The 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(1), two equivalent O(3), and two equivalent O(4) atoms to form distorted CaO5 trigonal bipyramids that share corners with four equivalent Ca(2)O4 tetrahedra, corners with two equivalent Ni(2)O5 trigonal bipyramids, edges with two equivalent Ca(1)O5 trigonal bipyramids, and  a faceface with one Ni(2)O5 trigonal bipyramid. In the second Ca site, Ca(2) is bonded to one O(3), one O(4), and two equivalent O(2) atoms to form CaO4 tetrahedra that share corners with two equivalent Ca(2)O4 tetrahedra, corners with four equivalent Ca(1)O5 trigonal bipyramids, corners with four equivalent Ni(2)O5 trigonal bipyramids, and  an edgeedge with one Ni(2)O5 trigonal bipyramid. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a rectangular see-saw-like geometry to two equivalent O(1) and two equivalent O(3) atoms. 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 trigonal bipyramids that share corners with four equivalent Ca(2)O4 tetrahedra, corners with two equivalent Ca(1)O5 trigonal bipyramids,  an edgeedge with one Ca(2)O4 tetrahedra, edges with two equivalent Ni(2)O5 trigonal bipyramids, and  a faceface with one Ca(1)O5 trigonal bipyramid. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1), one Ni(2), and two equivalent Ni(1) atoms to form OCaNi3 tetrahedra that share corners with two equivalent O(1)CaNi3 tetrahedra, corners with four equivalent O(3)Ca3Ni2 trigonal bipyramids,  an edgeedge with one O(3)Ca3Ni2 trigonal bipyramid, and edges with two equivalent O(4)Ca3Ni2 trigonal bipyramids. In the second O site, O(2) is bonded in a square co-planar geometry to two equivalent Ca(2) and two equivalent Ni(2) atoms. In the third O site, O(3) is bonded to one Ca(2), two equivalent Ca(1), and two equivalent Ni(1) atoms to form distorted OCa3Ni2 trigonal bipyramids that share corners with four equivalent O(1)CaNi3 tetrahedra, corners with three equivalent O(4)Ca3Ni2 trigonal bipyramids,  an edgeedge with one O(1)CaNi3 tetrahedra,  an edgeedge with one O(4)Ca3Ni2 trigonal bipyramid, and edges with two equivalent O(3)Ca3Ni2 trigonal bipyramids. In the fourth O site, O(4) is bonded to one Ca(2), two equivalent Ca(1), and two equivalent Ni(2) atoms to form distorted OCa3Ni2 trigonal bipyramids that share corners with three equivalent O(3)Ca3Ni2 trigonal bipyramids, edges with two equivalent O(1)CaNi3 tetrahedra,  an edgeedge with one O(3)Ca3Ni2 trigonal bipyramid, and edges with two equivalent O(4)Ca3Ni2 trigonal bipyramids. is represented by the CIF card [CIF]
data_CaNiO2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.022
_cell_length_b   8.543
_cell_length_c   9.332
_cell_angle_alpha   81.665
_cell_angle_beta   80.707
_cell_angle_gamma   80.354
_symmetry_Int_Tables_number   1
_cell_volume   232.688
_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  0.840  0.238  0.565  1.0
  Ca  Ca1  1  0.160  0.762  0.435  1.0
  Ca  Ca2  1  0.585  0.141  0.185  1.0
  Ca  Ca3  1  0.415  0.859  0.815  1.0
  Ni  Ni4  1  0.132  0.544  0.697  1.0
  Ni  Ni5  1  0.715  0.198  0.869  1.0
  Ni  Ni6  1  0.285  0.802  0.131  1.0
  Ni  Ni7  1  0.868  0.456  0.303  1.0
  O  O8  1  0.323  0.594  0.263  1.0
  O  O9  1  0.851  0.815  0.985  1.0
  O  O10  1  0.149  0.185  0.015  1.0
  O  O11  1  0.677  0.406  0.737  1.0
  O  O12  1  0.594  0.694  0.631  1.0
  O  O13  1  0.322  0.113  0.719  1.0
  O  O14  1  0.406  0.306  0.369  1.0
  O  O15  1  0.678  0.887  0.281  1.0
[/CIF]
.
The 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(1), two equivalent O(3), and two equivalent O(4) atoms to form distorted CaO5 trigonal bipyramids that share corners with four equivalent Ca(2)O4 tetrahedra, corners with two equivalent Ni(2)O5 trigonal bipyramids, edges with two equivalent Ca(1)O5 trigonal bipyramids, and  a faceface with one Ni(2)O5 trigonal bipyramid. In the second Ca site, Ca(2) is bonded to one O(3), one O(4), and two equivalent O(2) atoms to form CaO4 tetrahedra that share corners with two equivalent Ca(2)O4 tetrahedra, corners with four equivalent Ca(1)O5 trigonal bipyramids, corners with four equivalent Ni(2)O5 trigonal bipyramids, and  an edgeedge with one Ni(2)O5 trigonal bipyramid. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a rectangular see-saw-like geometry to two equivalent O(1) and two equivalent O(3) atoms. 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 trigonal bipyramids that share corners with four equivalent Ca(2)O4 tetrahedra, corners with two equivalent Ca(1)O5 trigonal bipyramids,  an edgeedge with one Ca(2)O4 tetrahedra, edges with two equivalent Ni(2)O5 trigonal bipyramids, and  a faceface with one Ca(1)O5 trigonal bipyramid. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1), one Ni(2), and two equivalent Ni(1) atoms to form OCaNi3 tetrahedra that share corners with two equivalent O(1)CaNi3 tetrahedra, corners with four equivalent O(3)Ca3Ni2 trigonal bipyramids,  an edgeedge with one O(3)Ca3Ni2 trigonal bipyramid, and edges with two equivalent O(4)Ca3Ni2 trigonal bipyramids. In the second O site, O(2) is bonded in a square co-planar geometry to two equivalent Ca(2) and two equivalent Ni(2) atoms. In the third O site, O(3) is bonded to one Ca(2), two equivalent Ca(1), and two equivalent Ni(1) atoms to form distorted OCa3Ni2 trigonal bipyramids that share corners with four equivalent O(1)CaNi3 tetrahedra, corners with three equivalent O(4)Ca3Ni2 trigonal bipyramids,  an edgeedge with one O(1)CaNi3 tetrahedra,  an edgeedge with one O(4)Ca3Ni2 trigonal bipyramid, and edges with two equivalent O(3)Ca3Ni2 trigonal bipyramids. In the fourth O site, O(4) is bonded to one Ca(2), two equivalent Ca(1), and two equivalent Ni(2) atoms to form distorted OCa3Ni2 trigonal bipyramids that share corners with three equivalent O(3)Ca3Ni2 trigonal bipyramids, edges with two equivalent O(1)CaNi3 tetrahedra,  an edgeedge with one O(3)Ca3Ni2 trigonal bipyramid, and edges with two equivalent O(4)Ca3Ni2 trigonal bipyramids. is represented by the CIF card [CIF]
data_CaNiO2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.022
_cell_length_b   8.543
_cell_length_c   9.332
_cell_angle_alpha   81.665
_cell_angle_beta   80.707
_cell_angle_gamma   80.354
_symmetry_Int_Tables_number   1
_cell_volume   232.688
_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  0.840  0.238  0.565  1.0
  Ca  Ca1  1  0.160  0.762  0.435  1.0
  Ca  Ca2  1  0.585  0.141  0.185  1.0
  Ca  Ca3  1  0.415  0.859  0.815  1.0
  Ni  Ni4  1  0.132  0.544  0.697  1.0
  Ni  Ni5  1  0.715  0.198  0.869  1.0
  Ni  Ni6  1  0.285  0.802  0.131  1.0
  Ni  Ni7  1  0.868  0.456  0.303  1.0
  O  O8  1  0.323  0.594  0.263  1.0
  O  O9  1  0.851  0.815  0.985  1.0
  O  O10  1  0.149  0.185  0.015  1.0
  O  O11  1  0.677  0.406  0.737  1.0
  O  O12  1  0.594  0.694  0.631  1.0
  O  O13  1  0.322  0.113  0.719  1.0
  O  O14  1  0.406  0.306  0.369  1.0
  O  O15  1  0.678  0.887  0.281  1.0
[/CIF]
.