The structure described by Na6Ge2Se7 crystallizes in the monoclinic C2/c space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms to form NaSe6 octahedra that share corners with two equivalent Ge(1)Se4 tetrahedra and edges with two equivalent Ge(1)Se4 tetrahedra. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to one Se(1), one Se(4), two equivalent Se(2), and two equivalent Se(3) atoms. In the third Na site, Na(3) is bonded in a 4-coordinate geometry to two equivalent Se(1) and two equivalent Se(3) atoms. In the fourth Na site, Na(4) is bonded in a 6-coordinate geometry to one Se(3), one Se(4), two equivalent Se(1), and two equivalent Se(2) atoms. Ge(1) is bonded to one Se(1), one Se(2), one Se(3), and one Se(4) atom to form GeSe4 tetrahedra that share  a cornercorner with one Na(1)Se6 octahedra,  a cornercorner with one Ge(1)Se4 tetrahedra, and  an edgeedge with one Na(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 20°. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to one Na(1), one Na(2), one Na(3), two equivalent Na(4), and one Ge(1) atom to form a mixture of distorted edge, corner, and face-sharing SeNa5Ge octahedra. The corner-sharing octahedral tilt angles range from 0-71°. In the second Se site, Se(2) is bonded to one Na(1), two equivalent Na(2), two equivalent Na(4), and one Ge(1) atom to form a mixture of edge and corner-sharing SeNa5Ge octahedra. The corner-sharing octahedral tilt angles range from 0-54°. In the third Se site, Se(3) is bonded to one Na(1), one Na(3), one Na(4), two equivalent Na(2), and one Ge(1) atom to form a mixture of edge and corner-sharing SeNa5Ge octahedra. The corner-sharing octahedral tilt angles range from 0-75°. In the fourth Se site, Se(4) is bonded in a 2-coordinate geometry to two equivalent Na(2), two equivalent Na(4), and two equivalent Ge(1) atoms. is represented by the CIF file [CIF]
data_Na6Ge2Se7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.220
_cell_length_b   7.220
_cell_length_c   15.838
_cell_angle_alpha   80.545
_cell_angle_beta   80.545
_cell_angle_gamma   98.404
_symmetry_Int_Tables_number   1
_cell_volume   790.559
_cell_formula_units_Z   2
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  0.500  0.500  0.000  1.0
  Na  Na1  1  0.500  0.500  0.500  1.0
  Na  Na2  1  0.971  0.263  0.928  1.0
  Na  Na3  1  0.737  0.029  0.572  1.0
  Na  Na4  1  0.029  0.737  0.072  1.0
  Na  Na5  1  0.263  0.971  0.428  1.0
  Na  Na6  1  0.420  0.580  0.750  1.0
  Na  Na7  1  0.580  0.420  0.250  1.0
  Na  Na8  1  0.952  0.508  0.641  1.0
  Na  Na9  1  0.492  0.048  0.859  1.0
  Na  Na10  1  0.048  0.492  0.359  1.0
  Na  Na11  1  0.508  0.952  0.141  1.0
  Ge  Ge12  1  0.924  0.759  0.861  1.0
  Ge  Ge13  1  0.241  0.076  0.639  1.0
  Ge  Ge14  1  0.076  0.241  0.139  1.0
  Ge  Ge15  1  0.759  0.924  0.361  1.0
  Se  Se16  1  0.751  0.497  0.821  1.0
  Se  Se17  1  0.503  0.249  0.679  1.0
  Se  Se18  1  0.249  0.503  0.179  1.0
  Se  Se19  1  0.497  0.751  0.321  1.0
  Se  Se20  1  0.736  0.871  0.972  1.0
  Se  Se21  1  0.129  0.264  0.528  1.0
  Se  Se22  1  0.264  0.129  0.028  1.0
  Se  Se23  1  0.871  0.736  0.472  1.0
  Se  Se24  1  0.210  0.686  0.896  1.0
  Se  Se25  1  0.314  0.790  0.604  1.0
  Se  Se26  1  0.790  0.314  0.104  1.0
  Se  Se27  1  0.686  0.210  0.396  1.0
  Se  Se28  1  0.961  0.039  0.750  1.0
  Se  Se29  1  0.039  0.961  0.250  1.0
[/CIF]
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The structure described by Na6Ge2Se7 crystallizes in the monoclinic C2/c space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms to form NaSe6 octahedra that share corners with two equivalent Ge(1)Se4 tetrahedra and edges with two equivalent Ge(1)Se4 tetrahedra. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to one Se(1), one Se(4), two equivalent Se(2), and two equivalent Se(3) atoms. In the third Na site, Na(3) is bonded in a 4-coordinate geometry to two equivalent Se(1) and two equivalent Se(3) atoms. In the fourth Na site, Na(4) is bonded in a 6-coordinate geometry to one Se(3), one Se(4), two equivalent Se(1), and two equivalent Se(2) atoms. Ge(1) is bonded to one Se(1), one Se(2), one Se(3), and one Se(4) atom to form GeSe4 tetrahedra that share  a cornercorner with one Na(1)Se6 octahedra,  a cornercorner with one Ge(1)Se4 tetrahedra, and  an edgeedge with one Na(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 20°. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to one Na(1), one Na(2), one Na(3), two equivalent Na(4), and one Ge(1) atom to form a mixture of distorted edge, corner, and face-sharing SeNa5Ge octahedra. The corner-sharing octahedral tilt angles range from 0-71°. In the second Se site, Se(2) is bonded to one Na(1), two equivalent Na(2), two equivalent Na(4), and one Ge(1) atom to form a mixture of edge and corner-sharing SeNa5Ge octahedra. The corner-sharing octahedral tilt angles range from 0-54°. In the third Se site, Se(3) is bonded to one Na(1), one Na(3), one Na(4), two equivalent Na(2), and one Ge(1) atom to form a mixture of edge and corner-sharing SeNa5Ge octahedra. The corner-sharing octahedral tilt angles range from 0-75°. In the fourth Se site, Se(4) is bonded in a 2-coordinate geometry to two equivalent Na(2), two equivalent Na(4), and two equivalent Ge(1) atoms. is represented by the CIF file [CIF]
data_Na6Ge2Se7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.220
_cell_length_b   7.220
_cell_length_c   15.838
_cell_angle_alpha   80.545
_cell_angle_beta   80.545
_cell_angle_gamma   98.404
_symmetry_Int_Tables_number   1
_cell_volume   790.559
_cell_formula_units_Z   2
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  0.500  0.500  0.000  1.0
  Na  Na1  1  0.500  0.500  0.500  1.0
  Na  Na2  1  0.971  0.263  0.928  1.0
  Na  Na3  1  0.737  0.029  0.572  1.0
  Na  Na4  1  0.029  0.737  0.072  1.0
  Na  Na5  1  0.263  0.971  0.428  1.0
  Na  Na6  1  0.420  0.580  0.750  1.0
  Na  Na7  1  0.580  0.420  0.250  1.0
  Na  Na8  1  0.952  0.508  0.641  1.0
  Na  Na9  1  0.492  0.048  0.859  1.0
  Na  Na10  1  0.048  0.492  0.359  1.0
  Na  Na11  1  0.508  0.952  0.141  1.0
  Ge  Ge12  1  0.924  0.759  0.861  1.0
  Ge  Ge13  1  0.241  0.076  0.639  1.0
  Ge  Ge14  1  0.076  0.241  0.139  1.0
  Ge  Ge15  1  0.759  0.924  0.361  1.0
  Se  Se16  1  0.751  0.497  0.821  1.0
  Se  Se17  1  0.503  0.249  0.679  1.0
  Se  Se18  1  0.249  0.503  0.179  1.0
  Se  Se19  1  0.497  0.751  0.321  1.0
  Se  Se20  1  0.736  0.871  0.972  1.0
  Se  Se21  1  0.129  0.264  0.528  1.0
  Se  Se22  1  0.264  0.129  0.028  1.0
  Se  Se23  1  0.871  0.736  0.472  1.0
  Se  Se24  1  0.210  0.686  0.896  1.0
  Se  Se25  1  0.314  0.790  0.604  1.0
  Se  Se26  1  0.790  0.314  0.104  1.0
  Se  Se27  1  0.686  0.210  0.396  1.0
  Se  Se28  1  0.961  0.039  0.750  1.0
  Se  Se29  1  0.039  0.961  0.250  1.0
[/CIF]
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