The compound described by Mg(NiO2)4 crystallizes in the monoclinic Cm space group. Mg(1) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Ni(2)O5 trigonal bipyramids, corners with two equivalent Ni(3)O5 trigonal bipyramids, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, edges with two equivalent Ni(4)O6 octahedra,  an edgeedge with one Ni(2)O5 trigonal bipyramid, and  an edgeedge with one Ni(3)O5 trigonal bipyramid. There are four inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(2), one O(7), two equivalent O(4), and two equivalent O(5) atoms to form NiO6 octahedra that share corners with two equivalent Ni(3)O5 trigonal bipyramids, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, and edges with two equivalent Ni(4)O6 octahedra. In the second Ni site, Ni(2) is bonded to one O(8), two equivalent O(3), and two equivalent O(6) atoms to form distorted NiO5 trigonal bipyramids that share corners with two equivalent Mg(1)O6 octahedra, corners with two equivalent Ni(4)O6 octahedra,  an edgeedge with one Mg(1)O6 octahedra, edges with two equivalent Ni(2)O5 trigonal bipyramids, and edges with two equivalent Ni(3)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 33-61°. In the third Ni site, Ni(3) is bonded to one O(6), two equivalent O(2), and two equivalent O(8) atoms to form distorted NiO5 trigonal bipyramids that share corners with two equivalent Mg(1)O6 octahedra, corners with two equivalent Ni(1)O6 octahedra,  an edgeedge with one Mg(1)O6 octahedra, edges with two equivalent Ni(2)O5 trigonal bipyramids, and edges with two equivalent Ni(3)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 33-61°. In the fourth Ni site, Ni(4) is bonded to one O(3), one O(5), two equivalent O(1), and two equivalent O(7) atoms to form NiO6 octahedra that share corners with two equivalent Ni(2)O5 trigonal bipyramids, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, and edges with two equivalent Ni(4)O6 octahedra. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1) and two equivalent Ni(4) atoms. In the second O site, O(2) is bonded to two equivalent Mg(1), one Ni(1), and two equivalent Ni(3) atoms to form a mixture of distorted edge and corner-sharing OMg2Ni3 trigonal bipyramids. In the third O site, O(3) is bonded to two equivalent Mg(1), one Ni(4), and two equivalent Ni(2) atoms to form a mixture of distorted edge and corner-sharing OMg2Ni3 trigonal bipyramids. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1) and two equivalent Ni(1) atoms. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Ni(4) and two equivalent Ni(1) atoms. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to one Ni(3) and two equivalent Ni(2) atoms. In the seventh O site, O(7) is bonded in a distorted T-shaped geometry to one Ni(1) and two equivalent Ni(4) atoms. In the eighth O site, O(8) is bonded in a distorted T-shaped geometry to one Ni(2) and two equivalent Ni(3) atoms. is represented by the CIF card [CIF]
data_Mg(NiO2)4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   2.811
_cell_length_b   7.664
_cell_length_c   8.071
_cell_angle_alpha   107.850
_cell_angle_beta   79.970
_cell_angle_gamma   79.436
_symmetry_Int_Tables_number   1
_cell_volume   157.685
_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
  Mg  Mg0  1  0.985  0.499  0.500  1.0
  Ni  Ni1  1  0.647  0.163  0.513  1.0
  Ni  Ni2  1  0.173  0.476  0.148  1.0
  Ni  Ni3  1  0.795  0.527  0.853  1.0
  Ni  Ni4  1  0.321  0.836  0.491  1.0
  O  O5  1  0.787  0.778  0.618  1.0
  O  O6  1  0.435  0.432  0.668  1.0
  O  O7  1  0.534  0.568  0.333  1.0
  O  O8  1  0.182  0.219  0.385  1.0
  O  O9  1  0.122  0.091  0.634  1.0
  O  O10  1  0.810  0.352  0.996  1.0
  O  O11  1  0.845  0.908  0.371  1.0
  O  O12  1  0.157  0.652  0.004  1.0
[/CIF]
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The compound described by Mg(NiO2)4 crystallizes in the monoclinic Cm space group. Mg(1) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Ni(2)O5 trigonal bipyramids, corners with two equivalent Ni(3)O5 trigonal bipyramids, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, edges with two equivalent Ni(4)O6 octahedra,  an edgeedge with one Ni(2)O5 trigonal bipyramid, and  an edgeedge with one Ni(3)O5 trigonal bipyramid. There are four inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(2), one O(7), two equivalent O(4), and two equivalent O(5) atoms to form NiO6 octahedra that share corners with two equivalent Ni(3)O5 trigonal bipyramids, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, and edges with two equivalent Ni(4)O6 octahedra. In the second Ni site, Ni(2) is bonded to one O(8), two equivalent O(3), and two equivalent O(6) atoms to form distorted NiO5 trigonal bipyramids that share corners with two equivalent Mg(1)O6 octahedra, corners with two equivalent Ni(4)O6 octahedra,  an edgeedge with one Mg(1)O6 octahedra, edges with two equivalent Ni(2)O5 trigonal bipyramids, and edges with two equivalent Ni(3)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 33-61°. In the third Ni site, Ni(3) is bonded to one O(6), two equivalent O(2), and two equivalent O(8) atoms to form distorted NiO5 trigonal bipyramids that share corners with two equivalent Mg(1)O6 octahedra, corners with two equivalent Ni(1)O6 octahedra,  an edgeedge with one Mg(1)O6 octahedra, edges with two equivalent Ni(2)O5 trigonal bipyramids, and edges with two equivalent Ni(3)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 33-61°. In the fourth Ni site, Ni(4) is bonded to one O(3), one O(5), two equivalent O(1), and two equivalent O(7) atoms to form NiO6 octahedra that share corners with two equivalent Ni(2)O5 trigonal bipyramids, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, and edges with two equivalent Ni(4)O6 octahedra. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1) and two equivalent Ni(4) atoms. In the second O site, O(2) is bonded to two equivalent Mg(1), one Ni(1), and two equivalent Ni(3) atoms to form a mixture of distorted edge and corner-sharing OMg2Ni3 trigonal bipyramids. In the third O site, O(3) is bonded to two equivalent Mg(1), one Ni(4), and two equivalent Ni(2) atoms to form a mixture of distorted edge and corner-sharing OMg2Ni3 trigonal bipyramids. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1) and two equivalent Ni(1) atoms. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Ni(4) and two equivalent Ni(1) atoms. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to one Ni(3) and two equivalent Ni(2) atoms. In the seventh O site, O(7) is bonded in a distorted T-shaped geometry to one Ni(1) and two equivalent Ni(4) atoms. In the eighth O site, O(8) is bonded in a distorted T-shaped geometry to one Ni(2) and two equivalent Ni(3) atoms. is represented by the CIF card [CIF]
data_Mg(NiO2)4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   2.811
_cell_length_b   7.664
_cell_length_c   8.071
_cell_angle_alpha   107.850
_cell_angle_beta   79.970
_cell_angle_gamma   79.436
_symmetry_Int_Tables_number   1
_cell_volume   157.685
_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
  Mg  Mg0  1  0.985  0.499  0.500  1.0
  Ni  Ni1  1  0.647  0.163  0.513  1.0
  Ni  Ni2  1  0.173  0.476  0.148  1.0
  Ni  Ni3  1  0.795  0.527  0.853  1.0
  Ni  Ni4  1  0.321  0.836  0.491  1.0
  O  O5  1  0.787  0.778  0.618  1.0
  O  O6  1  0.435  0.432  0.668  1.0
  O  O7  1  0.534  0.568  0.333  1.0
  O  O8  1  0.182  0.219  0.385  1.0
  O  O9  1  0.122  0.091  0.634  1.0
  O  O10  1  0.810  0.352  0.996  1.0
  O  O11  1  0.845  0.908  0.371  1.0
  O  O12  1  0.157  0.652  0.004  1.0
[/CIF]
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