The structure described by Mg3Si4(SnO7)2 crystallizes in the monoclinic C2/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1), one O(2), one O(4), and two equivalent O(7) atoms to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one Sn(2)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with three equivalent Si(1)O4 tetrahedra,  an edgeedge with one Sn(2)O6 octahedra, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 35°. In the second Mg site, Mg(2) is bonded in a 4-coordinate geometry to two equivalent O(1) and two equivalent O(3) atoms. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. In the second Sn site, Sn(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted SnO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids, and edges with two equivalent Mg(1)O5 trigonal bipyramids. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Sn(2)O6 octahedra, corners with two equivalent Si(2)O4 tetrahedra, and corners with three equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 48°. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Sn(2)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, and  a cornercorner with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 64°. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Mg(2), one Sn(2), and one Si(2) atom to form distorted corner-sharing OMg2SiSn tetrahedra. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(1), one Sn(1), and one Sn(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Mg(2), one Sn(1), and one Si(2) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Mg(1), one Sn(1), one Sn(2), and one Si(1) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Mg(1) and one Si(1) atom. is represented by the CIF file [CIF]
data_Mg3Si4(SnO7)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.487
_cell_length_b   9.487
_cell_length_c   10.278
_cell_angle_alpha   59.768
_cell_angle_beta   59.768
_cell_angle_gamma   48.656
_symmetry_Int_Tables_number   1
_cell_volume   578.865
_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  0.060  0.285  0.105  1.0
  Mg  Mg1  1  0.715  0.940  0.395  1.0
  Mg  Mg2  1  0.285  0.060  0.605  1.0
  Mg  Mg3  1  0.379  0.621  0.750  1.0
  Mg  Mg4  1  0.940  0.715  0.895  1.0
  Mg  Mg5  1  0.621  0.379  0.250  1.0
  Si  Si6  1  0.546  0.065  0.719  1.0
  Si  Si7  1  0.065  0.546  0.219  1.0
  Si  Si8  1  0.482  0.276  0.111  1.0
  Si  Si9  1  0.276  0.482  0.611  1.0
  Si  Si10  1  0.935  0.454  0.781  1.0
  Si  Si11  1  0.518  0.724  0.889  1.0
  Si  Si12  1  0.724  0.518  0.389  1.0
  Si  Si13  1  0.454  0.935  0.281  1.0
  Sn  Sn14  1  0.772  0.228  0.750  1.0
  Sn  Sn15  1  0.228  0.772  0.250  1.0
  Sn  Sn16  1  0.000  0.000  0.000  1.0
  Sn  Sn17  1  0.000  0.000  0.500  1.0
  O  O18  1  0.825  0.326  0.328  1.0
  O  O19  1  0.934  0.916  0.412  1.0
  O  O20  1  0.530  0.581  0.062  1.0
  O  O21  1  0.916  0.934  0.912  1.0
  O  O22  1  0.235  0.999  0.299  1.0
  O  O23  1  0.092  0.489  0.619  1.0
  O  O24  1  0.581  0.530  0.562  1.0
  O  O25  1  0.001  0.765  0.201  1.0
  O  O26  1  0.908  0.511  0.381  1.0
  O  O27  1  0.615  0.714  0.252  1.0
  O  O28  1  0.066  0.084  0.588  1.0
  O  O29  1  0.765  0.001  0.701  1.0
  O  O30  1  0.511  0.908  0.881  1.0
  O  O31  1  0.326  0.825  0.828  1.0
  O  O32  1  0.714  0.615  0.752  1.0
  O  O33  1  0.999  0.235  0.799  1.0
  O  O34  1  0.939  0.485  0.921  1.0
  O  O35  1  0.385  0.286  0.748  1.0
  O  O36  1  0.515  0.061  0.579  1.0
  O  O37  1  0.286  0.385  0.248  1.0
  O  O38  1  0.489  0.092  0.119  1.0
  O  O39  1  0.084  0.066  0.088  1.0
  O  O40  1  0.485  0.939  0.421  1.0
  O  O41  1  0.470  0.419  0.938  1.0
  O  O42  1  0.061  0.515  0.079  1.0
  O  O43  1  0.419  0.470  0.438  1.0
  O  O44  1  0.674  0.175  0.172  1.0
  O  O45  1  0.175  0.674  0.672  1.0
[/CIF]
.
The structure described by Mg3Si4(SnO7)2 crystallizes in the monoclinic C2/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1), one O(2), one O(4), and two equivalent O(7) atoms to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one Sn(2)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with three equivalent Si(1)O4 tetrahedra,  an edgeedge with one Sn(2)O6 octahedra, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 35°. In the second Mg site, Mg(2) is bonded in a 4-coordinate geometry to two equivalent O(1) and two equivalent O(3) atoms. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. In the second Sn site, Sn(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted SnO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids, and edges with two equivalent Mg(1)O5 trigonal bipyramids. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Sn(2)O6 octahedra, corners with two equivalent Si(2)O4 tetrahedra, and corners with three equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 48°. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Sn(2)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, and  a cornercorner with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 64°. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Mg(2), one Sn(2), and one Si(2) atom to form distorted corner-sharing OMg2SiSn tetrahedra. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(1), one Sn(1), and one Sn(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Mg(2), one Sn(1), and one Si(2) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Mg(1), one Sn(1), one Sn(2), and one Si(1) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Mg(1) and one Si(1) atom. is represented by the CIF file [CIF]
data_Mg3Si4(SnO7)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.487
_cell_length_b   9.487
_cell_length_c   10.278
_cell_angle_alpha   59.768
_cell_angle_beta   59.768
_cell_angle_gamma   48.656
_symmetry_Int_Tables_number   1
_cell_volume   578.865
_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  0.060  0.285  0.105  1.0
  Mg  Mg1  1  0.715  0.940  0.395  1.0
  Mg  Mg2  1  0.285  0.060  0.605  1.0
  Mg  Mg3  1  0.379  0.621  0.750  1.0
  Mg  Mg4  1  0.940  0.715  0.895  1.0
  Mg  Mg5  1  0.621  0.379  0.250  1.0
  Si  Si6  1  0.546  0.065  0.719  1.0
  Si  Si7  1  0.065  0.546  0.219  1.0
  Si  Si8  1  0.482  0.276  0.111  1.0
  Si  Si9  1  0.276  0.482  0.611  1.0
  Si  Si10  1  0.935  0.454  0.781  1.0
  Si  Si11  1  0.518  0.724  0.889  1.0
  Si  Si12  1  0.724  0.518  0.389  1.0
  Si  Si13  1  0.454  0.935  0.281  1.0
  Sn  Sn14  1  0.772  0.228  0.750  1.0
  Sn  Sn15  1  0.228  0.772  0.250  1.0
  Sn  Sn16  1  0.000  0.000  0.000  1.0
  Sn  Sn17  1  0.000  0.000  0.500  1.0
  O  O18  1  0.825  0.326  0.328  1.0
  O  O19  1  0.934  0.916  0.412  1.0
  O  O20  1  0.530  0.581  0.062  1.0
  O  O21  1  0.916  0.934  0.912  1.0
  O  O22  1  0.235  0.999  0.299  1.0
  O  O23  1  0.092  0.489  0.619  1.0
  O  O24  1  0.581  0.530  0.562  1.0
  O  O25  1  0.001  0.765  0.201  1.0
  O  O26  1  0.908  0.511  0.381  1.0
  O  O27  1  0.615  0.714  0.252  1.0
  O  O28  1  0.066  0.084  0.588  1.0
  O  O29  1  0.765  0.001  0.701  1.0
  O  O30  1  0.511  0.908  0.881  1.0
  O  O31  1  0.326  0.825  0.828  1.0
  O  O32  1  0.714  0.615  0.752  1.0
  O  O33  1  0.999  0.235  0.799  1.0
  O  O34  1  0.939  0.485  0.921  1.0
  O  O35  1  0.385  0.286  0.748  1.0
  O  O36  1  0.515  0.061  0.579  1.0
  O  O37  1  0.286  0.385  0.248  1.0
  O  O38  1  0.489  0.092  0.119  1.0
  O  O39  1  0.084  0.066  0.088  1.0
  O  O40  1  0.485  0.939  0.421  1.0
  O  O41  1  0.470  0.419  0.938  1.0
  O  O42  1  0.061  0.515  0.079  1.0
  O  O43  1  0.419  0.470  0.438  1.0
  O  O44  1  0.674  0.175  0.172  1.0
  O  O45  1  0.175  0.674  0.672  1.0
[/CIF]
.