The structure described by Mg2Ta4O9 is Ilmenite-like structured and crystallizes in the trigonal P-3c1 space group. Mg(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form MgO6 octahedra that share corners with three equivalent Ta(2)O6 octahedra, corners with six equivalent Ta(1)O6 octahedra, edges with three equivalent Ta(2)O6 octahedra, and  a faceface with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-54°. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to six equivalent O(1) atoms to form TaO6 octahedra that share corners with three equivalent Ta(2)O6 octahedra, corners with six equivalent Mg(1)O6 octahedra, edges with three equivalent Ta(1)O6 octahedra, and  a faceface with one Ta(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-54°. In the second Ta site, Ta(2) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form TaO6 octahedra that share corners with three equivalent Mg(1)O6 octahedra, corners with three equivalent Ta(1)O6 octahedra, corners with three equivalent Ta(2)O6 octahedra, edges with three equivalent Mg(1)O6 octahedra, and  a faceface with one Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-57°. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Ta(2), and two equivalent Ta(1) atoms. In the second O site, O(2) is bonded to two equivalent Mg(1) and two equivalent Ta(2) atoms to form a mixture of distorted edge and corner-sharing OMg2Ta2 trigonal pyramids. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg2Ta4O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.275
_cell_length_b   5.275
_cell_length_c   14.090
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   339.554
_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  0.000  0.651  1.0
  Mg  Mg1  1  0.000  0.000  0.349  1.0
  Mg  Mg2  1  0.000  0.000  0.849  1.0
  Mg  Mg3  1  0.000  0.000  0.151  1.0
  Ta  Ta4  1  0.333  0.667  0.509  1.0
  Ta  Ta5  1  0.667  0.333  0.491  1.0
  Ta  Ta6  1  0.667  0.333  0.991  1.0
  Ta  Ta7  1  0.333  0.667  0.009  1.0
  Ta  Ta8  1  0.333  0.667  0.820  1.0
  Ta  Ta9  1  0.667  0.333  0.180  1.0
  Ta  Ta10  1  0.667  0.333  0.680  1.0
  Ta  Ta11  1  0.333  0.667  0.320  1.0
  O  O12  1  0.342  0.331  0.588  1.0
  O  O13  1  0.658  0.669  0.412  1.0
  O  O14  1  0.669  0.010  0.588  1.0
  O  O15  1  0.331  0.342  0.912  1.0
  O  O16  1  0.331  0.990  0.412  1.0
  O  O17  1  0.669  0.658  0.088  1.0
  O  O18  1  0.990  0.658  0.588  1.0
  O  O19  1  0.010  0.669  0.912  1.0
  O  O20  1  0.010  0.342  0.412  1.0
  O  O21  1  0.990  0.331  0.088  1.0
  O  O22  1  0.658  0.990  0.912  1.0
  O  O23  1  0.342  0.010  0.088  1.0
  O  O24  1  0.314  0.000  0.750  1.0
  O  O25  1  0.686  0.000  0.250  1.0
  O  O26  1  0.000  0.314  0.750  1.0
  O  O27  1  0.000  0.686  0.250  1.0
  O  O28  1  0.686  0.686  0.750  1.0
  O  O29  1  0.314  0.314  0.250  1.0
[/CIF]
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The structure described by Mg2Ta4O9 is Ilmenite-like structured and crystallizes in the trigonal P-3c1 space group. Mg(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form MgO6 octahedra that share corners with three equivalent Ta(2)O6 octahedra, corners with six equivalent Ta(1)O6 octahedra, edges with three equivalent Ta(2)O6 octahedra, and  a faceface with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-54°. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to six equivalent O(1) atoms to form TaO6 octahedra that share corners with three equivalent Ta(2)O6 octahedra, corners with six equivalent Mg(1)O6 octahedra, edges with three equivalent Ta(1)O6 octahedra, and  a faceface with one Ta(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-54°. In the second Ta site, Ta(2) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form TaO6 octahedra that share corners with three equivalent Mg(1)O6 octahedra, corners with three equivalent Ta(1)O6 octahedra, corners with three equivalent Ta(2)O6 octahedra, edges with three equivalent Mg(1)O6 octahedra, and  a faceface with one Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-57°. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Ta(2), and two equivalent Ta(1) atoms. In the second O site, O(2) is bonded to two equivalent Mg(1) and two equivalent Ta(2) atoms to form a mixture of distorted edge and corner-sharing OMg2Ta2 trigonal pyramids. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg2Ta4O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.275
_cell_length_b   5.275
_cell_length_c   14.090
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   339.554
_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  0.000  0.651  1.0
  Mg  Mg1  1  0.000  0.000  0.349  1.0
  Mg  Mg2  1  0.000  0.000  0.849  1.0
  Mg  Mg3  1  0.000  0.000  0.151  1.0
  Ta  Ta4  1  0.333  0.667  0.509  1.0
  Ta  Ta5  1  0.667  0.333  0.491  1.0
  Ta  Ta6  1  0.667  0.333  0.991  1.0
  Ta  Ta7  1  0.333  0.667  0.009  1.0
  Ta  Ta8  1  0.333  0.667  0.820  1.0
  Ta  Ta9  1  0.667  0.333  0.180  1.0
  Ta  Ta10  1  0.667  0.333  0.680  1.0
  Ta  Ta11  1  0.333  0.667  0.320  1.0
  O  O12  1  0.342  0.331  0.588  1.0
  O  O13  1  0.658  0.669  0.412  1.0
  O  O14  1  0.669  0.010  0.588  1.0
  O  O15  1  0.331  0.342  0.912  1.0
  O  O16  1  0.331  0.990  0.412  1.0
  O  O17  1  0.669  0.658  0.088  1.0
  O  O18  1  0.990  0.658  0.588  1.0
  O  O19  1  0.010  0.669  0.912  1.0
  O  O20  1  0.010  0.342  0.412  1.0
  O  O21  1  0.990  0.331  0.088  1.0
  O  O22  1  0.658  0.990  0.912  1.0
  O  O23  1  0.342  0.010  0.088  1.0
  O  O24  1  0.314  0.000  0.750  1.0
  O  O25  1  0.686  0.000  0.250  1.0
  O  O26  1  0.000  0.314  0.750  1.0
  O  O27  1  0.000  0.686  0.250  1.0
  O  O28  1  0.686  0.686  0.750  1.0
  O  O29  1  0.314  0.314  0.250  1.0
[/CIF]
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