The material described by Bi2MgO4 crystallizes in the monoclinic Cm space group. Mg(1) is bonded to one O(1), one O(2), one O(3), and two equivalent O(4) atoms to form MgO5 trigonal bipyramids that share corners with two equivalent Mg(1)O5 trigonal bipyramids, corners with two equivalent Bi(1)O4 trigonal pyramids, corners with five equivalent Bi(2)O4 trigonal pyramids, and  an edgeedge with one Bi(1)O4 trigonal pyramid. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form BiO4 trigonal pyramids that share corners with two equivalent Mg(1)O5 trigonal bipyramids, corners with two equivalent Bi(1)O4 trigonal pyramids, corners with three equivalent Bi(2)O4 trigonal pyramids, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. In the second Bi site, Bi(2) is bonded to one O(1), one O(4), and two equivalent O(2) atoms to form BiO4 trigonal pyramids that share corners with five equivalent Mg(1)O5 trigonal bipyramids, corners with two equivalent Bi(2)O4 trigonal pyramids, and corners with three equivalent Bi(1)O4 trigonal pyramids. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Mg(1), one Bi(1), and one Bi(2) atom. In the second O site, O(2) is bonded to one Mg(1), one Bi(1), and two equivalent Bi(2) atoms to form corner-sharing OMgBi3 tetrahedra. In the third O site, O(3) is bonded in a trigonal planar geometry to one Mg(1) and two equivalent Bi(1) atoms. In the fourth O site, O(4) is bonded in a trigonal planar geometry to two equivalent Mg(1) and one Bi(2) atom. is represented by the CIF file [CIF]
data_Mg(BiO2)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.743
_cell_length_b   5.619
_cell_length_c   6.640
_cell_angle_alpha   61.795
_cell_angle_beta   73.561
_cell_angle_gamma   89.970
_symmetry_Int_Tables_number   1
_cell_volume   116.554
_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  0.348  0.564  0.305  1.0
  Bi  Bi1  1  0.150  0.886  0.702  1.0
  Bi  Bi2  1  0.964  0.170  0.076  1.0
  O  O3  1  0.164  0.276  0.673  1.0
  O  O4  1  0.363  0.197  0.277  1.0
  O  O5  1  0.539  0.803  0.923  1.0
  O  O6  1  0.855  0.738  0.291  1.0
[/CIF]
.
The material described by Bi2MgO4 crystallizes in the monoclinic Cm space group. Mg(1) is bonded to one O(1), one O(2), one O(3), and two equivalent O(4) atoms to form MgO5 trigonal bipyramids that share corners with two equivalent Mg(1)O5 trigonal bipyramids, corners with two equivalent Bi(1)O4 trigonal pyramids, corners with five equivalent Bi(2)O4 trigonal pyramids, and  an edgeedge with one Bi(1)O4 trigonal pyramid. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form BiO4 trigonal pyramids that share corners with two equivalent Mg(1)O5 trigonal bipyramids, corners with two equivalent Bi(1)O4 trigonal pyramids, corners with three equivalent Bi(2)O4 trigonal pyramids, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. In the second Bi site, Bi(2) is bonded to one O(1), one O(4), and two equivalent O(2) atoms to form BiO4 trigonal pyramids that share corners with five equivalent Mg(1)O5 trigonal bipyramids, corners with two equivalent Bi(2)O4 trigonal pyramids, and corners with three equivalent Bi(1)O4 trigonal pyramids. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Mg(1), one Bi(1), and one Bi(2) atom. In the second O site, O(2) is bonded to one Mg(1), one Bi(1), and two equivalent Bi(2) atoms to form corner-sharing OMgBi3 tetrahedra. In the third O site, O(3) is bonded in a trigonal planar geometry to one Mg(1) and two equivalent Bi(1) atoms. In the fourth O site, O(4) is bonded in a trigonal planar geometry to two equivalent Mg(1) and one Bi(2) atom. is represented by the CIF file [CIF]
data_Mg(BiO2)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.743
_cell_length_b   5.619
_cell_length_c   6.640
_cell_angle_alpha   61.795
_cell_angle_beta   73.561
_cell_angle_gamma   89.970
_symmetry_Int_Tables_number   1
_cell_volume   116.554
_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  0.348  0.564  0.305  1.0
  Bi  Bi1  1  0.150  0.886  0.702  1.0
  Bi  Bi2  1  0.964  0.170  0.076  1.0
  O  O3  1  0.164  0.276  0.673  1.0
  O  O4  1  0.363  0.197  0.277  1.0
  O  O5  1  0.539  0.803  0.923  1.0
  O  O6  1  0.855  0.738  0.291  1.0
[/CIF]
.