The material described by Ca(NiO2)2 crystallizes in the orthorhombic Cmcm space group. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), and four equivalent O(1) atoms. Ni(1) is bonded to one O(2), two equivalent O(3), and three equivalent O(1) atoms to form a mixture of corner and edge-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles range from 0-46°. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ca(1) and three equivalent Ni(1) atoms to form distorted OCa2Ni3 square pyramids that share corners with four equivalent O(3)Ca2Ni4 octahedra, corners with two equivalent O(1)Ca2Ni3 square pyramids, corners with five equivalent O(2)Ca2Ni2 tetrahedra, edges with three equivalent O(3)Ca2Ni4 octahedra, edges with five equivalent O(1)Ca2Ni3 square pyramids, and  an edgeedge with one O(2)Ca2Ni2 tetrahedra. The corner-sharing octahedral tilt angles range from 8-43°. In the second O site, O(2) is bonded to two equivalent Ca(1) and two equivalent Ni(1) atoms to form distorted OCa2Ni2 tetrahedra that share corners with ten equivalent O(1)Ca2Ni3 square pyramids, corners with two equivalent O(2)Ca2Ni2 tetrahedra, edges with four equivalent O(3)Ca2Ni4 octahedra, and edges with two equivalent O(1)Ca2Ni3 square pyramids. In the third O site, O(3) is bonded to two equivalent Ca(1) and four equivalent Ni(1) atoms to form OCa2Ni4 octahedra that share corners with two equivalent O(3)Ca2Ni4 octahedra, corners with eight equivalent O(1)Ca2Ni3 square pyramids, edges with two equivalent O(3)Ca2Ni4 octahedra, edges with six equivalent O(1)Ca2Ni3 square pyramids, and edges with four equivalent O(2)Ca2Ni2 tetrahedra. The corner-sharing octahedral tilt angles are 47°. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ca(NiO2)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.135
_cell_length_b   5.135
_cell_length_c   9.620
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   145.215
_symmetry_Int_Tables_number   1
_cell_volume   144.733
_cell_formula_units_Z   2
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  0.606  0.394  0.750  1.0
  Ca  Ca1  1  0.394  0.606  0.250  1.0
  Ni  Ni2  1  0.138  0.862  0.068  1.0
  Ni  Ni3  1  0.862  0.138  0.932  1.0
  Ni  Ni4  1  0.138  0.862  0.432  1.0
  Ni  Ni5  1  0.862  0.138  0.568  1.0
  O  O6  1  0.769  0.231  0.394  1.0
  O  O7  1  0.231  0.769  0.606  1.0
  O  O8  1  0.231  0.769  0.894  1.0
  O  O9  1  0.769  0.231  0.106  1.0
  O  O10  1  0.062  0.938  0.250  1.0
  O  O11  1  0.938  0.062  0.750  1.0
  O  O12  1  0.500  0.500  0.000  1.0
  O  O13  1  0.500  0.500  0.500  1.0
[/CIF]
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The material described by Ca(NiO2)2 crystallizes in the orthorhombic Cmcm space group. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), and four equivalent O(1) atoms. Ni(1) is bonded to one O(2), two equivalent O(3), and three equivalent O(1) atoms to form a mixture of corner and edge-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles range from 0-46°. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ca(1) and three equivalent Ni(1) atoms to form distorted OCa2Ni3 square pyramids that share corners with four equivalent O(3)Ca2Ni4 octahedra, corners with two equivalent O(1)Ca2Ni3 square pyramids, corners with five equivalent O(2)Ca2Ni2 tetrahedra, edges with three equivalent O(3)Ca2Ni4 octahedra, edges with five equivalent O(1)Ca2Ni3 square pyramids, and  an edgeedge with one O(2)Ca2Ni2 tetrahedra. The corner-sharing octahedral tilt angles range from 8-43°. In the second O site, O(2) is bonded to two equivalent Ca(1) and two equivalent Ni(1) atoms to form distorted OCa2Ni2 tetrahedra that share corners with ten equivalent O(1)Ca2Ni3 square pyramids, corners with two equivalent O(2)Ca2Ni2 tetrahedra, edges with four equivalent O(3)Ca2Ni4 octahedra, and edges with two equivalent O(1)Ca2Ni3 square pyramids. In the third O site, O(3) is bonded to two equivalent Ca(1) and four equivalent Ni(1) atoms to form OCa2Ni4 octahedra that share corners with two equivalent O(3)Ca2Ni4 octahedra, corners with eight equivalent O(1)Ca2Ni3 square pyramids, edges with two equivalent O(3)Ca2Ni4 octahedra, edges with six equivalent O(1)Ca2Ni3 square pyramids, and edges with four equivalent O(2)Ca2Ni2 tetrahedra. The corner-sharing octahedral tilt angles are 47°. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ca(NiO2)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.135
_cell_length_b   5.135
_cell_length_c   9.620
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   145.215
_symmetry_Int_Tables_number   1
_cell_volume   144.733
_cell_formula_units_Z   2
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  0.606  0.394  0.750  1.0
  Ca  Ca1  1  0.394  0.606  0.250  1.0
  Ni  Ni2  1  0.138  0.862  0.068  1.0
  Ni  Ni3  1  0.862  0.138  0.932  1.0
  Ni  Ni4  1  0.138  0.862  0.432  1.0
  Ni  Ni5  1  0.862  0.138  0.568  1.0
  O  O6  1  0.769  0.231  0.394  1.0
  O  O7  1  0.231  0.769  0.606  1.0
  O  O8  1  0.231  0.769  0.894  1.0
  O  O9  1  0.769  0.231  0.106  1.0
  O  O10  1  0.062  0.938  0.250  1.0
  O  O11  1  0.938  0.062  0.750  1.0
  O  O12  1  0.500  0.500  0.000  1.0
  O  O13  1  0.500  0.500  0.500  1.0
[/CIF]
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