The structure described by Mg2SiSe4 is Spinel-like structured and crystallizes in the orthorhombic Pnma space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms to form MgSe6 octahedra that share corners with four equivalent Mg(2)Se6 octahedra, corners with two equivalent Si(1)Se4 tetrahedra, edges with two equivalent Mg(1)Se6 octahedra, edges with two equivalent Mg(2)Se6 octahedra, and edges with two equivalent Si(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 52-58°. In the second Mg site, Mg(2) is bonded to one Se(1), one Se(2), and four equivalent Se(3) atoms to form MgSe6 octahedra that share corners with four equivalent Mg(1)Se6 octahedra, corners with four equivalent Mg(2)Se6 octahedra, corners with four equivalent Si(1)Se4 tetrahedra, edges with two equivalent Mg(1)Se6 octahedra, and  an edgeedge with one Si(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 48-58°. Si(1) is bonded to one Se(1), one Se(2), and two equivalent Se(3) atoms to form SiSe4 tetrahedra that share corners with two equivalent Mg(1)Se6 octahedra, corners with four equivalent Mg(2)Se6 octahedra,  an edgeedge with one Mg(2)Se6 octahedra, and edges with two equivalent Mg(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 57-59°. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to one Mg(2), two equivalent Mg(1), and one Si(1) atom to form distorted corner-sharing SeMg3Si trigonal pyramids. In the second Se site, Se(2) is bonded in a rectangular see-saw-like geometry to one Mg(2), two equivalent Mg(1), and one Si(1) atom. In the third Se site, Se(3) is bonded in a rectangular see-saw-like geometry to one Mg(1), two equivalent Mg(2), and one Si(1) atom. is represented by the CIF file [CIF]
data_Mg2SiSe4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.256
_cell_length_b   7.833
_cell_length_c   13.394
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   656.300
_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
  Mg  Mg0  1  0.000  0.500  0.000  1.0
  Mg  Mg1  1  0.500  0.000  0.500  1.0
  Mg  Mg2  1  0.000  0.000  0.000  1.0
  Mg  Mg3  1  0.500  0.500  0.500  1.0
  Mg  Mg4  1  0.496  0.750  0.231  1.0
  Mg  Mg5  1  0.004  0.750  0.731  1.0
  Mg  Mg6  1  0.504  0.250  0.769  1.0
  Mg  Mg7  1  0.996  0.250  0.269  1.0
  Si  Si8  1  0.906  0.750  0.411  1.0
  Si  Si9  1  0.594  0.750  0.911  1.0
  Si  Si10  1  0.094  0.250  0.589  1.0
  Si  Si11  1  0.406  0.250  0.089  1.0
  Se  Se12  1  0.266  0.750  0.408  1.0
  Se  Se13  1  0.234  0.750  0.908  1.0
  Se  Se14  1  0.734  0.250  0.592  1.0
  Se  Se15  1  0.766  0.250  0.092  1.0
  Se  Se16  1  0.757  0.750  0.567  1.0
  Se  Se17  1  0.743  0.750  0.067  1.0
  Se  Se18  1  0.243  0.250  0.433  1.0
  Se  Se19  1  0.257  0.250  0.933  1.0
  Se  Se20  1  0.751  0.521  0.332  1.0
  Se  Se21  1  0.749  0.979  0.832  1.0
  Se  Se22  1  0.249  0.021  0.668  1.0
  Se  Se23  1  0.251  0.479  0.168  1.0
  Se  Se24  1  0.249  0.479  0.668  1.0
  Se  Se25  1  0.251  0.021  0.168  1.0
  Se  Se26  1  0.751  0.979  0.332  1.0
  Se  Se27  1  0.749  0.521  0.832  1.0
[/CIF]
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The structure described by Mg2SiSe4 is Spinel-like structured and crystallizes in the orthorhombic Pnma space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms to form MgSe6 octahedra that share corners with four equivalent Mg(2)Se6 octahedra, corners with two equivalent Si(1)Se4 tetrahedra, edges with two equivalent Mg(1)Se6 octahedra, edges with two equivalent Mg(2)Se6 octahedra, and edges with two equivalent Si(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 52-58°. In the second Mg site, Mg(2) is bonded to one Se(1), one Se(2), and four equivalent Se(3) atoms to form MgSe6 octahedra that share corners with four equivalent Mg(1)Se6 octahedra, corners with four equivalent Mg(2)Se6 octahedra, corners with four equivalent Si(1)Se4 tetrahedra, edges with two equivalent Mg(1)Se6 octahedra, and  an edgeedge with one Si(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 48-58°. Si(1) is bonded to one Se(1), one Se(2), and two equivalent Se(3) atoms to form SiSe4 tetrahedra that share corners with two equivalent Mg(1)Se6 octahedra, corners with four equivalent Mg(2)Se6 octahedra,  an edgeedge with one Mg(2)Se6 octahedra, and edges with two equivalent Mg(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 57-59°. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to one Mg(2), two equivalent Mg(1), and one Si(1) atom to form distorted corner-sharing SeMg3Si trigonal pyramids. In the second Se site, Se(2) is bonded in a rectangular see-saw-like geometry to one Mg(2), two equivalent Mg(1), and one Si(1) atom. In the third Se site, Se(3) is bonded in a rectangular see-saw-like geometry to one Mg(1), two equivalent Mg(2), and one Si(1) atom. is represented by the CIF file [CIF]
data_Mg2SiSe4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.256
_cell_length_b   7.833
_cell_length_c   13.394
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   656.300
_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
  Mg  Mg0  1  0.000  0.500  0.000  1.0
  Mg  Mg1  1  0.500  0.000  0.500  1.0
  Mg  Mg2  1  0.000  0.000  0.000  1.0
  Mg  Mg3  1  0.500  0.500  0.500  1.0
  Mg  Mg4  1  0.496  0.750  0.231  1.0
  Mg  Mg5  1  0.004  0.750  0.731  1.0
  Mg  Mg6  1  0.504  0.250  0.769  1.0
  Mg  Mg7  1  0.996  0.250  0.269  1.0
  Si  Si8  1  0.906  0.750  0.411  1.0
  Si  Si9  1  0.594  0.750  0.911  1.0
  Si  Si10  1  0.094  0.250  0.589  1.0
  Si  Si11  1  0.406  0.250  0.089  1.0
  Se  Se12  1  0.266  0.750  0.408  1.0
  Se  Se13  1  0.234  0.750  0.908  1.0
  Se  Se14  1  0.734  0.250  0.592  1.0
  Se  Se15  1  0.766  0.250  0.092  1.0
  Se  Se16  1  0.757  0.750  0.567  1.0
  Se  Se17  1  0.743  0.750  0.067  1.0
  Se  Se18  1  0.243  0.250  0.433  1.0
  Se  Se19  1  0.257  0.250  0.933  1.0
  Se  Se20  1  0.751  0.521  0.332  1.0
  Se  Se21  1  0.749  0.979  0.832  1.0
  Se  Se22  1  0.249  0.021  0.668  1.0
  Se  Se23  1  0.251  0.479  0.168  1.0
  Se  Se24  1  0.249  0.479  0.668  1.0
  Se  Se25  1  0.251  0.021  0.168  1.0
  Se  Se26  1  0.751  0.979  0.332  1.0
  Se  Se27  1  0.749  0.521  0.832  1.0
[/CIF]
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