The material described by MgEr4S7 crystallizes in the monoclinic Cm space group. Mg(1) is bonded to one S(1), one S(5), two equivalent S(6), and two equivalent S(7) atoms to form MgS6 octahedra that share  a cornercorner with one Er(4)S6 octahedra, corners with two equivalent Er(3)S6 octahedra, edges with two equivalent Mg(1)S6 octahedra, and edges with three equivalent Er(3)S6 octahedra. The corner-sharing octahedral tilt angles range from 2-55°. There are four inequivalent Er sites. In the first Er site, Er(1) is bonded in a 7-coordinate geometry to one S(4), two equivalent S(1), two equivalent S(3), and two equivalent S(6) atoms. In the second Er site, Er(2) is bonded in a 7-coordinate geometry to one S(3), two equivalent S(2), two equivalent S(4), and two equivalent S(5) atoms. In the third Er site, Er(3) is bonded to one S(2), one S(6), two equivalent S(5), and two equivalent S(7) atoms to form ErS6 octahedra that share  a cornercorner with one Er(4)S6 octahedra, corners with two equivalent Mg(1)S6 octahedra, edges with two equivalent Er(3)S6 octahedra, and edges with three equivalent Mg(1)S6 octahedra. The corner-sharing octahedral tilt angles range from 2-54°. In the fourth Er site, Er(4) is bonded to one S(1), one S(2), two equivalent S(3), and two equivalent S(4) atoms to form ErS6 octahedra that share  a cornercorner with one Mg(1)S6 octahedra,  a cornercorner with one Er(3)S6 octahedra, and edges with two equivalent Er(4)S6 octahedra. The corner-sharing octahedral tilt angles range from 54-55°. There are seven inequivalent S sites. In the first S site, S(1) is bonded to one Mg(1), one Er(4), and two equivalent Er(1) atoms to form distorted SEr3Mg tetrahedra that share  a cornercorner with one S(2)Er4 tetrahedra, corners with two equivalent S(1)Er3Mg tetrahedra,  a cornercorner with one S(5)Er4Mg trigonal bipyramid, corners with four equivalent S(6)Er3Mg2 trigonal bipyramids, corners with four equivalent S(3)Er5 trigonal bipyramids,  an edgeedge with one S(6)Er3Mg2 trigonal bipyramid,  an edgeedge with one S(3)Er5 trigonal bipyramid, and edges with two equivalent S(4)Er5 trigonal bipyramids. In the second S site, S(2) is bonded to one Er(3), one Er(4), and two equivalent Er(2) atoms to form SEr4 tetrahedra that share  a cornercorner with one S(1)Er3Mg tetrahedra, corners with two equivalent S(2)Er4 tetrahedra,  a cornercorner with one S(6)Er3Mg2 trigonal bipyramid, corners with four equivalent S(5)Er4Mg trigonal bipyramids, corners with four equivalent S(4)Er5 trigonal bipyramids,  an edgeedge with one S(5)Er4Mg trigonal bipyramid,  an edgeedge with one S(4)Er5 trigonal bipyramid, and edges with two equivalent S(3)Er5 trigonal bipyramids. In the third S site, S(3) is bonded to one Er(2), two equivalent Er(1), and two equivalent Er(4) atoms to form distorted SEr5 trigonal bipyramids that share corners with four equivalent S(1)Er3Mg tetrahedra, corners with two equivalent S(6)Er3Mg2 trigonal bipyramids, corners with two equivalent S(5)Er4Mg trigonal bipyramids, corners with two equivalent S(4)Er5 trigonal bipyramids,  an edgeedge with one S(1)Er3Mg tetrahedra, edges with two equivalent S(2)Er4 tetrahedra,  an edgeedge with one S(6)Er3Mg2 trigonal bipyramid, edges with two equivalent S(3)Er5 trigonal bipyramids, and edges with three equivalent S(4)Er5 trigonal bipyramids. In the fourth S site, S(4) is bonded to one Er(1), two equivalent Er(2), and two equivalent Er(4) atoms to form distorted SEr5 trigonal bipyramids that share corners with four equivalent S(2)Er4 tetrahedra, corners with two equivalent S(6)Er3Mg2 trigonal bipyramids, corners with two equivalent S(5)Er4Mg trigonal bipyramids, corners with two equivalent S(3)Er5 trigonal bipyramids,  an edgeedge with one S(2)Er4 tetrahedra, edges with two equivalent S(1)Er3Mg tetrahedra,  an edgeedge with one S(5)Er4Mg trigonal bipyramid, edges with two equivalent S(4)Er5 trigonal bipyramids, and edges with three equivalent S(3)Er5 trigonal bipyramids. In the fifth S site, S(5) is bonded to one Mg(1), two equivalent Er(2), and two equivalent Er(3) atoms to form SEr4Mg trigonal bipyramids that share  a cornercorner with one S(1)Er3Mg tetrahedra, corners with four equivalent S(2)Er4 tetrahedra, corners with two equivalent S(3)Er5 trigonal bipyramids, corners with two equivalent S(4)Er5 trigonal bipyramids,  an edgeedge with one S(2)Er4 tetrahedra,  an edgeedge with one S(4)Er5 trigonal bipyramid, edges with two equivalent S(6)Er3Mg2 trigonal bipyramids, and edges with two equivalent S(5)Er4Mg trigonal bipyramids. In the sixth S site, S(6) is bonded to two equivalent Mg(1), one Er(3), and two equivalent Er(1) atoms to form SEr3Mg2 trigonal bipyramids that share  a cornercorner with one S(2)Er4 tetrahedra, corners with four equivalent S(1)Er3Mg tetrahedra, corners with two equivalent S(3)Er5 trigonal bipyramids, corners with two equivalent S(4)Er5 trigonal bipyramids,  an edgeedge with one S(1)Er3Mg tetrahedra,  an edgeedge with one S(3)Er5 trigonal bipyramid, edges with two equivalent S(6)Er3Mg2 trigonal bipyramids, and edges with two equivalent S(5)Er4Mg trigonal bipyramids. In the seventh S site, S(7) is bonded in a rectangular see-saw-like geometry to two equivalent Mg(1) and two equivalent Er(3) atoms. is represented by the CIF card [CIF]
data_Er4MgS7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.551
_cell_length_b   6.551
_cell_length_c   11.436
_cell_angle_alpha   76.177
_cell_angle_beta   76.177
_cell_angle_gamma   33.485
_symmetry_Int_Tables_number   1
_cell_volume   262.235
_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  0.695  0.695  0.200  1.0
  Er  Er1  1  0.305  0.305  0.804  1.0
  Er  Er2  1  0.114  0.114  0.570  1.0
  Er  Er3  1  0.000  0.000  0.003  1.0
  Mg  Mg4  1  0.887  0.887  0.421  1.0
  S  S5  1  0.038  0.038  0.220  1.0
  S  S6  1  0.960  0.960  0.785  1.0
  S  S7  1  0.340  0.340  0.050  1.0
  S  S8  1  0.659  0.659  0.949  1.0
  S  S9  1  0.742  0.742  0.644  1.0
  S  S10  1  0.264  0.264  0.354  1.0
  S  S11  1  0.496  0.496  0.499  1.0
[/CIF]
.
The material described by MgEr4S7 crystallizes in the monoclinic Cm space group. Mg(1) is bonded to one S(1), one S(5), two equivalent S(6), and two equivalent S(7) atoms to form MgS6 octahedra that share  a cornercorner with one Er(4)S6 octahedra, corners with two equivalent Er(3)S6 octahedra, edges with two equivalent Mg(1)S6 octahedra, and edges with three equivalent Er(3)S6 octahedra. The corner-sharing octahedral tilt angles range from 2-55°. There are four inequivalent Er sites. In the first Er site, Er(1) is bonded in a 7-coordinate geometry to one S(4), two equivalent S(1), two equivalent S(3), and two equivalent S(6) atoms. In the second Er site, Er(2) is bonded in a 7-coordinate geometry to one S(3), two equivalent S(2), two equivalent S(4), and two equivalent S(5) atoms. In the third Er site, Er(3) is bonded to one S(2), one S(6), two equivalent S(5), and two equivalent S(7) atoms to form ErS6 octahedra that share  a cornercorner with one Er(4)S6 octahedra, corners with two equivalent Mg(1)S6 octahedra, edges with two equivalent Er(3)S6 octahedra, and edges with three equivalent Mg(1)S6 octahedra. The corner-sharing octahedral tilt angles range from 2-54°. In the fourth Er site, Er(4) is bonded to one S(1), one S(2), two equivalent S(3), and two equivalent S(4) atoms to form ErS6 octahedra that share  a cornercorner with one Mg(1)S6 octahedra,  a cornercorner with one Er(3)S6 octahedra, and edges with two equivalent Er(4)S6 octahedra. The corner-sharing octahedral tilt angles range from 54-55°. There are seven inequivalent S sites. In the first S site, S(1) is bonded to one Mg(1), one Er(4), and two equivalent Er(1) atoms to form distorted SEr3Mg tetrahedra that share  a cornercorner with one S(2)Er4 tetrahedra, corners with two equivalent S(1)Er3Mg tetrahedra,  a cornercorner with one S(5)Er4Mg trigonal bipyramid, corners with four equivalent S(6)Er3Mg2 trigonal bipyramids, corners with four equivalent S(3)Er5 trigonal bipyramids,  an edgeedge with one S(6)Er3Mg2 trigonal bipyramid,  an edgeedge with one S(3)Er5 trigonal bipyramid, and edges with two equivalent S(4)Er5 trigonal bipyramids. In the second S site, S(2) is bonded to one Er(3), one Er(4), and two equivalent Er(2) atoms to form SEr4 tetrahedra that share  a cornercorner with one S(1)Er3Mg tetrahedra, corners with two equivalent S(2)Er4 tetrahedra,  a cornercorner with one S(6)Er3Mg2 trigonal bipyramid, corners with four equivalent S(5)Er4Mg trigonal bipyramids, corners with four equivalent S(4)Er5 trigonal bipyramids,  an edgeedge with one S(5)Er4Mg trigonal bipyramid,  an edgeedge with one S(4)Er5 trigonal bipyramid, and edges with two equivalent S(3)Er5 trigonal bipyramids. In the third S site, S(3) is bonded to one Er(2), two equivalent Er(1), and two equivalent Er(4) atoms to form distorted SEr5 trigonal bipyramids that share corners with four equivalent S(1)Er3Mg tetrahedra, corners with two equivalent S(6)Er3Mg2 trigonal bipyramids, corners with two equivalent S(5)Er4Mg trigonal bipyramids, corners with two equivalent S(4)Er5 trigonal bipyramids,  an edgeedge with one S(1)Er3Mg tetrahedra, edges with two equivalent S(2)Er4 tetrahedra,  an edgeedge with one S(6)Er3Mg2 trigonal bipyramid, edges with two equivalent S(3)Er5 trigonal bipyramids, and edges with three equivalent S(4)Er5 trigonal bipyramids. In the fourth S site, S(4) is bonded to one Er(1), two equivalent Er(2), and two equivalent Er(4) atoms to form distorted SEr5 trigonal bipyramids that share corners with four equivalent S(2)Er4 tetrahedra, corners with two equivalent S(6)Er3Mg2 trigonal bipyramids, corners with two equivalent S(5)Er4Mg trigonal bipyramids, corners with two equivalent S(3)Er5 trigonal bipyramids,  an edgeedge with one S(2)Er4 tetrahedra, edges with two equivalent S(1)Er3Mg tetrahedra,  an edgeedge with one S(5)Er4Mg trigonal bipyramid, edges with two equivalent S(4)Er5 trigonal bipyramids, and edges with three equivalent S(3)Er5 trigonal bipyramids. In the fifth S site, S(5) is bonded to one Mg(1), two equivalent Er(2), and two equivalent Er(3) atoms to form SEr4Mg trigonal bipyramids that share  a cornercorner with one S(1)Er3Mg tetrahedra, corners with four equivalent S(2)Er4 tetrahedra, corners with two equivalent S(3)Er5 trigonal bipyramids, corners with two equivalent S(4)Er5 trigonal bipyramids,  an edgeedge with one S(2)Er4 tetrahedra,  an edgeedge with one S(4)Er5 trigonal bipyramid, edges with two equivalent S(6)Er3Mg2 trigonal bipyramids, and edges with two equivalent S(5)Er4Mg trigonal bipyramids. In the sixth S site, S(6) is bonded to two equivalent Mg(1), one Er(3), and two equivalent Er(1) atoms to form SEr3Mg2 trigonal bipyramids that share  a cornercorner with one S(2)Er4 tetrahedra, corners with four equivalent S(1)Er3Mg tetrahedra, corners with two equivalent S(3)Er5 trigonal bipyramids, corners with two equivalent S(4)Er5 trigonal bipyramids,  an edgeedge with one S(1)Er3Mg tetrahedra,  an edgeedge with one S(3)Er5 trigonal bipyramid, edges with two equivalent S(6)Er3Mg2 trigonal bipyramids, and edges with two equivalent S(5)Er4Mg trigonal bipyramids. In the seventh S site, S(7) is bonded in a rectangular see-saw-like geometry to two equivalent Mg(1) and two equivalent Er(3) atoms. is represented by the CIF card [CIF]
data_Er4MgS7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.551
_cell_length_b   6.551
_cell_length_c   11.436
_cell_angle_alpha   76.177
_cell_angle_beta   76.177
_cell_angle_gamma   33.485
_symmetry_Int_Tables_number   1
_cell_volume   262.235
_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  0.695  0.695  0.200  1.0
  Er  Er1  1  0.305  0.305  0.804  1.0
  Er  Er2  1  0.114  0.114  0.570  1.0
  Er  Er3  1  0.000  0.000  0.003  1.0
  Mg  Mg4  1  0.887  0.887  0.421  1.0
  S  S5  1  0.038  0.038  0.220  1.0
  S  S6  1  0.960  0.960  0.785  1.0
  S  S7  1  0.340  0.340  0.050  1.0
  S  S8  1  0.659  0.659  0.949  1.0
  S  S9  1  0.742  0.742  0.644  1.0
  S  S10  1  0.264  0.264  0.354  1.0
  S  S11  1  0.496  0.496  0.499  1.0
[/CIF]
.