The structure described by MgY2S4 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 Y(1)S6 octahedra, corners with two equivalent Y(2)S6 octahedra,  an edgeedge with one Y(1)S6 octahedra, edges with three equivalent Y(2)S6 octahedra, and edges with four equivalent Mg(1)S5 square pyramids. The corner-sharing octahedral tilt angles range from 4-6°. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded to one S(3), two equivalent S(4), and three equivalent S(2) atoms to form YS6 octahedra that share corners with three equivalent Y(2)S6 octahedra, corners with two equivalent Mg(1)S5 square pyramids, edges with two equivalent Y(2)S6 octahedra, edges with four equivalent Y(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 Y site, Y(2) is bonded to one S(2), one S(4), two equivalent S(1), and two equivalent S(3) atoms to form YS6 octahedra that share corners with three equivalent Y(1)S6 octahedra, corners with two equivalent Mg(1)S5 square pyramids, edges with two equivalent Y(1)S6 octahedra, edges with two equivalent Y(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 Y(2) atoms to form SY2Mg3 square pyramids that share corners with two equivalent S(4)Y3Mg2 square pyramids, edges with three equivalent S(4)Y3Mg2 square pyramids, and edges with four equivalent S(1)Y2Mg3 square pyramids. In the second S site, S(2) is bonded in a rectangular see-saw-like geometry to one Y(2) and three equivalent Y(1) atoms. In the third S site, S(3) is bonded in a distorted T-shaped geometry to one Y(1) and two equivalent Y(2) atoms. In the fourth S site, S(4) is bonded to two equivalent Mg(1), one Y(2), and two equivalent Y(1) atoms to form SY3Mg2 square pyramids that share corners with two equivalent S(1)Y2Mg3 square pyramids, edges with two equivalent S(4)Y3Mg2 square pyramids, and edges with three equivalent S(1)Y2Mg3 square pyramids. is represented by the Crystallographic Information File (CIF) [CIF]
data_Y2MgS4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.854
_cell_length_b   12.628
_cell_length_c   13.485
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   656.342
_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
  Y  Y0  1  0.250  0.118  0.075  1.0
  Y  Y1  1  0.750  0.882  0.925  1.0
  Y  Y2  1  0.750  0.382  0.575  1.0
  Y  Y3  1  0.250  0.618  0.425  1.0
  Y  Y4  1  0.250  0.139  0.705  1.0
  Y  Y5  1  0.750  0.861  0.295  1.0
  Y  Y6  1  0.750  0.361  0.205  1.0
  Y  Y7  1  0.250  0.639  0.795  1.0
  Mg  Mg8  1  0.750  0.111  0.452  1.0
  Mg  Mg9  1  0.250  0.889  0.548  1.0
  Mg  Mg10  1  0.250  0.389  0.952  1.0
  Mg  Mg11  1  0.750  0.611  0.048  1.0
  S  S12  1  0.750  0.009  0.615  1.0
  S  S13  1  0.250  0.991  0.385  1.0
  S  S14  1  0.250  0.491  0.115  1.0
  S  S15  1  0.750  0.509  0.885  1.0
  S  S16  1  0.250  0.028  0.883  1.0
  S  S17  1  0.750  0.972  0.117  1.0
  S  S18  1  0.750  0.472  0.383  1.0
  S  S19  1  0.250  0.528  0.617  1.0
  S  S20  1  0.250  0.225  0.249  1.0
  S  S21  1  0.750  0.775  0.751  1.0
  S  S22  1  0.750  0.275  0.749  1.0
  S  S23  1  0.250  0.725  0.251  1.0
  S  S24  1  0.750  0.263  0.016  1.0
  S  S25  1  0.250  0.737  0.984  1.0
  S  S26  1  0.250  0.237  0.516  1.0
  S  S27  1  0.750  0.763  0.484  1.0
[/CIF]
.
The structure described by MgY2S4 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 Y(1)S6 octahedra, corners with two equivalent Y(2)S6 octahedra,  an edgeedge with one Y(1)S6 octahedra, edges with three equivalent Y(2)S6 octahedra, and edges with four equivalent Mg(1)S5 square pyramids. The corner-sharing octahedral tilt angles range from 4-6°. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded to one S(3), two equivalent S(4), and three equivalent S(2) atoms to form YS6 octahedra that share corners with three equivalent Y(2)S6 octahedra, corners with two equivalent Mg(1)S5 square pyramids, edges with two equivalent Y(2)S6 octahedra, edges with four equivalent Y(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 Y site, Y(2) is bonded to one S(2), one S(4), two equivalent S(1), and two equivalent S(3) atoms to form YS6 octahedra that share corners with three equivalent Y(1)S6 octahedra, corners with two equivalent Mg(1)S5 square pyramids, edges with two equivalent Y(1)S6 octahedra, edges with two equivalent Y(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 Y(2) atoms to form SY2Mg3 square pyramids that share corners with two equivalent S(4)Y3Mg2 square pyramids, edges with three equivalent S(4)Y3Mg2 square pyramids, and edges with four equivalent S(1)Y2Mg3 square pyramids. In the second S site, S(2) is bonded in a rectangular see-saw-like geometry to one Y(2) and three equivalent Y(1) atoms. In the third S site, S(3) is bonded in a distorted T-shaped geometry to one Y(1) and two equivalent Y(2) atoms. In the fourth S site, S(4) is bonded to two equivalent Mg(1), one Y(2), and two equivalent Y(1) atoms to form SY3Mg2 square pyramids that share corners with two equivalent S(1)Y2Mg3 square pyramids, edges with two equivalent S(4)Y3Mg2 square pyramids, and edges with three equivalent S(1)Y2Mg3 square pyramids. is represented by the Crystallographic Information File (CIF) [CIF]
data_Y2MgS4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.854
_cell_length_b   12.628
_cell_length_c   13.485
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   656.342
_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
  Y  Y0  1  0.250  0.118  0.075  1.0
  Y  Y1  1  0.750  0.882  0.925  1.0
  Y  Y2  1  0.750  0.382  0.575  1.0
  Y  Y3  1  0.250  0.618  0.425  1.0
  Y  Y4  1  0.250  0.139  0.705  1.0
  Y  Y5  1  0.750  0.861  0.295  1.0
  Y  Y6  1  0.750  0.361  0.205  1.0
  Y  Y7  1  0.250  0.639  0.795  1.0
  Mg  Mg8  1  0.750  0.111  0.452  1.0
  Mg  Mg9  1  0.250  0.889  0.548  1.0
  Mg  Mg10  1  0.250  0.389  0.952  1.0
  Mg  Mg11  1  0.750  0.611  0.048  1.0
  S  S12  1  0.750  0.009  0.615  1.0
  S  S13  1  0.250  0.991  0.385  1.0
  S  S14  1  0.250  0.491  0.115  1.0
  S  S15  1  0.750  0.509  0.885  1.0
  S  S16  1  0.250  0.028  0.883  1.0
  S  S17  1  0.750  0.972  0.117  1.0
  S  S18  1  0.750  0.472  0.383  1.0
  S  S19  1  0.250  0.528  0.617  1.0
  S  S20  1  0.250  0.225  0.249  1.0
  S  S21  1  0.750  0.775  0.751  1.0
  S  S22  1  0.750  0.275  0.749  1.0
  S  S23  1  0.250  0.725  0.251  1.0
  S  S24  1  0.750  0.263  0.016  1.0
  S  S25  1  0.250  0.737  0.984  1.0
  S  S26  1  0.250  0.237  0.516  1.0
  S  S27  1  0.750  0.763  0.484  1.0
[/CIF]
.