The compound described by Na8MgCr2O8 crystallizes in the triclinic P1 space group. There are eight inequivalent Na sites. In the first Na site, Na(1) is bonded in a 4-coordinate geometry to one O(3), one O(5), one O(6), and one O(8) atom. In the second Na site, Na(2) is bonded in a 4-coordinate geometry to one O(3), one O(4), one O(7), and one O(8) atom. In the third Na site, Na(3) is bonded in a 4-coordinate geometry to one O(1), one O(3), one O(4), and one O(8) atom. In the fourth Na site, Na(4) is bonded in a 4-coordinate geometry to one O(1), one O(4), one O(5), and one O(7) atom. In the fifth Na site, Na(5) is bonded to one O(1), one O(4), one O(5), and one O(7) atom to form distorted NaO4 tetrahedra that share  a cornercorner with one Mg(1)O4 tetrahedra, corners with two equivalent Cr(1)O4 tetrahedra, and corners with two equivalent Cr(2)O4 tetrahedra. In the sixth Na site, Na(6) is bonded in a 4-coordinate geometry to one O(2), one O(3), one O(5), one O(6), and one O(8) atom. In the seventh Na site, Na(7) is bonded in a distorted trigonal non-coplanar geometry to one O(3), one O(4), one O(6), and one O(8) atom. In the eighth Na site, Na(8) is bonded in a 3-coordinate geometry to one O(1), one O(2), one O(5), and one O(7) atom. Mg(1) is bonded to one O(2), one O(5), one O(6), and one O(8) atom to form MgO4 tetrahedra that share  a cornercorner with one Na(5)O4 tetrahedra,  a cornercorner with one Cr(2)O4 tetrahedra, and corners with three equivalent Cr(1)O4 tetrahedra. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(1), one O(2), one O(5), and one O(6) atom to form CrO4 tetrahedra that share corners with two equivalent Na(5)O4 tetrahedra and corners with three equivalent Mg(1)O4 tetrahedra. In the second Cr site, Cr(2) is bonded to one O(3), one O(4), one O(7), and one O(8) atom to form CrO4 tetrahedra that share  a cornercorner with one Mg(1)O4 tetrahedra and corners with two equivalent Na(5)O4 tetrahedra. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Na(3), one Na(4), one Na(5), one Na(8), and one Cr(1) atom to form distorted ONa4Cr trigonal bipyramids that share  a cornercorner with one O(3)Na5Cr octahedra,  a cornercorner with one O(7)Na4Cr trigonal bipyramid, and  an edgeedge with one O(7)Na4Cr trigonal bipyramid. The corner-sharing octahedral tilt angles are 66°. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Na(6), one Na(8), one Mg(1), and one Cr(1) atom. In the third O site, O(3) is bonded to one Na(1), one Na(2), one Na(3), one Na(6), one Na(7), and one Cr(2) atom to form corner-sharing ONa5Cr octahedra. In the fourth O site, O(4) is bonded in a 6-coordinate geometry to one Na(2), one Na(3), one Na(4), one Na(5), one Na(7), and one Cr(2) atom. In the fifth O site, O(5) is bonded in a 7-coordinate geometry to one Na(1), one Na(4), one Na(5), one Na(6), one Na(8), one Mg(1), and one Cr(1) atom. In the sixth O site, O(6) is bonded in a 5-coordinate geometry to one Na(1), one Na(6), one Na(7), one Mg(1), and one Cr(1) atom. In the seventh O site, O(7) is bonded to one Na(2), one Na(4), one Na(5), one Na(8), and one Cr(2) atom to form distorted ONa4Cr trigonal bipyramids that share corners with two equivalent O(3)Na5Cr octahedra,  a cornercorner with one O(1)Na4Cr trigonal bipyramid, and  an edgeedge with one O(1)Na4Cr trigonal bipyramid. The corner-sharing octahedral tilt angles range from 46-69°. In the eighth O site, O(8) is bonded in a 7-coordinate geometry to one Na(1), one Na(2), one Na(3), one Na(6), one Na(7), one Mg(1), and one Cr(2) atom. is represented by the CIF card [CIF]
data_Na8MgCr2O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.902
_cell_length_b   5.836
_cell_length_c   9.165
_cell_angle_alpha   68.870
_cell_angle_beta   83.130
_cell_angle_gamma   69.336
_symmetry_Int_Tables_number   1
_cell_volume   275.510
_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  0.756  0.943  0.403  1.0
  Na  Na1  1  0.777  0.371  0.701  1.0
  Na  Na2  1  0.268  0.399  0.821  1.0
  Na  Na3  1  0.249  0.798  0.010  1.0
  Na  Na4  1  0.725  0.219  0.026  1.0
  Na  Na5  1  0.189  0.510  0.456  1.0
  Na  Na6  1  0.246  0.902  0.602  1.0
  Na  Na7  1  0.823  0.587  0.078  1.0
  Mg  Mg8  1  0.636  0.445  0.382  1.0
  Cr  Cr9  1  0.268  0.165  0.244  1.0
  Cr  Cr10  1  0.717  0.869  0.742  1.0
  O  O11  1  0.124  0.205  0.062  1.0
  O  O12  1  0.980  0.364  0.338  1.0
  O  O13  1  0.964  0.675  0.634  1.0
  O  O14  1  0.528  0.640  0.830  1.0
  O  O15  1  0.501  0.343  0.231  1.0
  O  O16  1  0.452  0.809  0.368  1.0
  O  O17  1  0.857  0.954  0.883  1.0
  O  O18  1  0.555  0.219  0.590  1.0
[/CIF]
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The compound described by Na8MgCr2O8 crystallizes in the triclinic P1 space group. There are eight inequivalent Na sites. In the first Na site, Na(1) is bonded in a 4-coordinate geometry to one O(3), one O(5), one O(6), and one O(8) atom. In the second Na site, Na(2) is bonded in a 4-coordinate geometry to one O(3), one O(4), one O(7), and one O(8) atom. In the third Na site, Na(3) is bonded in a 4-coordinate geometry to one O(1), one O(3), one O(4), and one O(8) atom. In the fourth Na site, Na(4) is bonded in a 4-coordinate geometry to one O(1), one O(4), one O(5), and one O(7) atom. In the fifth Na site, Na(5) is bonded to one O(1), one O(4), one O(5), and one O(7) atom to form distorted NaO4 tetrahedra that share  a cornercorner with one Mg(1)O4 tetrahedra, corners with two equivalent Cr(1)O4 tetrahedra, and corners with two equivalent Cr(2)O4 tetrahedra. In the sixth Na site, Na(6) is bonded in a 4-coordinate geometry to one O(2), one O(3), one O(5), one O(6), and one O(8) atom. In the seventh Na site, Na(7) is bonded in a distorted trigonal non-coplanar geometry to one O(3), one O(4), one O(6), and one O(8) atom. In the eighth Na site, Na(8) is bonded in a 3-coordinate geometry to one O(1), one O(2), one O(5), and one O(7) atom. Mg(1) is bonded to one O(2), one O(5), one O(6), and one O(8) atom to form MgO4 tetrahedra that share  a cornercorner with one Na(5)O4 tetrahedra,  a cornercorner with one Cr(2)O4 tetrahedra, and corners with three equivalent Cr(1)O4 tetrahedra. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(1), one O(2), one O(5), and one O(6) atom to form CrO4 tetrahedra that share corners with two equivalent Na(5)O4 tetrahedra and corners with three equivalent Mg(1)O4 tetrahedra. In the second Cr site, Cr(2) is bonded to one O(3), one O(4), one O(7), and one O(8) atom to form CrO4 tetrahedra that share  a cornercorner with one Mg(1)O4 tetrahedra and corners with two equivalent Na(5)O4 tetrahedra. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Na(3), one Na(4), one Na(5), one Na(8), and one Cr(1) atom to form distorted ONa4Cr trigonal bipyramids that share  a cornercorner with one O(3)Na5Cr octahedra,  a cornercorner with one O(7)Na4Cr trigonal bipyramid, and  an edgeedge with one O(7)Na4Cr trigonal bipyramid. The corner-sharing octahedral tilt angles are 66°. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Na(6), one Na(8), one Mg(1), and one Cr(1) atom. In the third O site, O(3) is bonded to one Na(1), one Na(2), one Na(3), one Na(6), one Na(7), and one Cr(2) atom to form corner-sharing ONa5Cr octahedra. In the fourth O site, O(4) is bonded in a 6-coordinate geometry to one Na(2), one Na(3), one Na(4), one Na(5), one Na(7), and one Cr(2) atom. In the fifth O site, O(5) is bonded in a 7-coordinate geometry to one Na(1), one Na(4), one Na(5), one Na(6), one Na(8), one Mg(1), and one Cr(1) atom. In the sixth O site, O(6) is bonded in a 5-coordinate geometry to one Na(1), one Na(6), one Na(7), one Mg(1), and one Cr(1) atom. In the seventh O site, O(7) is bonded to one Na(2), one Na(4), one Na(5), one Na(8), and one Cr(2) atom to form distorted ONa4Cr trigonal bipyramids that share corners with two equivalent O(3)Na5Cr octahedra,  a cornercorner with one O(1)Na4Cr trigonal bipyramid, and  an edgeedge with one O(1)Na4Cr trigonal bipyramid. The corner-sharing octahedral tilt angles range from 46-69°. In the eighth O site, O(8) is bonded in a 7-coordinate geometry to one Na(1), one Na(2), one Na(3), one Na(6), one Na(7), one Mg(1), and one Cr(2) atom. is represented by the CIF card [CIF]
data_Na8MgCr2O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.902
_cell_length_b   5.836
_cell_length_c   9.165
_cell_angle_alpha   68.870
_cell_angle_beta   83.130
_cell_angle_gamma   69.336
_symmetry_Int_Tables_number   1
_cell_volume   275.510
_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  0.756  0.943  0.403  1.0
  Na  Na1  1  0.777  0.371  0.701  1.0
  Na  Na2  1  0.268  0.399  0.821  1.0
  Na  Na3  1  0.249  0.798  0.010  1.0
  Na  Na4  1  0.725  0.219  0.026  1.0
  Na  Na5  1  0.189  0.510  0.456  1.0
  Na  Na6  1  0.246  0.902  0.602  1.0
  Na  Na7  1  0.823  0.587  0.078  1.0
  Mg  Mg8  1  0.636  0.445  0.382  1.0
  Cr  Cr9  1  0.268  0.165  0.244  1.0
  Cr  Cr10  1  0.717  0.869  0.742  1.0
  O  O11  1  0.124  0.205  0.062  1.0
  O  O12  1  0.980  0.364  0.338  1.0
  O  O13  1  0.964  0.675  0.634  1.0
  O  O14  1  0.528  0.640  0.830  1.0
  O  O15  1  0.501  0.343  0.231  1.0
  O  O16  1  0.452  0.809  0.368  1.0
  O  O17  1  0.857  0.954  0.883  1.0
  O  O18  1  0.555  0.219  0.590  1.0
[/CIF]
.