The material structure described by MgEr2S4 crystallizes in the orthorhombic Cmc2_1 space group. Mg(1) is bonded to one S(1), one S(4), two equivalent S(2), and two equivalent S(3) atoms to form MgS6 octahedra that share corners with three equivalent Er(2)S6 octahedra, edges with two equivalent Mg(1)S6 octahedra, and edges with three equivalent Er(2)S6 octahedra. The corner-sharing octahedral tilt angles range from 10-54°. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 7-coordinate geometry to one S(2), two equivalent S(1), two equivalent S(3), and two equivalent S(4) atoms. In the second Er site, Er(2) is bonded to one S(3), one S(4), two equivalent S(1), and two equivalent S(2) atoms to form ErS6 octahedra that share corners with three equivalent Mg(1)S6 octahedra, edges with two equivalent Er(2)S6 octahedra, and edges with three equivalent Mg(1)S6 octahedra. The corner-sharing octahedral tilt angles range from 10-54°. There are four inequivalent S sites. In the first S site, S(1) is bonded to one Mg(1), two equivalent Er(1), and two equivalent Er(2) atoms to form distorted SEr4Mg trigonal bipyramids that share corners with two equivalent S(3)Er3Mg2 square pyramids, corners with six equivalent S(2)Er3Mg2 square pyramids, corners with five equivalent S(4)Er3Mg tetrahedra,  an edgeedge with one S(2)Er3Mg2 square pyramid, edges with three equivalent S(3)Er3Mg2 square pyramids,  an edgeedge with one S(4)Er3Mg tetrahedra, and edges with two equivalent S(1)Er4Mg trigonal bipyramids. In the second S site, S(2) is bonded to two equivalent Mg(1), one Er(1), and two equivalent Er(2) atoms to form SEr3Mg2 square pyramids that share corners with two equivalent S(3)Er3Mg2 square pyramids, corners with two equivalent S(4)Er3Mg tetrahedra, corners with six equivalent S(1)Er4Mg trigonal bipyramids, edges with two equivalent S(2)Er3Mg2 square pyramids, edges with three equivalent S(3)Er3Mg2 square pyramids, edges with two equivalent S(4)Er3Mg tetrahedra, and  an edgeedge with one S(1)Er4Mg trigonal bipyramid. In the third S site, S(3) 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(2)Er3Mg2 square pyramids, corners with five equivalent S(4)Er3Mg tetrahedra, corners with two equivalent S(1)Er4Mg trigonal bipyramids, edges with two equivalent S(3)Er3Mg2 square pyramids, edges with three equivalent S(2)Er3Mg2 square pyramids,  an edgeedge with one S(4)Er3Mg tetrahedra, and edges with three equivalent S(1)Er4Mg trigonal bipyramids. In the fourth S site, S(4) is bonded to one Mg(1), one Er(2), and two equivalent Er(1) atoms to form SEr3Mg tetrahedra that share corners with two equivalent S(2)Er3Mg2 square pyramids, corners with five equivalent S(3)Er3Mg2 square pyramids, corners with two equivalent S(4)Er3Mg tetrahedra, corners with five equivalent S(1)Er4Mg trigonal bipyramids,  an edgeedge with one S(3)Er3Mg2 square pyramid, edges with two equivalent S(2)Er3Mg2 square pyramids, and  an edgeedge with one S(1)Er4Mg trigonal bipyramid. is represented by the Crystallographic Information File (CIF) [CIF]
data_Er2MgS4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.508
_cell_length_b   6.508
_cell_length_c   12.786
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   146.434
_symmetry_Int_Tables_number   1
_cell_volume   299.408
_cell_formula_units_Z   2
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  0.382  0.618  0.783  1.0
  Er  Er1  1  0.618  0.382  0.283  1.0
  Er  Er2  1  0.138  0.862  0.582  1.0
  Er  Er3  1  0.862  0.138  0.082  1.0
  Mg  Mg4  1  0.126  0.874  0.946  1.0
  Mg  Mg5  1  0.874  0.126  0.446  1.0
  S  S6  1  0.789  0.211  0.636  1.0
  S  S7  1  0.211  0.789  0.136  1.0
  S  S8  1  0.488  0.512  0.998  1.0
  S  S9  1  0.512  0.488  0.498  1.0
  S  S10  1  0.764  0.236  0.895  1.0
  S  S11  1  0.236  0.764  0.395  1.0
  S  S12  1  0.036  0.964  0.768  1.0
  S  S13  1  0.964  0.036  0.268  1.0
[/CIF]
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The material structure described by MgEr2S4 crystallizes in the orthorhombic Cmc2_1 space group. Mg(1) is bonded to one S(1), one S(4), two equivalent S(2), and two equivalent S(3) atoms to form MgS6 octahedra that share corners with three equivalent Er(2)S6 octahedra, edges with two equivalent Mg(1)S6 octahedra, and edges with three equivalent Er(2)S6 octahedra. The corner-sharing octahedral tilt angles range from 10-54°. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 7-coordinate geometry to one S(2), two equivalent S(1), two equivalent S(3), and two equivalent S(4) atoms. In the second Er site, Er(2) is bonded to one S(3), one S(4), two equivalent S(1), and two equivalent S(2) atoms to form ErS6 octahedra that share corners with three equivalent Mg(1)S6 octahedra, edges with two equivalent Er(2)S6 octahedra, and edges with three equivalent Mg(1)S6 octahedra. The corner-sharing octahedral tilt angles range from 10-54°. There are four inequivalent S sites. In the first S site, S(1) is bonded to one Mg(1), two equivalent Er(1), and two equivalent Er(2) atoms to form distorted SEr4Mg trigonal bipyramids that share corners with two equivalent S(3)Er3Mg2 square pyramids, corners with six equivalent S(2)Er3Mg2 square pyramids, corners with five equivalent S(4)Er3Mg tetrahedra,  an edgeedge with one S(2)Er3Mg2 square pyramid, edges with three equivalent S(3)Er3Mg2 square pyramids,  an edgeedge with one S(4)Er3Mg tetrahedra, and edges with two equivalent S(1)Er4Mg trigonal bipyramids. In the second S site, S(2) is bonded to two equivalent Mg(1), one Er(1), and two equivalent Er(2) atoms to form SEr3Mg2 square pyramids that share corners with two equivalent S(3)Er3Mg2 square pyramids, corners with two equivalent S(4)Er3Mg tetrahedra, corners with six equivalent S(1)Er4Mg trigonal bipyramids, edges with two equivalent S(2)Er3Mg2 square pyramids, edges with three equivalent S(3)Er3Mg2 square pyramids, edges with two equivalent S(4)Er3Mg tetrahedra, and  an edgeedge with one S(1)Er4Mg trigonal bipyramid. In the third S site, S(3) 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(2)Er3Mg2 square pyramids, corners with five equivalent S(4)Er3Mg tetrahedra, corners with two equivalent S(1)Er4Mg trigonal bipyramids, edges with two equivalent S(3)Er3Mg2 square pyramids, edges with three equivalent S(2)Er3Mg2 square pyramids,  an edgeedge with one S(4)Er3Mg tetrahedra, and edges with three equivalent S(1)Er4Mg trigonal bipyramids. In the fourth S site, S(4) is bonded to one Mg(1), one Er(2), and two equivalent Er(1) atoms to form SEr3Mg tetrahedra that share corners with two equivalent S(2)Er3Mg2 square pyramids, corners with five equivalent S(3)Er3Mg2 square pyramids, corners with two equivalent S(4)Er3Mg tetrahedra, corners with five equivalent S(1)Er4Mg trigonal bipyramids,  an edgeedge with one S(3)Er3Mg2 square pyramid, edges with two equivalent S(2)Er3Mg2 square pyramids, and  an edgeedge with one S(1)Er4Mg trigonal bipyramid. is represented by the Crystallographic Information File (CIF) [CIF]
data_Er2MgS4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.508
_cell_length_b   6.508
_cell_length_c   12.786
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   146.434
_symmetry_Int_Tables_number   1
_cell_volume   299.408
_cell_formula_units_Z   2
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  0.382  0.618  0.783  1.0
  Er  Er1  1  0.618  0.382  0.283  1.0
  Er  Er2  1  0.138  0.862  0.582  1.0
  Er  Er3  1  0.862  0.138  0.082  1.0
  Mg  Mg4  1  0.126  0.874  0.946  1.0
  Mg  Mg5  1  0.874  0.126  0.446  1.0
  S  S6  1  0.789  0.211  0.636  1.0
  S  S7  1  0.211  0.789  0.136  1.0
  S  S8  1  0.488  0.512  0.998  1.0
  S  S9  1  0.512  0.488  0.498  1.0
  S  S10  1  0.764  0.236  0.895  1.0
  S  S11  1  0.236  0.764  0.395  1.0
  S  S12  1  0.036  0.964  0.768  1.0
  S  S13  1  0.964  0.036  0.268  1.0
[/CIF]
.