The crystal structure described by Mg7(SiO7)2 is beta indium sulfide-derived structured and crystallizes in the hexagonal P6_3 space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1), one O(2), one O(3), one O(5), and two equivalent O(4) atoms to form distorted MgO6 octahedra that share  a cornercorner with one Mg(3)O6 octahedra, corners with four equivalent Mg(2)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra,  an edgeedge with one Mg(2)O6 octahedra,  an edgeedge with one Mg(3)O6 octahedra, and edges with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 17-63°. In the second Mg site, Mg(2) is bonded to one O(2), one O(3), one O(4), one O(6), and two equivalent O(1) atoms to form MgO6 octahedra that share corners with four equivalent Mg(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  an edgeedge with one Mg(1)O6 octahedra,  an edgeedge with one Mg(3)O6 octahedra, edges with two equivalent Mg(2)O6 octahedra, and  an edgeedge with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 17-63°. In the third Mg site, Mg(3) is bonded to three equivalent O(2) and three equivalent O(4) atoms to form a mixture of distorted corner and edge-sharing MgO6 octahedra. The corner-sharing octahedral tilt angles are 55°. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(5) and three equivalent O(3) atoms to form SiO4 tetrahedra that share corners with three equivalent Mg(2)O6 octahedra and corners with six equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-58°. In the second Si site, Si(2) is bonded to one O(6) and three equivalent O(1) atoms to form SiO4 tetrahedra that share corners with three equivalent Mg(1)O6 octahedra, corners with three equivalent Mg(2)O6 octahedra, and edges with three equivalent Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 51-57°. There are six inequivalent O sites. In the first O site, O(4) is bonded in a see-saw-like geometry to one Mg(2), one Mg(3), and two equivalent Mg(1) atoms. In the second O site, O(5) is bonded in a distorted trigonal pyramidal geometry to three equivalent Mg(1) and one Si(1) atom. In the third O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to three equivalent Mg(2) and one Si(2) atom. In the fourth O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), two equivalent Mg(2), and one Si(2) atom. In the fifth O site, O(2) is bonded in a trigonal planar geometry to one Mg(1), one Mg(2), and one Mg(3) atom. In the sixth O site, O(3) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mg(2), and one Si(1) atom. is represented by the CIF card [CIF]
data_Mg7(SiO7)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.888
_cell_length_b   7.888
_cell_length_c   9.801
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   528.076
_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
  Mg  Mg0  1  0.078  0.463  0.117  1.0
  Mg  Mg1  1  0.537  0.615  0.117  1.0
  Mg  Mg2  1  0.385  0.922  0.117  1.0
  Mg  Mg3  1  0.922  0.537  0.617  1.0
  Mg  Mg4  1  0.463  0.385  0.617  1.0
  Mg  Mg5  1  0.615  0.078  0.617  1.0
  Mg  Mg6  1  0.025  0.241  0.388  1.0
  Mg  Mg7  1  0.759  0.784  0.388  1.0
  Mg  Mg8  1  0.216  0.975  0.388  1.0
  Mg  Mg9  1  0.975  0.759  0.888  1.0
  Mg  Mg10  1  0.241  0.216  0.888  1.0
  Mg  Mg11  1  0.784  0.025  0.888  1.0
  Mg  Mg12  1  0.333  0.667  0.413  1.0
  Mg  Mg13  1  0.667  0.333  0.913  1.0
  Si  Si14  1  0.667  0.333  0.330  1.0
  Si  Si15  1  0.333  0.667  0.830  1.0
  Si  Si16  1  0.000  0.000  0.101  1.0
  Si  Si17  1  0.000  0.000  0.601  1.0
  O  O18  1  0.825  0.026  0.527  1.0
  O  O19  1  0.974  0.799  0.527  1.0
  O  O20  1  0.201  0.175  0.527  1.0
  O  O21  1  0.175  0.974  0.027  1.0
  O  O22  1  0.026  0.201  0.027  1.0
  O  O23  1  0.799  0.825  0.027  1.0
  O  O24  1  0.613  0.085  0.000  1.0
  O  O25  1  0.915  0.527  0.000  1.0
  O  O26  1  0.473  0.387  0.000  1.0
  O  O27  1  0.387  0.915  0.500  1.0
  O  O28  1  0.085  0.473  0.500  1.0
  O  O29  1  0.527  0.613  0.500  1.0
  O  O30  1  0.861  0.324  0.274  1.0
  O  O31  1  0.676  0.537  0.274  1.0
  O  O32  1  0.463  0.139  0.274  1.0
  O  O33  1  0.139  0.676  0.774  1.0
  O  O34  1  0.324  0.463  0.774  1.0
  O  O35  1  0.537  0.861  0.774  1.0
  O  O36  1  0.282  0.471  0.256  1.0
  O  O37  1  0.529  0.811  0.256  1.0
  O  O38  1  0.189  0.718  0.256  1.0
  O  O39  1  0.718  0.529  0.756  1.0
  O  O40  1  0.471  0.189  0.756  1.0
  O  O41  1  0.811  0.282  0.756  1.0
  O  O42  1  0.667  0.333  0.499  1.0
  O  O43  1  0.333  0.667  0.999  1.0
  O  O44  1  0.000  0.000  0.269  1.0
  O  O45  1  0.000  0.000  0.769  1.0
[/CIF]
.
The crystal structure described by Mg7(SiO7)2 is beta indium sulfide-derived structured and crystallizes in the hexagonal P6_3 space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1), one O(2), one O(3), one O(5), and two equivalent O(4) atoms to form distorted MgO6 octahedra that share  a cornercorner with one Mg(3)O6 octahedra, corners with four equivalent Mg(2)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra,  an edgeedge with one Mg(2)O6 octahedra,  an edgeedge with one Mg(3)O6 octahedra, and edges with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 17-63°. In the second Mg site, Mg(2) is bonded to one O(2), one O(3), one O(4), one O(6), and two equivalent O(1) atoms to form MgO6 octahedra that share corners with four equivalent Mg(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  an edgeedge with one Mg(1)O6 octahedra,  an edgeedge with one Mg(3)O6 octahedra, edges with two equivalent Mg(2)O6 octahedra, and  an edgeedge with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 17-63°. In the third Mg site, Mg(3) is bonded to three equivalent O(2) and three equivalent O(4) atoms to form a mixture of distorted corner and edge-sharing MgO6 octahedra. The corner-sharing octahedral tilt angles are 55°. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(5) and three equivalent O(3) atoms to form SiO4 tetrahedra that share corners with three equivalent Mg(2)O6 octahedra and corners with six equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-58°. In the second Si site, Si(2) is bonded to one O(6) and three equivalent O(1) atoms to form SiO4 tetrahedra that share corners with three equivalent Mg(1)O6 octahedra, corners with three equivalent Mg(2)O6 octahedra, and edges with three equivalent Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 51-57°. There are six inequivalent O sites. In the first O site, O(4) is bonded in a see-saw-like geometry to one Mg(2), one Mg(3), and two equivalent Mg(1) atoms. In the second O site, O(5) is bonded in a distorted trigonal pyramidal geometry to three equivalent Mg(1) and one Si(1) atom. In the third O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to three equivalent Mg(2) and one Si(2) atom. In the fourth O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), two equivalent Mg(2), and one Si(2) atom. In the fifth O site, O(2) is bonded in a trigonal planar geometry to one Mg(1), one Mg(2), and one Mg(3) atom. In the sixth O site, O(3) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mg(2), and one Si(1) atom. is represented by the CIF card [CIF]
data_Mg7(SiO7)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.888
_cell_length_b   7.888
_cell_length_c   9.801
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   528.076
_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
  Mg  Mg0  1  0.078  0.463  0.117  1.0
  Mg  Mg1  1  0.537  0.615  0.117  1.0
  Mg  Mg2  1  0.385  0.922  0.117  1.0
  Mg  Mg3  1  0.922  0.537  0.617  1.0
  Mg  Mg4  1  0.463  0.385  0.617  1.0
  Mg  Mg5  1  0.615  0.078  0.617  1.0
  Mg  Mg6  1  0.025  0.241  0.388  1.0
  Mg  Mg7  1  0.759  0.784  0.388  1.0
  Mg  Mg8  1  0.216  0.975  0.388  1.0
  Mg  Mg9  1  0.975  0.759  0.888  1.0
  Mg  Mg10  1  0.241  0.216  0.888  1.0
  Mg  Mg11  1  0.784  0.025  0.888  1.0
  Mg  Mg12  1  0.333  0.667  0.413  1.0
  Mg  Mg13  1  0.667  0.333  0.913  1.0
  Si  Si14  1  0.667  0.333  0.330  1.0
  Si  Si15  1  0.333  0.667  0.830  1.0
  Si  Si16  1  0.000  0.000  0.101  1.0
  Si  Si17  1  0.000  0.000  0.601  1.0
  O  O18  1  0.825  0.026  0.527  1.0
  O  O19  1  0.974  0.799  0.527  1.0
  O  O20  1  0.201  0.175  0.527  1.0
  O  O21  1  0.175  0.974  0.027  1.0
  O  O22  1  0.026  0.201  0.027  1.0
  O  O23  1  0.799  0.825  0.027  1.0
  O  O24  1  0.613  0.085  0.000  1.0
  O  O25  1  0.915  0.527  0.000  1.0
  O  O26  1  0.473  0.387  0.000  1.0
  O  O27  1  0.387  0.915  0.500  1.0
  O  O28  1  0.085  0.473  0.500  1.0
  O  O29  1  0.527  0.613  0.500  1.0
  O  O30  1  0.861  0.324  0.274  1.0
  O  O31  1  0.676  0.537  0.274  1.0
  O  O32  1  0.463  0.139  0.274  1.0
  O  O33  1  0.139  0.676  0.774  1.0
  O  O34  1  0.324  0.463  0.774  1.0
  O  O35  1  0.537  0.861  0.774  1.0
  O  O36  1  0.282  0.471  0.256  1.0
  O  O37  1  0.529  0.811  0.256  1.0
  O  O38  1  0.189  0.718  0.256  1.0
  O  O39  1  0.718  0.529  0.756  1.0
  O  O40  1  0.471  0.189  0.756  1.0
  O  O41  1  0.811  0.282  0.756  1.0
  O  O42  1  0.667  0.333  0.499  1.0
  O  O43  1  0.333  0.667  0.999  1.0
  O  O44  1  0.000  0.000  0.269  1.0
  O  O45  1  0.000  0.000  0.769  1.0
[/CIF]
.