The crystal structure described by CuOMgO crystallizes in the triclinic P-1 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(4), two equivalent O(1), and two equivalent O(3) atoms to form edge-sharing MgO5 square pyramids. In the second Mg site, Mg(2) is bonded in a 5-coordinate geometry to one O(4), two equivalent O(2), and two equivalent O(3) atoms. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 4-coordinate geometry to one O(2), one O(3), and two equivalent O(1) atoms. In the second Cu site, Cu(2) is bonded in a distorted square co-planar geometry to two equivalent O(2) and two equivalent O(4) atoms. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Mg(1) and two equivalent Cu(1) atoms. In the second O site, O(2) is bonded to two equivalent Mg(2), one Cu(1), and two equivalent Cu(2) atoms to form distorted OMg2Cu3 trigonal bipyramids that share corners with four equivalent O(4)Mg2Cu2 tetrahedra,  an edgeedge with one O(4)Mg2Cu2 tetrahedra, and edges with two equivalent O(2)Mg2Cu3 trigonal bipyramids. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Mg(1), two equivalent Mg(2), and one Cu(1) atom. In the fourth O site, O(4) is bonded to one Mg(1), one Mg(2), and two equivalent Cu(2) atoms to form OMg2Cu2 tetrahedra that share corners with two equivalent O(4)Mg2Cu2 tetrahedra, corners with four equivalent O(2)Mg2Cu3 trigonal bipyramids, and  an edgeedge with one O(2)Mg2Cu3 trigonal bipyramid. is represented by the CIF file [CIF]
data_MgCuO2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   2.860
_cell_length_b   8.074
_cell_length_c   8.326
_cell_angle_alpha   89.483
_cell_angle_beta   98.992
_cell_angle_gamma   99.872
_symmetry_Int_Tables_number   1
_cell_volume   187.046
_cell_formula_units_Z   4
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  0.296  0.406  0.717  1.0
  Mg  Mg1  1  0.704  0.594  0.283  1.0
  Mg  Mg2  1  0.516  0.724  0.871  1.0
  Mg  Mg3  1  0.484  0.276  0.129  1.0
  Cu  Cu4  1  0.080  0.209  0.432  1.0
  Cu  Cu5  1  0.689  0.078  0.823  1.0
  Cu  Cu6  1  0.311  0.922  0.177  1.0
  Cu  Cu7  1  0.920  0.791  0.568  1.0
  O  O8  1  0.321  0.715  0.428  1.0
  O  O9  1  0.917  0.084  0.231  1.0
  O  O10  1  0.083  0.916  0.769  1.0
  O  O11  1  0.679  0.285  0.572  1.0
  O  O12  1  0.093  0.428  0.210  1.0
  O  O13  1  0.294  0.225  0.892  1.0
  O  O14  1  0.907  0.572  0.790  1.0
  O  O15  1  0.706  0.775  0.108  1.0
[/CIF]
.
The crystal structure described by CuOMgO crystallizes in the triclinic P-1 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(4), two equivalent O(1), and two equivalent O(3) atoms to form edge-sharing MgO5 square pyramids. In the second Mg site, Mg(2) is bonded in a 5-coordinate geometry to one O(4), two equivalent O(2), and two equivalent O(3) atoms. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 4-coordinate geometry to one O(2), one O(3), and two equivalent O(1) atoms. In the second Cu site, Cu(2) is bonded in a distorted square co-planar geometry to two equivalent O(2) and two equivalent O(4) atoms. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Mg(1) and two equivalent Cu(1) atoms. In the second O site, O(2) is bonded to two equivalent Mg(2), one Cu(1), and two equivalent Cu(2) atoms to form distorted OMg2Cu3 trigonal bipyramids that share corners with four equivalent O(4)Mg2Cu2 tetrahedra,  an edgeedge with one O(4)Mg2Cu2 tetrahedra, and edges with two equivalent O(2)Mg2Cu3 trigonal bipyramids. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Mg(1), two equivalent Mg(2), and one Cu(1) atom. In the fourth O site, O(4) is bonded to one Mg(1), one Mg(2), and two equivalent Cu(2) atoms to form OMg2Cu2 tetrahedra that share corners with two equivalent O(4)Mg2Cu2 tetrahedra, corners with four equivalent O(2)Mg2Cu3 trigonal bipyramids, and  an edgeedge with one O(2)Mg2Cu3 trigonal bipyramid. is represented by the CIF file [CIF]
data_MgCuO2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   2.860
_cell_length_b   8.074
_cell_length_c   8.326
_cell_angle_alpha   89.483
_cell_angle_beta   98.992
_cell_angle_gamma   99.872
_symmetry_Int_Tables_number   1
_cell_volume   187.046
_cell_formula_units_Z   4
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  0.296  0.406  0.717  1.0
  Mg  Mg1  1  0.704  0.594  0.283  1.0
  Mg  Mg2  1  0.516  0.724  0.871  1.0
  Mg  Mg3  1  0.484  0.276  0.129  1.0
  Cu  Cu4  1  0.080  0.209  0.432  1.0
  Cu  Cu5  1  0.689  0.078  0.823  1.0
  Cu  Cu6  1  0.311  0.922  0.177  1.0
  Cu  Cu7  1  0.920  0.791  0.568  1.0
  O  O8  1  0.321  0.715  0.428  1.0
  O  O9  1  0.917  0.084  0.231  1.0
  O  O10  1  0.083  0.916  0.769  1.0
  O  O11  1  0.679  0.285  0.572  1.0
  O  O12  1  0.093  0.428  0.210  1.0
  O  O13  1  0.294  0.225  0.892  1.0
  O  O14  1  0.907  0.572  0.790  1.0
  O  O15  1  0.706  0.775  0.108  1.0
[/CIF]
.