The material described by NaAlSe2 crystallizes in the monoclinic C2/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to one Se(1), one Se(2), one Se(3), one Se(5), and two equivalent Se(4) atoms to form distorted NaSe6 pentagonal pyramids that share corners with four equivalent Al(1)Se4 tetrahedra, corners with six equivalent Al(2)Se4 tetrahedra, edges with two equivalent Na(2)Se6 pentagonal pyramids,  an edgeedge with one Al(1)Se4 tetrahedra,  a faceface with one Na(1)Se6 pentagonal pyramid, and faces with two equivalent Na(2)Se6 pentagonal pyramids. In the second Na site, Na(2) is bonded to one Se(1), one Se(2), one Se(3), one Se(5), and two equivalent Se(4) atoms to form distorted NaSe6 pentagonal pyramids that share corners with four equivalent Na(2)Se6 pentagonal pyramids, corners with two equivalent Al(2)Se4 tetrahedra, corners with four equivalent Al(1)Se4 tetrahedra, edges with two equivalent Na(1)Se6 pentagonal pyramids,  an edgeedge with one Al(1)Se4 tetrahedra, edges with two equivalent Al(2)Se4 tetrahedra, and faces with two equivalent Na(1)Se6 pentagonal pyramids. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one Se(1), one Se(3), one Se(4), and one Se(5) atom to form AlSe4 tetrahedra that share corners with four equivalent Na(1)Se6 pentagonal pyramids, corners with four equivalent Na(2)Se6 pentagonal pyramids,  a cornercorner with one Al(1)Se4 tetrahedra, corners with three equivalent Al(2)Se4 tetrahedra,  an edgeedge with one Na(1)Se6 pentagonal pyramid, and  an edgeedge with one Na(2)Se6 pentagonal pyramid. In the second Al site, Al(2) is bonded to one Se(2), one Se(3), one Se(4), and one Se(5) atom to form AlSe4 tetrahedra that share corners with two equivalent Na(2)Se6 pentagonal pyramids, corners with six equivalent Na(1)Se6 pentagonal pyramids,  a cornercorner with one Al(2)Se4 tetrahedra, corners with three equivalent Al(1)Se4 tetrahedra, and edges with two equivalent Na(2)Se6 pentagonal pyramids. There are five inequivalent Se sites. In the first Se site, Se(1) is bonded in a 6-coordinate geometry to two equivalent Na(1), two equivalent Na(2), and two equivalent Al(1) atoms. In the second Se site, Se(2) is bonded in a 6-coordinate geometry to two equivalent Na(1), two equivalent Na(2), and two equivalent Al(2) atoms. In the third Se site, Se(3) is bonded in a rectangular see-saw-like geometry to one Na(1), one Na(2), one Al(1), and one Al(2) atom. In the fourth Se site, Se(4) is bonded in a 6-coordinate geometry to two equivalent Na(1), two equivalent Na(2), one Al(1), and one Al(2) atom. In the fifth Se site, Se(5) is bonded in a rectangular see-saw-like geometry to one Na(1), one Na(2), one Al(1), and one Al(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_NaAlSe2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.582
_cell_length_b   7.582
_cell_length_c   14.069
_cell_angle_alpha   82.111
_cell_angle_beta   82.111
_cell_angle_gamma   89.972
_symmetry_Int_Tables_number   1
_cell_volume   793.402
_cell_formula_units_Z   8
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  0.222  0.847  0.121  1.0
  Na  Na1  1  0.153  0.778  0.379  1.0
  Na  Na2  1  0.778  0.153  0.879  1.0
  Na  Na3  1  0.847  0.222  0.621  1.0
  Na  Na4  1  0.656  0.781  0.373  1.0
  Na  Na5  1  0.219  0.344  0.127  1.0
  Na  Na6  1  0.344  0.219  0.627  1.0
  Na  Na7  1  0.781  0.656  0.873  1.0
  Al  Al8  1  0.713  0.091  0.150  1.0
  Al  Al9  1  0.909  0.287  0.350  1.0
  Al  Al10  1  0.287  0.909  0.850  1.0
  Al  Al11  1  0.091  0.713  0.650  1.0
  Al  Al12  1  0.416  0.287  0.350  1.0
  Al  Al13  1  0.713  0.584  0.150  1.0
  Al  Al14  1  0.584  0.713  0.650  1.0
  Al  Al15  1  0.287  0.416  0.850  1.0
  Se  Se16  1  0.945  0.055  0.250  1.0
  Se  Se17  1  0.055  0.945  0.750  1.0
  Se  Se18  1  0.431  0.569  0.250  1.0
  Se  Se19  1  0.569  0.431  0.750  1.0
  Se  Se20  1  0.739  0.863  0.048  1.0
  Se  Se21  1  0.137  0.261  0.452  1.0
  Se  Se22  1  0.261  0.137  0.952  1.0
  Se  Se23  1  0.863  0.739  0.548  1.0
  Se  Se24  1  0.431  0.055  0.251  1.0
  Se  Se25  1  0.945  0.569  0.249  1.0
  Se  Se26  1  0.569  0.945  0.749  1.0
  Se  Se27  1  0.055  0.431  0.751  1.0
  Se  Se28  1  0.636  0.261  0.456  1.0
  Se  Se29  1  0.739  0.364  0.044  1.0
  Se  Se30  1  0.364  0.739  0.544  1.0
  Se  Se31  1  0.261  0.636  0.956  1.0
[/CIF]
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The material described by NaAlSe2 crystallizes in the monoclinic C2/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to one Se(1), one Se(2), one Se(3), one Se(5), and two equivalent Se(4) atoms to form distorted NaSe6 pentagonal pyramids that share corners with four equivalent Al(1)Se4 tetrahedra, corners with six equivalent Al(2)Se4 tetrahedra, edges with two equivalent Na(2)Se6 pentagonal pyramids,  an edgeedge with one Al(1)Se4 tetrahedra,  a faceface with one Na(1)Se6 pentagonal pyramid, and faces with two equivalent Na(2)Se6 pentagonal pyramids. In the second Na site, Na(2) is bonded to one Se(1), one Se(2), one Se(3), one Se(5), and two equivalent Se(4) atoms to form distorted NaSe6 pentagonal pyramids that share corners with four equivalent Na(2)Se6 pentagonal pyramids, corners with two equivalent Al(2)Se4 tetrahedra, corners with four equivalent Al(1)Se4 tetrahedra, edges with two equivalent Na(1)Se6 pentagonal pyramids,  an edgeedge with one Al(1)Se4 tetrahedra, edges with two equivalent Al(2)Se4 tetrahedra, and faces with two equivalent Na(1)Se6 pentagonal pyramids. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one Se(1), one Se(3), one Se(4), and one Se(5) atom to form AlSe4 tetrahedra that share corners with four equivalent Na(1)Se6 pentagonal pyramids, corners with four equivalent Na(2)Se6 pentagonal pyramids,  a cornercorner with one Al(1)Se4 tetrahedra, corners with three equivalent Al(2)Se4 tetrahedra,  an edgeedge with one Na(1)Se6 pentagonal pyramid, and  an edgeedge with one Na(2)Se6 pentagonal pyramid. In the second Al site, Al(2) is bonded to one Se(2), one Se(3), one Se(4), and one Se(5) atom to form AlSe4 tetrahedra that share corners with two equivalent Na(2)Se6 pentagonal pyramids, corners with six equivalent Na(1)Se6 pentagonal pyramids,  a cornercorner with one Al(2)Se4 tetrahedra, corners with three equivalent Al(1)Se4 tetrahedra, and edges with two equivalent Na(2)Se6 pentagonal pyramids. There are five inequivalent Se sites. In the first Se site, Se(1) is bonded in a 6-coordinate geometry to two equivalent Na(1), two equivalent Na(2), and two equivalent Al(1) atoms. In the second Se site, Se(2) is bonded in a 6-coordinate geometry to two equivalent Na(1), two equivalent Na(2), and two equivalent Al(2) atoms. In the third Se site, Se(3) is bonded in a rectangular see-saw-like geometry to one Na(1), one Na(2), one Al(1), and one Al(2) atom. In the fourth Se site, Se(4) is bonded in a 6-coordinate geometry to two equivalent Na(1), two equivalent Na(2), one Al(1), and one Al(2) atom. In the fifth Se site, Se(5) is bonded in a rectangular see-saw-like geometry to one Na(1), one Na(2), one Al(1), and one Al(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_NaAlSe2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.582
_cell_length_b   7.582
_cell_length_c   14.069
_cell_angle_alpha   82.111
_cell_angle_beta   82.111
_cell_angle_gamma   89.972
_symmetry_Int_Tables_number   1
_cell_volume   793.402
_cell_formula_units_Z   8
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  0.222  0.847  0.121  1.0
  Na  Na1  1  0.153  0.778  0.379  1.0
  Na  Na2  1  0.778  0.153  0.879  1.0
  Na  Na3  1  0.847  0.222  0.621  1.0
  Na  Na4  1  0.656  0.781  0.373  1.0
  Na  Na5  1  0.219  0.344  0.127  1.0
  Na  Na6  1  0.344  0.219  0.627  1.0
  Na  Na7  1  0.781  0.656  0.873  1.0
  Al  Al8  1  0.713  0.091  0.150  1.0
  Al  Al9  1  0.909  0.287  0.350  1.0
  Al  Al10  1  0.287  0.909  0.850  1.0
  Al  Al11  1  0.091  0.713  0.650  1.0
  Al  Al12  1  0.416  0.287  0.350  1.0
  Al  Al13  1  0.713  0.584  0.150  1.0
  Al  Al14  1  0.584  0.713  0.650  1.0
  Al  Al15  1  0.287  0.416  0.850  1.0
  Se  Se16  1  0.945  0.055  0.250  1.0
  Se  Se17  1  0.055  0.945  0.750  1.0
  Se  Se18  1  0.431  0.569  0.250  1.0
  Se  Se19  1  0.569  0.431  0.750  1.0
  Se  Se20  1  0.739  0.863  0.048  1.0
  Se  Se21  1  0.137  0.261  0.452  1.0
  Se  Se22  1  0.261  0.137  0.952  1.0
  Se  Se23  1  0.863  0.739  0.548  1.0
  Se  Se24  1  0.431  0.055  0.251  1.0
  Se  Se25  1  0.945  0.569  0.249  1.0
  Se  Se26  1  0.569  0.945  0.749  1.0
  Se  Se27  1  0.055  0.431  0.751  1.0
  Se  Se28  1  0.636  0.261  0.456  1.0
  Se  Se29  1  0.739  0.364  0.044  1.0
  Se  Se30  1  0.364  0.739  0.544  1.0
  Se  Se31  1  0.261  0.636  0.956  1.0
[/CIF]
.