The crystal structure described by MgGd2S4 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 Gd(1)S6 octahedra, corners with two equivalent Gd(2)S6 octahedra,  an edgeedge with one Gd(1)S6 octahedra, edges with three equivalent Gd(2)S6 octahedra, and edges with four equivalent Mg(1)S5 square pyramids. The corner-sharing octahedral tilt angles are 5°. There are two inequivalent Gd sites. In the first Gd site, Gd(1) is bonded to one S(3), two equivalent S(4), and three equivalent S(2) atoms to form GdS6 octahedra that share corners with three equivalent Gd(2)S6 octahedra, corners with two equivalent Mg(1)S5 square pyramids, edges with two equivalent Gd(2)S6 octahedra, edges with four equivalent Gd(1)S6 octahedra, and  an edgeedge with one Mg(1)S5 square pyramid. The corner-sharing octahedral tilt angles range from 54-59°. In the second Gd site, Gd(2) is bonded to one S(2), one S(4), two equivalent S(1), and two equivalent S(3) atoms to form GdS6 octahedra that share corners with three equivalent Gd(1)S6 octahedra, corners with two equivalent Mg(1)S5 square pyramids, edges with two equivalent Gd(1)S6 octahedra, edges with two equivalent Gd(2)S6 octahedra, and edges with three equivalent Mg(1)S5 square pyramids. The corner-sharing octahedral tilt angles range from 54-59°. There are four inequivalent S sites. In the first S site, S(1) is bonded to three equivalent Mg(1) and two equivalent Gd(2) atoms to form SGd2Mg3 square pyramids that share corners with two equivalent S(4)Gd3Mg2 square pyramids, edges with three equivalent S(4)Gd3Mg2 square pyramids, and edges with four equivalent S(1)Gd2Mg3 square pyramids. In the second S site, S(2) is bonded in a rectangular see-saw-like geometry to one Gd(2) and three equivalent Gd(1) atoms. In the third S site, S(3) is bonded in a distorted T-shaped geometry to one Gd(1) and two equivalent Gd(2) atoms. In the fourth S site, S(4) is bonded to two equivalent Mg(1), one Gd(2), and two equivalent Gd(1) atoms to form SGd3Mg2 square pyramids that share corners with two equivalent S(1)Gd2Mg3 square pyramids, edges with two equivalent S(4)Gd3Mg2 square pyramids, and edges with three equivalent S(1)Gd2Mg3 square pyramids. is represented by the CIF file [CIF]
data_Gd2MgS4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   12.728
_cell_length_b   3.885
_cell_length_c   13.620
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   673.415
_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
  Gd  Gd0  1  0.119  0.250  0.075  1.0
  Gd  Gd1  1  0.881  0.750  0.925  1.0
  Gd  Gd2  1  0.381  0.750  0.575  1.0
  Gd  Gd3  1  0.619  0.250  0.425  1.0
  Gd  Gd4  1  0.135  0.250  0.706  1.0
  Gd  Gd5  1  0.865  0.750  0.294  1.0
  Gd  Gd6  1  0.365  0.750  0.206  1.0
  Gd  Gd7  1  0.635  0.250  0.794  1.0
  Mg  Mg8  1  0.110  0.750  0.456  1.0
  Mg  Mg9  1  0.890  0.250  0.544  1.0
  Mg  Mg10  1  0.390  0.250  0.956  1.0
  Mg  Mg11  1  0.610  0.750  0.044  1.0
  S  S12  1  0.006  0.750  0.615  1.0
  S  S13  1  0.994  0.250  0.385  1.0
  S  S14  1  0.494  0.250  0.115  1.0
  S  S15  1  0.506  0.750  0.885  1.0
  S  S16  1  0.027  0.250  0.885  1.0
  S  S17  1  0.973  0.750  0.115  1.0
  S  S18  1  0.473  0.750  0.385  1.0
  S  S19  1  0.527  0.250  0.615  1.0
  S  S20  1  0.228  0.250  0.247  1.0
  S  S21  1  0.772  0.750  0.753  1.0
  S  S22  1  0.272  0.750  0.747  1.0
  S  S23  1  0.728  0.250  0.253  1.0
  S  S24  1  0.265  0.750  0.017  1.0
  S  S25  1  0.735  0.250  0.983  1.0
  S  S26  1  0.235  0.250  0.517  1.0
  S  S27  1  0.765  0.750  0.483  1.0
[/CIF]
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The crystal structure described by MgGd2S4 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 Gd(1)S6 octahedra, corners with two equivalent Gd(2)S6 octahedra,  an edgeedge with one Gd(1)S6 octahedra, edges with three equivalent Gd(2)S6 octahedra, and edges with four equivalent Mg(1)S5 square pyramids. The corner-sharing octahedral tilt angles are 5°. There are two inequivalent Gd sites. In the first Gd site, Gd(1) is bonded to one S(3), two equivalent S(4), and three equivalent S(2) atoms to form GdS6 octahedra that share corners with three equivalent Gd(2)S6 octahedra, corners with two equivalent Mg(1)S5 square pyramids, edges with two equivalent Gd(2)S6 octahedra, edges with four equivalent Gd(1)S6 octahedra, and  an edgeedge with one Mg(1)S5 square pyramid. The corner-sharing octahedral tilt angles range from 54-59°. In the second Gd site, Gd(2) is bonded to one S(2), one S(4), two equivalent S(1), and two equivalent S(3) atoms to form GdS6 octahedra that share corners with three equivalent Gd(1)S6 octahedra, corners with two equivalent Mg(1)S5 square pyramids, edges with two equivalent Gd(1)S6 octahedra, edges with two equivalent Gd(2)S6 octahedra, and edges with three equivalent Mg(1)S5 square pyramids. The corner-sharing octahedral tilt angles range from 54-59°. There are four inequivalent S sites. In the first S site, S(1) is bonded to three equivalent Mg(1) and two equivalent Gd(2) atoms to form SGd2Mg3 square pyramids that share corners with two equivalent S(4)Gd3Mg2 square pyramids, edges with three equivalent S(4)Gd3Mg2 square pyramids, and edges with four equivalent S(1)Gd2Mg3 square pyramids. In the second S site, S(2) is bonded in a rectangular see-saw-like geometry to one Gd(2) and three equivalent Gd(1) atoms. In the third S site, S(3) is bonded in a distorted T-shaped geometry to one Gd(1) and two equivalent Gd(2) atoms. In the fourth S site, S(4) is bonded to two equivalent Mg(1), one Gd(2), and two equivalent Gd(1) atoms to form SGd3Mg2 square pyramids that share corners with two equivalent S(1)Gd2Mg3 square pyramids, edges with two equivalent S(4)Gd3Mg2 square pyramids, and edges with three equivalent S(1)Gd2Mg3 square pyramids. is represented by the CIF file [CIF]
data_Gd2MgS4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   12.728
_cell_length_b   3.885
_cell_length_c   13.620
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   673.415
_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
  Gd  Gd0  1  0.119  0.250  0.075  1.0
  Gd  Gd1  1  0.881  0.750  0.925  1.0
  Gd  Gd2  1  0.381  0.750  0.575  1.0
  Gd  Gd3  1  0.619  0.250  0.425  1.0
  Gd  Gd4  1  0.135  0.250  0.706  1.0
  Gd  Gd5  1  0.865  0.750  0.294  1.0
  Gd  Gd6  1  0.365  0.750  0.206  1.0
  Gd  Gd7  1  0.635  0.250  0.794  1.0
  Mg  Mg8  1  0.110  0.750  0.456  1.0
  Mg  Mg9  1  0.890  0.250  0.544  1.0
  Mg  Mg10  1  0.390  0.250  0.956  1.0
  Mg  Mg11  1  0.610  0.750  0.044  1.0
  S  S12  1  0.006  0.750  0.615  1.0
  S  S13  1  0.994  0.250  0.385  1.0
  S  S14  1  0.494  0.250  0.115  1.0
  S  S15  1  0.506  0.750  0.885  1.0
  S  S16  1  0.027  0.250  0.885  1.0
  S  S17  1  0.973  0.750  0.115  1.0
  S  S18  1  0.473  0.750  0.385  1.0
  S  S19  1  0.527  0.250  0.615  1.0
  S  S20  1  0.228  0.250  0.247  1.0
  S  S21  1  0.772  0.750  0.753  1.0
  S  S22  1  0.272  0.750  0.747  1.0
  S  S23  1  0.728  0.250  0.253  1.0
  S  S24  1  0.265  0.750  0.017  1.0
  S  S25  1  0.735  0.250  0.983  1.0
  S  S26  1  0.235  0.250  0.517  1.0
  S  S27  1  0.765  0.750  0.483  1.0
[/CIF]
.