The crystal structure described by Mg3MnNi3O8 crystallizes in the trigonal R-3m space group. Mg(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent Ni(1)O6 octahedra, edges with two equivalent Mn(1)O6 octahedra, edges with four equivalent Mg(1)O6 octahedra, and edges with four equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 1-9°. Mn(1) is bonded to six equivalent O(2) atoms to form MnO6 octahedra that share edges with six equivalent Mg(1)O6 octahedra and edges with six equivalent Ni(1)O6 octahedra. Ni(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form NiO6 octahedra that share corners with six equivalent Mg(1)O6 octahedra, edges with two equivalent Mn(1)O6 octahedra, edges with four equivalent Mg(1)O6 octahedra, and edges with four equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 1-9°. There are two inequivalent O sites. In the first O site, O(1) is bonded to three equivalent Mg(1) and three equivalent Ni(1) atoms to form OMg3Ni3 octahedra that share corners with six equivalent O(1)Mg3Ni3 octahedra and edges with twelve equivalent O(2)Mg2MnNi2 square pyramids. The corner-sharing octahedra are not tilted. In the second O site, O(2) is bonded to two equivalent Mg(1), one Mn(1), and two equivalent Ni(1) atoms to form OMg2MnNi2 square pyramids that share corners with nine equivalent O(2)Mg2MnNi2 square pyramids, edges with four equivalent O(1)Mg3Ni3 octahedra, and edges with four equivalent O(2)Mg2MnNi2 square pyramids. is represented by the CIF file [CIF]
data_Mg3MnNi3O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.948
_cell_length_b   5.948
_cell_length_c   5.948
_cell_angle_alpha   60.517
_cell_angle_beta   60.517
_cell_angle_gamma   60.517
_symmetry_Int_Tables_number   1
_cell_volume   150.556
_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  0.500  0.500  0.000  1.0
  Mg  Mg1  1  0.000  0.500  0.500  1.0
  Mg  Mg2  1  0.500  0.000  0.500  1.0
  Mn  Mn3  1  0.000  0.000  0.000  1.0
  Ni  Ni4  1  0.000  0.000  0.500  1.0
  Ni  Ni5  1  0.500  0.000  0.000  1.0
  Ni  Ni6  1  0.000  0.500  0.000  1.0
  O  O7  1  0.749  0.749  0.749  1.0
  O  O8  1  0.251  0.251  0.251  1.0
  O  O9  1  0.771  0.771  0.230  1.0
  O  O10  1  0.230  0.771  0.771  1.0
  O  O11  1  0.771  0.230  0.771  1.0
  O  O12  1  0.229  0.229  0.770  1.0
  O  O13  1  0.770  0.229  0.229  1.0
  O  O14  1  0.229  0.770  0.229  1.0
[/CIF]
.
The crystal structure described by Mg3MnNi3O8 crystallizes in the trigonal R-3m space group. Mg(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent Ni(1)O6 octahedra, edges with two equivalent Mn(1)O6 octahedra, edges with four equivalent Mg(1)O6 octahedra, and edges with four equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 1-9°. Mn(1) is bonded to six equivalent O(2) atoms to form MnO6 octahedra that share edges with six equivalent Mg(1)O6 octahedra and edges with six equivalent Ni(1)O6 octahedra. Ni(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form NiO6 octahedra that share corners with six equivalent Mg(1)O6 octahedra, edges with two equivalent Mn(1)O6 octahedra, edges with four equivalent Mg(1)O6 octahedra, and edges with four equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 1-9°. There are two inequivalent O sites. In the first O site, O(1) is bonded to three equivalent Mg(1) and three equivalent Ni(1) atoms to form OMg3Ni3 octahedra that share corners with six equivalent O(1)Mg3Ni3 octahedra and edges with twelve equivalent O(2)Mg2MnNi2 square pyramids. The corner-sharing octahedra are not tilted. In the second O site, O(2) is bonded to two equivalent Mg(1), one Mn(1), and two equivalent Ni(1) atoms to form OMg2MnNi2 square pyramids that share corners with nine equivalent O(2)Mg2MnNi2 square pyramids, edges with four equivalent O(1)Mg3Ni3 octahedra, and edges with four equivalent O(2)Mg2MnNi2 square pyramids. is represented by the CIF file [CIF]
data_Mg3MnNi3O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.948
_cell_length_b   5.948
_cell_length_c   5.948
_cell_angle_alpha   60.517
_cell_angle_beta   60.517
_cell_angle_gamma   60.517
_symmetry_Int_Tables_number   1
_cell_volume   150.556
_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  0.500  0.500  0.000  1.0
  Mg  Mg1  1  0.000  0.500  0.500  1.0
  Mg  Mg2  1  0.500  0.000  0.500  1.0
  Mn  Mn3  1  0.000  0.000  0.000  1.0
  Ni  Ni4  1  0.000  0.000  0.500  1.0
  Ni  Ni5  1  0.500  0.000  0.000  1.0
  Ni  Ni6  1  0.000  0.500  0.000  1.0
  O  O7  1  0.749  0.749  0.749  1.0
  O  O8  1  0.251  0.251  0.251  1.0
  O  O9  1  0.771  0.771  0.230  1.0
  O  O10  1  0.230  0.771  0.771  1.0
  O  O11  1  0.771  0.230  0.771  1.0
  O  O12  1  0.229  0.229  0.770  1.0
  O  O13  1  0.770  0.229  0.229  1.0
  O  O14  1  0.229  0.770  0.229  1.0
[/CIF]
.