The compound described by MgNb2Al2O8 crystallizes in the monoclinic C2/m space group. Mg(1) is bonded in a distorted rectangular see-saw-like geometry to four equivalent O(3) atoms. Nb(1) is bonded in a 6-coordinate geometry to one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms. Al(1) is bonded to one O(1), one O(3), one O(4), and three equivalent O(2) atoms to form a mixture of corner and edge-sharing AlO6 octahedra. The corner-sharing octahedral tilt angles are 24°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a trigonal non-coplanar geometry to two equivalent Nb(1) and one Al(1) atom. In the second O site, O(2) is bonded to one Nb(1) and three equivalent Al(1) atoms to form distorted ONbAl3 trigonal pyramids that share corners with four equivalent O(3)Mg2NbAl tetrahedra, corners with two equivalent O(2)NbAl3 trigonal pyramids, and edges with two equivalent O(2)NbAl3 trigonal pyramids. In the third O site, O(3) is bonded to two equivalent Mg(1), one Nb(1), and one Al(1) atom to form distorted OMg2NbAl tetrahedra that share corners with four equivalent O(3)Mg2NbAl tetrahedra, corners with four equivalent O(2)NbAl3 trigonal pyramids, and  an edgeedge with one O(3)Mg2NbAl tetrahedra. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Nb(1) and one Al(1) atom. is represented by the CIF card [CIF]
data_MgNb2Al2O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.677
_cell_length_b   6.681
_cell_length_c   6.673
_cell_angle_alpha   110.489
_cell_angle_beta   90.000
_cell_angle_gamma   105.975
_symmetry_Int_Tables_number   1
_cell_volume   146.797
_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  0.500  0.000  0.500  1.0
  Nb  Nb1  1  0.113  0.225  0.221  1.0
  Nb  Nb2  1  0.887  0.775  0.779  1.0
  Al  Al3  1  0.807  0.614  0.183  1.0
  Al  Al4  1  0.193  0.386  0.817  1.0
  O  O5  1  0.327  0.654  0.743  1.0
  O  O6  1  0.673  0.346  0.257  1.0
  O  O7  1  0.725  0.449  0.857  1.0
  O  O8  1  0.275  0.551  0.143  1.0
  O  O9  1  0.896  0.793  0.475  1.0
  O  O10  1  0.104  0.207  0.525  1.0
  O  O11  1  0.943  0.885  0.120  1.0
  O  O12  1  0.057  0.115  0.880  1.0
[/CIF]
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The compound described by MgNb2Al2O8 crystallizes in the monoclinic C2/m space group. Mg(1) is bonded in a distorted rectangular see-saw-like geometry to four equivalent O(3) atoms. Nb(1) is bonded in a 6-coordinate geometry to one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms. Al(1) is bonded to one O(1), one O(3), one O(4), and three equivalent O(2) atoms to form a mixture of corner and edge-sharing AlO6 octahedra. The corner-sharing octahedral tilt angles are 24°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a trigonal non-coplanar geometry to two equivalent Nb(1) and one Al(1) atom. In the second O site, O(2) is bonded to one Nb(1) and three equivalent Al(1) atoms to form distorted ONbAl3 trigonal pyramids that share corners with four equivalent O(3)Mg2NbAl tetrahedra, corners with two equivalent O(2)NbAl3 trigonal pyramids, and edges with two equivalent O(2)NbAl3 trigonal pyramids. In the third O site, O(3) is bonded to two equivalent Mg(1), one Nb(1), and one Al(1) atom to form distorted OMg2NbAl tetrahedra that share corners with four equivalent O(3)Mg2NbAl tetrahedra, corners with four equivalent O(2)NbAl3 trigonal pyramids, and  an edgeedge with one O(3)Mg2NbAl tetrahedra. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Nb(1) and one Al(1) atom. is represented by the CIF card [CIF]
data_MgNb2Al2O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.677
_cell_length_b   6.681
_cell_length_c   6.673
_cell_angle_alpha   110.489
_cell_angle_beta   90.000
_cell_angle_gamma   105.975
_symmetry_Int_Tables_number   1
_cell_volume   146.797
_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  0.500  0.000  0.500  1.0
  Nb  Nb1  1  0.113  0.225  0.221  1.0
  Nb  Nb2  1  0.887  0.775  0.779  1.0
  Al  Al3  1  0.807  0.614  0.183  1.0
  Al  Al4  1  0.193  0.386  0.817  1.0
  O  O5  1  0.327  0.654  0.743  1.0
  O  O6  1  0.673  0.346  0.257  1.0
  O  O7  1  0.725  0.449  0.857  1.0
  O  O8  1  0.275  0.551  0.143  1.0
  O  O9  1  0.896  0.793  0.475  1.0
  O  O10  1  0.104  0.207  0.525  1.0
  O  O11  1  0.943  0.885  0.120  1.0
  O  O12  1  0.057  0.115  0.880  1.0
[/CIF]
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