The crystal structure described by NiOCaO crystallizes in the triclinic P-1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(4), two equivalent O(3), and three equivalent O(1) atoms to form CaO6 octahedra that share  a cornercorner with one Ni(2)O5 square pyramid, corners with two equivalent Ni(1)O5 trigonal bipyramids, edges with four equivalent Ca(1)O6 octahedra, edges with two equivalent Ni(2)O5 square pyramids, and edges with three equivalent Ni(1)O5 trigonal bipyramids. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form NiO5 trigonal bipyramids that share corners with two equivalent Ca(1)O6 octahedra, corners with two equivalent Ni(2)O5 square pyramids, corners with two equivalent Ni(1)O5 trigonal bipyramids, edges with three equivalent Ca(1)O6 octahedra, edges with two equivalent Ni(2)O5 square pyramids, and  an edgeedge with one Ni(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 8°. In the second Ni site, Ni(2) is bonded to one O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted NiO5 square pyramids that share  a cornercorner with one Ca(1)O6 octahedra, corners with two equivalent Ni(1)O5 trigonal bipyramids, edges with two equivalent Ca(1)O6 octahedra, edges with two equivalent Ni(2)O5 square pyramids, and edges with two equivalent Ni(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 4°. There are four inequivalent O sites. In the first O site, O(1) is bonded to three equivalent Ca(1), one Ni(2), and two equivalent Ni(1) atoms to form OCa3Ni3 octahedra that share corners with two equivalent O(3)Ca4Ni square pyramids,  a cornercorner with one O(4)Ca3Ni2 trigonal bipyramid, edges with four equivalent O(1)Ca3Ni3 octahedra, edges with three equivalent O(3)Ca4Ni square pyramids, and edges with two equivalent O(4)Ca3Ni2 trigonal bipyramids. In the second O site, O(2) is bonded in a 6-coordinate geometry to two equivalent Ca(2), two equivalent Ni(1), and two equivalent Ni(2) atoms. In the third O site, O(3) is bonded to two equivalent Ca(1), two equivalent Ca(2), and one Ni(1) atom to form OCa4Ni square pyramids that share corners with two equivalent O(1)Ca3Ni3 octahedra, corners with four equivalent O(4)Ca3Ni2 trigonal bipyramids, edges with three equivalent O(1)Ca3Ni3 octahedra, edges with two equivalent O(3)Ca4Ni square pyramids, and  an edgeedge with one O(4)Ca3Ni2 trigonal bipyramid. The corner-sharing octahedral tilt angles are 10°. In the fourth O site, O(4) is bonded to one Ca(1), two equivalent Ca(2), and two equivalent Ni(2) atoms to form OCa3Ni2 trigonal bipyramids that share  a cornercorner with one O(1)Ca3Ni3 octahedra, corners with four equivalent O(3)Ca4Ni square pyramids, edges with two equivalent O(1)Ca3Ni3 octahedra,  an edgeedge with one O(3)Ca4Ni square pyramid, and edges with two equivalent O(4)Ca3Ni2 trigonal bipyramids. The corner-sharing octahedral tilt angles are 9°. is represented by the CIF card [CIF]
data_CaNiO2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.130
_cell_length_b   8.351
_cell_length_c   8.136
_cell_angle_alpha   77.488
_cell_angle_beta   89.772
_cell_angle_gamma   102.202
_symmetry_Int_Tables_number   1
_cell_volume   202.620
_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  0.269  0.028  0.323  1.0
  Ca  Ca1  1  0.727  0.952  0.705  1.0
  Ca  Ca2  1  0.099  0.723  0.119  1.0
  Ca  Ca3  1  0.897  0.257  0.909  1.0
  Ni  Ni4  1  0.415  0.302  0.560  1.0
  Ni  Ni5  1  0.948  0.360  0.249  1.0
  Ni  Ni6  1  0.047  0.620  0.779  1.0
  Ni  Ni7  1  0.581  0.678  0.468  1.0
  O  O8  1  0.148  0.800  0.566  1.0
  O  O9  1  0.470  0.482  0.698  1.0
  O  O10  1  0.526  0.498  0.330  1.0
  O  O11  1  0.848  0.180  0.462  1.0
  O  O12  1  0.318  0.117  0.788  1.0
  O  O13  1  0.402  0.274  0.119  1.0
  O  O14  1  0.678  0.863  0.240  1.0
  O  O15  1  0.594  0.705  0.909  1.0
[/CIF]
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The crystal structure described by NiOCaO crystallizes in the triclinic P-1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(4), two equivalent O(3), and three equivalent O(1) atoms to form CaO6 octahedra that share  a cornercorner with one Ni(2)O5 square pyramid, corners with two equivalent Ni(1)O5 trigonal bipyramids, edges with four equivalent Ca(1)O6 octahedra, edges with two equivalent Ni(2)O5 square pyramids, and edges with three equivalent Ni(1)O5 trigonal bipyramids. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form NiO5 trigonal bipyramids that share corners with two equivalent Ca(1)O6 octahedra, corners with two equivalent Ni(2)O5 square pyramids, corners with two equivalent Ni(1)O5 trigonal bipyramids, edges with three equivalent Ca(1)O6 octahedra, edges with two equivalent Ni(2)O5 square pyramids, and  an edgeedge with one Ni(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 8°. In the second Ni site, Ni(2) is bonded to one O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted NiO5 square pyramids that share  a cornercorner with one Ca(1)O6 octahedra, corners with two equivalent Ni(1)O5 trigonal bipyramids, edges with two equivalent Ca(1)O6 octahedra, edges with two equivalent Ni(2)O5 square pyramids, and edges with two equivalent Ni(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 4°. There are four inequivalent O sites. In the first O site, O(1) is bonded to three equivalent Ca(1), one Ni(2), and two equivalent Ni(1) atoms to form OCa3Ni3 octahedra that share corners with two equivalent O(3)Ca4Ni square pyramids,  a cornercorner with one O(4)Ca3Ni2 trigonal bipyramid, edges with four equivalent O(1)Ca3Ni3 octahedra, edges with three equivalent O(3)Ca4Ni square pyramids, and edges with two equivalent O(4)Ca3Ni2 trigonal bipyramids. In the second O site, O(2) is bonded in a 6-coordinate geometry to two equivalent Ca(2), two equivalent Ni(1), and two equivalent Ni(2) atoms. In the third O site, O(3) is bonded to two equivalent Ca(1), two equivalent Ca(2), and one Ni(1) atom to form OCa4Ni square pyramids that share corners with two equivalent O(1)Ca3Ni3 octahedra, corners with four equivalent O(4)Ca3Ni2 trigonal bipyramids, edges with three equivalent O(1)Ca3Ni3 octahedra, edges with two equivalent O(3)Ca4Ni square pyramids, and  an edgeedge with one O(4)Ca3Ni2 trigonal bipyramid. The corner-sharing octahedral tilt angles are 10°. In the fourth O site, O(4) is bonded to one Ca(1), two equivalent Ca(2), and two equivalent Ni(2) atoms to form OCa3Ni2 trigonal bipyramids that share  a cornercorner with one O(1)Ca3Ni3 octahedra, corners with four equivalent O(3)Ca4Ni square pyramids, edges with two equivalent O(1)Ca3Ni3 octahedra,  an edgeedge with one O(3)Ca4Ni square pyramid, and edges with two equivalent O(4)Ca3Ni2 trigonal bipyramids. The corner-sharing octahedral tilt angles are 9°. is represented by the CIF card [CIF]
data_CaNiO2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.130
_cell_length_b   8.351
_cell_length_c   8.136
_cell_angle_alpha   77.488
_cell_angle_beta   89.772
_cell_angle_gamma   102.202
_symmetry_Int_Tables_number   1
_cell_volume   202.620
_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  0.269  0.028  0.323  1.0
  Ca  Ca1  1  0.727  0.952  0.705  1.0
  Ca  Ca2  1  0.099  0.723  0.119  1.0
  Ca  Ca3  1  0.897  0.257  0.909  1.0
  Ni  Ni4  1  0.415  0.302  0.560  1.0
  Ni  Ni5  1  0.948  0.360  0.249  1.0
  Ni  Ni6  1  0.047  0.620  0.779  1.0
  Ni  Ni7  1  0.581  0.678  0.468  1.0
  O  O8  1  0.148  0.800  0.566  1.0
  O  O9  1  0.470  0.482  0.698  1.0
  O  O10  1  0.526  0.498  0.330  1.0
  O  O11  1  0.848  0.180  0.462  1.0
  O  O12  1  0.318  0.117  0.788  1.0
  O  O13  1  0.402  0.274  0.119  1.0
  O  O14  1  0.678  0.863  0.240  1.0
  O  O15  1  0.594  0.705  0.909  1.0
[/CIF]
.