The crystal structure described by SrCuGdSe3 crystallizes in the orthorhombic Pnma space group. Sr(1) is bonded in a 7-coordinate geometry to two equivalent Se(1), two equivalent Se(3), and three equivalent Se(2) atoms. Gd(1) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms to form GdSe6 octahedra that share corners with two equivalent Gd(1)Se6 octahedra, edges with two equivalent Gd(1)Se6 octahedra, and edges with four equivalent Cu(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles are 43°. Cu(1) is bonded to one Se(2), one Se(3), and two equivalent Se(1) atoms to form CuSe4 tetrahedra that share corners with two equivalent Cu(1)Se4 tetrahedra and edges with four equivalent Gd(1)Se6 octahedra. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Sr(1), two equivalent Gd(1), and two equivalent Cu(1) atoms to form distorted SeSr2Gd2Cu2 octahedra that share corners with two equivalent Se(1)Sr2Gd2Cu2 octahedra, corners with two equivalent Se(2)Sr3Gd2Cu octahedra, corners with four equivalent Se(3)Sr2Gd2Cu square pyramids, edges with two equivalent Se(1)Sr2Gd2Cu2 octahedra, edges with five equivalent Se(2)Sr3Gd2Cu octahedra, and edges with three equivalent Se(3)Sr2Gd2Cu square pyramids. The corner-sharing octahedral tilt angles range from 3-33°. In the second Se site, Se(2) is bonded to three equivalent Sr(1), two equivalent Gd(1), and one Cu(1) atom to form distorted SeSr3Gd2Cu octahedra that share corners with two equivalent Se(1)Sr2Gd2Cu2 octahedra, corners with six equivalent Se(3)Sr2Gd2Cu square pyramids, edges with four equivalent Se(2)Sr3Gd2Cu octahedra, edges with five equivalent Se(1)Sr2Gd2Cu2 octahedra,  an edgeedge with one Se(3)Sr2Gd2Cu square pyramid, and  a faceface with one Se(3)Sr2Gd2Cu square pyramid. The corner-sharing octahedral tilt angles are 33°. In the third Se site, Se(3) is bonded to two equivalent Sr(1), two equivalent Gd(1), and one Cu(1) atom to form distorted SeSr2Gd2Cu square pyramids that share corners with four equivalent Se(1)Sr2Gd2Cu2 octahedra, corners with six equivalent Se(2)Sr3Gd2Cu octahedra,  an edgeedge with one Se(2)Sr3Gd2Cu octahedra, edges with three equivalent Se(1)Sr2Gd2Cu2 octahedra, edges with two equivalent Se(3)Sr2Gd2Cu square pyramids, and  a faceface with one Se(2)Sr3Gd2Cu octahedra. The corner-sharing octahedral tilt angles range from 1-88°. is represented by the CIF file [CIF]
data_SrGdCuSe3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.141
_cell_length_b   10.780
_cell_length_c   13.608
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   607.381
_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
  Sr  Sr0  1  0.250  0.269  1.000  1.0
  Sr  Sr1  1  0.250  0.769  0.500  1.0
  Sr  Sr2  1  0.750  0.731  0.000  1.0
  Sr  Sr3  1  0.750  0.231  0.500  1.0
  Gd  Gd4  1  0.250  0.013  0.756  1.0
  Gd  Gd5  1  0.250  0.513  0.744  1.0
  Gd  Gd6  1  0.750  0.987  0.244  1.0
  Gd  Gd7  1  0.750  0.487  0.256  1.0
  Cu  Cu8  1  0.250  0.240  0.278  1.0
  Cu  Cu9  1  0.250  0.740  0.222  1.0
  Cu  Cu10  1  0.750  0.760  0.722  1.0
  Cu  Cu11  1  0.750  0.260  0.778  1.0
  Se  Se12  1  0.250  0.260  0.671  1.0
  Se  Se13  1  0.250  0.760  0.829  1.0
  Se  Se14  1  0.750  0.740  0.329  1.0
  Se  Se15  1  0.750  0.240  0.171  1.0
  Se  Se16  1  0.250  0.054  0.386  1.0
  Se  Se17  1  0.250  0.554  0.114  1.0
  Se  Se18  1  0.750  0.946  0.614  1.0
  Se  Se19  1  0.750  0.446  0.886  1.0
  Se  Se20  1  0.250  0.416  0.394  1.0
  Se  Se21  1  0.250  0.916  0.106  1.0
  Se  Se22  1  0.750  0.584  0.606  1.0
  Se  Se23  1  0.750  0.084  0.894  1.0
[/CIF]
.
The crystal structure described by SrCuGdSe3 crystallizes in the orthorhombic Pnma space group. Sr(1) is bonded in a 7-coordinate geometry to two equivalent Se(1), two equivalent Se(3), and three equivalent Se(2) atoms. Gd(1) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms to form GdSe6 octahedra that share corners with two equivalent Gd(1)Se6 octahedra, edges with two equivalent Gd(1)Se6 octahedra, and edges with four equivalent Cu(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles are 43°. Cu(1) is bonded to one Se(2), one Se(3), and two equivalent Se(1) atoms to form CuSe4 tetrahedra that share corners with two equivalent Cu(1)Se4 tetrahedra and edges with four equivalent Gd(1)Se6 octahedra. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Sr(1), two equivalent Gd(1), and two equivalent Cu(1) atoms to form distorted SeSr2Gd2Cu2 octahedra that share corners with two equivalent Se(1)Sr2Gd2Cu2 octahedra, corners with two equivalent Se(2)Sr3Gd2Cu octahedra, corners with four equivalent Se(3)Sr2Gd2Cu square pyramids, edges with two equivalent Se(1)Sr2Gd2Cu2 octahedra, edges with five equivalent Se(2)Sr3Gd2Cu octahedra, and edges with three equivalent Se(3)Sr2Gd2Cu square pyramids. The corner-sharing octahedral tilt angles range from 3-33°. In the second Se site, Se(2) is bonded to three equivalent Sr(1), two equivalent Gd(1), and one Cu(1) atom to form distorted SeSr3Gd2Cu octahedra that share corners with two equivalent Se(1)Sr2Gd2Cu2 octahedra, corners with six equivalent Se(3)Sr2Gd2Cu square pyramids, edges with four equivalent Se(2)Sr3Gd2Cu octahedra, edges with five equivalent Se(1)Sr2Gd2Cu2 octahedra,  an edgeedge with one Se(3)Sr2Gd2Cu square pyramid, and  a faceface with one Se(3)Sr2Gd2Cu square pyramid. The corner-sharing octahedral tilt angles are 33°. In the third Se site, Se(3) is bonded to two equivalent Sr(1), two equivalent Gd(1), and one Cu(1) atom to form distorted SeSr2Gd2Cu square pyramids that share corners with four equivalent Se(1)Sr2Gd2Cu2 octahedra, corners with six equivalent Se(2)Sr3Gd2Cu octahedra,  an edgeedge with one Se(2)Sr3Gd2Cu octahedra, edges with three equivalent Se(1)Sr2Gd2Cu2 octahedra, edges with two equivalent Se(3)Sr2Gd2Cu square pyramids, and  a faceface with one Se(2)Sr3Gd2Cu octahedra. The corner-sharing octahedral tilt angles range from 1-88°. is represented by the CIF file [CIF]
data_SrGdCuSe3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.141
_cell_length_b   10.780
_cell_length_c   13.608
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   607.381
_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
  Sr  Sr0  1  0.250  0.269  1.000  1.0
  Sr  Sr1  1  0.250  0.769  0.500  1.0
  Sr  Sr2  1  0.750  0.731  0.000  1.0
  Sr  Sr3  1  0.750  0.231  0.500  1.0
  Gd  Gd4  1  0.250  0.013  0.756  1.0
  Gd  Gd5  1  0.250  0.513  0.744  1.0
  Gd  Gd6  1  0.750  0.987  0.244  1.0
  Gd  Gd7  1  0.750  0.487  0.256  1.0
  Cu  Cu8  1  0.250  0.240  0.278  1.0
  Cu  Cu9  1  0.250  0.740  0.222  1.0
  Cu  Cu10  1  0.750  0.760  0.722  1.0
  Cu  Cu11  1  0.750  0.260  0.778  1.0
  Se  Se12  1  0.250  0.260  0.671  1.0
  Se  Se13  1  0.250  0.760  0.829  1.0
  Se  Se14  1  0.750  0.740  0.329  1.0
  Se  Se15  1  0.750  0.240  0.171  1.0
  Se  Se16  1  0.250  0.054  0.386  1.0
  Se  Se17  1  0.250  0.554  0.114  1.0
  Se  Se18  1  0.750  0.946  0.614  1.0
  Se  Se19  1  0.750  0.446  0.886  1.0
  Se  Se20  1  0.250  0.416  0.394  1.0
  Se  Se21  1  0.250  0.916  0.106  1.0
  Se  Se22  1  0.750  0.584  0.606  1.0
  Se  Se23  1  0.750  0.084  0.894  1.0
[/CIF]
.