The structure described by Sr2Er2Al3Si5N11O3 crystallizes in the trigonal P3m1 space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded to three equivalent N(1) and three equivalent O(1) atoms to form SrN3O3 octahedra that share corners with three equivalent Al(1)N4 tetrahedra, corners with three equivalent Si(2)N4 tetrahedra, and corners with six equivalent Si(3)N2O2 tetrahedra. In the second Sr site, Sr(2) is bonded to three equivalent N(4) and three equivalent N(5) atoms to form SrN6 octahedra that share corners with three equivalent Si(3)N2O2 tetrahedra, corners with three equivalent Si(1)N4 tetrahedra, and corners with six equivalent Al(1)N4 tetrahedra. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 3-coordinate geometry to three equivalent N(5) atoms. In the second Er site, Er(2) is bonded in a 3-coordinate geometry to three equivalent N(5) atoms. Al(1) is bonded to one N(1), one N(2), and two equivalent N(5) atoms to form AlN4 tetrahedra that share  a cornercorner with one Sr(1)N3O3 octahedra, corners with two equivalent Sr(2)N6 octahedra,  a cornercorner with one Si(1)N4 tetrahedra,  a cornercorner with one Si(2)N4 tetrahedra, and corners with four equivalent Al(1)N4 tetrahedra. The corner-sharing octahedral tilt angles range from 58-60°. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one N(2) and three equivalent N(4) atoms to form SiN4 tetrahedra that share corners with three equivalent Sr(2)N6 octahedra, corners with three equivalent Al(1)N4 tetrahedra, and corners with three equivalent Si(3)N2O2 tetrahedra. The corner-sharing octahedral tilt angles are 58°. In the second Si site, Si(2) is bonded to one N(3) and three equivalent N(1) atoms to form SiN4 tetrahedra that share corners with three equivalent Sr(1)N3O3 octahedra, corners with three equivalent Al(1)N4 tetrahedra, and corners with three equivalent Si(3)N2O2 tetrahedra. The corner-sharing octahedral tilt angles are 52°. In the third Si site, Si(3) is bonded to one N(3), one N(4), and two equivalent O(1) atoms to form SiN2O2 tetrahedra that share  a cornercorner with one Sr(2)N6 octahedra, corners with two equivalent Sr(1)N3O3 octahedra,  a cornercorner with one Si(1)N4 tetrahedra,  a cornercorner with one Si(2)N4 tetrahedra, and corners with four equivalent Si(3)N2O2 tetrahedra. The corner-sharing octahedral tilt angles range from 62-65°. There are five inequivalent N sites. In the first N site, N(1) is bonded in a distorted trigonal planar geometry to one Sr(1), one Al(1), and one Si(2) atom. In the second N site, N(2) is bonded to three equivalent Al(1) and one Si(1) atom to form distorted corner-sharing NAl3Si trigonal pyramids. In the third N site, N(3) is bonded in a tetrahedral geometry to one Si(2) and three equivalent Si(3) atoms. In the fourth N site, N(4) is bonded in a trigonal planar geometry to one Sr(2), one Si(1), and one Si(3) atom. In the fifth N site, N(5) is bonded to one Sr(2), one Er(1), one Er(2), and two equivalent Al(1) atoms to form NSrEr2Al2 trigonal bipyramids that share corners with two equivalent N(2)Al3Si trigonal pyramids and edges with four equivalent N(5)SrEr2Al2 trigonal bipyramids. O(1) is bonded in a trigonal planar geometry to one Sr(1) and two equivalent Si(3) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Sr2Er2Al3Si5N11O3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.196
_cell_length_b   6.196
_cell_length_c   10.425
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   346.634
_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  0.333  0.667  0.133  1.0
  Sr  Sr1  1  0.667  0.333  0.649  1.0
  Er  Er2  1  0.333  0.667  0.640  1.0
  Er  Er3  1  0.667  0.333  0.348  1.0
  Al  Al4  1  0.161  0.839  0.435  1.0
  Al  Al5  1  0.161  0.323  0.435  1.0
  Al  Al6  1  0.677  0.839  0.435  1.0
  Si  Si7  1  0.000  0.000  0.708  1.0
  Si  Si8  1  0.000  0.000  0.213  1.0
  Si  Si9  1  0.340  0.170  0.933  1.0
  Si  Si10  1  0.830  0.660  0.933  1.0
  Si  Si11  1  0.830  0.170  0.933  1.0
  N  N12  1  0.150  0.850  0.261  1.0
  N  N13  1  0.000  0.000  0.533  1.0
  N  N14  1  0.000  0.000  0.016  1.0
  N  N15  1  0.150  0.300  0.261  1.0
  N  N16  1  0.294  0.147  0.776  1.0
  N  N17  1  0.491  0.509  0.494  1.0
  N  N18  1  0.700  0.850  0.261  1.0
  N  N19  1  0.491  0.983  0.494  1.0
  N  N20  1  0.853  0.706  0.776  1.0
  N  N21  1  0.017  0.509  0.494  1.0
  N  N22  1  0.853  0.147  0.776  1.0
  O  O23  1  0.948  0.474  0.982  1.0
  O  O24  1  0.526  0.052  0.982  1.0
  O  O25  1  0.526  0.474  0.982  1.0
[/CIF]
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The structure described by Sr2Er2Al3Si5N11O3 crystallizes in the trigonal P3m1 space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded to three equivalent N(1) and three equivalent O(1) atoms to form SrN3O3 octahedra that share corners with three equivalent Al(1)N4 tetrahedra, corners with three equivalent Si(2)N4 tetrahedra, and corners with six equivalent Si(3)N2O2 tetrahedra. In the second Sr site, Sr(2) is bonded to three equivalent N(4) and three equivalent N(5) atoms to form SrN6 octahedra that share corners with three equivalent Si(3)N2O2 tetrahedra, corners with three equivalent Si(1)N4 tetrahedra, and corners with six equivalent Al(1)N4 tetrahedra. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 3-coordinate geometry to three equivalent N(5) atoms. In the second Er site, Er(2) is bonded in a 3-coordinate geometry to three equivalent N(5) atoms. Al(1) is bonded to one N(1), one N(2), and two equivalent N(5) atoms to form AlN4 tetrahedra that share  a cornercorner with one Sr(1)N3O3 octahedra, corners with two equivalent Sr(2)N6 octahedra,  a cornercorner with one Si(1)N4 tetrahedra,  a cornercorner with one Si(2)N4 tetrahedra, and corners with four equivalent Al(1)N4 tetrahedra. The corner-sharing octahedral tilt angles range from 58-60°. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one N(2) and three equivalent N(4) atoms to form SiN4 tetrahedra that share corners with three equivalent Sr(2)N6 octahedra, corners with three equivalent Al(1)N4 tetrahedra, and corners with three equivalent Si(3)N2O2 tetrahedra. The corner-sharing octahedral tilt angles are 58°. In the second Si site, Si(2) is bonded to one N(3) and three equivalent N(1) atoms to form SiN4 tetrahedra that share corners with three equivalent Sr(1)N3O3 octahedra, corners with three equivalent Al(1)N4 tetrahedra, and corners with three equivalent Si(3)N2O2 tetrahedra. The corner-sharing octahedral tilt angles are 52°. In the third Si site, Si(3) is bonded to one N(3), one N(4), and two equivalent O(1) atoms to form SiN2O2 tetrahedra that share  a cornercorner with one Sr(2)N6 octahedra, corners with two equivalent Sr(1)N3O3 octahedra,  a cornercorner with one Si(1)N4 tetrahedra,  a cornercorner with one Si(2)N4 tetrahedra, and corners with four equivalent Si(3)N2O2 tetrahedra. The corner-sharing octahedral tilt angles range from 62-65°. There are five inequivalent N sites. In the first N site, N(1) is bonded in a distorted trigonal planar geometry to one Sr(1), one Al(1), and one Si(2) atom. In the second N site, N(2) is bonded to three equivalent Al(1) and one Si(1) atom to form distorted corner-sharing NAl3Si trigonal pyramids. In the third N site, N(3) is bonded in a tetrahedral geometry to one Si(2) and three equivalent Si(3) atoms. In the fourth N site, N(4) is bonded in a trigonal planar geometry to one Sr(2), one Si(1), and one Si(3) atom. In the fifth N site, N(5) is bonded to one Sr(2), one Er(1), one Er(2), and two equivalent Al(1) atoms to form NSrEr2Al2 trigonal bipyramids that share corners with two equivalent N(2)Al3Si trigonal pyramids and edges with four equivalent N(5)SrEr2Al2 trigonal bipyramids. O(1) is bonded in a trigonal planar geometry to one Sr(1) and two equivalent Si(3) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Sr2Er2Al3Si5N11O3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.196
_cell_length_b   6.196
_cell_length_c   10.425
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   346.634
_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  0.333  0.667  0.133  1.0
  Sr  Sr1  1  0.667  0.333  0.649  1.0
  Er  Er2  1  0.333  0.667  0.640  1.0
  Er  Er3  1  0.667  0.333  0.348  1.0
  Al  Al4  1  0.161  0.839  0.435  1.0
  Al  Al5  1  0.161  0.323  0.435  1.0
  Al  Al6  1  0.677  0.839  0.435  1.0
  Si  Si7  1  0.000  0.000  0.708  1.0
  Si  Si8  1  0.000  0.000  0.213  1.0
  Si  Si9  1  0.340  0.170  0.933  1.0
  Si  Si10  1  0.830  0.660  0.933  1.0
  Si  Si11  1  0.830  0.170  0.933  1.0
  N  N12  1  0.150  0.850  0.261  1.0
  N  N13  1  0.000  0.000  0.533  1.0
  N  N14  1  0.000  0.000  0.016  1.0
  N  N15  1  0.150  0.300  0.261  1.0
  N  N16  1  0.294  0.147  0.776  1.0
  N  N17  1  0.491  0.509  0.494  1.0
  N  N18  1  0.700  0.850  0.261  1.0
  N  N19  1  0.491  0.983  0.494  1.0
  N  N20  1  0.853  0.706  0.776  1.0
  N  N21  1  0.017  0.509  0.494  1.0
  N  N22  1  0.853  0.147  0.776  1.0
  O  O23  1  0.948  0.474  0.982  1.0
  O  O24  1  0.526  0.052  0.982  1.0
  O  O25  1  0.526  0.474  0.982  1.0
[/CIF]
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