The structure described by CaNi4O9 crystallizes in the monoclinic P2/c space group. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(1), one O(3), one O(4), and two equivalent O(5) atoms to form a mixture of edge and corner-sharing NiO5 trigonal bipyramids. In the second Ni site, Ni(2) is bonded to one O(1), one O(2), one O(5), and two equivalent O(4) atoms to form a mixture of edge and corner-sharing NiO5 trigonal bipyramids. There are five inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to two equivalent Ni(1) and two equivalent Ni(2) atoms. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Ca(1), one Ni(2), and one O(3) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Ca(1), one Ni(1), and one O(2) atom. In the fourth O site, O(4) is bonded to one Ca(1), one Ni(1), and two equivalent Ni(2) atoms to form a mixture of distorted edge and corner-sharing OCaNi3 trigonal pyramids. In the fifth O site, O(5) is bonded in a see-saw-like geometry to one Ca(1), one Ni(2), and two equivalent Ni(1) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_CaNi4O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.850
_cell_length_b   8.228
_cell_length_c   11.540
_cell_angle_alpha   47.048
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   406.568
_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  0.192  0.500  0.250  1.0
  Ca  Ca1  1  0.808  0.500  0.750  1.0
  Ni  Ni2  1  0.563  0.131  0.339  1.0
  Ni  Ni3  1  0.458  0.700  0.467  1.0
  Ni  Ni4  1  0.542  0.700  0.967  1.0
  Ni  Ni5  1  0.437  0.131  0.839  1.0
  Ni  Ni6  1  0.563  0.869  0.161  1.0
  Ni  Ni7  1  0.542  0.300  0.533  1.0
  Ni  Ni8  1  0.437  0.869  0.661  1.0
  Ni  Ni9  1  0.458  0.300  0.033  1.0
  O  O10  1  0.489  0.000  0.250  1.0
  O  O11  1  0.511  0.000  0.750  1.0
  O  O12  1  0.148  0.329  0.926  1.0
  O  O13  1  0.148  0.742  0.650  1.0
  O  O14  1  0.148  0.258  0.850  1.0
  O  O15  1  0.148  0.671  0.574  1.0
  O  O16  1  0.852  0.671  0.074  1.0
  O  O17  1  0.852  0.258  0.350  1.0
  O  O18  1  0.852  0.742  0.150  1.0
  O  O19  1  0.852  0.329  0.426  1.0
  O  O20  1  0.435  0.600  0.356  1.0
  O  O21  1  0.385  0.825  0.037  1.0
  O  O22  1  0.385  0.175  0.463  1.0
  O  O23  1  0.435  0.400  0.144  1.0
  O  O24  1  0.565  0.600  0.856  1.0
  O  O25  1  0.615  0.175  0.963  1.0
  O  O26  1  0.615  0.825  0.537  1.0
  O  O27  1  0.565  0.400  0.644  1.0
[/CIF]
.
The structure described by CaNi4O9 crystallizes in the monoclinic P2/c space group. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(1), one O(3), one O(4), and two equivalent O(5) atoms to form a mixture of edge and corner-sharing NiO5 trigonal bipyramids. In the second Ni site, Ni(2) is bonded to one O(1), one O(2), one O(5), and two equivalent O(4) atoms to form a mixture of edge and corner-sharing NiO5 trigonal bipyramids. There are five inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to two equivalent Ni(1) and two equivalent Ni(2) atoms. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Ca(1), one Ni(2), and one O(3) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Ca(1), one Ni(1), and one O(2) atom. In the fourth O site, O(4) is bonded to one Ca(1), one Ni(1), and two equivalent Ni(2) atoms to form a mixture of distorted edge and corner-sharing OCaNi3 trigonal pyramids. In the fifth O site, O(5) is bonded in a see-saw-like geometry to one Ca(1), one Ni(2), and two equivalent Ni(1) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_CaNi4O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.850
_cell_length_b   8.228
_cell_length_c   11.540
_cell_angle_alpha   47.048
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   406.568
_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  0.192  0.500  0.250  1.0
  Ca  Ca1  1  0.808  0.500  0.750  1.0
  Ni  Ni2  1  0.563  0.131  0.339  1.0
  Ni  Ni3  1  0.458  0.700  0.467  1.0
  Ni  Ni4  1  0.542  0.700  0.967  1.0
  Ni  Ni5  1  0.437  0.131  0.839  1.0
  Ni  Ni6  1  0.563  0.869  0.161  1.0
  Ni  Ni7  1  0.542  0.300  0.533  1.0
  Ni  Ni8  1  0.437  0.869  0.661  1.0
  Ni  Ni9  1  0.458  0.300  0.033  1.0
  O  O10  1  0.489  0.000  0.250  1.0
  O  O11  1  0.511  0.000  0.750  1.0
  O  O12  1  0.148  0.329  0.926  1.0
  O  O13  1  0.148  0.742  0.650  1.0
  O  O14  1  0.148  0.258  0.850  1.0
  O  O15  1  0.148  0.671  0.574  1.0
  O  O16  1  0.852  0.671  0.074  1.0
  O  O17  1  0.852  0.258  0.350  1.0
  O  O18  1  0.852  0.742  0.150  1.0
  O  O19  1  0.852  0.329  0.426  1.0
  O  O20  1  0.435  0.600  0.356  1.0
  O  O21  1  0.385  0.825  0.037  1.0
  O  O22  1  0.385  0.175  0.463  1.0
  O  O23  1  0.435  0.400  0.144  1.0
  O  O24  1  0.565  0.600  0.856  1.0
  O  O25  1  0.615  0.175  0.963  1.0
  O  O26  1  0.615  0.825  0.537  1.0
  O  O27  1  0.565  0.400  0.644  1.0
[/CIF]
.