The structure described by Na2Mg(NiO2)5 crystallizes in the triclinic P1 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one O(10), one O(2), one O(5), one O(6), one O(8), and one O(9) atom. In the second Na site, Na(2) is bonded in a 5-coordinate geometry to one O(10), one O(4), one O(6), one O(8), and one O(9) atom. Mg(1) is bonded to one O(1), one O(3), one O(4), one O(5), and one O(7) atom to form distorted MgO5 trigonal bipyramids that share corners with two equivalent Ni(2)O6 octahedra, corners with two equivalent Ni(5)O6 octahedra, corners with three equivalent Ni(4)O6 octahedra,  an edgeedge with one Ni(1)O6 octahedra,  an edgeedge with one Ni(2)O6 octahedra, and edges with two equivalent Ni(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 10-58°. There are five inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(1), one O(10), one O(2), one O(5), one O(6), and one O(9) atom to form NiO6 octahedra that share  an edgeedge with one Ni(3)O6 octahedra,  an edgeedge with one Ni(4)O6 octahedra, edges with two equivalent Ni(2)O6 octahedra, edges with two equivalent Ni(5)O6 octahedra, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. In the second Ni site, Ni(2) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form NiO6 octahedra that share corners with two equivalent Mg(1)O5 trigonal bipyramids,  an edgeedge with one Ni(4)O6 octahedra,  an edgeedge with one Ni(5)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, edges with two equivalent Ni(3)O6 octahedra, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. In the third Ni site, Ni(3) is bonded to one O(1), one O(2), one O(3), one O(4), one O(7), and one O(8) atom to form NiO6 octahedra that share  an edgeedge with one Ni(1)O6 octahedra,  an edgeedge with one Ni(5)O6 octahedra, edges with two equivalent Ni(2)O6 octahedra, edges with two equivalent Ni(4)O6 octahedra, and edges with two equivalent Mg(1)O5 trigonal bipyramids. In the fourth Ni site, Ni(4) is bonded to one O(10), one O(3), one O(4), one O(7), one O(8), and one O(9) atom to form NiO6 octahedra that share corners with three equivalent Mg(1)O5 trigonal bipyramids,  an edgeedge with one Ni(1)O6 octahedra,  an edgeedge with one Ni(2)O6 octahedra, edges with two equivalent Ni(3)O6 octahedra, and edges with two equivalent Ni(5)O6 octahedra. In the fifth Ni site, Ni(5) is bonded to one O(10), one O(5), one O(6), one O(7), one O(8), and one O(9) atom to form NiO6 octahedra that share corners with two equivalent Mg(1)O5 trigonal bipyramids,  an edgeedge with one Ni(2)O6 octahedra,  an edgeedge with one Ni(3)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, and edges with two equivalent Ni(4)O6 octahedra. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Ni(1), one Ni(2), and one Ni(3) atom. In the second O site, O(2) is bonded to one Na(1), one Ni(1), one Ni(2), and one Ni(3) atom to form distorted ONaNi3 trigonal pyramids that share  a cornercorner with one O(5)NaMgNi3 square pyramid, corners with two equivalent O(8)Na2Ni3 square pyramids, corners with two equivalent O(9)Na2Ni3 square pyramids,  a cornercorner with one O(6)Na2Ni3 trigonal bipyramid, corners with two equivalent O(3)MgNi3 trigonal pyramids,  an edgeedge with one O(4)NaMgNi3 square pyramid,  an edgeedge with one O(5)NaMgNi3 square pyramid, and  an edgeedge with one O(6)Na2Ni3 trigonal bipyramid. In the third O site, O(3) is bonded to one Mg(1), one Ni(2), one Ni(3), and one Ni(4) atom to form OMgNi3 trigonal pyramids that share  a cornercorner with one O(9)Na2Ni3 square pyramid, corners with two equivalent O(4)NaMgNi3 square pyramids, corners with two equivalent O(5)NaMgNi3 square pyramids,  a cornercorner with one O(6)Na2Ni3 trigonal bipyramid, corners with two equivalent O(2)NaNi3 trigonal pyramids,  an edgeedge with one O(8)Na2Ni3 square pyramid, and  an edgeedge with one O(4)NaMgNi3 square pyramid. In the fourth O site, O(4) is bonded to one Na(2), one Mg(1), one Ni(2), one Ni(3), and one Ni(4) atom to form ONaMgNi3 square pyramids that share  a cornercorner with one O(8)Na2Ni3 square pyramid, corners with two equivalent O(6)Na2Ni3 trigonal bipyramids, corners with two equivalent O(3)MgNi3 trigonal pyramids,  an edgeedge with one O(8)Na2Ni3 square pyramid,  an edgeedge with one O(9)Na2Ni3 square pyramid,  an edgeedge with one O(5)NaMgNi3 square pyramid,  an edgeedge with one O(3)MgNi3 trigonal pyramid, and  an edgeedge with one O(2)NaNi3 trigonal pyramid. In the fifth O site, O(5) is bonded to one Na(1), one Mg(1), one Ni(1), one Ni(2), and one Ni(5) atom to form ONaMgNi3 square pyramids that share  a cornercorner with one O(9)Na2Ni3 square pyramid, corners with two equivalent O(6)Na2Ni3 trigonal bipyramids,  a cornercorner with one O(2)NaNi3 trigonal pyramid, corners with two equivalent O(3)MgNi3 trigonal pyramids,  an edgeedge with one O(8)Na2Ni3 square pyramid,  an edgeedge with one O(9)Na2Ni3 square pyramid,  an edgeedge with one O(4)NaMgNi3 square pyramid,  an edgeedge with one O(6)Na2Ni3 trigonal bipyramid, and  an edgeedge with one O(2)NaNi3 trigonal pyramid. In the sixth O site, O(6) is bonded to one Na(1), one Na(2), one Ni(1), one Ni(2), and one Ni(5) atom to form distorted ONa2Ni3 trigonal bipyramids that share corners with two equivalent O(4)NaMgNi3 square pyramids, corners with two equivalent O(5)NaMgNi3 square pyramids, corners with three equivalent O(8)Na2Ni3 square pyramids,  a cornercorner with one O(3)MgNi3 trigonal pyramid,  a cornercorner with one O(2)NaNi3 trigonal pyramid,  an edgeedge with one O(5)NaMgNi3 square pyramid, edges with two equivalent O(9)Na2Ni3 square pyramids, and  an edgeedge with one O(2)NaNi3 trigonal pyramid. In the seventh O site, O(7) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Ni(3), one Ni(4), and one Ni(5) atom. In the eighth O site, O(8) is bonded to one Na(1), one Na(2), one Ni(3), one Ni(4), and one Ni(5) atom to form ONa2Ni3 square pyramids that share  a cornercorner with one O(4)NaMgNi3 square pyramid, corners with three equivalent O(6)Na2Ni3 trigonal bipyramids, corners with two equivalent O(2)NaNi3 trigonal pyramids,  an edgeedge with one O(4)NaMgNi3 square pyramid,  an edgeedge with one O(5)NaMgNi3 square pyramid, edges with two equivalent O(9)Na2Ni3 square pyramids, and  an edgeedge with one O(3)MgNi3 trigonal pyramid. In the ninth O site, O(9) is bonded to one Na(1), one Na(2), one Ni(1), one Ni(4), and one Ni(5) atom to form ONa2Ni3 square pyramids that share  a cornercorner with one O(5)NaMgNi3 square pyramid,  a cornercorner with one O(3)MgNi3 trigonal pyramid, corners with two equivalent O(2)NaNi3 trigonal pyramids,  an edgeedge with one O(4)NaMgNi3 square pyramid,  an edgeedge with one O(5)NaMgNi3 square pyramid, edges with two equivalent O(8)Na2Ni3 square pyramids, and edges with two equivalent O(6)Na2Ni3 trigonal bipyramids. In the tenth O site, O(10) is bonded in a 5-coordinate geometry to one Na(1), one Na(2), one Ni(1), one Ni(4), and one Ni(5) atom. is represented by the CIF card [CIF]
data_Na2Mg(NiO2)5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.636
_cell_length_b   5.014
_cell_length_c   5.746
_cell_angle_alpha   79.112
_cell_angle_beta   111.676
_cell_angle_gamma   79.335
_symmetry_Int_Tables_number   1
_cell_volume   192.783
_cell_formula_units_Z   1
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  0.887  0.998  0.407  1.0
  Na  Na1  1  0.727  0.574  0.253  1.0
  Mg  Mg2  1  0.311  0.785  0.847  1.0
  Ni  Ni3  1  0.992  0.013  0.989  1.0
  Ni  Ni4  1  0.189  0.413  0.193  1.0
  Ni  Ni5  1  0.383  0.814  0.393  1.0
  Ni  Ni6  1  0.574  0.209  0.614  1.0
  Ni  Ni7  1  0.788  0.610  0.798  1.0
  O  O8  1  0.244  0.074  0.050  1.0
  O  O9  1  0.137  0.758  0.325  1.0
  O  O10  1  0.334  0.098  0.554  1.0
  O  O11  1  0.438  0.529  0.241  1.0
  O  O12  1  0.050  0.730  0.835  1.0
  O  O13  1  0.932  0.324  0.118  1.0
  O  O14  1  0.502  0.550  0.729  1.0
  O  O15  1  0.629  0.886  0.469  1.0
  O  O16  1  0.826  0.291  0.663  1.0
  O  O17  1  0.762  0.907  0.962  1.0
[/CIF]
.
The structure described by Na2Mg(NiO2)5 crystallizes in the triclinic P1 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one O(10), one O(2), one O(5), one O(6), one O(8), and one O(9) atom. In the second Na site, Na(2) is bonded in a 5-coordinate geometry to one O(10), one O(4), one O(6), one O(8), and one O(9) atom. Mg(1) is bonded to one O(1), one O(3), one O(4), one O(5), and one O(7) atom to form distorted MgO5 trigonal bipyramids that share corners with two equivalent Ni(2)O6 octahedra, corners with two equivalent Ni(5)O6 octahedra, corners with three equivalent Ni(4)O6 octahedra,  an edgeedge with one Ni(1)O6 octahedra,  an edgeedge with one Ni(2)O6 octahedra, and edges with two equivalent Ni(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 10-58°. There are five inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(1), one O(10), one O(2), one O(5), one O(6), and one O(9) atom to form NiO6 octahedra that share  an edgeedge with one Ni(3)O6 octahedra,  an edgeedge with one Ni(4)O6 octahedra, edges with two equivalent Ni(2)O6 octahedra, edges with two equivalent Ni(5)O6 octahedra, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. In the second Ni site, Ni(2) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form NiO6 octahedra that share corners with two equivalent Mg(1)O5 trigonal bipyramids,  an edgeedge with one Ni(4)O6 octahedra,  an edgeedge with one Ni(5)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, edges with two equivalent Ni(3)O6 octahedra, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. In the third Ni site, Ni(3) is bonded to one O(1), one O(2), one O(3), one O(4), one O(7), and one O(8) atom to form NiO6 octahedra that share  an edgeedge with one Ni(1)O6 octahedra,  an edgeedge with one Ni(5)O6 octahedra, edges with two equivalent Ni(2)O6 octahedra, edges with two equivalent Ni(4)O6 octahedra, and edges with two equivalent Mg(1)O5 trigonal bipyramids. In the fourth Ni site, Ni(4) is bonded to one O(10), one O(3), one O(4), one O(7), one O(8), and one O(9) atom to form NiO6 octahedra that share corners with three equivalent Mg(1)O5 trigonal bipyramids,  an edgeedge with one Ni(1)O6 octahedra,  an edgeedge with one Ni(2)O6 octahedra, edges with two equivalent Ni(3)O6 octahedra, and edges with two equivalent Ni(5)O6 octahedra. In the fifth Ni site, Ni(5) is bonded to one O(10), one O(5), one O(6), one O(7), one O(8), and one O(9) atom to form NiO6 octahedra that share corners with two equivalent Mg(1)O5 trigonal bipyramids,  an edgeedge with one Ni(2)O6 octahedra,  an edgeedge with one Ni(3)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, and edges with two equivalent Ni(4)O6 octahedra. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Ni(1), one Ni(2), and one Ni(3) atom. In the second O site, O(2) is bonded to one Na(1), one Ni(1), one Ni(2), and one Ni(3) atom to form distorted ONaNi3 trigonal pyramids that share  a cornercorner with one O(5)NaMgNi3 square pyramid, corners with two equivalent O(8)Na2Ni3 square pyramids, corners with two equivalent O(9)Na2Ni3 square pyramids,  a cornercorner with one O(6)Na2Ni3 trigonal bipyramid, corners with two equivalent O(3)MgNi3 trigonal pyramids,  an edgeedge with one O(4)NaMgNi3 square pyramid,  an edgeedge with one O(5)NaMgNi3 square pyramid, and  an edgeedge with one O(6)Na2Ni3 trigonal bipyramid. In the third O site, O(3) is bonded to one Mg(1), one Ni(2), one Ni(3), and one Ni(4) atom to form OMgNi3 trigonal pyramids that share  a cornercorner with one O(9)Na2Ni3 square pyramid, corners with two equivalent O(4)NaMgNi3 square pyramids, corners with two equivalent O(5)NaMgNi3 square pyramids,  a cornercorner with one O(6)Na2Ni3 trigonal bipyramid, corners with two equivalent O(2)NaNi3 trigonal pyramids,  an edgeedge with one O(8)Na2Ni3 square pyramid, and  an edgeedge with one O(4)NaMgNi3 square pyramid. In the fourth O site, O(4) is bonded to one Na(2), one Mg(1), one Ni(2), one Ni(3), and one Ni(4) atom to form ONaMgNi3 square pyramids that share  a cornercorner with one O(8)Na2Ni3 square pyramid, corners with two equivalent O(6)Na2Ni3 trigonal bipyramids, corners with two equivalent O(3)MgNi3 trigonal pyramids,  an edgeedge with one O(8)Na2Ni3 square pyramid,  an edgeedge with one O(9)Na2Ni3 square pyramid,  an edgeedge with one O(5)NaMgNi3 square pyramid,  an edgeedge with one O(3)MgNi3 trigonal pyramid, and  an edgeedge with one O(2)NaNi3 trigonal pyramid. In the fifth O site, O(5) is bonded to one Na(1), one Mg(1), one Ni(1), one Ni(2), and one Ni(5) atom to form ONaMgNi3 square pyramids that share  a cornercorner with one O(9)Na2Ni3 square pyramid, corners with two equivalent O(6)Na2Ni3 trigonal bipyramids,  a cornercorner with one O(2)NaNi3 trigonal pyramid, corners with two equivalent O(3)MgNi3 trigonal pyramids,  an edgeedge with one O(8)Na2Ni3 square pyramid,  an edgeedge with one O(9)Na2Ni3 square pyramid,  an edgeedge with one O(4)NaMgNi3 square pyramid,  an edgeedge with one O(6)Na2Ni3 trigonal bipyramid, and  an edgeedge with one O(2)NaNi3 trigonal pyramid. In the sixth O site, O(6) is bonded to one Na(1), one Na(2), one Ni(1), one Ni(2), and one Ni(5) atom to form distorted ONa2Ni3 trigonal bipyramids that share corners with two equivalent O(4)NaMgNi3 square pyramids, corners with two equivalent O(5)NaMgNi3 square pyramids, corners with three equivalent O(8)Na2Ni3 square pyramids,  a cornercorner with one O(3)MgNi3 trigonal pyramid,  a cornercorner with one O(2)NaNi3 trigonal pyramid,  an edgeedge with one O(5)NaMgNi3 square pyramid, edges with two equivalent O(9)Na2Ni3 square pyramids, and  an edgeedge with one O(2)NaNi3 trigonal pyramid. In the seventh O site, O(7) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Ni(3), one Ni(4), and one Ni(5) atom. In the eighth O site, O(8) is bonded to one Na(1), one Na(2), one Ni(3), one Ni(4), and one Ni(5) atom to form ONa2Ni3 square pyramids that share  a cornercorner with one O(4)NaMgNi3 square pyramid, corners with three equivalent O(6)Na2Ni3 trigonal bipyramids, corners with two equivalent O(2)NaNi3 trigonal pyramids,  an edgeedge with one O(4)NaMgNi3 square pyramid,  an edgeedge with one O(5)NaMgNi3 square pyramid, edges with two equivalent O(9)Na2Ni3 square pyramids, and  an edgeedge with one O(3)MgNi3 trigonal pyramid. In the ninth O site, O(9) is bonded to one Na(1), one Na(2), one Ni(1), one Ni(4), and one Ni(5) atom to form ONa2Ni3 square pyramids that share  a cornercorner with one O(5)NaMgNi3 square pyramid,  a cornercorner with one O(3)MgNi3 trigonal pyramid, corners with two equivalent O(2)NaNi3 trigonal pyramids,  an edgeedge with one O(4)NaMgNi3 square pyramid,  an edgeedge with one O(5)NaMgNi3 square pyramid, edges with two equivalent O(8)Na2Ni3 square pyramids, and edges with two equivalent O(6)Na2Ni3 trigonal bipyramids. In the tenth O site, O(10) is bonded in a 5-coordinate geometry to one Na(1), one Na(2), one Ni(1), one Ni(4), and one Ni(5) atom. is represented by the CIF card [CIF]
data_Na2Mg(NiO2)5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.636
_cell_length_b   5.014
_cell_length_c   5.746
_cell_angle_alpha   79.112
_cell_angle_beta   111.676
_cell_angle_gamma   79.335
_symmetry_Int_Tables_number   1
_cell_volume   192.783
_cell_formula_units_Z   1
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  0.887  0.998  0.407  1.0
  Na  Na1  1  0.727  0.574  0.253  1.0
  Mg  Mg2  1  0.311  0.785  0.847  1.0
  Ni  Ni3  1  0.992  0.013  0.989  1.0
  Ni  Ni4  1  0.189  0.413  0.193  1.0
  Ni  Ni5  1  0.383  0.814  0.393  1.0
  Ni  Ni6  1  0.574  0.209  0.614  1.0
  Ni  Ni7  1  0.788  0.610  0.798  1.0
  O  O8  1  0.244  0.074  0.050  1.0
  O  O9  1  0.137  0.758  0.325  1.0
  O  O10  1  0.334  0.098  0.554  1.0
  O  O11  1  0.438  0.529  0.241  1.0
  O  O12  1  0.050  0.730  0.835  1.0
  O  O13  1  0.932  0.324  0.118  1.0
  O  O14  1  0.502  0.550  0.729  1.0
  O  O15  1  0.629  0.886  0.469  1.0
  O  O16  1  0.826  0.291  0.663  1.0
  O  O17  1  0.762  0.907  0.962  1.0
[/CIF]
.