The material described by Na4MgCr2O8 crystallizes in the monoclinic C2/m space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 4-coordinate geometry to one O(1), one O(2), and two equivalent O(3) atoms. In the second Na site, Na(2) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form NaO6 octahedra that share corners with six equivalent Cr(1)O4 tetrahedra and edges with two equivalent Na(3)O6 octahedra. In the third Na site, Na(3) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form NaO6 octahedra that share corners with six equivalent Cr(1)O4 tetrahedra and edges with two equivalent Na(2)O6 octahedra. Mg(1) is bonded in a 6-coordinate geometry to two equivalent O(1) and four equivalent O(3) atoms. Cr(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form distorted CrO4 tetrahedra that share corners with three equivalent Na(2)O6 octahedra and corners with three equivalent Na(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 46-63°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Na(3), one Mg(1), and one Cr(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Na(1), one Na(2), and one Cr(1) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Na(1), one Na(2), one Na(3), one Mg(1), and one Cr(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na4MgCr2O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.571
_cell_length_b   5.571
_cell_length_c   7.594
_cell_angle_alpha   88.088
_cell_angle_beta   91.912
_cell_angle_gamma   112.619
_symmetry_Int_Tables_number   1
_cell_volume   217.374
_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
  Na  Na0  1  0.202  0.798  0.730  1.0
  Na  Na1  1  0.798  0.202  0.270  1.0
  Na  Na2  1  0.500  0.500  0.500  1.0
  Na  Na3  1  0.500  0.500  0.000  1.0
  Mg  Mg4  1  0.000  0.000  0.000  1.0
  Cr  Cr5  1  0.838  0.162  0.743  1.0
  Cr  Cr6  1  0.162  0.838  0.257  1.0
  O  O7  1  0.236  0.764  0.053  1.0
  O  O8  1  0.743  0.257  0.552  1.0
  O  O9  1  0.764  0.236  0.947  1.0
  O  O10  1  0.257  0.743  0.448  1.0
  O  O11  1  0.178  0.245  0.777  1.0
  O  O12  1  0.822  0.755  0.223  1.0
  O  O13  1  0.755  0.822  0.777  1.0
  O  O14  1  0.245  0.178  0.223  1.0
[/CIF]
.
The material described by Na4MgCr2O8 crystallizes in the monoclinic C2/m space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 4-coordinate geometry to one O(1), one O(2), and two equivalent O(3) atoms. In the second Na site, Na(2) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form NaO6 octahedra that share corners with six equivalent Cr(1)O4 tetrahedra and edges with two equivalent Na(3)O6 octahedra. In the third Na site, Na(3) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form NaO6 octahedra that share corners with six equivalent Cr(1)O4 tetrahedra and edges with two equivalent Na(2)O6 octahedra. Mg(1) is bonded in a 6-coordinate geometry to two equivalent O(1) and four equivalent O(3) atoms. Cr(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form distorted CrO4 tetrahedra that share corners with three equivalent Na(2)O6 octahedra and corners with three equivalent Na(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 46-63°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Na(3), one Mg(1), and one Cr(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Na(1), one Na(2), and one Cr(1) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Na(1), one Na(2), one Na(3), one Mg(1), and one Cr(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na4MgCr2O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.571
_cell_length_b   5.571
_cell_length_c   7.594
_cell_angle_alpha   88.088
_cell_angle_beta   91.912
_cell_angle_gamma   112.619
_symmetry_Int_Tables_number   1
_cell_volume   217.374
_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
  Na  Na0  1  0.202  0.798  0.730  1.0
  Na  Na1  1  0.798  0.202  0.270  1.0
  Na  Na2  1  0.500  0.500  0.500  1.0
  Na  Na3  1  0.500  0.500  0.000  1.0
  Mg  Mg4  1  0.000  0.000  0.000  1.0
  Cr  Cr5  1  0.838  0.162  0.743  1.0
  Cr  Cr6  1  0.162  0.838  0.257  1.0
  O  O7  1  0.236  0.764  0.053  1.0
  O  O8  1  0.743  0.257  0.552  1.0
  O  O9  1  0.764  0.236  0.947  1.0
  O  O10  1  0.257  0.743  0.448  1.0
  O  O11  1  0.178  0.245  0.777  1.0
  O  O12  1  0.822  0.755  0.223  1.0
  O  O13  1  0.755  0.822  0.777  1.0
  O  O14  1  0.245  0.178  0.223  1.0
[/CIF]
.