The compound described by Sr7Al12O25 crystallizes in the trigonal R3 space group. There are three inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom. In the second Sr site, Sr(2) is bonded in a 6-coordinate geometry to one O(3), one O(4), one O(5), one O(6), one O(7), and one O(8) atom. In the third Sr site, Sr(3) is bonded in a 4-coordinate geometry to one O(9) and three equivalent O(8) atoms. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(2), one O(5), and two equivalent O(3) atoms to form corner-sharing AlO4 tetrahedra. In the second Al site, Al(2) is bonded to one O(1), one O(2), one O(4), and one O(8) atom to form corner-sharing AlO4 tetrahedra. In the third Al site, Al(3) is bonded to one O(1), one O(5), one O(7), and one O(8) atom to form corner-sharing AlO4 trigonal pyramids. In the fourth Al site, Al(4) is bonded to one O(4), one O(7), and two equivalent O(6) atoms to form corner-sharing AlO4 tetrahedra. There are nine inequivalent O sites. In the first O site, O(7) is bonded in a 2-coordinate geometry to one Sr(1), one Sr(2), one Al(3), and one Al(4) atom. In the second O site, O(8) is bonded to one Sr(2), one Sr(3), one Al(2), and one Al(3) atom to form a mixture of distorted edge and corner-sharing OSr2Al2 tetrahedra. In the third O site, O(9) is bonded in a single-bond geometry to one Sr(3) atom. In the fourth O site, O(2) is bonded in a 3-coordinate geometry to one Sr(1), one Al(1), and one Al(2) atom. In the fifth O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Sr(1), one Sr(2), and two equivalent Al(1) atoms. In the sixth O site, O(4) is bonded in a 4-coordinate geometry to one Sr(1), one Sr(2), one Al(2), and one Al(4) atom. In the seventh O site, O(5) is bonded to one Sr(1), one Sr(2), one Al(1), and one Al(3) atom to form distorted edge-sharing OSr2Al2 tetrahedra. In the eighth O site, O(6) is bonded in a 4-coordinate geometry to one Sr(1), one Sr(2), and two equivalent Al(4) atoms. In the ninth O site, O(1) is bonded in a distorted trigonal planar geometry to one Sr(1), one Al(2), and one Al(3) atom. is represented by the CIF card [CIF]
data_Sr7Al12O25
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   10.827
_cell_length_b   10.827
_cell_length_c   10.827
_cell_angle_alpha   115.575
_cell_angle_beta   115.575
_cell_angle_gamma   115.575
_symmetry_Int_Tables_number   1
_cell_volume   671.672
_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
  Sr  Sr0  1  0.019  0.971  0.593  1.0
  Sr  Sr1  1  0.971  0.593  0.019  1.0
  Sr  Sr2  1  0.503  0.551  0.913  1.0
  Sr  Sr3  1  0.913  0.503  0.551  1.0
  Sr  Sr4  1  0.467  0.467  0.467  1.0
  Sr  Sr5  1  0.593  0.019  0.971  1.0
  Sr  Sr6  1  0.551  0.913  0.503  1.0
  Al  Al7  1  0.725  0.482  0.198  1.0
  Al  Al8  1  0.379  0.417  0.107  1.0
  Al  Al9  1  0.482  0.198  0.725  1.0
  Al  Al10  1  0.133  0.094  0.384  1.0
  Al  Al11  1  0.787  0.029  0.320  1.0
  Al  Al12  1  0.417  0.107  0.379  1.0
  Al  Al13  1  0.320  0.787  0.029  1.0
  Al  Al14  1  0.107  0.379  0.417  1.0
  Al  Al15  1  0.384  0.133  0.094  1.0
  Al  Al16  1  0.198  0.725  0.482  1.0
  Al  Al17  1  0.094  0.384  0.133  1.0
  Al  Al18  1  0.029  0.320  0.787  1.0
  O  O19  1  0.267  0.166  0.959  1.0
  O  O20  1  0.651  0.593  0.268  1.0
  O  O21  1  0.682  0.438  0.999  1.0
  O  O22  1  0.256  0.389  0.906  1.0
  O  O23  1  0.274  0.160  0.618  1.0
  O  O24  1  0.829  0.071  0.518  1.0
  O  O25  1  0.593  0.268  0.651  1.0
  O  O26  1  0.874  0.934  0.259  1.0
  O  O27  1  0.389  0.906  0.256  1.0
  O  O28  1  0.071  0.518  0.829  1.0
  O  O29  1  0.166  0.959  0.267  1.0
  O  O30  1  0.518  0.829  0.071  1.0
  O  O31  1  0.267  0.362  0.534  1.0
  O  O32  1  0.906  0.256  0.389  1.0
  O  O33  1  0.534  0.267  0.362  1.0
  O  O34  1  0.259  0.874  0.934  1.0
  O  O35  1  0.161  0.161  0.161  1.0
  O  O36  1  0.268  0.651  0.593  1.0
  O  O37  1  0.959  0.267  0.166  1.0
  O  O38  1  0.618  0.274  0.160  1.0
  O  O39  1  0.362  0.534  0.267  1.0
  O  O40  1  0.999  0.682  0.438  1.0
  O  O41  1  0.438  0.999  0.682  1.0
  O  O42  1  0.160  0.618  0.274  1.0
  O  O43  1  0.934  0.259  0.874  1.0
[/CIF]
.
The compound described by Sr7Al12O25 crystallizes in the trigonal R3 space group. There are three inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom. In the second Sr site, Sr(2) is bonded in a 6-coordinate geometry to one O(3), one O(4), one O(5), one O(6), one O(7), and one O(8) atom. In the third Sr site, Sr(3) is bonded in a 4-coordinate geometry to one O(9) and three equivalent O(8) atoms. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(2), one O(5), and two equivalent O(3) atoms to form corner-sharing AlO4 tetrahedra. In the second Al site, Al(2) is bonded to one O(1), one O(2), one O(4), and one O(8) atom to form corner-sharing AlO4 tetrahedra. In the third Al site, Al(3) is bonded to one O(1), one O(5), one O(7), and one O(8) atom to form corner-sharing AlO4 trigonal pyramids. In the fourth Al site, Al(4) is bonded to one O(4), one O(7), and two equivalent O(6) atoms to form corner-sharing AlO4 tetrahedra. There are nine inequivalent O sites. In the first O site, O(7) is bonded in a 2-coordinate geometry to one Sr(1), one Sr(2), one Al(3), and one Al(4) atom. In the second O site, O(8) is bonded to one Sr(2), one Sr(3), one Al(2), and one Al(3) atom to form a mixture of distorted edge and corner-sharing OSr2Al2 tetrahedra. In the third O site, O(9) is bonded in a single-bond geometry to one Sr(3) atom. In the fourth O site, O(2) is bonded in a 3-coordinate geometry to one Sr(1), one Al(1), and one Al(2) atom. In the fifth O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Sr(1), one Sr(2), and two equivalent Al(1) atoms. In the sixth O site, O(4) is bonded in a 4-coordinate geometry to one Sr(1), one Sr(2), one Al(2), and one Al(4) atom. In the seventh O site, O(5) is bonded to one Sr(1), one Sr(2), one Al(1), and one Al(3) atom to form distorted edge-sharing OSr2Al2 tetrahedra. In the eighth O site, O(6) is bonded in a 4-coordinate geometry to one Sr(1), one Sr(2), and two equivalent Al(4) atoms. In the ninth O site, O(1) is bonded in a distorted trigonal planar geometry to one Sr(1), one Al(2), and one Al(3) atom. is represented by the CIF card [CIF]
data_Sr7Al12O25
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   10.827
_cell_length_b   10.827
_cell_length_c   10.827
_cell_angle_alpha   115.575
_cell_angle_beta   115.575
_cell_angle_gamma   115.575
_symmetry_Int_Tables_number   1
_cell_volume   671.672
_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
  Sr  Sr0  1  0.019  0.971  0.593  1.0
  Sr  Sr1  1  0.971  0.593  0.019  1.0
  Sr  Sr2  1  0.503  0.551  0.913  1.0
  Sr  Sr3  1  0.913  0.503  0.551  1.0
  Sr  Sr4  1  0.467  0.467  0.467  1.0
  Sr  Sr5  1  0.593  0.019  0.971  1.0
  Sr  Sr6  1  0.551  0.913  0.503  1.0
  Al  Al7  1  0.725  0.482  0.198  1.0
  Al  Al8  1  0.379  0.417  0.107  1.0
  Al  Al9  1  0.482  0.198  0.725  1.0
  Al  Al10  1  0.133  0.094  0.384  1.0
  Al  Al11  1  0.787  0.029  0.320  1.0
  Al  Al12  1  0.417  0.107  0.379  1.0
  Al  Al13  1  0.320  0.787  0.029  1.0
  Al  Al14  1  0.107  0.379  0.417  1.0
  Al  Al15  1  0.384  0.133  0.094  1.0
  Al  Al16  1  0.198  0.725  0.482  1.0
  Al  Al17  1  0.094  0.384  0.133  1.0
  Al  Al18  1  0.029  0.320  0.787  1.0
  O  O19  1  0.267  0.166  0.959  1.0
  O  O20  1  0.651  0.593  0.268  1.0
  O  O21  1  0.682  0.438  0.999  1.0
  O  O22  1  0.256  0.389  0.906  1.0
  O  O23  1  0.274  0.160  0.618  1.0
  O  O24  1  0.829  0.071  0.518  1.0
  O  O25  1  0.593  0.268  0.651  1.0
  O  O26  1  0.874  0.934  0.259  1.0
  O  O27  1  0.389  0.906  0.256  1.0
  O  O28  1  0.071  0.518  0.829  1.0
  O  O29  1  0.166  0.959  0.267  1.0
  O  O30  1  0.518  0.829  0.071  1.0
  O  O31  1  0.267  0.362  0.534  1.0
  O  O32  1  0.906  0.256  0.389  1.0
  O  O33  1  0.534  0.267  0.362  1.0
  O  O34  1  0.259  0.874  0.934  1.0
  O  O35  1  0.161  0.161  0.161  1.0
  O  O36  1  0.268  0.651  0.593  1.0
  O  O37  1  0.959  0.267  0.166  1.0
  O  O38  1  0.618  0.274  0.160  1.0
  O  O39  1  0.362  0.534  0.267  1.0
  O  O40  1  0.999  0.682  0.438  1.0
  O  O41  1  0.438  0.999  0.682  1.0
  O  O42  1  0.160  0.618  0.274  1.0
  O  O43  1  0.934  0.259  0.874  1.0
[/CIF]
.