The compound described by Mg3Si4(BiO7)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 distorted rectangular see-saw-like geometry to one O(1), one O(2), 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 Bi(2)O6 octahedra, corners with four equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Bi(1)O6 octahedra. The corner-sharing octahedral tilt angles are 60°. 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 Bi(1)O6 octahedra,  a cornercorner with one Bi(2)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 41-50°. 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 Bi(1)O6 octahedra,  a cornercorner with one Bi(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 range from 69-72°. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted BiO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, edges with two equivalent Bi(2)O6 octahedra, and  an edgeedge with one Mg(2)O4 trigonal pyramid. In the second Bi site, Bi(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form BiO6 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 Bi(1)O6 octahedra. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Mg(1), one Mg(2), one Si(2), and one Bi(2) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Mg(1), one Bi(1), and one Bi(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Mg(2), one Si(2), and one Bi(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Si(1), one Bi(1), and one Bi(2) 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 Crystallographic Information File (CIF) [CIF]
data_Mg3Si4(BiO7)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.676
_cell_length_b   9.676
_cell_length_c   10.389
_cell_angle_alpha   58.236
_cell_angle_beta   58.236
_cell_angle_gamma   51.429
_symmetry_Int_Tables_number   1
_cell_volume   617.124
_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  0.068  0.299  0.075  1.0
  Mg  Mg1  1  0.701  0.932  0.425  1.0
  Mg  Mg2  1  0.299  0.068  0.575  1.0
  Mg  Mg3  1  0.388  0.612  0.750  1.0
  Mg  Mg4  1  0.932  0.701  0.925  1.0
  Mg  Mg5  1  0.612  0.388  0.250  1.0
  Si  Si6  1  0.516  0.090  0.719  1.0
  Si  Si7  1  0.090  0.516  0.219  1.0
  Si  Si8  1  0.492  0.264  0.118  1.0
  Si  Si9  1  0.264  0.492  0.618  1.0
  Si  Si10  1  0.910  0.484  0.781  1.0
  Si  Si11  1  0.508  0.736  0.882  1.0
  Si  Si12  1  0.736  0.508  0.382  1.0
  Si  Si13  1  0.484  0.910  0.281  1.0
  Bi  Bi14  1  0.775  0.225  0.750  1.0
  Bi  Bi15  1  0.225  0.775  0.250  1.0
  Bi  Bi16  1  0.000  0.000  0.000  1.0
  Bi  Bi17  1  0.000  0.000  0.500  1.0
  O  O18  1  0.810  0.342  0.315  1.0
  O  O19  1  0.935  0.886  0.408  1.0
  O  O20  1  0.508  0.598  0.063  1.0
  O  O21  1  0.886  0.935  0.908  1.0
  O  O22  1  0.287  0.935  0.313  1.0
  O  O23  1  0.079  0.509  0.623  1.0
  O  O24  1  0.598  0.508  0.563  1.0
  O  O25  1  0.065  0.713  0.187  1.0
  O  O26  1  0.921  0.491  0.377  1.0
  O  O27  1  0.650  0.707  0.244  1.0
  O  O28  1  0.065  0.114  0.592  1.0
  O  O29  1  0.713  0.065  0.687  1.0
  O  O30  1  0.491  0.921  0.877  1.0
  O  O31  1  0.342  0.810  0.815  1.0
  O  O32  1  0.707  0.650  0.744  1.0
  O  O33  1  0.935  0.287  0.813  1.0
  O  O34  1  0.915  0.503  0.926  1.0
  O  O35  1  0.350  0.293  0.756  1.0
  O  O36  1  0.497  0.085  0.574  1.0
  O  O37  1  0.293  0.350  0.256  1.0
  O  O38  1  0.509  0.079  0.123  1.0
  O  O39  1  0.114  0.065  0.092  1.0
  O  O40  1  0.503  0.915  0.426  1.0
  O  O41  1  0.492  0.402  0.937  1.0
  O  O42  1  0.085  0.497  0.074  1.0
  O  O43  1  0.402  0.492  0.437  1.0
  O  O44  1  0.658  0.190  0.185  1.0
  O  O45  1  0.190  0.658  0.685  1.0
[/CIF]
.
The compound described by Mg3Si4(BiO7)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 distorted rectangular see-saw-like geometry to one O(1), one O(2), 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 Bi(2)O6 octahedra, corners with four equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Bi(1)O6 octahedra. The corner-sharing octahedral tilt angles are 60°. 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 Bi(1)O6 octahedra,  a cornercorner with one Bi(2)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 41-50°. 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 Bi(1)O6 octahedra,  a cornercorner with one Bi(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 range from 69-72°. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted BiO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, edges with two equivalent Bi(2)O6 octahedra, and  an edgeedge with one Mg(2)O4 trigonal pyramid. In the second Bi site, Bi(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form BiO6 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 Bi(1)O6 octahedra. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Mg(1), one Mg(2), one Si(2), and one Bi(2) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Mg(1), one Bi(1), and one Bi(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Mg(2), one Si(2), and one Bi(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Si(1), one Bi(1), and one Bi(2) 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 Crystallographic Information File (CIF) [CIF]
data_Mg3Si4(BiO7)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.676
_cell_length_b   9.676
_cell_length_c   10.389
_cell_angle_alpha   58.236
_cell_angle_beta   58.236
_cell_angle_gamma   51.429
_symmetry_Int_Tables_number   1
_cell_volume   617.124
_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  0.068  0.299  0.075  1.0
  Mg  Mg1  1  0.701  0.932  0.425  1.0
  Mg  Mg2  1  0.299  0.068  0.575  1.0
  Mg  Mg3  1  0.388  0.612  0.750  1.0
  Mg  Mg4  1  0.932  0.701  0.925  1.0
  Mg  Mg5  1  0.612  0.388  0.250  1.0
  Si  Si6  1  0.516  0.090  0.719  1.0
  Si  Si7  1  0.090  0.516  0.219  1.0
  Si  Si8  1  0.492  0.264  0.118  1.0
  Si  Si9  1  0.264  0.492  0.618  1.0
  Si  Si10  1  0.910  0.484  0.781  1.0
  Si  Si11  1  0.508  0.736  0.882  1.0
  Si  Si12  1  0.736  0.508  0.382  1.0
  Si  Si13  1  0.484  0.910  0.281  1.0
  Bi  Bi14  1  0.775  0.225  0.750  1.0
  Bi  Bi15  1  0.225  0.775  0.250  1.0
  Bi  Bi16  1  0.000  0.000  0.000  1.0
  Bi  Bi17  1  0.000  0.000  0.500  1.0
  O  O18  1  0.810  0.342  0.315  1.0
  O  O19  1  0.935  0.886  0.408  1.0
  O  O20  1  0.508  0.598  0.063  1.0
  O  O21  1  0.886  0.935  0.908  1.0
  O  O22  1  0.287  0.935  0.313  1.0
  O  O23  1  0.079  0.509  0.623  1.0
  O  O24  1  0.598  0.508  0.563  1.0
  O  O25  1  0.065  0.713  0.187  1.0
  O  O26  1  0.921  0.491  0.377  1.0
  O  O27  1  0.650  0.707  0.244  1.0
  O  O28  1  0.065  0.114  0.592  1.0
  O  O29  1  0.713  0.065  0.687  1.0
  O  O30  1  0.491  0.921  0.877  1.0
  O  O31  1  0.342  0.810  0.815  1.0
  O  O32  1  0.707  0.650  0.744  1.0
  O  O33  1  0.935  0.287  0.813  1.0
  O  O34  1  0.915  0.503  0.926  1.0
  O  O35  1  0.350  0.293  0.756  1.0
  O  O36  1  0.497  0.085  0.574  1.0
  O  O37  1  0.293  0.350  0.256  1.0
  O  O38  1  0.509  0.079  0.123  1.0
  O  O39  1  0.114  0.065  0.092  1.0
  O  O40  1  0.503  0.915  0.426  1.0
  O  O41  1  0.492  0.402  0.937  1.0
  O  O42  1  0.085  0.497  0.074  1.0
  O  O43  1  0.402  0.492  0.437  1.0
  O  O44  1  0.658  0.190  0.185  1.0
  O  O45  1  0.190  0.658  0.685  1.0
[/CIF]
.