The material described by Ca2SiSe4 is Spinel-like structured and crystallizes in the orthorhombic Pnma space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms to form CaSe6 octahedra that share corners with four equivalent Ca(2)Se6 octahedra, corners with two equivalent Si(1)Se4 tetrahedra, edges with two equivalent Ca(1)Se6 octahedra, edges with two equivalent Ca(2)Se6 octahedra, and edges with two equivalent Si(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 55-66°. In the second Ca site, Ca(2) is bonded to one Se(1), one Se(2), and four equivalent Se(3) atoms to form CaSe6 octahedra that share corners with four equivalent Ca(1)Se6 octahedra, corners with four equivalent Ca(2)Se6 octahedra, corners with four equivalent Si(1)Se4 tetrahedra, edges with two equivalent Ca(1)Se6 octahedra, and  an edgeedge with one Si(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 49-66°. Si(1) is bonded to one Se(1), one Se(2), and two equivalent Se(3) atoms to form SiSe4 tetrahedra that share corners with two equivalent Ca(1)Se6 octahedra, corners with four equivalent Ca(2)Se6 octahedra,  an edgeedge with one Ca(2)Se6 octahedra, and edges with two equivalent Ca(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 53-59°. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to one Ca(2), two equivalent Ca(1), and one Si(1) atom to form distorted corner-sharing SeCa3Si trigonal pyramids. In the second Se site, Se(2) is bonded in a rectangular see-saw-like geometry to one Ca(2), two equivalent Ca(1), and one Si(1) atom. In the third Se site, Se(3) is bonded in a rectangular see-saw-like geometry to one Ca(1), two equivalent Ca(2), and one Si(1) atom. is represented by the CIF card [CIF]
data_Ca2SiSe4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.547
_cell_length_b   8.563
_cell_length_c   14.239
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   798.292
_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  0.000  0.500  0.000  1.0
  Ca  Ca1  1  0.500  0.000  0.500  1.0
  Ca  Ca2  1  0.000  0.000  0.000  1.0
  Ca  Ca3  1  0.500  0.500  0.500  1.0
  Ca  Ca4  1  0.482  0.750  0.228  1.0
  Ca  Ca5  1  0.018  0.750  0.728  1.0
  Ca  Ca6  1  0.518  0.250  0.772  1.0
  Ca  Ca7  1  0.982  0.250  0.272  1.0
  Si  Si8  1  0.902  0.750  0.408  1.0
  Si  Si9  1  0.598  0.750  0.908  1.0
  Si  Si10  1  0.098  0.250  0.592  1.0
  Si  Si11  1  0.402  0.250  0.092  1.0
  Se  Se12  1  0.247  0.750  0.407  1.0
  Se  Se13  1  0.253  0.750  0.907  1.0
  Se  Se14  1  0.753  0.250  0.593  1.0
  Se  Se15  1  0.747  0.250  0.093  1.0
  Se  Se16  1  0.773  0.750  0.557  1.0
  Se  Se17  1  0.727  0.750  0.057  1.0
  Se  Se18  1  0.227  0.250  0.443  1.0
  Se  Se19  1  0.273  0.250  0.943  1.0
  Se  Se20  1  0.763  0.540  0.332  1.0
  Se  Se21  1  0.737  0.960  0.832  1.0
  Se  Se22  1  0.237  0.040  0.668  1.0
  Se  Se23  1  0.263  0.460  0.168  1.0
  Se  Se24  1  0.237  0.460  0.668  1.0
  Se  Se25  1  0.263  0.040  0.168  1.0
  Se  Se26  1  0.763  0.960  0.332  1.0
  Se  Se27  1  0.737  0.540  0.832  1.0
[/CIF]
.
The material described by Ca2SiSe4 is Spinel-like structured and crystallizes in the orthorhombic Pnma space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms to form CaSe6 octahedra that share corners with four equivalent Ca(2)Se6 octahedra, corners with two equivalent Si(1)Se4 tetrahedra, edges with two equivalent Ca(1)Se6 octahedra, edges with two equivalent Ca(2)Se6 octahedra, and edges with two equivalent Si(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 55-66°. In the second Ca site, Ca(2) is bonded to one Se(1), one Se(2), and four equivalent Se(3) atoms to form CaSe6 octahedra that share corners with four equivalent Ca(1)Se6 octahedra, corners with four equivalent Ca(2)Se6 octahedra, corners with four equivalent Si(1)Se4 tetrahedra, edges with two equivalent Ca(1)Se6 octahedra, and  an edgeedge with one Si(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 49-66°. Si(1) is bonded to one Se(1), one Se(2), and two equivalent Se(3) atoms to form SiSe4 tetrahedra that share corners with two equivalent Ca(1)Se6 octahedra, corners with four equivalent Ca(2)Se6 octahedra,  an edgeedge with one Ca(2)Se6 octahedra, and edges with two equivalent Ca(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 53-59°. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to one Ca(2), two equivalent Ca(1), and one Si(1) atom to form distorted corner-sharing SeCa3Si trigonal pyramids. In the second Se site, Se(2) is bonded in a rectangular see-saw-like geometry to one Ca(2), two equivalent Ca(1), and one Si(1) atom. In the third Se site, Se(3) is bonded in a rectangular see-saw-like geometry to one Ca(1), two equivalent Ca(2), and one Si(1) atom. is represented by the CIF card [CIF]
data_Ca2SiSe4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.547
_cell_length_b   8.563
_cell_length_c   14.239
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   798.292
_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  0.000  0.500  0.000  1.0
  Ca  Ca1  1  0.500  0.000  0.500  1.0
  Ca  Ca2  1  0.000  0.000  0.000  1.0
  Ca  Ca3  1  0.500  0.500  0.500  1.0
  Ca  Ca4  1  0.482  0.750  0.228  1.0
  Ca  Ca5  1  0.018  0.750  0.728  1.0
  Ca  Ca6  1  0.518  0.250  0.772  1.0
  Ca  Ca7  1  0.982  0.250  0.272  1.0
  Si  Si8  1  0.902  0.750  0.408  1.0
  Si  Si9  1  0.598  0.750  0.908  1.0
  Si  Si10  1  0.098  0.250  0.592  1.0
  Si  Si11  1  0.402  0.250  0.092  1.0
  Se  Se12  1  0.247  0.750  0.407  1.0
  Se  Se13  1  0.253  0.750  0.907  1.0
  Se  Se14  1  0.753  0.250  0.593  1.0
  Se  Se15  1  0.747  0.250  0.093  1.0
  Se  Se16  1  0.773  0.750  0.557  1.0
  Se  Se17  1  0.727  0.750  0.057  1.0
  Se  Se18  1  0.227  0.250  0.443  1.0
  Se  Se19  1  0.273  0.250  0.943  1.0
  Se  Se20  1  0.763  0.540  0.332  1.0
  Se  Se21  1  0.737  0.960  0.832  1.0
  Se  Se22  1  0.237  0.040  0.668  1.0
  Se  Se23  1  0.263  0.460  0.168  1.0
  Se  Se24  1  0.237  0.460  0.668  1.0
  Se  Se25  1  0.263  0.040  0.168  1.0
  Se  Se26  1  0.763  0.960  0.332  1.0
  Se  Se27  1  0.737  0.540  0.832  1.0
[/CIF]
.