The structure described by MgEr2Se4 crystallizes in the orthorhombic Pnma space group. Mg(1) is bonded in a trigonal pyramidal geometry to one Se(2), one Se(3), and two equivalent Se(1) atoms. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 7-coordinate geometry to one Se(2), two equivalent Se(3), and four equivalent Se(1) atoms. In the second Er site, Er(2) is bonded in a 6-coordinate geometry to one Se(2), one Se(3), and four equivalent Se(1) atoms. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a 5-coordinate geometry to one Mg(1), two equivalent Er(1), and two equivalent Er(2) atoms. In the second Se site, Se(2) is bonded in a T-shaped geometry to one Mg(1), one Er(1), and one Er(2) atom. In the third Se site, Se(3) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Er(2), and two equivalent Er(1) atoms. is represented by the CIF file [CIF]
data_Er2MgSe4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.166
_cell_length_b   7.716
_cell_length_c   11.935
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   752.064
_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
  Er  Er0  1  0.045  0.750  0.312  1.0
  Er  Er1  1  0.955  0.250  0.688  1.0
  Er  Er2  1  0.455  0.250  0.812  1.0
  Er  Er3  1  0.545  0.750  0.188  1.0
  Er  Er4  1  0.063  0.250  0.019  1.0
  Er  Er5  1  0.937  0.750  0.981  1.0
  Er  Er6  1  0.437  0.750  0.519  1.0
  Er  Er7  1  0.563  0.250  0.481  1.0
  Mg  Mg8  1  0.183  0.250  0.407  1.0
  Mg  Mg9  1  0.817  0.750  0.593  1.0
  Mg  Mg10  1  0.317  0.750  0.907  1.0
  Mg  Mg11  1  0.683  0.250  0.093  1.0
  Se  Se12  1  0.125  0.503  0.843  1.0
  Se  Se13  1  0.875  0.497  0.157  1.0
  Se  Se14  1  0.375  0.497  0.343  1.0
  Se  Se15  1  0.625  0.503  0.657  1.0
  Se  Se16  1  0.625  0.997  0.657  1.0
  Se  Se17  1  0.375  0.003  0.343  1.0
  Se  Se18  1  0.875  0.003  0.157  1.0
  Se  Se19  1  0.125  0.997  0.843  1.0
  Se  Se20  1  0.890  0.250  0.457  1.0
  Se  Se21  1  0.110  0.750  0.543  1.0
  Se  Se22  1  0.610  0.750  0.957  1.0
  Se  Se23  1  0.390  0.250  0.043  1.0
  Se  Se24  1  0.223  0.750  0.115  1.0
  Se  Se25  1  0.777  0.250  0.885  1.0
  Se  Se26  1  0.277  0.250  0.615  1.0
  Se  Se27  1  0.723  0.750  0.385  1.0
[/CIF]
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The structure described by MgEr2Se4 crystallizes in the orthorhombic Pnma space group. Mg(1) is bonded in a trigonal pyramidal geometry to one Se(2), one Se(3), and two equivalent Se(1) atoms. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 7-coordinate geometry to one Se(2), two equivalent Se(3), and four equivalent Se(1) atoms. In the second Er site, Er(2) is bonded in a 6-coordinate geometry to one Se(2), one Se(3), and four equivalent Se(1) atoms. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a 5-coordinate geometry to one Mg(1), two equivalent Er(1), and two equivalent Er(2) atoms. In the second Se site, Se(2) is bonded in a T-shaped geometry to one Mg(1), one Er(1), and one Er(2) atom. In the third Se site, Se(3) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Er(2), and two equivalent Er(1) atoms. is represented by the CIF file [CIF]
data_Er2MgSe4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.166
_cell_length_b   7.716
_cell_length_c   11.935
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   752.064
_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
  Er  Er0  1  0.045  0.750  0.312  1.0
  Er  Er1  1  0.955  0.250  0.688  1.0
  Er  Er2  1  0.455  0.250  0.812  1.0
  Er  Er3  1  0.545  0.750  0.188  1.0
  Er  Er4  1  0.063  0.250  0.019  1.0
  Er  Er5  1  0.937  0.750  0.981  1.0
  Er  Er6  1  0.437  0.750  0.519  1.0
  Er  Er7  1  0.563  0.250  0.481  1.0
  Mg  Mg8  1  0.183  0.250  0.407  1.0
  Mg  Mg9  1  0.817  0.750  0.593  1.0
  Mg  Mg10  1  0.317  0.750  0.907  1.0
  Mg  Mg11  1  0.683  0.250  0.093  1.0
  Se  Se12  1  0.125  0.503  0.843  1.0
  Se  Se13  1  0.875  0.497  0.157  1.0
  Se  Se14  1  0.375  0.497  0.343  1.0
  Se  Se15  1  0.625  0.503  0.657  1.0
  Se  Se16  1  0.625  0.997  0.657  1.0
  Se  Se17  1  0.375  0.003  0.343  1.0
  Se  Se18  1  0.875  0.003  0.157  1.0
  Se  Se19  1  0.125  0.997  0.843  1.0
  Se  Se20  1  0.890  0.250  0.457  1.0
  Se  Se21  1  0.110  0.750  0.543  1.0
  Se  Se22  1  0.610  0.750  0.957  1.0
  Se  Se23  1  0.390  0.250  0.043  1.0
  Se  Se24  1  0.223  0.750  0.115  1.0
  Se  Se25  1  0.777  0.250  0.885  1.0
  Se  Se26  1  0.277  0.250  0.615  1.0
  Se  Se27  1  0.723  0.750  0.385  1.0
[/CIF]
.