The material structure described by NaMgCr3O8 crystallizes in the monoclinic Cm space group. Na(1) is bonded to one O(5), one O(6), two equivalent O(1), and two equivalent O(2) atoms to form NaO6 octahedra that share corners with three equivalent Mg(1)O4 tetrahedra, corners with three equivalent Cr(1)O4 tetrahedra, corners with three equivalent Cr(3)O4 tetrahedra, and edges with two equivalent Cr(2)O6 octahedra. Mg(1) is bonded to one O(4), one O(5), and two equivalent O(2) atoms to form distorted MgO4 tetrahedra that share corners with three equivalent Na(1)O6 octahedra, corners with three equivalent Cr(2)O6 octahedra, corners with two equivalent Cr(1)O4 tetrahedra, and  an edgeedge with one Cr(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 61-78°. There are three inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(4), one O(5), and two equivalent O(1) atoms to form CrO4 tetrahedra that share corners with three equivalent Na(1)O6 octahedra, corners with three equivalent Cr(2)O6 octahedra, and corners with two equivalent Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 44-63°. In the second Cr site, Cr(2) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form CrO6 octahedra that share corners with three equivalent Mg(1)O4 tetrahedra, corners with three equivalent Cr(1)O4 tetrahedra, corners with three equivalent Cr(3)O4 tetrahedra, and edges with two equivalent Na(1)O6 octahedra. In the third Cr site, Cr(3) is bonded to one O(3), one O(6), and two equivalent O(2) atoms to form CrO4 tetrahedra that share corners with three equivalent Na(1)O6 octahedra, corners with three equivalent Cr(2)O6 octahedra, and  an edgeedge with one Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 45-64°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Na(1), one Cr(1), and one Cr(2) atom. In the second O site, O(2) is bonded to one Na(1), one Mg(1), one Cr(2), and one Cr(3) atom to form distorted edge-sharing ONaMgCr2 tetrahedra. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Cr(2) and one Cr(3) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Mg(1), one Cr(1), and one Cr(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Na(1), one Mg(1), and one Cr(1) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Na(1) and one Cr(3) atom. is represented by the CIF card [CIF]
data_NaMgCr3O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.251
_cell_length_b   5.251
_cell_length_c   6.581
_cell_angle_alpha   89.587
_cell_angle_beta   89.587
_cell_angle_gamma   65.122
_symmetry_Int_Tables_number   1
_cell_volume   164.648
_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  0.004  0.004  0.990  1.0
  Mg  Mg1  1  0.663  0.663  0.259  1.0
  Cr  Cr2  1  0.641  0.641  0.737  1.0
  Cr  Cr3  1  0.002  0.002  0.498  1.0
  Cr  Cr4  1  0.349  0.349  0.272  1.0
  O  O5  1  0.776  0.282  0.710  1.0
  O  O6  1  0.729  0.253  0.282  1.0
  O  O7  1  0.253  0.729  0.282  1.0
  O  O8  1  0.282  0.776  0.710  1.0
  O  O9  1  0.227  0.227  0.469  1.0
  O  O10  1  0.773  0.773  0.525  1.0
  O  O11  1  0.728  0.728  0.967  1.0
  O  O12  1  0.273  0.273  0.049  1.0
[/CIF]
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The material structure described by NaMgCr3O8 crystallizes in the monoclinic Cm space group. Na(1) is bonded to one O(5), one O(6), two equivalent O(1), and two equivalent O(2) atoms to form NaO6 octahedra that share corners with three equivalent Mg(1)O4 tetrahedra, corners with three equivalent Cr(1)O4 tetrahedra, corners with three equivalent Cr(3)O4 tetrahedra, and edges with two equivalent Cr(2)O6 octahedra. Mg(1) is bonded to one O(4), one O(5), and two equivalent O(2) atoms to form distorted MgO4 tetrahedra that share corners with three equivalent Na(1)O6 octahedra, corners with three equivalent Cr(2)O6 octahedra, corners with two equivalent Cr(1)O4 tetrahedra, and  an edgeedge with one Cr(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 61-78°. There are three inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(4), one O(5), and two equivalent O(1) atoms to form CrO4 tetrahedra that share corners with three equivalent Na(1)O6 octahedra, corners with three equivalent Cr(2)O6 octahedra, and corners with two equivalent Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 44-63°. In the second Cr site, Cr(2) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form CrO6 octahedra that share corners with three equivalent Mg(1)O4 tetrahedra, corners with three equivalent Cr(1)O4 tetrahedra, corners with three equivalent Cr(3)O4 tetrahedra, and edges with two equivalent Na(1)O6 octahedra. In the third Cr site, Cr(3) is bonded to one O(3), one O(6), and two equivalent O(2) atoms to form CrO4 tetrahedra that share corners with three equivalent Na(1)O6 octahedra, corners with three equivalent Cr(2)O6 octahedra, and  an edgeedge with one Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 45-64°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Na(1), one Cr(1), and one Cr(2) atom. In the second O site, O(2) is bonded to one Na(1), one Mg(1), one Cr(2), and one Cr(3) atom to form distorted edge-sharing ONaMgCr2 tetrahedra. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Cr(2) and one Cr(3) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Mg(1), one Cr(1), and one Cr(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Na(1), one Mg(1), and one Cr(1) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Na(1) and one Cr(3) atom. is represented by the CIF card [CIF]
data_NaMgCr3O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.251
_cell_length_b   5.251
_cell_length_c   6.581
_cell_angle_alpha   89.587
_cell_angle_beta   89.587
_cell_angle_gamma   65.122
_symmetry_Int_Tables_number   1
_cell_volume   164.648
_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  0.004  0.004  0.990  1.0
  Mg  Mg1  1  0.663  0.663  0.259  1.0
  Cr  Cr2  1  0.641  0.641  0.737  1.0
  Cr  Cr3  1  0.002  0.002  0.498  1.0
  Cr  Cr4  1  0.349  0.349  0.272  1.0
  O  O5  1  0.776  0.282  0.710  1.0
  O  O6  1  0.729  0.253  0.282  1.0
  O  O7  1  0.253  0.729  0.282  1.0
  O  O8  1  0.282  0.776  0.710  1.0
  O  O9  1  0.227  0.227  0.469  1.0
  O  O10  1  0.773  0.773  0.525  1.0
  O  O11  1  0.728  0.728  0.967  1.0
  O  O12  1  0.273  0.273  0.049  1.0
[/CIF]
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