The material described by Mg3Ni2O7 crystallizes in the orthorhombic Cmc2_1 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 6-coordinate geometry to two equivalent O(4) and four equivalent O(3) atoms. In the second Mg site, Mg(2) is bonded in a 6-coordinate geometry to one O(3), two equivalent O(2), and three equivalent O(1) atoms. Ni(1) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms to form corner-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles range from 39-45°. There are four inequivalent O sites. In the first O site, O(1) is bonded to three equivalent Mg(2) and one Ni(1) atom to form distorted OMg3Ni tetrahedra that share corners with six equivalent O(1)Mg3Ni tetrahedra,  a cornercorner with one O(3)Mg3Ni2 trigonal bipyramid,  a cornercorner with one O(4)Mg2Ni2 trigonal pyramid, and edges with two equivalent O(3)Mg3Ni2 trigonal bipyramids. In the second O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Mg(2) and two equivalent Ni(1) atoms. In the third O site, O(3) is bonded to one Mg(2), two equivalent Mg(1), and two equivalent Ni(1) atoms to form distorted OMg3Ni2 trigonal bipyramids that share  a cornercorner with one O(1)Mg3Ni tetrahedra, corners with two equivalent O(3)Mg3Ni2 trigonal bipyramids, corners with four equivalent O(4)Mg2Ni2 trigonal pyramids, edges with two equivalent O(1)Mg3Ni tetrahedra, edges with three equivalent O(3)Mg3Ni2 trigonal bipyramids, and  an edgeedge with one O(4)Mg2Ni2 trigonal pyramid. In the fourth O site, O(4) is bonded to two equivalent Mg(1) and two equivalent Ni(1) atoms to form OMg2Ni2 trigonal pyramids that share corners with two equivalent O(1)Mg3Ni tetrahedra, corners with eight equivalent O(3)Mg3Ni2 trigonal bipyramids, corners with two equivalent O(4)Mg2Ni2 trigonal pyramids, and edges with two equivalent O(3)Mg3Ni2 trigonal bipyramids. is represented by the CIF card [CIF]
data_Mg3Ni2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.103
_cell_length_b   9.103
_cell_length_c   5.197
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   148.333
_symmetry_Int_Tables_number   1
_cell_volume   226.092
_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  0.223  0.223  0.325  1.0
  Mg  Mg1  1  0.777  0.777  0.825  1.0
  Mg  Mg2  1  0.050  0.434  0.172  1.0
  Mg  Mg3  1  0.950  0.566  0.672  1.0
  Mg  Mg4  1  0.434  0.050  0.172  1.0
  Mg  Mg5  1  0.566  0.950  0.672  1.0
  Ni  Ni6  1  0.849  0.645  0.251  1.0
  Ni  Ni7  1  0.151  0.355  0.751  1.0
  Ni  Ni8  1  0.355  0.151  0.751  1.0
  Ni  Ni9  1  0.645  0.849  0.251  1.0
  O  O10  1  0.660  0.065  0.293  1.0
  O  O11  1  0.340  0.935  0.793  1.0
  O  O12  1  0.935  0.340  0.793  1.0
  O  O13  1  0.065  0.660  0.293  1.0
  O  O14  1  0.415  0.687  0.960  1.0
  O  O15  1  0.585  0.313  0.460  1.0
  O  O16  1  0.313  0.585  0.460  1.0
  O  O17  1  0.687  0.415  0.960  1.0
  O  O18  1  0.986  0.136  0.058  1.0
  O  O19  1  0.014  0.864  0.558  1.0
  O  O20  1  0.612  0.612  0.189  1.0
  O  O21  1  0.388  0.388  0.689  1.0
  O  O22  1  0.136  0.986  0.058  1.0
  O  O23  1  0.864  0.014  0.558  1.0
[/CIF]
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The material described by Mg3Ni2O7 crystallizes in the orthorhombic Cmc2_1 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 6-coordinate geometry to two equivalent O(4) and four equivalent O(3) atoms. In the second Mg site, Mg(2) is bonded in a 6-coordinate geometry to one O(3), two equivalent O(2), and three equivalent O(1) atoms. Ni(1) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms to form corner-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles range from 39-45°. There are four inequivalent O sites. In the first O site, O(1) is bonded to three equivalent Mg(2) and one Ni(1) atom to form distorted OMg3Ni tetrahedra that share corners with six equivalent O(1)Mg3Ni tetrahedra,  a cornercorner with one O(3)Mg3Ni2 trigonal bipyramid,  a cornercorner with one O(4)Mg2Ni2 trigonal pyramid, and edges with two equivalent O(3)Mg3Ni2 trigonal bipyramids. In the second O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Mg(2) and two equivalent Ni(1) atoms. In the third O site, O(3) is bonded to one Mg(2), two equivalent Mg(1), and two equivalent Ni(1) atoms to form distorted OMg3Ni2 trigonal bipyramids that share  a cornercorner with one O(1)Mg3Ni tetrahedra, corners with two equivalent O(3)Mg3Ni2 trigonal bipyramids, corners with four equivalent O(4)Mg2Ni2 trigonal pyramids, edges with two equivalent O(1)Mg3Ni tetrahedra, edges with three equivalent O(3)Mg3Ni2 trigonal bipyramids, and  an edgeedge with one O(4)Mg2Ni2 trigonal pyramid. In the fourth O site, O(4) is bonded to two equivalent Mg(1) and two equivalent Ni(1) atoms to form OMg2Ni2 trigonal pyramids that share corners with two equivalent O(1)Mg3Ni tetrahedra, corners with eight equivalent O(3)Mg3Ni2 trigonal bipyramids, corners with two equivalent O(4)Mg2Ni2 trigonal pyramids, and edges with two equivalent O(3)Mg3Ni2 trigonal bipyramids. is represented by the CIF card [CIF]
data_Mg3Ni2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.103
_cell_length_b   9.103
_cell_length_c   5.197
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   148.333
_symmetry_Int_Tables_number   1
_cell_volume   226.092
_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  0.223  0.223  0.325  1.0
  Mg  Mg1  1  0.777  0.777  0.825  1.0
  Mg  Mg2  1  0.050  0.434  0.172  1.0
  Mg  Mg3  1  0.950  0.566  0.672  1.0
  Mg  Mg4  1  0.434  0.050  0.172  1.0
  Mg  Mg5  1  0.566  0.950  0.672  1.0
  Ni  Ni6  1  0.849  0.645  0.251  1.0
  Ni  Ni7  1  0.151  0.355  0.751  1.0
  Ni  Ni8  1  0.355  0.151  0.751  1.0
  Ni  Ni9  1  0.645  0.849  0.251  1.0
  O  O10  1  0.660  0.065  0.293  1.0
  O  O11  1  0.340  0.935  0.793  1.0
  O  O12  1  0.935  0.340  0.793  1.0
  O  O13  1  0.065  0.660  0.293  1.0
  O  O14  1  0.415  0.687  0.960  1.0
  O  O15  1  0.585  0.313  0.460  1.0
  O  O16  1  0.313  0.585  0.460  1.0
  O  O17  1  0.687  0.415  0.960  1.0
  O  O18  1  0.986  0.136  0.058  1.0
  O  O19  1  0.014  0.864  0.558  1.0
  O  O20  1  0.612  0.612  0.189  1.0
  O  O21  1  0.388  0.388  0.689  1.0
  O  O22  1  0.136  0.986  0.058  1.0
  O  O23  1  0.864  0.014  0.558  1.0
[/CIF]
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