The material described by MgEr2S4 crystallizes in the orthorhombic Pnma space group. Mg(1) is bonded to two equivalent S(4) and three equivalent S(1) atoms to form MgS5 square pyramids that share corners with two equivalent Er(1)S6 octahedra, corners with two equivalent Er(2)S6 octahedra,  an edgeedge with one Er(1)S6 octahedra, edges with three equivalent Er(2)S6 octahedra, and edges with four equivalent Mg(1)S5 square pyramids. The corner-sharing octahedral tilt angles range from 5-8°. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to one S(3), two equivalent S(4), and three equivalent S(2) atoms to form ErS6 octahedra that share corners with three equivalent Er(2)S6 octahedra, corners with two equivalent Mg(1)S5 square pyramids, edges with two equivalent Er(2)S6 octahedra, edges with four equivalent Er(1)S6 octahedra, and  an edgeedge with one Mg(1)S5 square pyramid. The corner-sharing octahedral tilt angles range from 53-59°. In the second Er site, Er(2) is bonded to one S(2), one S(4), two equivalent S(1), and two equivalent S(3) atoms to form ErS6 octahedra that share corners with three equivalent Er(1)S6 octahedra, corners with two equivalent Mg(1)S5 square pyramids, edges with two equivalent Er(1)S6 octahedra, edges with two equivalent Er(2)S6 octahedra, and edges with three equivalent Mg(1)S5 square pyramids. The corner-sharing octahedral tilt angles range from 53-59°. There are four inequivalent S sites. In the first S site, S(1) is bonded to three equivalent Mg(1) and two equivalent Er(2) atoms to form SEr2Mg3 square pyramids that share corners with two equivalent S(4)Er3Mg2 square pyramids, edges with three equivalent S(4)Er3Mg2 square pyramids, and edges with four equivalent S(1)Er2Mg3 square pyramids. In the second S site, S(2) is bonded in a rectangular see-saw-like geometry to one Er(2) and three equivalent Er(1) atoms. In the third S site, S(3) is bonded in a distorted T-shaped geometry to one Er(1) and two equivalent Er(2) atoms. In the fourth S site, S(4) is bonded to two equivalent Mg(1), one Er(2), and two equivalent Er(1) atoms to form SEr3Mg2 square pyramids that share corners with two equivalent S(1)Er2Mg3 square pyramids, edges with two equivalent S(4)Er3Mg2 square pyramids, and edges with three equivalent S(1)Er2Mg3 square pyramids. is represented by the CIF card [CIF]
data_Er2MgS4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   12.521
_cell_length_b   3.814
_cell_length_c   13.272
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   633.877
_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  0.115  0.250  0.077  1.0
  Er  Er1  1  0.885  0.750  0.923  1.0
  Er  Er2  1  0.385  0.750  0.577  1.0
  Er  Er3  1  0.615  0.250  0.423  1.0
  Er  Er4  1  0.142  0.250  0.704  1.0
  Er  Er5  1  0.858  0.750  0.296  1.0
  Er  Er6  1  0.358  0.750  0.204  1.0
  Er  Er7  1  0.642  0.250  0.796  1.0
  Mg  Mg8  1  0.115  0.750  0.445  1.0
  Mg  Mg9  1  0.885  0.250  0.555  1.0
  Mg  Mg10  1  0.385  0.250  0.945  1.0
  Mg  Mg11  1  0.615  0.750  0.055  1.0
  S  S12  1  0.014  0.750  0.614  1.0
  S  S13  1  0.986  0.250  0.386  1.0
  S  S14  1  0.486  0.250  0.114  1.0
  S  S15  1  0.514  0.750  0.886  1.0
  S  S16  1  0.030  0.250  0.883  1.0
  S  S17  1  0.970  0.750  0.117  1.0
  S  S18  1  0.470  0.750  0.383  1.0
  S  S19  1  0.530  0.250  0.617  1.0
  S  S20  1  0.222  0.250  0.252  1.0
  S  S21  1  0.778  0.750  0.748  1.0
  S  S22  1  0.278  0.750  0.752  1.0
  S  S23  1  0.722  0.250  0.248  1.0
  S  S24  1  0.258  0.750  0.017  1.0
  S  S25  1  0.742  0.250  0.983  1.0
  S  S26  1  0.242  0.250  0.517  1.0
  S  S27  1  0.758  0.750  0.483  1.0
[/CIF]
.
The material described by MgEr2S4 crystallizes in the orthorhombic Pnma space group. Mg(1) is bonded to two equivalent S(4) and three equivalent S(1) atoms to form MgS5 square pyramids that share corners with two equivalent Er(1)S6 octahedra, corners with two equivalent Er(2)S6 octahedra,  an edgeedge with one Er(1)S6 octahedra, edges with three equivalent Er(2)S6 octahedra, and edges with four equivalent Mg(1)S5 square pyramids. The corner-sharing octahedral tilt angles range from 5-8°. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to one S(3), two equivalent S(4), and three equivalent S(2) atoms to form ErS6 octahedra that share corners with three equivalent Er(2)S6 octahedra, corners with two equivalent Mg(1)S5 square pyramids, edges with two equivalent Er(2)S6 octahedra, edges with four equivalent Er(1)S6 octahedra, and  an edgeedge with one Mg(1)S5 square pyramid. The corner-sharing octahedral tilt angles range from 53-59°. In the second Er site, Er(2) is bonded to one S(2), one S(4), two equivalent S(1), and two equivalent S(3) atoms to form ErS6 octahedra that share corners with three equivalent Er(1)S6 octahedra, corners with two equivalent Mg(1)S5 square pyramids, edges with two equivalent Er(1)S6 octahedra, edges with two equivalent Er(2)S6 octahedra, and edges with three equivalent Mg(1)S5 square pyramids. The corner-sharing octahedral tilt angles range from 53-59°. There are four inequivalent S sites. In the first S site, S(1) is bonded to three equivalent Mg(1) and two equivalent Er(2) atoms to form SEr2Mg3 square pyramids that share corners with two equivalent S(4)Er3Mg2 square pyramids, edges with three equivalent S(4)Er3Mg2 square pyramids, and edges with four equivalent S(1)Er2Mg3 square pyramids. In the second S site, S(2) is bonded in a rectangular see-saw-like geometry to one Er(2) and three equivalent Er(1) atoms. In the third S site, S(3) is bonded in a distorted T-shaped geometry to one Er(1) and two equivalent Er(2) atoms. In the fourth S site, S(4) is bonded to two equivalent Mg(1), one Er(2), and two equivalent Er(1) atoms to form SEr3Mg2 square pyramids that share corners with two equivalent S(1)Er2Mg3 square pyramids, edges with two equivalent S(4)Er3Mg2 square pyramids, and edges with three equivalent S(1)Er2Mg3 square pyramids. is represented by the CIF card [CIF]
data_Er2MgS4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   12.521
_cell_length_b   3.814
_cell_length_c   13.272
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   633.877
_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  0.115  0.250  0.077  1.0
  Er  Er1  1  0.885  0.750  0.923  1.0
  Er  Er2  1  0.385  0.750  0.577  1.0
  Er  Er3  1  0.615  0.250  0.423  1.0
  Er  Er4  1  0.142  0.250  0.704  1.0
  Er  Er5  1  0.858  0.750  0.296  1.0
  Er  Er6  1  0.358  0.750  0.204  1.0
  Er  Er7  1  0.642  0.250  0.796  1.0
  Mg  Mg8  1  0.115  0.750  0.445  1.0
  Mg  Mg9  1  0.885  0.250  0.555  1.0
  Mg  Mg10  1  0.385  0.250  0.945  1.0
  Mg  Mg11  1  0.615  0.750  0.055  1.0
  S  S12  1  0.014  0.750  0.614  1.0
  S  S13  1  0.986  0.250  0.386  1.0
  S  S14  1  0.486  0.250  0.114  1.0
  S  S15  1  0.514  0.750  0.886  1.0
  S  S16  1  0.030  0.250  0.883  1.0
  S  S17  1  0.970  0.750  0.117  1.0
  S  S18  1  0.470  0.750  0.383  1.0
  S  S19  1  0.530  0.250  0.617  1.0
  S  S20  1  0.222  0.250  0.252  1.0
  S  S21  1  0.778  0.750  0.748  1.0
  S  S22  1  0.278  0.750  0.752  1.0
  S  S23  1  0.722  0.250  0.248  1.0
  S  S24  1  0.258  0.750  0.017  1.0
  S  S25  1  0.742  0.250  0.983  1.0
  S  S26  1  0.242  0.250  0.517  1.0
  S  S27  1  0.758  0.750  0.483  1.0
[/CIF]
.