The structure described by MgMo4O9 crystallizes in the tetragonal P4/n space group. Mg(1) is bonded in a 8-coordinate geometry to four equivalent O(2) and four equivalent O(3) atoms. Mo(1) is bonded to one O(1), one O(2), and three equivalent O(3) atoms to form a mixture of distorted corner and edge-sharing MoO5 trigonal bipyramids. There are three inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Mo(1) atoms to form a mixture of distorted corner and edge-sharing OMo4 trigonal pyramids. In the second O site, O(2) is bonded in a bent 120 degrees geometry to one Mg(1) and one Mo(1) atom. In the third O site, O(3) is bonded to one Mg(1) and three equivalent Mo(1) atoms to form distorted OMgMo3 tetrahedra that share corners with three equivalent O(3)MgMo3 tetrahedra,  a cornercorner with one O(1)Mo4 trigonal pyramid, edges with three equivalent O(3)MgMo3 tetrahedra, and  an edgeedge with one O(1)Mo4 trigonal pyramid. is represented by the CIF file [CIF]
data_MgMo4O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.789
_cell_length_b   8.789
_cell_length_c   5.009
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   386.972
_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  0.000  0.500  0.857  1.0
  Mg  Mg1  1  0.500  0.000  0.143  1.0
  Mo  Mo2  1  0.711  0.403  0.341  1.0
  Mo  Mo3  1  0.403  0.289  0.659  1.0
  Mo  Mo4  1  0.903  0.789  0.341  1.0
  Mo  Mo5  1  0.211  0.903  0.659  1.0
  Mo  Mo6  1  0.289  0.597  0.341  1.0
  Mo  Mo7  1  0.097  0.211  0.341  1.0
  Mo  Mo8  1  0.789  0.097  0.659  1.0
  Mo  Mo9  1  0.597  0.711  0.659  1.0
  O  O10  1  0.500  0.500  0.500  1.0
  O  O11  1  0.000  0.000  0.500  1.0
  O  O12  1  0.546  0.777  0.991  1.0
  O  O13  1  0.723  0.046  0.991  1.0
  O  O14  1  0.277  0.954  0.991  1.0
  O  O15  1  0.454  0.223  0.991  1.0
  O  O16  1  0.954  0.723  0.009  1.0
  O  O17  1  0.777  0.454  0.009  1.0
  O  O18  1  0.223  0.546  0.009  1.0
  O  O19  1  0.046  0.277  0.009  1.0
  O  O20  1  0.202  0.390  0.519  1.0
  O  O21  1  0.110  0.702  0.519  1.0
  O  O22  1  0.890  0.298  0.519  1.0
  O  O23  1  0.798  0.610  0.519  1.0
  O  O24  1  0.702  0.890  0.481  1.0
  O  O25  1  0.390  0.798  0.481  1.0
  O  O26  1  0.610  0.202  0.481  1.0
  O  O27  1  0.298  0.110  0.481  1.0
[/CIF]
.
The structure described by MgMo4O9 crystallizes in the tetragonal P4/n space group. Mg(1) is bonded in a 8-coordinate geometry to four equivalent O(2) and four equivalent O(3) atoms. Mo(1) is bonded to one O(1), one O(2), and three equivalent O(3) atoms to form a mixture of distorted corner and edge-sharing MoO5 trigonal bipyramids. There are three inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Mo(1) atoms to form a mixture of distorted corner and edge-sharing OMo4 trigonal pyramids. In the second O site, O(2) is bonded in a bent 120 degrees geometry to one Mg(1) and one Mo(1) atom. In the third O site, O(3) is bonded to one Mg(1) and three equivalent Mo(1) atoms to form distorted OMgMo3 tetrahedra that share corners with three equivalent O(3)MgMo3 tetrahedra,  a cornercorner with one O(1)Mo4 trigonal pyramid, edges with three equivalent O(3)MgMo3 tetrahedra, and  an edgeedge with one O(1)Mo4 trigonal pyramid. is represented by the CIF file [CIF]
data_MgMo4O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.789
_cell_length_b   8.789
_cell_length_c   5.009
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   386.972
_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  0.000  0.500  0.857  1.0
  Mg  Mg1  1  0.500  0.000  0.143  1.0
  Mo  Mo2  1  0.711  0.403  0.341  1.0
  Mo  Mo3  1  0.403  0.289  0.659  1.0
  Mo  Mo4  1  0.903  0.789  0.341  1.0
  Mo  Mo5  1  0.211  0.903  0.659  1.0
  Mo  Mo6  1  0.289  0.597  0.341  1.0
  Mo  Mo7  1  0.097  0.211  0.341  1.0
  Mo  Mo8  1  0.789  0.097  0.659  1.0
  Mo  Mo9  1  0.597  0.711  0.659  1.0
  O  O10  1  0.500  0.500  0.500  1.0
  O  O11  1  0.000  0.000  0.500  1.0
  O  O12  1  0.546  0.777  0.991  1.0
  O  O13  1  0.723  0.046  0.991  1.0
  O  O14  1  0.277  0.954  0.991  1.0
  O  O15  1  0.454  0.223  0.991  1.0
  O  O16  1  0.954  0.723  0.009  1.0
  O  O17  1  0.777  0.454  0.009  1.0
  O  O18  1  0.223  0.546  0.009  1.0
  O  O19  1  0.046  0.277  0.009  1.0
  O  O20  1  0.202  0.390  0.519  1.0
  O  O21  1  0.110  0.702  0.519  1.0
  O  O22  1  0.890  0.298  0.519  1.0
  O  O23  1  0.798  0.610  0.519  1.0
  O  O24  1  0.702  0.890  0.481  1.0
  O  O25  1  0.390  0.798  0.481  1.0
  O  O26  1  0.610  0.202  0.481  1.0
  O  O27  1  0.298  0.110  0.481  1.0
[/CIF]
.