The material described by Mg3Si4(WO7)2 crystallizes in the monoclinic C2/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(4), and two equivalent O(7) atoms. In the second Mg site, Mg(2) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form distorted MgO4 trigonal pyramids that share corners with two equivalent W(2)O6 octahedra, corners with four equivalent Si(2)O4 tetrahedra, and  an edgeedge with one W(1)O6 octahedra. The corner-sharing octahedral tilt angles are 61°. There are two inequivalent W sites. In the first W site, W(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted WO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, edges with two equivalent W(2)O6 octahedra, and  an edgeedge with one Mg(2)O4 trigonal pyramid. In the second W site, W(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form WO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Mg(2)O4 trigonal pyramids, and edges with two equivalent W(1)O6 octahedra. 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 W(1)O6 octahedra,  a cornercorner with one W(2)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 49-50°. 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 W(1)O6 octahedra,  a cornercorner with one W(2)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, and corners with two equivalent Mg(2)O4 trigonal pyramids. The corner-sharing octahedral tilt angles are 68°. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Mg(2), one W(2), and one Si(2) atom to form distorted corner-sharing OMg2SiW tetrahedra. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Mg(1), one W(1), and one W(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Mg(2), one W(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 W(1), one W(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(WO7)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.534
_cell_length_b   9.534
_cell_length_c   10.104
_cell_angle_alpha   59.398
_cell_angle_beta   59.398
_cell_angle_gamma   47.393
_symmetry_Int_Tables_number   1
_cell_volume   561.913
_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  0.069  0.284  0.103  1.0
  Mg  Mg1  1  0.716  0.931  0.397  1.0
  Mg  Mg2  1  0.284  0.069  0.603  1.0
  Mg  Mg3  1  0.379  0.621  0.750  1.0
  Mg  Mg4  1  0.931  0.716  0.897  1.0
  Mg  Mg5  1  0.621  0.379  0.250  1.0
  Si  Si6  1  0.534  0.088  0.714  1.0
  Si  Si7  1  0.088  0.534  0.214  1.0
  Si  Si8  1  0.512  0.246  0.101  1.0
  Si  Si9  1  0.246  0.512  0.601  1.0
  Si  Si10  1  0.912  0.466  0.786  1.0
  Si  Si11  1  0.488  0.754  0.899  1.0
  Si  Si12  1  0.754  0.488  0.399  1.0
  Si  Si13  1  0.466  0.912  0.286  1.0
  W  W14  1  0.806  0.194  0.750  1.0
  W  W15  1  0.194  0.806  0.250  1.0
  W  W16  1  0.000  0.000  0.000  1.0
  W  W17  1  0.000  0.000  0.500  1.0
  O  O18  1  0.837  0.307  0.334  1.0
  O  O19  1  0.915  0.920  0.411  1.0
  O  O20  1  0.477  0.628  0.085  1.0
  O  O21  1  0.920  0.915  0.911  1.0
  O  O22  1  0.255  0.970  0.297  1.0
  O  O23  1  0.065  0.510  0.620  1.0
  O  O24  1  0.628  0.477  0.585  1.0
  O  O25  1  0.030  0.745  0.203  1.0
  O  O26  1  0.935  0.490  0.380  1.0
  O  O27  1  0.630  0.684  0.268  1.0
  O  O28  1  0.085  0.080  0.589  1.0
  O  O29  1  0.745  0.030  0.703  1.0
  O  O30  1  0.490  0.935  0.880  1.0
  O  O31  1  0.307  0.837  0.834  1.0
  O  O32  1  0.684  0.630  0.768  1.0
  O  O33  1  0.970  0.255  0.797  1.0
  O  O34  1  0.920  0.494  0.928  1.0
  O  O35  1  0.370  0.316  0.732  1.0
  O  O36  1  0.506  0.080  0.572  1.0
  O  O37  1  0.316  0.370  0.232  1.0
  O  O38  1  0.510  0.065  0.120  1.0
  O  O39  1  0.080  0.085  0.089  1.0
  O  O40  1  0.494  0.920  0.428  1.0
  O  O41  1  0.523  0.372  0.915  1.0
  O  O42  1  0.080  0.506  0.072  1.0
  O  O43  1  0.372  0.523  0.415  1.0
  O  O44  1  0.693  0.163  0.166  1.0
  O  O45  1  0.163  0.693  0.666  1.0
[/CIF]
.
The material described by Mg3Si4(WO7)2 crystallizes in the monoclinic C2/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(4), and two equivalent O(7) atoms. In the second Mg site, Mg(2) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form distorted MgO4 trigonal pyramids that share corners with two equivalent W(2)O6 octahedra, corners with four equivalent Si(2)O4 tetrahedra, and  an edgeedge with one W(1)O6 octahedra. The corner-sharing octahedral tilt angles are 61°. There are two inequivalent W sites. In the first W site, W(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted WO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, edges with two equivalent W(2)O6 octahedra, and  an edgeedge with one Mg(2)O4 trigonal pyramid. In the second W site, W(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form WO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Mg(2)O4 trigonal pyramids, and edges with two equivalent W(1)O6 octahedra. 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 W(1)O6 octahedra,  a cornercorner with one W(2)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 49-50°. 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 W(1)O6 octahedra,  a cornercorner with one W(2)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, and corners with two equivalent Mg(2)O4 trigonal pyramids. The corner-sharing octahedral tilt angles are 68°. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Mg(2), one W(2), and one Si(2) atom to form distorted corner-sharing OMg2SiW tetrahedra. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Mg(1), one W(1), and one W(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Mg(2), one W(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 W(1), one W(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(WO7)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.534
_cell_length_b   9.534
_cell_length_c   10.104
_cell_angle_alpha   59.398
_cell_angle_beta   59.398
_cell_angle_gamma   47.393
_symmetry_Int_Tables_number   1
_cell_volume   561.913
_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  0.069  0.284  0.103  1.0
  Mg  Mg1  1  0.716  0.931  0.397  1.0
  Mg  Mg2  1  0.284  0.069  0.603  1.0
  Mg  Mg3  1  0.379  0.621  0.750  1.0
  Mg  Mg4  1  0.931  0.716  0.897  1.0
  Mg  Mg5  1  0.621  0.379  0.250  1.0
  Si  Si6  1  0.534  0.088  0.714  1.0
  Si  Si7  1  0.088  0.534  0.214  1.0
  Si  Si8  1  0.512  0.246  0.101  1.0
  Si  Si9  1  0.246  0.512  0.601  1.0
  Si  Si10  1  0.912  0.466  0.786  1.0
  Si  Si11  1  0.488  0.754  0.899  1.0
  Si  Si12  1  0.754  0.488  0.399  1.0
  Si  Si13  1  0.466  0.912  0.286  1.0
  W  W14  1  0.806  0.194  0.750  1.0
  W  W15  1  0.194  0.806  0.250  1.0
  W  W16  1  0.000  0.000  0.000  1.0
  W  W17  1  0.000  0.000  0.500  1.0
  O  O18  1  0.837  0.307  0.334  1.0
  O  O19  1  0.915  0.920  0.411  1.0
  O  O20  1  0.477  0.628  0.085  1.0
  O  O21  1  0.920  0.915  0.911  1.0
  O  O22  1  0.255  0.970  0.297  1.0
  O  O23  1  0.065  0.510  0.620  1.0
  O  O24  1  0.628  0.477  0.585  1.0
  O  O25  1  0.030  0.745  0.203  1.0
  O  O26  1  0.935  0.490  0.380  1.0
  O  O27  1  0.630  0.684  0.268  1.0
  O  O28  1  0.085  0.080  0.589  1.0
  O  O29  1  0.745  0.030  0.703  1.0
  O  O30  1  0.490  0.935  0.880  1.0
  O  O31  1  0.307  0.837  0.834  1.0
  O  O32  1  0.684  0.630  0.768  1.0
  O  O33  1  0.970  0.255  0.797  1.0
  O  O34  1  0.920  0.494  0.928  1.0
  O  O35  1  0.370  0.316  0.732  1.0
  O  O36  1  0.506  0.080  0.572  1.0
  O  O37  1  0.316  0.370  0.232  1.0
  O  O38  1  0.510  0.065  0.120  1.0
  O  O39  1  0.080  0.085  0.089  1.0
  O  O40  1  0.494  0.920  0.428  1.0
  O  O41  1  0.523  0.372  0.915  1.0
  O  O42  1  0.080  0.506  0.072  1.0
  O  O43  1  0.372  0.523  0.415  1.0
  O  O44  1  0.693  0.163  0.166  1.0
  O  O45  1  0.163  0.693  0.666  1.0
[/CIF]
.