The material structure described by Er7FeI12 is trigonal omega-derived structured and crystallizes in the trigonal R-3 space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to one Fe(1), two equivalent I(1), and three equivalent I(2) atoms to form distorted ErFeI5 octahedra that share corners with three equivalent Er(1)FeI5 octahedra,  an edgeedge with one Er(2)I6 octahedra, and edges with five equivalent Er(1)FeI5 octahedra. The corner-sharing octahedral tilt angles range from 0-11°. In the second Er site, Er(2) is bonded to six equivalent I(1) atoms to form edge-sharing ErI6 octahedra. Fe(1) is bonded in an octahedral geometry to six equivalent Er(1) atoms. There are two inequivalent I sites. In the first I site, I(1) is bonded in a distorted T-shaped geometry to one Er(2) and two equivalent Er(1) atoms. In the second I site, I(2) is bonded in a 3-coordinate geometry to three equivalent Er(1) atoms. is represented by the CIF file [CIF]
data_Er7FeI12
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.598
_cell_length_b   9.598
_cell_length_c   9.598
_cell_angle_alpha   107.065
_cell_angle_beta   107.065
_cell_angle_gamma   107.065
_symmetry_Int_Tables_number   1
_cell_volume   734.967
_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
  Er  Er0  1  0.910  0.980  0.713  1.0
  Er  Er1  1  0.713  0.910  0.980  1.0
  Er  Er2  1  0.980  0.713  0.910  1.0
  Er  Er3  1  0.090  0.020  0.287  1.0
  Er  Er4  1  0.287  0.090  0.020  1.0
  Er  Er5  1  0.020  0.287  0.090  1.0
  Er  Er6  1  0.500  0.500  0.500  1.0
  Fe  Fe7  1  0.000  0.000  0.000  1.0
  I  I8  1  0.840  0.614  0.536  1.0
  I  I9  1  0.536  0.840  0.614  1.0
  I  I10  1  0.614  0.536  0.840  1.0
  I  I11  1  0.160  0.386  0.464  1.0
  I  I12  1  0.464  0.160  0.386  1.0
  I  I13  1  0.386  0.464  0.160  1.0
  I  I14  1  0.928  0.323  0.773  1.0
  I  I15  1  0.773  0.928  0.323  1.0
  I  I16  1  0.323  0.773  0.928  1.0
  I  I17  1  0.072  0.677  0.227  1.0
  I  I18  1  0.227  0.072  0.677  1.0
  I  I19  1  0.677  0.227  0.072  1.0
[/CIF]
.
The material structure described by Er7FeI12 is trigonal omega-derived structured and crystallizes in the trigonal R-3 space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to one Fe(1), two equivalent I(1), and three equivalent I(2) atoms to form distorted ErFeI5 octahedra that share corners with three equivalent Er(1)FeI5 octahedra,  an edgeedge with one Er(2)I6 octahedra, and edges with five equivalent Er(1)FeI5 octahedra. The corner-sharing octahedral tilt angles range from 0-11°. In the second Er site, Er(2) is bonded to six equivalent I(1) atoms to form edge-sharing ErI6 octahedra. Fe(1) is bonded in an octahedral geometry to six equivalent Er(1) atoms. There are two inequivalent I sites. In the first I site, I(1) is bonded in a distorted T-shaped geometry to one Er(2) and two equivalent Er(1) atoms. In the second I site, I(2) is bonded in a 3-coordinate geometry to three equivalent Er(1) atoms. is represented by the CIF file [CIF]
data_Er7FeI12
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.598
_cell_length_b   9.598
_cell_length_c   9.598
_cell_angle_alpha   107.065
_cell_angle_beta   107.065
_cell_angle_gamma   107.065
_symmetry_Int_Tables_number   1
_cell_volume   734.967
_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
  Er  Er0  1  0.910  0.980  0.713  1.0
  Er  Er1  1  0.713  0.910  0.980  1.0
  Er  Er2  1  0.980  0.713  0.910  1.0
  Er  Er3  1  0.090  0.020  0.287  1.0
  Er  Er4  1  0.287  0.090  0.020  1.0
  Er  Er5  1  0.020  0.287  0.090  1.0
  Er  Er6  1  0.500  0.500  0.500  1.0
  Fe  Fe7  1  0.000  0.000  0.000  1.0
  I  I8  1  0.840  0.614  0.536  1.0
  I  I9  1  0.536  0.840  0.614  1.0
  I  I10  1  0.614  0.536  0.840  1.0
  I  I11  1  0.160  0.386  0.464  1.0
  I  I12  1  0.464  0.160  0.386  1.0
  I  I13  1  0.386  0.464  0.160  1.0
  I  I14  1  0.928  0.323  0.773  1.0
  I  I15  1  0.773  0.928  0.323  1.0
  I  I16  1  0.323  0.773  0.928  1.0
  I  I17  1  0.072  0.677  0.227  1.0
  I  I18  1  0.227  0.072  0.677  1.0
  I  I19  1  0.677  0.227  0.072  1.0
[/CIF]
.