The structure described by CaNi2O5 crystallizes in the orthorhombic Pmmn space group. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), and four equivalent O(3) atoms. Ni(1) is bonded to one O(1), one O(3), and three equivalent O(2) atoms to form a mixture of edge and corner-sharing NiO5 trigonal bipyramids. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ca(1) and two equivalent Ni(1) atoms to form OCa2Ni2 tetrahedra that share corners with two equivalent O(1)Ca2Ni2 tetrahedra, corners with two equivalent O(2)CaNi3 trigonal pyramids, and edges with four equivalent O(2)CaNi3 trigonal pyramids. In the second O site, O(2) is bonded to one Ca(1) and three equivalent Ni(1) atoms to form distorted OCaNi3 trigonal pyramids that share  a cornercorner with one O(1)Ca2Ni2 tetrahedra, corners with three equivalent O(2)CaNi3 trigonal pyramids, edges with two equivalent O(1)Ca2Ni2 tetrahedra, and edges with two equivalent O(2)CaNi3 trigonal pyramids. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Ca(1), one Ni(1), and one O(3) atom. is represented by the CIF file [CIF]
data_CaNi2O5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.719
_cell_length_b   5.404
_cell_length_c   10.853
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   218.147
_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  0.500  0.131  0.000  1.0
  Ca  Ca1  1  0.000  0.869  0.500  1.0
  Ni  Ni2  1  0.000  0.529  0.848  1.0
  Ni  Ni3  1  0.500  0.471  0.652  1.0
  Ni  Ni4  1  0.500  0.471  0.348  1.0
  Ni  Ni5  1  0.000  0.529  0.152  1.0
  O  O6  1  0.500  0.625  0.500  1.0
  O  O7  1  0.000  0.375  0.000  1.0
  O  O8  1  0.500  0.431  0.823  1.0
  O  O9  1  0.000  0.569  0.677  1.0
  O  O10  1  0.500  0.431  0.177  1.0
  O  O11  1  0.000  0.569  0.323  1.0
  O  O12  1  0.000  0.861  0.066  1.0
  O  O13  1  0.500  0.139  0.434  1.0
  O  O14  1  0.500  0.139  0.566  1.0
  O  O15  1  0.000  0.861  0.934  1.0
[/CIF]
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The structure described by CaNi2O5 crystallizes in the orthorhombic Pmmn space group. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), and four equivalent O(3) atoms. Ni(1) is bonded to one O(1), one O(3), and three equivalent O(2) atoms to form a mixture of edge and corner-sharing NiO5 trigonal bipyramids. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ca(1) and two equivalent Ni(1) atoms to form OCa2Ni2 tetrahedra that share corners with two equivalent O(1)Ca2Ni2 tetrahedra, corners with two equivalent O(2)CaNi3 trigonal pyramids, and edges with four equivalent O(2)CaNi3 trigonal pyramids. In the second O site, O(2) is bonded to one Ca(1) and three equivalent Ni(1) atoms to form distorted OCaNi3 trigonal pyramids that share  a cornercorner with one O(1)Ca2Ni2 tetrahedra, corners with three equivalent O(2)CaNi3 trigonal pyramids, edges with two equivalent O(1)Ca2Ni2 tetrahedra, and edges with two equivalent O(2)CaNi3 trigonal pyramids. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Ca(1), one Ni(1), and one O(3) atom. is represented by the CIF file [CIF]
data_CaNi2O5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.719
_cell_length_b   5.404
_cell_length_c   10.853
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   218.147
_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  0.500  0.131  0.000  1.0
  Ca  Ca1  1  0.000  0.869  0.500  1.0
  Ni  Ni2  1  0.000  0.529  0.848  1.0
  Ni  Ni3  1  0.500  0.471  0.652  1.0
  Ni  Ni4  1  0.500  0.471  0.348  1.0
  Ni  Ni5  1  0.000  0.529  0.152  1.0
  O  O6  1  0.500  0.625  0.500  1.0
  O  O7  1  0.000  0.375  0.000  1.0
  O  O8  1  0.500  0.431  0.823  1.0
  O  O9  1  0.000  0.569  0.677  1.0
  O  O10  1  0.500  0.431  0.177  1.0
  O  O11  1  0.000  0.569  0.323  1.0
  O  O12  1  0.000  0.861  0.066  1.0
  O  O13  1  0.500  0.139  0.434  1.0
  O  O14  1  0.500  0.139  0.566  1.0
  O  O15  1  0.000  0.861  0.934  1.0
[/CIF]
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