The compound described by NiSi2Se4 crystallizes in the monoclinic C2/m space group. Ni(1) is bonded to two equivalent Se(1) and four equivalent Se(2) atoms to form NiSe6 octahedra that share corners with twelve equivalent Si(1)Se6 octahedra, edges with two equivalent Ni(1)Se6 octahedra, and faces with two equivalent Si(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 43-55°. Si(1) is bonded to three equivalent Se(1) and three equivalent Se(2) atoms to form SiSe6 octahedra that share corners with six equivalent Ni(1)Se6 octahedra, edges with six equivalent Si(1)Se6 octahedra, and  a faceface with one Ni(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 43-55°. There are two inequivalent Se sites. In the first Se site, Se(2) is bonded to two equivalent Ni(1) and three equivalent Si(1) atoms to form a mixture of distorted edge and corner-sharing SeSi3Ni2 trigonal bipyramids. In the second Se site, Se(1) is bonded in a rectangular see-saw-like geometry to one Ni(1) and three equivalent Si(1) atoms. is represented by the CIF card [CIF]
data_Si2NiSe4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.887
_cell_length_b   6.887
_cell_length_c   6.451
_cell_angle_alpha   69.275
_cell_angle_beta   69.275
_cell_angle_gamma   29.262
_symmetry_Int_Tables_number   1
_cell_volume   139.196
_cell_formula_units_Z   1
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
  Si  Si0  1  0.740  0.740  0.280  1.0
  Si  Si1  1  0.260  0.260  0.720  1.0
  Ni  Ni2  1  0.000  0.000  0.000  1.0
  Se  Se3  1  0.872  0.872  0.474  1.0
  Se  Se4  1  0.128  0.128  0.526  1.0
  Se  Se5  1  0.623  0.623  0.012  1.0
  Se  Se6  1  0.377  0.377  0.988  1.0
[/CIF]
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The compound described by NiSi2Se4 crystallizes in the monoclinic C2/m space group. Ni(1) is bonded to two equivalent Se(1) and four equivalent Se(2) atoms to form NiSe6 octahedra that share corners with twelve equivalent Si(1)Se6 octahedra, edges with two equivalent Ni(1)Se6 octahedra, and faces with two equivalent Si(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 43-55°. Si(1) is bonded to three equivalent Se(1) and three equivalent Se(2) atoms to form SiSe6 octahedra that share corners with six equivalent Ni(1)Se6 octahedra, edges with six equivalent Si(1)Se6 octahedra, and  a faceface with one Ni(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 43-55°. There are two inequivalent Se sites. In the first Se site, Se(2) is bonded to two equivalent Ni(1) and three equivalent Si(1) atoms to form a mixture of distorted edge and corner-sharing SeSi3Ni2 trigonal bipyramids. In the second Se site, Se(1) is bonded in a rectangular see-saw-like geometry to one Ni(1) and three equivalent Si(1) atoms. is represented by the CIF card [CIF]
data_Si2NiSe4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.887
_cell_length_b   6.887
_cell_length_c   6.451
_cell_angle_alpha   69.275
_cell_angle_beta   69.275
_cell_angle_gamma   29.262
_symmetry_Int_Tables_number   1
_cell_volume   139.196
_cell_formula_units_Z   1
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
  Si  Si0  1  0.740  0.740  0.280  1.0
  Si  Si1  1  0.260  0.260  0.720  1.0
  Ni  Ni2  1  0.000  0.000  0.000  1.0
  Se  Se3  1  0.872  0.872  0.474  1.0
  Se  Se4  1  0.128  0.128  0.526  1.0
  Se  Se5  1  0.623  0.623  0.012  1.0
  Se  Se6  1  0.377  0.377  0.988  1.0
[/CIF]
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