The crystal structure described by Mg5F2(SiO4)2 is beta indium sulfide-derived structured and crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent F(1) atoms to form MgO4F2 octahedra that share corners with two equivalent Mg(1)O4F2 octahedra, corners with four equivalent Mg(2)O5F octahedra, corners with two equivalent Si(1)O4 tetrahedra,  an edgeedge with one Mg(1)O4F2 octahedra,  an edgeedge with one Mg(2)O5F octahedra,  an edgeedge with one Mg(3)O6 octahedra, and  an edgeedge with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 49-59°. In the second Mg site, Mg(2) is bonded to one O(1), one O(2), one O(4), two equivalent O(3), and one F(1) atom to form MgO5F octahedra that share corners with two equivalent Mg(2)O5F octahedra, corners with two equivalent Mg(3)O6 octahedra, corners with four equivalent Mg(1)O4F2 octahedra, corners with three equivalent Si(1)O4 tetrahedra,  an edgeedge with one Mg(1)O4F2 octahedra,  an edgeedge with one Mg(3)O6 octahedra, and  an edgeedge with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 49-62°. In the third Mg site, Mg(3) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with four equivalent Mg(2)O5F octahedra, corners with two equivalent Si(1)O4 tetrahedra, edges with two equivalent Mg(1)O4F2 octahedra, edges with two equivalent Mg(2)O5F octahedra, and edges with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 58-62°. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(3)O6 octahedra, corners with two equivalent Mg(1)O4F2 octahedra, corners with three equivalent Mg(2)O5F octahedra,  an edgeedge with one Mg(1)O4F2 octahedra,  an edgeedge with one Mg(2)O5F octahedra, and  an edgeedge with one Mg(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 56-60°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Mg(2), one Mg(3), and one Si(1) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Mg(2), two equivalent Mg(1), and one Si(1) atom. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to one Mg(3), two equivalent Mg(2), and one Si(1) atom. In the fourth O site, O(4) is bonded to one Mg(1), one Mg(2), one Mg(3), and one Si(1) atom to form distorted corner-sharing OMg3Si trigonal pyramids. F(1) is bonded in a distorted trigonal planar geometry to one Mg(2) and two equivalent Mg(1) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg5Si2(O4F)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.777
_cell_length_b   7.902
_cell_length_c   10.374
_cell_angle_alpha   70.870
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   369.942
_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  0.491  0.421  0.386  1.0
  Mg  Mg1  1  0.991  0.579  0.114  1.0
  Mg  Mg2  1  0.509  0.579  0.614  1.0
  Mg  Mg3  1  0.009  0.421  0.886  1.0
  Mg  Mg4  1  0.007  0.198  0.672  1.0
  Mg  Mg5  1  0.507  0.802  0.828  1.0
  Mg  Mg6  1  0.993  0.802  0.328  1.0
  Mg  Mg7  1  0.493  0.198  0.172  1.0
  Mg  Mg8  1  0.500  0.000  0.500  1.0
  Mg  Mg9  1  0.000  0.000  0.000  1.0
  Si  Si10  1  0.077  0.797  0.642  1.0
  Si  Si11  1  0.577  0.203  0.858  1.0
  Si  Si12  1  0.923  0.203  0.358  1.0
  Si  Si13  1  0.423  0.797  0.142  1.0
  O  O14  1  0.776  0.207  0.502  1.0
  O  O15  1  0.276  0.793  0.998  1.0
  O  O16  1  0.224  0.793  0.498  1.0
  O  O17  1  0.724  0.207  0.002  1.0
  O  O18  1  0.271  0.625  0.259  1.0
  O  O19  1  0.771  0.375  0.241  1.0
  O  O20  1  0.729  0.375  0.741  1.0
  O  O21  1  0.229  0.625  0.759  1.0
  O  O22  1  0.224  0.974  0.667  1.0
  O  O23  1  0.724  0.026  0.833  1.0
  O  O24  1  0.776  0.026  0.333  1.0
  O  O25  1  0.276  0.974  0.167  1.0
  O  O26  1  0.735  0.793  0.645  1.0
  O  O27  1  0.235  0.207  0.855  1.0
  O  O28  1  0.265  0.207  0.355  1.0
  O  O29  1  0.765  0.793  0.145  1.0
  F  F30  1  0.273  0.396  0.559  1.0
  F  F31  1  0.773  0.604  0.941  1.0
  F  F32  1  0.727  0.604  0.441  1.0
  F  F33  1  0.227  0.396  0.059  1.0
[/CIF]
.
The crystal structure described by Mg5F2(SiO4)2 is beta indium sulfide-derived structured and crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent F(1) atoms to form MgO4F2 octahedra that share corners with two equivalent Mg(1)O4F2 octahedra, corners with four equivalent Mg(2)O5F octahedra, corners with two equivalent Si(1)O4 tetrahedra,  an edgeedge with one Mg(1)O4F2 octahedra,  an edgeedge with one Mg(2)O5F octahedra,  an edgeedge with one Mg(3)O6 octahedra, and  an edgeedge with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 49-59°. In the second Mg site, Mg(2) is bonded to one O(1), one O(2), one O(4), two equivalent O(3), and one F(1) atom to form MgO5F octahedra that share corners with two equivalent Mg(2)O5F octahedra, corners with two equivalent Mg(3)O6 octahedra, corners with four equivalent Mg(1)O4F2 octahedra, corners with three equivalent Si(1)O4 tetrahedra,  an edgeedge with one Mg(1)O4F2 octahedra,  an edgeedge with one Mg(3)O6 octahedra, and  an edgeedge with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 49-62°. In the third Mg site, Mg(3) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with four equivalent Mg(2)O5F octahedra, corners with two equivalent Si(1)O4 tetrahedra, edges with two equivalent Mg(1)O4F2 octahedra, edges with two equivalent Mg(2)O5F octahedra, and edges with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 58-62°. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(3)O6 octahedra, corners with two equivalent Mg(1)O4F2 octahedra, corners with three equivalent Mg(2)O5F octahedra,  an edgeedge with one Mg(1)O4F2 octahedra,  an edgeedge with one Mg(2)O5F octahedra, and  an edgeedge with one Mg(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 56-60°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Mg(2), one Mg(3), and one Si(1) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Mg(2), two equivalent Mg(1), and one Si(1) atom. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to one Mg(3), two equivalent Mg(2), and one Si(1) atom. In the fourth O site, O(4) is bonded to one Mg(1), one Mg(2), one Mg(3), and one Si(1) atom to form distorted corner-sharing OMg3Si trigonal pyramids. F(1) is bonded in a distorted trigonal planar geometry to one Mg(2) and two equivalent Mg(1) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg5Si2(O4F)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.777
_cell_length_b   7.902
_cell_length_c   10.374
_cell_angle_alpha   70.870
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   369.942
_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  0.491  0.421  0.386  1.0
  Mg  Mg1  1  0.991  0.579  0.114  1.0
  Mg  Mg2  1  0.509  0.579  0.614  1.0
  Mg  Mg3  1  0.009  0.421  0.886  1.0
  Mg  Mg4  1  0.007  0.198  0.672  1.0
  Mg  Mg5  1  0.507  0.802  0.828  1.0
  Mg  Mg6  1  0.993  0.802  0.328  1.0
  Mg  Mg7  1  0.493  0.198  0.172  1.0
  Mg  Mg8  1  0.500  0.000  0.500  1.0
  Mg  Mg9  1  0.000  0.000  0.000  1.0
  Si  Si10  1  0.077  0.797  0.642  1.0
  Si  Si11  1  0.577  0.203  0.858  1.0
  Si  Si12  1  0.923  0.203  0.358  1.0
  Si  Si13  1  0.423  0.797  0.142  1.0
  O  O14  1  0.776  0.207  0.502  1.0
  O  O15  1  0.276  0.793  0.998  1.0
  O  O16  1  0.224  0.793  0.498  1.0
  O  O17  1  0.724  0.207  0.002  1.0
  O  O18  1  0.271  0.625  0.259  1.0
  O  O19  1  0.771  0.375  0.241  1.0
  O  O20  1  0.729  0.375  0.741  1.0
  O  O21  1  0.229  0.625  0.759  1.0
  O  O22  1  0.224  0.974  0.667  1.0
  O  O23  1  0.724  0.026  0.833  1.0
  O  O24  1  0.776  0.026  0.333  1.0
  O  O25  1  0.276  0.974  0.167  1.0
  O  O26  1  0.735  0.793  0.645  1.0
  O  O27  1  0.235  0.207  0.855  1.0
  O  O28  1  0.265  0.207  0.355  1.0
  O  O29  1  0.765  0.793  0.145  1.0
  F  F30  1  0.273  0.396  0.559  1.0
  F  F31  1  0.773  0.604  0.941  1.0
  F  F32  1  0.727  0.604  0.441  1.0
  F  F33  1  0.227  0.396  0.059  1.0
[/CIF]
.