The compound described by Ho2SrAl2O7 crystallizes in the tetragonal I4/mmm space group. Sr(1) is bonded to four equivalent O(2) and eight equivalent O(1) atoms to form SrO12 cuboctahedra that share corners with four equivalent Sr(1)O12 cuboctahedra, faces with four equivalent Sr(1)O12 cuboctahedra, and faces with eight equivalent Al(1)O6 octahedra. Ho(1) is bonded in a 9-coordinate geometry to four equivalent O(1) and five equivalent O(3) atoms. Al(1) is bonded to one O(2), one O(3), and four equivalent O(1) atoms to form AlO6 octahedra that share corners with five equivalent Al(1)O6 octahedra and faces with four equivalent Sr(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-11°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to two equivalent Sr(1), two equivalent Ho(1), and two equivalent Al(1) atoms. In the second O site, O(2) is bonded to four equivalent Sr(1) and two equivalent Al(1) atoms to form distorted OSr4Al2 octahedra that share corners with two equivalent O(3)Ho5Al octahedra, corners with four equivalent O(2)Sr4Al2 octahedra, and edges with four equivalent O(2)Sr4Al2 octahedra. The corner-sharing octahedra are not tilted. In the third O site, O(3) is bonded to five equivalent Ho(1) and one Al(1) atom to form distorted OHo5Al octahedra that share  a cornercorner with one O(2)Sr4Al2 octahedra, corners with four equivalent O(3)Ho5Al octahedra, and edges with eight equivalent O(3)Ho5Al octahedra. The corner-sharing octahedral tilt angles range from 0-20°. is represented by the CIF card [CIF]
data_SrHo2Al2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   10.114
_cell_length_b   10.114
_cell_length_c   10.114
_cell_angle_alpha   158.787
_cell_angle_beta   158.787
_cell_angle_gamma   30.177
_symmetry_Int_Tables_number   1
_cell_volume   135.375
_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  0.500  0.500  0.000  1.0
  Ho  Ho1  1  0.318  0.318  0.000  1.0
  Ho  Ho2  1  0.682  0.682  0.000  1.0
  Al  Al3  1  0.098  0.098  0.000  1.0
  Al  Al4  1  0.902  0.902  0.000  1.0
  O  O5  1  0.607  0.107  0.500  1.0
  O  O6  1  0.393  0.893  0.500  1.0
  O  O7  1  0.107  0.607  0.500  1.0
  O  O8  1  0.893  0.393  0.500  1.0
  O  O9  1  0.000  0.000  0.000  1.0
  O  O10  1  0.206  0.206  0.000  1.0
  O  O11  1  0.794  0.794  0.000  1.0
[/CIF]
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The compound described by Ho2SrAl2O7 crystallizes in the tetragonal I4/mmm space group. Sr(1) is bonded to four equivalent O(2) and eight equivalent O(1) atoms to form SrO12 cuboctahedra that share corners with four equivalent Sr(1)O12 cuboctahedra, faces with four equivalent Sr(1)O12 cuboctahedra, and faces with eight equivalent Al(1)O6 octahedra. Ho(1) is bonded in a 9-coordinate geometry to four equivalent O(1) and five equivalent O(3) atoms. Al(1) is bonded to one O(2), one O(3), and four equivalent O(1) atoms to form AlO6 octahedra that share corners with five equivalent Al(1)O6 octahedra and faces with four equivalent Sr(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-11°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to two equivalent Sr(1), two equivalent Ho(1), and two equivalent Al(1) atoms. In the second O site, O(2) is bonded to four equivalent Sr(1) and two equivalent Al(1) atoms to form distorted OSr4Al2 octahedra that share corners with two equivalent O(3)Ho5Al octahedra, corners with four equivalent O(2)Sr4Al2 octahedra, and edges with four equivalent O(2)Sr4Al2 octahedra. The corner-sharing octahedra are not tilted. In the third O site, O(3) is bonded to five equivalent Ho(1) and one Al(1) atom to form distorted OHo5Al octahedra that share  a cornercorner with one O(2)Sr4Al2 octahedra, corners with four equivalent O(3)Ho5Al octahedra, and edges with eight equivalent O(3)Ho5Al octahedra. The corner-sharing octahedral tilt angles range from 0-20°. is represented by the CIF card [CIF]
data_SrHo2Al2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   10.114
_cell_length_b   10.114
_cell_length_c   10.114
_cell_angle_alpha   158.787
_cell_angle_beta   158.787
_cell_angle_gamma   30.177
_symmetry_Int_Tables_number   1
_cell_volume   135.375
_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  0.500  0.500  0.000  1.0
  Ho  Ho1  1  0.318  0.318  0.000  1.0
  Ho  Ho2  1  0.682  0.682  0.000  1.0
  Al  Al3  1  0.098  0.098  0.000  1.0
  Al  Al4  1  0.902  0.902  0.000  1.0
  O  O5  1  0.607  0.107  0.500  1.0
  O  O6  1  0.393  0.893  0.500  1.0
  O  O7  1  0.107  0.607  0.500  1.0
  O  O8  1  0.893  0.393  0.500  1.0
  O  O9  1  0.000  0.000  0.000  1.0
  O  O10  1  0.206  0.206  0.000  1.0
  O  O11  1  0.794  0.794  0.000  1.0
[/CIF]
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