The structure described by Mg6NbCO8 crystallizes in the tetragonal P4/mmm space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra, corners with four equivalent Mg(1)O6 octahedra, edges with four equivalent Nb(1)O6 octahedra, and edges with eight equivalent Mg(3)O6 octahedra. The corner-sharing octahedra are not tilted. In the second Mg site, Mg(2) is bonded to two equivalent O(2) and four equivalent O(4) atoms to form a mixture of edge and corner-sharing MgO6 octahedra. The corner-sharing octahedra are not tilted. In the third Mg site, Mg(3) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form distorted MgO6 octahedra that share corners with six equivalent Mg(3)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mg(2)O6 octahedra, edges with two equivalent Nb(1)O6 octahedra, and edges with four equivalent Mg(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-25°. Nb(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form NbO6 octahedra that share corners with four equivalent Nb(1)O6 octahedra, edges with four equivalent Mg(1)O6 octahedra, and edges with eight equivalent Mg(3)O6 octahedra. The corner-sharing octahedra are not tilted. C(1) is bonded in a square co-planar geometry to four equivalent O(4) atoms. There are four inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Mg(3) and one Nb(1) atom to form distorted OMg4Nb square pyramids that share corners with four equivalent O(4)Mg4C2 octahedra, corners with five equivalent O(1)Mg4Nb square pyramids, edges with four equivalent O(3)Mg4Nb2 octahedra, and edges with four equivalent O(2)Mg6 octahedra. The corner-sharing octahedral tilt angles are 78°. In the second O site, O(2) is bonded to one Mg(1), one Mg(2), and four equivalent Mg(3) atoms to form OMg6 octahedra that share corners with six equivalent O(2)Mg6 octahedra, edges with four equivalent O(4)Mg4C2 octahedra, edges with four equivalent O(3)Mg4Nb2 octahedra, and edges with four equivalent O(1)Mg4Nb square pyramids. The corner-sharing octahedral tilt angles range from 0-9°. In the third O site, O(3) is bonded to two equivalent Mg(1), two equivalent Mg(3), and two equivalent Nb(1) atoms to form OMg4Nb2 octahedra that share corners with two equivalent O(4)Mg4C2 octahedra, corners with four equivalent O(3)Mg4Nb2 octahedra, edges with four equivalent O(3)Mg4Nb2 octahedra, edges with four equivalent O(2)Mg6 octahedra, and edges with four equivalent O(1)Mg4Nb square pyramids. The corner-sharing octahedra are not tilted. In the fourth O site, O(4) is bonded to two equivalent Mg(2), two equivalent Mg(3), and two equivalent C(1) atoms to form distorted OMg4C2 octahedra that share corners with two equivalent O(3)Mg4Nb2 octahedra, corners with four equivalent O(4)Mg4C2 octahedra, corners with four equivalent O(1)Mg4Nb square pyramids, edges with four equivalent O(4)Mg4C2 octahedra, and edges with four equivalent O(2)Mg6 octahedra. The corner-sharing octahedra are not tilted. is represented by the CIF file [CIF]
data_Mg6NbCO8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.316
_cell_length_b   4.224
_cell_length_c   4.224
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   166.188
_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  0.000  0.500  0.500  1.0
  Mg  Mg1  1  0.500  0.500  0.500  1.0
  Mg  Mg2  1  0.275  0.000  0.500  1.0
  Mg  Mg3  1  0.725  0.000  0.500  1.0
  Mg  Mg4  1  0.275  0.500  0.000  1.0
  Mg  Mg5  1  0.725  0.500  0.000  1.0
  Nb  Nb6  1  0.000  0.000  0.000  1.0
  C  C7  1  0.500  0.000  0.000  1.0
  O  O8  1  0.226  0.000  0.000  1.0
  O  O9  1  0.774  0.000  0.000  1.0
  O  O10  1  0.257  0.500  0.500  1.0
  O  O11  1  0.743  0.500  0.500  1.0
  O  O12  1  0.000  0.000  0.500  1.0
  O  O13  1  0.500  0.000  0.500  1.0
  O  O14  1  0.000  0.500  0.000  1.0
  O  O15  1  0.500  0.500  0.000  1.0
[/CIF]
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The structure described by Mg6NbCO8 crystallizes in the tetragonal P4/mmm space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra, corners with four equivalent Mg(1)O6 octahedra, edges with four equivalent Nb(1)O6 octahedra, and edges with eight equivalent Mg(3)O6 octahedra. The corner-sharing octahedra are not tilted. In the second Mg site, Mg(2) is bonded to two equivalent O(2) and four equivalent O(4) atoms to form a mixture of edge and corner-sharing MgO6 octahedra. The corner-sharing octahedra are not tilted. In the third Mg site, Mg(3) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form distorted MgO6 octahedra that share corners with six equivalent Mg(3)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mg(2)O6 octahedra, edges with two equivalent Nb(1)O6 octahedra, and edges with four equivalent Mg(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-25°. Nb(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form NbO6 octahedra that share corners with four equivalent Nb(1)O6 octahedra, edges with four equivalent Mg(1)O6 octahedra, and edges with eight equivalent Mg(3)O6 octahedra. The corner-sharing octahedra are not tilted. C(1) is bonded in a square co-planar geometry to four equivalent O(4) atoms. There are four inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Mg(3) and one Nb(1) atom to form distorted OMg4Nb square pyramids that share corners with four equivalent O(4)Mg4C2 octahedra, corners with five equivalent O(1)Mg4Nb square pyramids, edges with four equivalent O(3)Mg4Nb2 octahedra, and edges with four equivalent O(2)Mg6 octahedra. The corner-sharing octahedral tilt angles are 78°. In the second O site, O(2) is bonded to one Mg(1), one Mg(2), and four equivalent Mg(3) atoms to form OMg6 octahedra that share corners with six equivalent O(2)Mg6 octahedra, edges with four equivalent O(4)Mg4C2 octahedra, edges with four equivalent O(3)Mg4Nb2 octahedra, and edges with four equivalent O(1)Mg4Nb square pyramids. The corner-sharing octahedral tilt angles range from 0-9°. In the third O site, O(3) is bonded to two equivalent Mg(1), two equivalent Mg(3), and two equivalent Nb(1) atoms to form OMg4Nb2 octahedra that share corners with two equivalent O(4)Mg4C2 octahedra, corners with four equivalent O(3)Mg4Nb2 octahedra, edges with four equivalent O(3)Mg4Nb2 octahedra, edges with four equivalent O(2)Mg6 octahedra, and edges with four equivalent O(1)Mg4Nb square pyramids. The corner-sharing octahedra are not tilted. In the fourth O site, O(4) is bonded to two equivalent Mg(2), two equivalent Mg(3), and two equivalent C(1) atoms to form distorted OMg4C2 octahedra that share corners with two equivalent O(3)Mg4Nb2 octahedra, corners with four equivalent O(4)Mg4C2 octahedra, corners with four equivalent O(1)Mg4Nb square pyramids, edges with four equivalent O(4)Mg4C2 octahedra, and edges with four equivalent O(2)Mg6 octahedra. The corner-sharing octahedra are not tilted. is represented by the CIF file [CIF]
data_Mg6NbCO8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.316
_cell_length_b   4.224
_cell_length_c   4.224
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   166.188
_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  0.000  0.500  0.500  1.0
  Mg  Mg1  1  0.500  0.500  0.500  1.0
  Mg  Mg2  1  0.275  0.000  0.500  1.0
  Mg  Mg3  1  0.725  0.000  0.500  1.0
  Mg  Mg4  1  0.275  0.500  0.000  1.0
  Mg  Mg5  1  0.725  0.500  0.000  1.0
  Nb  Nb6  1  0.000  0.000  0.000  1.0
  C  C7  1  0.500  0.000  0.000  1.0
  O  O8  1  0.226  0.000  0.000  1.0
  O  O9  1  0.774  0.000  0.000  1.0
  O  O10  1  0.257  0.500  0.500  1.0
  O  O11  1  0.743  0.500  0.500  1.0
  O  O12  1  0.000  0.000  0.500  1.0
  O  O13  1  0.500  0.000  0.500  1.0
  O  O14  1  0.000  0.500  0.000  1.0
  O  O15  1  0.500  0.500  0.000  1.0
[/CIF]
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