The material described by Mg(NiO2)2 is Spinel-like structured and crystallizes in the trigonal R3m space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(3) and three equivalent O(4) atoms to form MgO4 tetrahedra that share corners with three equivalent Mg(2)O6 octahedra and corners with nine equivalent Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-60°. In the second Mg site, Mg(2) is bonded to three equivalent O(1) and three equivalent O(4) atoms to form MgO6 octahedra that share corners with three equivalent Mg(1)O4 tetrahedra, corners with three equivalent Ni(1)O4 tetrahedra, and edges with six equivalent Ni(2)O6 octahedra. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(2) and three equivalent O(1) atoms to form NiO4 tetrahedra that share corners with three equivalent Mg(2)O6 octahedra and corners with nine equivalent Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 54-60°. In the second Ni site, Ni(2) is bonded to one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms to form NiO6 octahedra that share corners with three equivalent Mg(1)O4 tetrahedra, corners with three equivalent Ni(1)O4 tetrahedra, edges with two equivalent Mg(2)O6 octahedra, and edges with four equivalent Ni(2)O6 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Mg(2), one Ni(1), and two equivalent Ni(2) atoms to form distorted OMgNi3 trigonal pyramids that share corners with two equivalent O(1)MgNi3 trigonal pyramids, corners with seven equivalent O(4)Mg2Ni2 trigonal pyramids, and edges with two equivalent O(1)MgNi3 trigonal pyramids. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Ni(1) and three equivalent Ni(2) atoms. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to one Mg(1) and three equivalent Ni(2) atoms. In the fourth O site, O(4) is bonded to one Mg(1), one Mg(2), and two equivalent Ni(2) atoms to form distorted OMg2Ni2 trigonal pyramids that share corners with two equivalent O(4)Mg2Ni2 trigonal pyramids, corners with seven equivalent O(1)MgNi3 trigonal pyramids, and edges with two equivalent O(4)Mg2Ni2 trigonal pyramids. is represented by the CIF file [CIF]
data_Mg(NiO2)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.868
_cell_length_b   5.868
_cell_length_c   5.868
_cell_angle_alpha   60.089
_cell_angle_beta   60.089
_cell_angle_gamma   60.089
_symmetry_Int_Tables_number   1
_cell_volume   143.167
_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
  Mg  Mg0  1  0.009  0.009  0.009  1.0
  Mg  Mg1  1  0.625  0.625  0.625  1.0
  Ni  Ni2  1  0.243  0.243  0.243  1.0
  Ni  Ni3  1  0.630  0.117  0.630  1.0
  Ni  Ni4  1  0.630  0.630  0.117  1.0
  Ni  Ni5  1  0.117  0.630  0.630  1.0
  O  O6  1  0.843  0.375  0.375  1.0
  O  O7  1  0.375  0.375  0.843  1.0
  O  O8  1  0.375  0.843  0.375  1.0
  O  O9  1  0.370  0.370  0.370  1.0
  O  O10  1  0.874  0.874  0.874  1.0
  O  O11  1  0.869  0.419  0.869  1.0
  O  O12  1  0.869  0.869  0.419  1.0
  O  O13  1  0.419  0.869  0.869  1.0
[/CIF]
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The material described by Mg(NiO2)2 is Spinel-like structured and crystallizes in the trigonal R3m space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(3) and three equivalent O(4) atoms to form MgO4 tetrahedra that share corners with three equivalent Mg(2)O6 octahedra and corners with nine equivalent Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-60°. In the second Mg site, Mg(2) is bonded to three equivalent O(1) and three equivalent O(4) atoms to form MgO6 octahedra that share corners with three equivalent Mg(1)O4 tetrahedra, corners with three equivalent Ni(1)O4 tetrahedra, and edges with six equivalent Ni(2)O6 octahedra. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(2) and three equivalent O(1) atoms to form NiO4 tetrahedra that share corners with three equivalent Mg(2)O6 octahedra and corners with nine equivalent Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 54-60°. In the second Ni site, Ni(2) is bonded to one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms to form NiO6 octahedra that share corners with three equivalent Mg(1)O4 tetrahedra, corners with three equivalent Ni(1)O4 tetrahedra, edges with two equivalent Mg(2)O6 octahedra, and edges with four equivalent Ni(2)O6 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Mg(2), one Ni(1), and two equivalent Ni(2) atoms to form distorted OMgNi3 trigonal pyramids that share corners with two equivalent O(1)MgNi3 trigonal pyramids, corners with seven equivalent O(4)Mg2Ni2 trigonal pyramids, and edges with two equivalent O(1)MgNi3 trigonal pyramids. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Ni(1) and three equivalent Ni(2) atoms. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to one Mg(1) and three equivalent Ni(2) atoms. In the fourth O site, O(4) is bonded to one Mg(1), one Mg(2), and two equivalent Ni(2) atoms to form distorted OMg2Ni2 trigonal pyramids that share corners with two equivalent O(4)Mg2Ni2 trigonal pyramids, corners with seven equivalent O(1)MgNi3 trigonal pyramids, and edges with two equivalent O(4)Mg2Ni2 trigonal pyramids. is represented by the CIF file [CIF]
data_Mg(NiO2)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.868
_cell_length_b   5.868
_cell_length_c   5.868
_cell_angle_alpha   60.089
_cell_angle_beta   60.089
_cell_angle_gamma   60.089
_symmetry_Int_Tables_number   1
_cell_volume   143.167
_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
  Mg  Mg0  1  0.009  0.009  0.009  1.0
  Mg  Mg1  1  0.625  0.625  0.625  1.0
  Ni  Ni2  1  0.243  0.243  0.243  1.0
  Ni  Ni3  1  0.630  0.117  0.630  1.0
  Ni  Ni4  1  0.630  0.630  0.117  1.0
  Ni  Ni5  1  0.117  0.630  0.630  1.0
  O  O6  1  0.843  0.375  0.375  1.0
  O  O7  1  0.375  0.375  0.843  1.0
  O  O8  1  0.375  0.843  0.375  1.0
  O  O9  1  0.370  0.370  0.370  1.0
  O  O10  1  0.874  0.874  0.874  1.0
  O  O11  1  0.869  0.419  0.869  1.0
  O  O12  1  0.869  0.869  0.419  1.0
  O  O13  1  0.419  0.869  0.869  1.0
[/CIF]
.