The crystal structure described by Sr4Cr3O9 crystallizes in the trigonal P3 space group. There are four inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 8-coordinate geometry to one O(1), one O(6), one O(7), one O(8), two equivalent O(4), and two equivalent O(5) atoms. In the second Sr site, Sr(2) is bonded in a 8-coordinate geometry to one O(2), one O(4), one O(5), one O(9), two equivalent O(6), and two equivalent O(8) atoms. In the third Sr site, Sr(3) is bonded in a 9-coordinate geometry to one O(2), one O(3), one O(4), one O(5), one O(9), two equivalent O(1), and two equivalent O(7) atoms. In the fourth Sr site, Sr(4) is bonded in a 9-coordinate geometry to one O(1), one O(3), one O(6), one O(7), one O(8), two equivalent O(2), and two equivalent O(9) atoms. There are nine inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to three equivalent O(5) and three equivalent O(8) atoms to form face-sharing CrO6 octahedra. In the second Cr site, Cr(2) is bonded to three equivalent O(1) and three equivalent O(9) atoms to form face-sharing CrO6 octahedra. In the third Cr site, Cr(3) is bonded to three equivalent O(2) and three equivalent O(7) atoms to form face-sharing CrO6 octahedra. In the fourth Cr site, Cr(4) is bonded to three equivalent O(4) and three equivalent O(9) atoms to form distorted face-sharing CrO6 pentagonal pyramids. In the fifth Cr site, Cr(5) is bonded to three equivalent O(3) and three equivalent O(5) atoms to form face-sharing CrO6 octahedra. In the sixth Cr site, Cr(6) is bonded to three equivalent O(2) and three equivalent O(6) atoms to form face-sharing CrO6 octahedra. In the seventh Cr site, Cr(7) is bonded to three equivalent O(3) and three equivalent O(8) atoms to form distorted face-sharing CrO6 pentagonal pyramids. In the eighth Cr site, Cr(8) is bonded to three equivalent O(1) and three equivalent O(4) atoms to form face-sharing CrO6 octahedra. In the ninth Cr site, Cr(9) is bonded to three equivalent O(6) and three equivalent O(7) atoms to form distorted face-sharing CrO6 pentagonal pyramids. There are nine inequivalent O sites. In the first O site, O(1) is bonded to one Sr(1), one Sr(4), two equivalent Sr(3), one Cr(2), and one Cr(8) atom to form a mixture of distorted corner, edge, and face-sharing OSr4Cr2 octahedra. The corner-sharing octahedral tilt angles range from 29-60°. In the second O site, O(2) is bonded to one Sr(2), one Sr(3), two equivalent Sr(4), one Cr(3), and one Cr(6) atom to form a mixture of distorted corner, edge, and face-sharing OSr4Cr2 octahedra. The corner-sharing octahedral tilt angles range from 27-64°. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Sr(3), one Sr(4), one Cr(5), and one Cr(7) atom. In the fourth O site, O(4) is bonded in a 6-coordinate geometry to one Sr(2), one Sr(3), two equivalent Sr(1), one Cr(4), and one Cr(8) atom. In the fifth O site, O(5) is bonded to one Sr(2), one Sr(3), two equivalent Sr(1), one Cr(1), and one Cr(5) atom to form a mixture of distorted corner, edge, and face-sharing OSr4Cr2 octahedra. The corner-sharing octahedral tilt angles range from 5-60°. In the sixth O site, O(6) is bonded in a 6-coordinate geometry to one Sr(1), one Sr(4), two equivalent Sr(2), one Cr(6), and one Cr(9) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Sr(1), one Sr(4), two equivalent Sr(3), one Cr(3), and one Cr(9) atom. In the eighth O site, O(8) is bonded to one Sr(1), one Sr(4), two equivalent Sr(2), one Cr(1), and one Cr(7) atom to form a mixture of distorted corner, edge, and face-sharing OSr4Cr2 octahedra. The corner-sharing octahedral tilt angles range from 5-64°. In the ninth O site, O(9) is bonded in a 6-coordinate geometry to one Sr(2), one Sr(3), two equivalent Sr(4), one Cr(2), and one Cr(4) atom. is represented by the CIF card [CIF]
data_Sr4Cr3O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.747
_cell_length_b   9.747
_cell_length_c   7.941
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   653.427
_cell_formula_units_Z   3
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  0.694  0.664  0.003  1.0
  Sr  Sr1  1  0.026  0.694  0.756  1.0
  Sr  Sr2  1  0.340  0.348  0.251  1.0
  Sr  Sr3  1  0.652  0.993  0.251  1.0
  Sr  Sr4  1  0.667  0.974  0.756  1.0
  Sr  Sr5  1  0.007  0.660  0.251  1.0
  Sr  Sr6  1  0.336  0.030  0.003  1.0
  Sr  Sr7  1  0.970  0.306  0.003  1.0
  Sr  Sr8  1  0.355  0.999  0.510  1.0
  Sr  Sr9  1  0.306  0.333  0.756  1.0
  Sr  Sr10  1  0.001  0.356  0.510  1.0
  Sr  Sr11  1  0.644  0.645  0.510  1.0
  Cr  Cr12  1  0.000  0.000  0.866  1.0
  Cr  Cr13  1  0.667  0.333  0.422  1.0
  Cr  Cr14  1  0.333  0.667  0.334  1.0
  Cr  Cr15  1  0.667  0.333  0.762  1.0
  Cr  Cr16  1  0.000  0.000  0.194  1.0
  Cr  Cr17  1  0.333  0.667  0.657  1.0
  Cr  Cr18  1  0.000  0.000  0.526  1.0
  Cr  Cr19  1  0.667  0.333  0.098  1.0
  Cr  Cr20  1  0.333  0.667  0.998  1.0
  O  O21  1  0.675  0.496  0.264  1.0
  O  O22  1  0.174  0.673  0.497  1.0
  O  O23  1  0.830  0.876  0.347  1.0
  O  O24  1  0.047  0.170  0.347  1.0
  O  O25  1  0.835  0.477  0.939  1.0
  O  O26  1  0.158  0.161  0.030  1.0
  O  O27  1  0.341  0.825  0.822  1.0
  O  O28  1  0.335  0.820  0.167  1.0
  O  O29  1  0.003  0.842  0.030  1.0
  O  O30  1  0.504  0.179  0.264  1.0
  O  O31  1  0.523  0.358  0.939  1.0
  O  O32  1  0.124  0.953  0.347  1.0
  O  O33  1  0.642  0.165  0.939  1.0
  O  O34  1  0.180  0.515  0.167  1.0
  O  O35  1  0.839  0.997  0.030  1.0
  O  O36  1  0.499  0.826  0.497  1.0
  O  O37  1  0.485  0.665  0.167  1.0
  O  O38  1  0.854  0.832  0.706  1.0
  O  O39  1  0.505  0.317  0.576  1.0
  O  O40  1  0.978  0.146  0.706  1.0
  O  O41  1  0.812  0.495  0.576  1.0
  O  O42  1  0.821  0.325  0.264  1.0
  O  O43  1  0.175  0.516  0.822  1.0
  O  O44  1  0.484  0.659  0.822  1.0
  O  O45  1  0.683  0.188  0.576  1.0
  O  O46  1  0.327  0.501  0.497  1.0
  O  O47  1  0.168  0.022  0.706  1.0
[/CIF]
.
The crystal structure described by Sr4Cr3O9 crystallizes in the trigonal P3 space group. There are four inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 8-coordinate geometry to one O(1), one O(6), one O(7), one O(8), two equivalent O(4), and two equivalent O(5) atoms. In the second Sr site, Sr(2) is bonded in a 8-coordinate geometry to one O(2), one O(4), one O(5), one O(9), two equivalent O(6), and two equivalent O(8) atoms. In the third Sr site, Sr(3) is bonded in a 9-coordinate geometry to one O(2), one O(3), one O(4), one O(5), one O(9), two equivalent O(1), and two equivalent O(7) atoms. In the fourth Sr site, Sr(4) is bonded in a 9-coordinate geometry to one O(1), one O(3), one O(6), one O(7), one O(8), two equivalent O(2), and two equivalent O(9) atoms. There are nine inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to three equivalent O(5) and three equivalent O(8) atoms to form face-sharing CrO6 octahedra. In the second Cr site, Cr(2) is bonded to three equivalent O(1) and three equivalent O(9) atoms to form face-sharing CrO6 octahedra. In the third Cr site, Cr(3) is bonded to three equivalent O(2) and three equivalent O(7) atoms to form face-sharing CrO6 octahedra. In the fourth Cr site, Cr(4) is bonded to three equivalent O(4) and three equivalent O(9) atoms to form distorted face-sharing CrO6 pentagonal pyramids. In the fifth Cr site, Cr(5) is bonded to three equivalent O(3) and three equivalent O(5) atoms to form face-sharing CrO6 octahedra. In the sixth Cr site, Cr(6) is bonded to three equivalent O(2) and three equivalent O(6) atoms to form face-sharing CrO6 octahedra. In the seventh Cr site, Cr(7) is bonded to three equivalent O(3) and three equivalent O(8) atoms to form distorted face-sharing CrO6 pentagonal pyramids. In the eighth Cr site, Cr(8) is bonded to three equivalent O(1) and three equivalent O(4) atoms to form face-sharing CrO6 octahedra. In the ninth Cr site, Cr(9) is bonded to three equivalent O(6) and three equivalent O(7) atoms to form distorted face-sharing CrO6 pentagonal pyramids. There are nine inequivalent O sites. In the first O site, O(1) is bonded to one Sr(1), one Sr(4), two equivalent Sr(3), one Cr(2), and one Cr(8) atom to form a mixture of distorted corner, edge, and face-sharing OSr4Cr2 octahedra. The corner-sharing octahedral tilt angles range from 29-60°. In the second O site, O(2) is bonded to one Sr(2), one Sr(3), two equivalent Sr(4), one Cr(3), and one Cr(6) atom to form a mixture of distorted corner, edge, and face-sharing OSr4Cr2 octahedra. The corner-sharing octahedral tilt angles range from 27-64°. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Sr(3), one Sr(4), one Cr(5), and one Cr(7) atom. In the fourth O site, O(4) is bonded in a 6-coordinate geometry to one Sr(2), one Sr(3), two equivalent Sr(1), one Cr(4), and one Cr(8) atom. In the fifth O site, O(5) is bonded to one Sr(2), one Sr(3), two equivalent Sr(1), one Cr(1), and one Cr(5) atom to form a mixture of distorted corner, edge, and face-sharing OSr4Cr2 octahedra. The corner-sharing octahedral tilt angles range from 5-60°. In the sixth O site, O(6) is bonded in a 6-coordinate geometry to one Sr(1), one Sr(4), two equivalent Sr(2), one Cr(6), and one Cr(9) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Sr(1), one Sr(4), two equivalent Sr(3), one Cr(3), and one Cr(9) atom. In the eighth O site, O(8) is bonded to one Sr(1), one Sr(4), two equivalent Sr(2), one Cr(1), and one Cr(7) atom to form a mixture of distorted corner, edge, and face-sharing OSr4Cr2 octahedra. The corner-sharing octahedral tilt angles range from 5-64°. In the ninth O site, O(9) is bonded in a 6-coordinate geometry to one Sr(2), one Sr(3), two equivalent Sr(4), one Cr(2), and one Cr(4) atom. is represented by the CIF card [CIF]
data_Sr4Cr3O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.747
_cell_length_b   9.747
_cell_length_c   7.941
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   653.427
_cell_formula_units_Z   3
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  0.694  0.664  0.003  1.0
  Sr  Sr1  1  0.026  0.694  0.756  1.0
  Sr  Sr2  1  0.340  0.348  0.251  1.0
  Sr  Sr3  1  0.652  0.993  0.251  1.0
  Sr  Sr4  1  0.667  0.974  0.756  1.0
  Sr  Sr5  1  0.007  0.660  0.251  1.0
  Sr  Sr6  1  0.336  0.030  0.003  1.0
  Sr  Sr7  1  0.970  0.306  0.003  1.0
  Sr  Sr8  1  0.355  0.999  0.510  1.0
  Sr  Sr9  1  0.306  0.333  0.756  1.0
  Sr  Sr10  1  0.001  0.356  0.510  1.0
  Sr  Sr11  1  0.644  0.645  0.510  1.0
  Cr  Cr12  1  0.000  0.000  0.866  1.0
  Cr  Cr13  1  0.667  0.333  0.422  1.0
  Cr  Cr14  1  0.333  0.667  0.334  1.0
  Cr  Cr15  1  0.667  0.333  0.762  1.0
  Cr  Cr16  1  0.000  0.000  0.194  1.0
  Cr  Cr17  1  0.333  0.667  0.657  1.0
  Cr  Cr18  1  0.000  0.000  0.526  1.0
  Cr  Cr19  1  0.667  0.333  0.098  1.0
  Cr  Cr20  1  0.333  0.667  0.998  1.0
  O  O21  1  0.675  0.496  0.264  1.0
  O  O22  1  0.174  0.673  0.497  1.0
  O  O23  1  0.830  0.876  0.347  1.0
  O  O24  1  0.047  0.170  0.347  1.0
  O  O25  1  0.835  0.477  0.939  1.0
  O  O26  1  0.158  0.161  0.030  1.0
  O  O27  1  0.341  0.825  0.822  1.0
  O  O28  1  0.335  0.820  0.167  1.0
  O  O29  1  0.003  0.842  0.030  1.0
  O  O30  1  0.504  0.179  0.264  1.0
  O  O31  1  0.523  0.358  0.939  1.0
  O  O32  1  0.124  0.953  0.347  1.0
  O  O33  1  0.642  0.165  0.939  1.0
  O  O34  1  0.180  0.515  0.167  1.0
  O  O35  1  0.839  0.997  0.030  1.0
  O  O36  1  0.499  0.826  0.497  1.0
  O  O37  1  0.485  0.665  0.167  1.0
  O  O38  1  0.854  0.832  0.706  1.0
  O  O39  1  0.505  0.317  0.576  1.0
  O  O40  1  0.978  0.146  0.706  1.0
  O  O41  1  0.812  0.495  0.576  1.0
  O  O42  1  0.821  0.325  0.264  1.0
  O  O43  1  0.175  0.516  0.822  1.0
  O  O44  1  0.484  0.659  0.822  1.0
  O  O45  1  0.683  0.188  0.576  1.0
  O  O46  1  0.327  0.501  0.497  1.0
  O  O47  1  0.168  0.022  0.706  1.0
[/CIF]
.