The compound described by CoNi2Se4 crystallizes in the monoclinic Cm space group. Co(1) is bonded to one Se(1), one Se(3), two equivalent Se(2), and two equivalent Se(4) atoms to form distorted CoSe6 octahedra that share corners with six equivalent Ni(1)Se6 octahedra, edges with two equivalent Co(1)Se6 octahedra, edges with four equivalent Ni(2)Se6 octahedra, and  a faceface with one Ni(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 49-54°. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one Se(1), one Se(2), two equivalent Se(3), and two equivalent Se(4) atoms to form NiSe6 octahedra that share corners with six equivalent Co(1)Se6 octahedra, corners with six equivalent Ni(2)Se6 octahedra, edges with two equivalent Ni(1)Se6 octahedra,  a faceface with one Co(1)Se6 octahedra, and  a faceface with one Ni(2)Se6 octahedra. The corner-sharing octahedral tilt angles range from 49-54°. In the second Ni site, Ni(2) is bonded to one Se(2), one Se(4), two equivalent Se(1), and two equivalent Se(3) atoms to form distorted NiSe6 octahedra that share corners with six equivalent Ni(1)Se6 octahedra, edges with two equivalent Ni(2)Se6 octahedra, edges with four equivalent Co(1)Se6 octahedra, and  a faceface with one Ni(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 50-53°. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to one Co(1), one Ni(1), and two equivalent Ni(2) atoms to form SeCoNi3 trigonal pyramids that share  a cornercorner with one Se(2)Co2Ni2 trigonal pyramid, corners with two equivalent Se(1)CoNi3 trigonal pyramids, and edges with two equivalent Se(2)Co2Ni2 trigonal pyramids. In the second Se site, Se(2) is bonded to two equivalent Co(1), one Ni(1), and one Ni(2) atom to form distorted SeCo2Ni2 trigonal pyramids that share  a cornercorner with one Se(1)CoNi3 trigonal pyramid, corners with two equivalent Se(2)Co2Ni2 trigonal pyramids, and edges with two equivalent Se(1)CoNi3 trigonal pyramids. In the third Se site, Se(3) is bonded in a 5-coordinate geometry to one Co(1), two equivalent Ni(1), and two equivalent Ni(2) atoms. In the fourth Se site, Se(4) is bonded in a 5-coordinate geometry to two equivalent Co(1), one Ni(2), and two equivalent Ni(1) atoms. is represented by the CIF file [CIF]
data_Co(NiSe2)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.264
_cell_length_b   6.264
_cell_length_c   6.165
_cell_angle_alpha   61.311
_cell_angle_beta   61.311
_cell_angle_gamma   33.699
_symmetry_Int_Tables_number   1
_cell_volume   116.115
_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
  Co  Co0  1  0.740  0.740  0.279  1.0
  Ni  Ni1  1  0.002  0.002  0.002  1.0
  Ni  Ni2  1  0.260  0.260  0.722  1.0
  Se  Se3  1  0.877  0.877  0.454  1.0
  Se  Se4  1  0.122  0.122  0.536  1.0
  Se  Se5  1  0.636  0.636  0.026  1.0
  Se  Se6  1  0.364  0.364  0.981  1.0
[/CIF]
.
The compound described by CoNi2Se4 crystallizes in the monoclinic Cm space group. Co(1) is bonded to one Se(1), one Se(3), two equivalent Se(2), and two equivalent Se(4) atoms to form distorted CoSe6 octahedra that share corners with six equivalent Ni(1)Se6 octahedra, edges with two equivalent Co(1)Se6 octahedra, edges with four equivalent Ni(2)Se6 octahedra, and  a faceface with one Ni(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 49-54°. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one Se(1), one Se(2), two equivalent Se(3), and two equivalent Se(4) atoms to form NiSe6 octahedra that share corners with six equivalent Co(1)Se6 octahedra, corners with six equivalent Ni(2)Se6 octahedra, edges with two equivalent Ni(1)Se6 octahedra,  a faceface with one Co(1)Se6 octahedra, and  a faceface with one Ni(2)Se6 octahedra. The corner-sharing octahedral tilt angles range from 49-54°. In the second Ni site, Ni(2) is bonded to one Se(2), one Se(4), two equivalent Se(1), and two equivalent Se(3) atoms to form distorted NiSe6 octahedra that share corners with six equivalent Ni(1)Se6 octahedra, edges with two equivalent Ni(2)Se6 octahedra, edges with four equivalent Co(1)Se6 octahedra, and  a faceface with one Ni(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 50-53°. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to one Co(1), one Ni(1), and two equivalent Ni(2) atoms to form SeCoNi3 trigonal pyramids that share  a cornercorner with one Se(2)Co2Ni2 trigonal pyramid, corners with two equivalent Se(1)CoNi3 trigonal pyramids, and edges with two equivalent Se(2)Co2Ni2 trigonal pyramids. In the second Se site, Se(2) is bonded to two equivalent Co(1), one Ni(1), and one Ni(2) atom to form distorted SeCo2Ni2 trigonal pyramids that share  a cornercorner with one Se(1)CoNi3 trigonal pyramid, corners with two equivalent Se(2)Co2Ni2 trigonal pyramids, and edges with two equivalent Se(1)CoNi3 trigonal pyramids. In the third Se site, Se(3) is bonded in a 5-coordinate geometry to one Co(1), two equivalent Ni(1), and two equivalent Ni(2) atoms. In the fourth Se site, Se(4) is bonded in a 5-coordinate geometry to two equivalent Co(1), one Ni(2), and two equivalent Ni(1) atoms. is represented by the CIF file [CIF]
data_Co(NiSe2)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.264
_cell_length_b   6.264
_cell_length_c   6.165
_cell_angle_alpha   61.311
_cell_angle_beta   61.311
_cell_angle_gamma   33.699
_symmetry_Int_Tables_number   1
_cell_volume   116.115
_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
  Co  Co0  1  0.740  0.740  0.279  1.0
  Ni  Ni1  1  0.002  0.002  0.002  1.0
  Ni  Ni2  1  0.260  0.260  0.722  1.0
  Se  Se3  1  0.877  0.877  0.454  1.0
  Se  Se4  1  0.122  0.122  0.536  1.0
  Se  Se5  1  0.636  0.636  0.026  1.0
  Se  Se6  1  0.364  0.364  0.981  1.0
[/CIF]
.