The material described by MgYb2Se4 crystallizes in the orthorhombic Pnma space group. Mg(1) is bonded to two equivalent Se(4) and three equivalent Se(1) atoms to form MgSe5 square pyramids that share corners with two equivalent Yb(1)Se6 octahedra, corners with two equivalent Yb(2)Se6 octahedra,  an edgeedge with one Yb(1)Se6 octahedra, edges with three equivalent Yb(2)Se6 octahedra, and edges with four equivalent Mg(1)Se5 square pyramids. The corner-sharing octahedral tilt angles range from 5-7°. There are two inequivalent Yb sites. In the first Yb site, Yb(1) is bonded to one Se(3), two equivalent Se(4), and three equivalent Se(2) atoms to form YbSe6 octahedra that share corners with three equivalent Yb(2)Se6 octahedra, corners with two equivalent Mg(1)Se5 square pyramids, edges with two equivalent Yb(2)Se6 octahedra, edges with four equivalent Yb(1)Se6 octahedra, and  an edgeedge with one Mg(1)Se5 square pyramid. The corner-sharing octahedral tilt angles range from 55-74°. In the second Yb site, Yb(2) is bonded to one Se(2), one Se(4), two equivalent Se(1), and two equivalent Se(3) atoms to form YbSe6 octahedra that share corners with three equivalent Yb(1)Se6 octahedra, corners with two equivalent Mg(1)Se5 square pyramids, edges with two equivalent Yb(1)Se6 octahedra, edges with two equivalent Yb(2)Se6 octahedra, and edges with three equivalent Mg(1)Se5 square pyramids. The corner-sharing octahedral tilt angles range from 55-74°. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to three equivalent Mg(1) and two equivalent Yb(2) atoms to form SeYb2Mg3 square pyramids that share corners with two equivalent Se(2)Yb4 tetrahedra and edges with four equivalent Se(1)Yb2Mg3 square pyramids. In the second Se site, Se(2) is bonded to one Yb(2) and three equivalent Yb(1) atoms to form SeYb4 tetrahedra that share corners with two equivalent Se(1)Yb2Mg3 square pyramids, corners with two equivalent Se(2)Yb4 tetrahedra, and edges with two equivalent Se(2)Yb4 tetrahedra. In the third Se site, Se(3) is bonded in a 3-coordinate geometry to one Yb(1), two equivalent Yb(2), and one Se(4) atom. In the fourth Se site, Se(4) is bonded in a 6-coordinate geometry to two equivalent Mg(1), one Yb(2), two equivalent Yb(1), and one Se(3) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Yb2MgSe4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   14.641
_cell_length_b   4.077
_cell_length_c   12.295
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   733.867
_cell_formula_units_Z   4
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
  Yb  Yb0  1  0.118  0.250  0.073  1.0
  Yb  Yb1  1  0.882  0.750  0.927  1.0
  Yb  Yb2  1  0.382  0.750  0.573  1.0
  Yb  Yb3  1  0.618  0.250  0.427  1.0
  Yb  Yb4  1  0.131  0.250  0.707  1.0
  Yb  Yb5  1  0.869  0.750  0.293  1.0
  Yb  Yb6  1  0.369  0.750  0.207  1.0
  Yb  Yb7  1  0.631  0.250  0.793  1.0
  Mg  Mg8  1  0.101  0.750  0.438  1.0
  Mg  Mg9  1  0.899  0.250  0.562  1.0
  Mg  Mg10  1  0.399  0.250  0.938  1.0
  Mg  Mg11  1  0.601  0.750  0.062  1.0
  Se  Se12  1  0.007  0.750  0.626  1.0
  Se  Se13  1  0.993  0.250  0.374  1.0
  Se  Se14  1  0.493  0.250  0.126  1.0
  Se  Se15  1  0.507  0.750  0.874  1.0
  Se  Se16  1  0.010  0.250  0.880  1.0
  Se  Se17  1  0.990  0.750  0.120  1.0
  Se  Se18  1  0.490  0.750  0.380  1.0
  Se  Se19  1  0.510  0.250  0.620  1.0
  Se  Se20  1  0.236  0.250  0.273  1.0
  Se  Se21  1  0.764  0.750  0.727  1.0
  Se  Se22  1  0.264  0.750  0.773  1.0
  Se  Se23  1  0.736  0.250  0.227  1.0
  Se  Se24  1  0.264  0.750  0.988  1.0
  Se  Se25  1  0.736  0.250  0.012  1.0
  Se  Se26  1  0.236  0.250  0.488  1.0
  Se  Se27  1  0.764  0.750  0.512  1.0
[/CIF]
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The material described by MgYb2Se4 crystallizes in the orthorhombic Pnma space group. Mg(1) is bonded to two equivalent Se(4) and three equivalent Se(1) atoms to form MgSe5 square pyramids that share corners with two equivalent Yb(1)Se6 octahedra, corners with two equivalent Yb(2)Se6 octahedra,  an edgeedge with one Yb(1)Se6 octahedra, edges with three equivalent Yb(2)Se6 octahedra, and edges with four equivalent Mg(1)Se5 square pyramids. The corner-sharing octahedral tilt angles range from 5-7°. There are two inequivalent Yb sites. In the first Yb site, Yb(1) is bonded to one Se(3), two equivalent Se(4), and three equivalent Se(2) atoms to form YbSe6 octahedra that share corners with three equivalent Yb(2)Se6 octahedra, corners with two equivalent Mg(1)Se5 square pyramids, edges with two equivalent Yb(2)Se6 octahedra, edges with four equivalent Yb(1)Se6 octahedra, and  an edgeedge with one Mg(1)Se5 square pyramid. The corner-sharing octahedral tilt angles range from 55-74°. In the second Yb site, Yb(2) is bonded to one Se(2), one Se(4), two equivalent Se(1), and two equivalent Se(3) atoms to form YbSe6 octahedra that share corners with three equivalent Yb(1)Se6 octahedra, corners with two equivalent Mg(1)Se5 square pyramids, edges with two equivalent Yb(1)Se6 octahedra, edges with two equivalent Yb(2)Se6 octahedra, and edges with three equivalent Mg(1)Se5 square pyramids. The corner-sharing octahedral tilt angles range from 55-74°. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to three equivalent Mg(1) and two equivalent Yb(2) atoms to form SeYb2Mg3 square pyramids that share corners with two equivalent Se(2)Yb4 tetrahedra and edges with four equivalent Se(1)Yb2Mg3 square pyramids. In the second Se site, Se(2) is bonded to one Yb(2) and three equivalent Yb(1) atoms to form SeYb4 tetrahedra that share corners with two equivalent Se(1)Yb2Mg3 square pyramids, corners with two equivalent Se(2)Yb4 tetrahedra, and edges with two equivalent Se(2)Yb4 tetrahedra. In the third Se site, Se(3) is bonded in a 3-coordinate geometry to one Yb(1), two equivalent Yb(2), and one Se(4) atom. In the fourth Se site, Se(4) is bonded in a 6-coordinate geometry to two equivalent Mg(1), one Yb(2), two equivalent Yb(1), and one Se(3) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Yb2MgSe4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   14.641
_cell_length_b   4.077
_cell_length_c   12.295
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   733.867
_cell_formula_units_Z   4
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
  Yb  Yb0  1  0.118  0.250  0.073  1.0
  Yb  Yb1  1  0.882  0.750  0.927  1.0
  Yb  Yb2  1  0.382  0.750  0.573  1.0
  Yb  Yb3  1  0.618  0.250  0.427  1.0
  Yb  Yb4  1  0.131  0.250  0.707  1.0
  Yb  Yb5  1  0.869  0.750  0.293  1.0
  Yb  Yb6  1  0.369  0.750  0.207  1.0
  Yb  Yb7  1  0.631  0.250  0.793  1.0
  Mg  Mg8  1  0.101  0.750  0.438  1.0
  Mg  Mg9  1  0.899  0.250  0.562  1.0
  Mg  Mg10  1  0.399  0.250  0.938  1.0
  Mg  Mg11  1  0.601  0.750  0.062  1.0
  Se  Se12  1  0.007  0.750  0.626  1.0
  Se  Se13  1  0.993  0.250  0.374  1.0
  Se  Se14  1  0.493  0.250  0.126  1.0
  Se  Se15  1  0.507  0.750  0.874  1.0
  Se  Se16  1  0.010  0.250  0.880  1.0
  Se  Se17  1  0.990  0.750  0.120  1.0
  Se  Se18  1  0.490  0.750  0.380  1.0
  Se  Se19  1  0.510  0.250  0.620  1.0
  Se  Se20  1  0.236  0.250  0.273  1.0
  Se  Se21  1  0.764  0.750  0.727  1.0
  Se  Se22  1  0.264  0.750  0.773  1.0
  Se  Se23  1  0.736  0.250  0.227  1.0
  Se  Se24  1  0.264  0.750  0.988  1.0
  Se  Se25  1  0.736  0.250  0.012  1.0
  Se  Se26  1  0.236  0.250  0.488  1.0
  Se  Se27  1  0.764  0.750  0.512  1.0
[/CIF]
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