The structure described by MgU2(SiO9)2 crystallizes in the monoclinic C2/m space group. Mg(1) is bonded in a square co-planar geometry to two equivalent O(2), two equivalent O(5), and four equivalent O(7) atoms. U(1) is bonded to one O(2), one O(4), one O(6), and four equivalent O(3) atoms to form distorted UO7 pentagonal bipyramids that share corners with three equivalent Si(1)O4 trigonal pyramids, edges with two equivalent U(1)O7 pentagonal bipyramids, and  an edgeedge with one Si(1)O4 trigonal pyramid. Si(1) is bonded to one O(1), one O(4), and two equivalent O(3) atoms to form distorted SiO4 trigonal pyramids that share corners with three equivalent U(1)O7 pentagonal bipyramids and  an edgeedge with one U(1)O7 pentagonal bipyramid. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Si(1) and two equivalent O(7) atoms. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Mg(1) and one U(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to two equivalent U(1) and one Si(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one U(1) and one Si(1) atom. In the fifth O site, O(5) is bonded in a single-bond geometry to one Mg(1) atom. In the sixth O site, O(6) is bonded in a single-bond geometry to one U(1) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Mg(1) and one O(1) atom. is represented by the CIF file [CIF]
data_MgU2(SiO9)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.945
_cell_length_b   7.149
_cell_length_c   8.725
_cell_angle_alpha   114.183
_cell_angle_beta   111.516
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   361.795
_cell_formula_units_Z   1
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  0.000  0.000  0.000  1.0
  U  U1  1  0.640  0.753  0.507  1.0
  U  U2  1  0.360  0.247  0.493  1.0
  Si  Si3  1  0.835  0.264  0.528  1.0
  Si  Si4  1  0.165  0.736  0.472  1.0
  O  O5  1  0.974  0.597  0.193  1.0
  O  O6  1  0.026  0.403  0.807  1.0
  O  O7  1  0.739  0.880  0.761  1.0
  O  O8  1  0.261  0.120  0.239  1.0
  O  O9  1  0.690  0.436  0.518  1.0
  O  O10  1  0.310  0.564  0.482  1.0
  O  O11  1  0.310  0.918  0.482  1.0
  O  O12  1  0.690  0.082  0.518  1.0
  O  O13  1  0.971  0.764  0.529  1.0
  O  O14  1  0.029  0.236  0.471  1.0
  O  O15  1  0.206  0.934  0.868  1.0
  O  O16  1  0.794  0.066  0.132  1.0
  O  O17  1  0.542  0.631  0.262  1.0
  O  O18  1  0.458  0.369  0.738  1.0
  O  O19  1  0.904  0.712  0.103  1.0
  O  O20  1  0.096  0.288  0.897  1.0
  O  O21  1  0.096  0.609  0.897  1.0
  O  O22  1  0.904  0.391  0.103  1.0
[/CIF]
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The structure described by MgU2(SiO9)2 crystallizes in the monoclinic C2/m space group. Mg(1) is bonded in a square co-planar geometry to two equivalent O(2), two equivalent O(5), and four equivalent O(7) atoms. U(1) is bonded to one O(2), one O(4), one O(6), and four equivalent O(3) atoms to form distorted UO7 pentagonal bipyramids that share corners with three equivalent Si(1)O4 trigonal pyramids, edges with two equivalent U(1)O7 pentagonal bipyramids, and  an edgeedge with one Si(1)O4 trigonal pyramid. Si(1) is bonded to one O(1), one O(4), and two equivalent O(3) atoms to form distorted SiO4 trigonal pyramids that share corners with three equivalent U(1)O7 pentagonal bipyramids and  an edgeedge with one U(1)O7 pentagonal bipyramid. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Si(1) and two equivalent O(7) atoms. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Mg(1) and one U(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to two equivalent U(1) and one Si(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one U(1) and one Si(1) atom. In the fifth O site, O(5) is bonded in a single-bond geometry to one Mg(1) atom. In the sixth O site, O(6) is bonded in a single-bond geometry to one U(1) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Mg(1) and one O(1) atom. is represented by the CIF file [CIF]
data_MgU2(SiO9)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.945
_cell_length_b   7.149
_cell_length_c   8.725
_cell_angle_alpha   114.183
_cell_angle_beta   111.516
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   361.795
_cell_formula_units_Z   1
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  0.000  0.000  0.000  1.0
  U  U1  1  0.640  0.753  0.507  1.0
  U  U2  1  0.360  0.247  0.493  1.0
  Si  Si3  1  0.835  0.264  0.528  1.0
  Si  Si4  1  0.165  0.736  0.472  1.0
  O  O5  1  0.974  0.597  0.193  1.0
  O  O6  1  0.026  0.403  0.807  1.0
  O  O7  1  0.739  0.880  0.761  1.0
  O  O8  1  0.261  0.120  0.239  1.0
  O  O9  1  0.690  0.436  0.518  1.0
  O  O10  1  0.310  0.564  0.482  1.0
  O  O11  1  0.310  0.918  0.482  1.0
  O  O12  1  0.690  0.082  0.518  1.0
  O  O13  1  0.971  0.764  0.529  1.0
  O  O14  1  0.029  0.236  0.471  1.0
  O  O15  1  0.206  0.934  0.868  1.0
  O  O16  1  0.794  0.066  0.132  1.0
  O  O17  1  0.542  0.631  0.262  1.0
  O  O18  1  0.458  0.369  0.738  1.0
  O  O19  1  0.904  0.712  0.103  1.0
  O  O20  1  0.096  0.288  0.897  1.0
  O  O21  1  0.096  0.609  0.897  1.0
  O  O22  1  0.904  0.391  0.103  1.0
[/CIF]
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