The structure described by Na4Ni2O5 crystallizes in the monoclinic P2_1/c space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded in a 5-coordinate geometry to one O(1), one O(4), one O(5), and two equivalent O(3) atoms. In the second Na site, Na(2) is bonded to one O(2), one O(3), one O(5), and two equivalent O(1) atoms to form distorted NaO5 trigonal bipyramids that share  a cornercorner with one Ni(1)O4 tetrahedra, corners with two equivalent Ni(2)O4 tetrahedra, edges with two equivalent Ni(1)O4 tetrahedra, and  an edgeedge with one Na(2)O5 trigonal bipyramid. In the third Na site, Na(3) is bonded in a 5-coordinate geometry to one O(2), one O(4), one O(5), and two equivalent O(1) atoms. In the fourth Na site, Na(4) is bonded in a 5-coordinate geometry to one O(2), one O(4), one O(5), and two equivalent O(3) atoms. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(1), one O(5), and two equivalent O(2) atoms to form NiO4 tetrahedra that share  a cornercorner with one Ni(2)O4 tetrahedra, corners with two equivalent Ni(1)O4 tetrahedra,  a cornercorner with one Na(2)O5 trigonal bipyramid, and edges with two equivalent Na(2)O5 trigonal bipyramids. In the second Ni site, Ni(2) is bonded to one O(3), one O(5), and two equivalent O(4) atoms to form NiO4 tetrahedra that share  a cornercorner with one Ni(1)O4 tetrahedra, corners with two equivalent Ni(2)O4 tetrahedra, and corners with two equivalent Na(2)O5 trigonal bipyramids. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), two equivalent Na(2), two equivalent Na(3), and one Ni(1) atom to form distorted ONa5Ni octahedra that share corners with two equivalent O(5)Na4Ni2 octahedra, corners with four equivalent O(3)Na5Ni octahedra, edges with two equivalent O(5)Na4Ni2 octahedra, and edges with two equivalent O(1)Na5Ni octahedra. The corner-sharing octahedral tilt angles range from 11-73°. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Na(2), one Na(3), one Na(4), and two equivalent Ni(1) atoms. In the third O site, O(3) is bonded to one Na(2), two equivalent Na(1), two equivalent Na(4), and one Ni(2) atom to form ONa5Ni octahedra that share corners with two equivalent O(5)Na4Ni2 octahedra, corners with four equivalent O(1)Na5Ni octahedra, edges with two equivalent O(5)Na4Ni2 octahedra, and edges with two equivalent O(3)Na5Ni octahedra. The corner-sharing octahedral tilt angles range from 16-75°. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to one Na(1), one Na(3), one Na(4), and two equivalent Ni(2) atoms. In the fifth O site, O(5) is bonded to one Na(1), one Na(2), one Na(3), one Na(4), one Ni(1), and one Ni(2) atom to form a mixture of distorted corner and edge-sharing ONa4Ni2 octahedra. The corner-sharing octahedral tilt angles range from 11-75°. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na4Ni2O5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.620
_cell_length_b   9.074
_cell_length_c   12.694
_cell_angle_alpha   62.513
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   574.250
_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
  Na  Na0  1  0.928  0.199  0.963  1.0
  Na  Na1  1  0.588  0.702  0.960  1.0
  Na  Na2  1  0.119  0.609  0.870  1.0
  Na  Na3  1  0.373  0.125  0.861  1.0
  Na  Na4  1  0.619  0.391  0.630  1.0
  Na  Na5  1  0.873  0.875  0.639  1.0
  Na  Na6  1  0.428  0.801  0.537  1.0
  Na  Na7  1  0.912  0.702  0.460  1.0
  Na  Na8  1  0.088  0.298  0.540  1.0
  Na  Na9  1  0.572  0.199  0.463  1.0
  Na  Na10  1  0.127  0.125  0.361  1.0
  Na  Na11  1  0.381  0.609  0.370  1.0
  Na  Na12  1  0.627  0.875  0.139  1.0
  Na  Na13  1  0.881  0.391  0.130  1.0
  Na  Na14  1  0.412  0.298  0.040  1.0
  Na  Na15  1  0.072  0.801  0.037  1.0
  Ni  Ni16  1  0.617  0.542  0.800  1.0
  Ni  Ni17  1  0.117  0.458  0.700  1.0
  Ni  Ni18  1  0.844  0.044  0.797  1.0
  Ni  Ni19  1  0.344  0.956  0.703  1.0
  Ni  Ni20  1  0.656  0.044  0.297  1.0
  Ni  Ni21  1  0.156  0.956  0.203  1.0
  Ni  Ni22  1  0.883  0.542  0.300  1.0
  Ni  Ni23  1  0.383  0.458  0.200  1.0
  O  O24  1  0.764  0.451  0.944  1.0
  O  O25  1  0.341  0.411  0.823  1.0
  O  O26  1  0.735  0.971  0.947  1.0
  O  O27  1  0.082  0.891  0.807  1.0
  O  O28  1  0.520  0.758  0.759  1.0
  O  O29  1  0.841  0.589  0.677  1.0
  O  O30  1  0.020  0.242  0.741  1.0
  O  O31  1  0.582  0.109  0.693  1.0
  O  O32  1  0.264  0.549  0.556  1.0
  O  O33  1  0.235  0.029  0.553  1.0
  O  O34  1  0.765  0.971  0.447  1.0
  O  O35  1  0.736  0.451  0.444  1.0
  O  O36  1  0.418  0.891  0.307  1.0
  O  O37  1  0.980  0.758  0.259  1.0
  O  O38  1  0.159  0.411  0.323  1.0
  O  O39  1  0.480  0.242  0.241  1.0
  O  O40  1  0.918  0.109  0.193  1.0
  O  O41  1  0.265  0.029  0.053  1.0
  O  O42  1  0.659  0.589  0.177  1.0
  O  O43  1  0.236  0.549  0.056  1.0
[/CIF]
.
The structure described by Na4Ni2O5 crystallizes in the monoclinic P2_1/c space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded in a 5-coordinate geometry to one O(1), one O(4), one O(5), and two equivalent O(3) atoms. In the second Na site, Na(2) is bonded to one O(2), one O(3), one O(5), and two equivalent O(1) atoms to form distorted NaO5 trigonal bipyramids that share  a cornercorner with one Ni(1)O4 tetrahedra, corners with two equivalent Ni(2)O4 tetrahedra, edges with two equivalent Ni(1)O4 tetrahedra, and  an edgeedge with one Na(2)O5 trigonal bipyramid. In the third Na site, Na(3) is bonded in a 5-coordinate geometry to one O(2), one O(4), one O(5), and two equivalent O(1) atoms. In the fourth Na site, Na(4) is bonded in a 5-coordinate geometry to one O(2), one O(4), one O(5), and two equivalent O(3) atoms. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(1), one O(5), and two equivalent O(2) atoms to form NiO4 tetrahedra that share  a cornercorner with one Ni(2)O4 tetrahedra, corners with two equivalent Ni(1)O4 tetrahedra,  a cornercorner with one Na(2)O5 trigonal bipyramid, and edges with two equivalent Na(2)O5 trigonal bipyramids. In the second Ni site, Ni(2) is bonded to one O(3), one O(5), and two equivalent O(4) atoms to form NiO4 tetrahedra that share  a cornercorner with one Ni(1)O4 tetrahedra, corners with two equivalent Ni(2)O4 tetrahedra, and corners with two equivalent Na(2)O5 trigonal bipyramids. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), two equivalent Na(2), two equivalent Na(3), and one Ni(1) atom to form distorted ONa5Ni octahedra that share corners with two equivalent O(5)Na4Ni2 octahedra, corners with four equivalent O(3)Na5Ni octahedra, edges with two equivalent O(5)Na4Ni2 octahedra, and edges with two equivalent O(1)Na5Ni octahedra. The corner-sharing octahedral tilt angles range from 11-73°. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Na(2), one Na(3), one Na(4), and two equivalent Ni(1) atoms. In the third O site, O(3) is bonded to one Na(2), two equivalent Na(1), two equivalent Na(4), and one Ni(2) atom to form ONa5Ni octahedra that share corners with two equivalent O(5)Na4Ni2 octahedra, corners with four equivalent O(1)Na5Ni octahedra, edges with two equivalent O(5)Na4Ni2 octahedra, and edges with two equivalent O(3)Na5Ni octahedra. The corner-sharing octahedral tilt angles range from 16-75°. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to one Na(1), one Na(3), one Na(4), and two equivalent Ni(2) atoms. In the fifth O site, O(5) is bonded to one Na(1), one Na(2), one Na(3), one Na(4), one Ni(1), and one Ni(2) atom to form a mixture of distorted corner and edge-sharing ONa4Ni2 octahedra. The corner-sharing octahedral tilt angles range from 11-75°. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na4Ni2O5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.620
_cell_length_b   9.074
_cell_length_c   12.694
_cell_angle_alpha   62.513
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   574.250
_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
  Na  Na0  1  0.928  0.199  0.963  1.0
  Na  Na1  1  0.588  0.702  0.960  1.0
  Na  Na2  1  0.119  0.609  0.870  1.0
  Na  Na3  1  0.373  0.125  0.861  1.0
  Na  Na4  1  0.619  0.391  0.630  1.0
  Na  Na5  1  0.873  0.875  0.639  1.0
  Na  Na6  1  0.428  0.801  0.537  1.0
  Na  Na7  1  0.912  0.702  0.460  1.0
  Na  Na8  1  0.088  0.298  0.540  1.0
  Na  Na9  1  0.572  0.199  0.463  1.0
  Na  Na10  1  0.127  0.125  0.361  1.0
  Na  Na11  1  0.381  0.609  0.370  1.0
  Na  Na12  1  0.627  0.875  0.139  1.0
  Na  Na13  1  0.881  0.391  0.130  1.0
  Na  Na14  1  0.412  0.298  0.040  1.0
  Na  Na15  1  0.072  0.801  0.037  1.0
  Ni  Ni16  1  0.617  0.542  0.800  1.0
  Ni  Ni17  1  0.117  0.458  0.700  1.0
  Ni  Ni18  1  0.844  0.044  0.797  1.0
  Ni  Ni19  1  0.344  0.956  0.703  1.0
  Ni  Ni20  1  0.656  0.044  0.297  1.0
  Ni  Ni21  1  0.156  0.956  0.203  1.0
  Ni  Ni22  1  0.883  0.542  0.300  1.0
  Ni  Ni23  1  0.383  0.458  0.200  1.0
  O  O24  1  0.764  0.451  0.944  1.0
  O  O25  1  0.341  0.411  0.823  1.0
  O  O26  1  0.735  0.971  0.947  1.0
  O  O27  1  0.082  0.891  0.807  1.0
  O  O28  1  0.520  0.758  0.759  1.0
  O  O29  1  0.841  0.589  0.677  1.0
  O  O30  1  0.020  0.242  0.741  1.0
  O  O31  1  0.582  0.109  0.693  1.0
  O  O32  1  0.264  0.549  0.556  1.0
  O  O33  1  0.235  0.029  0.553  1.0
  O  O34  1  0.765  0.971  0.447  1.0
  O  O35  1  0.736  0.451  0.444  1.0
  O  O36  1  0.418  0.891  0.307  1.0
  O  O37  1  0.980  0.758  0.259  1.0
  O  O38  1  0.159  0.411  0.323  1.0
  O  O39  1  0.480  0.242  0.241  1.0
  O  O40  1  0.918  0.109  0.193  1.0
  O  O41  1  0.265  0.029  0.053  1.0
  O  O42  1  0.659  0.589  0.177  1.0
  O  O43  1  0.236  0.549  0.056  1.0
[/CIF]
.