivalent Se(3)CaU4 square pyramids, edges with four equivalent Se(4)CaU4 square pyramids, and edges with four equivalent Se(1)Ca2U2 tetrahedra. In the third Se site, Se(3) is bonded to one Ca(1) and four equivalent U(1) atoms to form SeCaU4 square pyramids that share corners with four equivalent Se(4)CaU4 square pyramids, corners with eight equivalent Se(1)Ca2U2 tetrahedra, corners with five equivalent Se(2)CaU4 trigonal bipyramids,  an edgeedge with one Se(4)CaU4 square pyramid, edges with two equivalent Se(3)CaU4 square pyramids, edges with two equivalent Se(1)Ca2U2 tetrahedra, edges with two equivalent Se(2)CaU4 trigonal bipyramids, and  a faceface with one Se(4)CaU4 square pyramid. In the fourth Se site, Se(4) is bonded to one Ca(1) and four equivalent U(1) atoms to form SeCaU4 square pyramids that share corners with four equivalent Se(3)CaU4 square pyramids, corners with four equivalent Se(4)CaU4 square pyramids, corners with four equivalent Se(1)Ca2U2 tetrahedra,  a cornercorner with one Se(2)CaU4 trigonal bipyramid,  an edgeedge with one Se(3)CaU4 square pyramid, edges with four equivalent Se(1)Ca2U2 tetrahedra, edges with four equivalent Se(2)CaU4 trigonal bipyramids, and  a faceface with one Se(3)CaU4 square pyramid. is represented by the Crystallographic Information File (CIF) [CIF]
data_CaU2Se5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.652
_cell_length_b   8.126
_cell_length_c   12.557
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   780.800
_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
  Ca  Ca0  1  0.423  0.750  0.007  1.0
  Ca  Ca1  1  0.077  0.750  0.507  1.0
  Ca  Ca2  1  0.577  0.250  0.993  1.0
  Ca  Ca3  1  0.923  0.250  0.493  1.0
  U  U4  1  0.991  0.999  0.181  1.0
  U  U5  1  0.509  0.501  0.681  1.0
  U  U6  1  0.009  0.499  0.819  1.0
  U  U7  1  0.491  0.001  0.319  1.0
  U  U8  1  0.009  0.001  0.819  1.0
  U  U9  1  0.491  0.499  0.319  1.0
  U  U10  1  0.991  0.501  0.181  1.0
  U  U11  1  0.509  0.999  0.681  1.0
  Se  Se12  1  0.663  0.544  0.887  1.0
  Se  Se13  1  0.837  0.956  0.387  1.0
  Se  Se14  1  0.337  0.044  0.113  1.0
  Se  Se15  1  0.163  0.456  0.613  1.0
  Se  Se16  1  0.337  0.456  0.113  1.0
  Se  Se17  1  0.163  0.044  0.613  1.0
  Se  Se18  1  0.663  0.956  0.887  1.0
  Se  Se19  1  0.837  0.544  0.387  1.0
  Se  Se20  1  0.680  0.750  0.184  1.0
  Se  Se21  1  0.820  0.750  0.684  1.0
  Se  Se22  1  0.320  0.250  0.816  1.0
  Se  Se23  1  0.180  0.250  0.316  1.0
  Se  Se24  1  0.024  0.750  0.003  1.0
  Se  Se25  1  0.476  0.750  0.503  1.0
  Se  Se26  1  0.976  0.250  0.997  1.0
  Se  Se27  1  0.524  0.250  0.497  1.0
  Se  Se28  1  0.291  0.750  0.788  1.0
  Se  Se29  1  0.209  0.750  0.288  1.0
  Se  Se30  1  0.709  0.250  0.212  1.0
  Se  Se31  1  0.791  0.250  0.712  1.0
[/CIF]
.