The material structure described by Sr9(CrN4)2 crystallizes in the monoclinic C2/m space group. There are five inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a linear geometry to two equivalent N(4) atoms. In the second Sr site, Sr(2) is bonded to one N(2), two equivalent N(1), and two equivalent N(4) atoms to form distorted SrN5 trigonal bipyramids that share  a cornercorner with one Sr(3)N5 trigonal bipyramid, corners with two equivalent Sr(2)N5 trigonal bipyramids,  an edgeedge with one Sr(2)N5 trigonal bipyramid, edges with two equivalent Sr(3)N5 trigonal bipyramids, and edges with four equivalent Sr(4)N4 trigonal pyramids. In the third Sr site, Sr(3) is bonded to one N(3), one N(4), and three equivalent N(2) atoms to form distorted SrN5 trigonal bipyramids that share  a cornercorner with one Sr(2)N5 trigonal bipyramid, corners with two equivalent Sr(3)N5 trigonal bipyramids, corners with two equivalent Sr(4)N4 trigonal pyramids, edges with two equivalent Sr(2)N5 trigonal bipyramids, and edges with two equivalent Sr(3)N5 trigonal bipyramids. In the fourth Sr site, Sr(4) is bonded to two equivalent N(1) and two equivalent N(4) atoms to form SrN4 trigonal pyramids that share corners with two equivalent Sr(3)N5 trigonal bipyramids, corners with two equivalent Sr(4)N4 trigonal pyramids, edges with four equivalent Sr(2)N5 trigonal bipyramids, and  an edgeedge with one Sr(4)N4 trigonal pyramid. In the fifth Sr site, Sr(5) is bonded in a distorted square co-planar geometry to one N(1) and three equivalent N(3) atoms. Cr(1) is bonded in a trigonal planar geometry to one N(1), one N(2), and one N(3) atom. There are four inequivalent N sites. In the first N site, N(1) is bonded in a 6-coordinate geometry to one Sr(5), two equivalent Sr(2), two equivalent Sr(4), and one Cr(1) atom. In the second N site, N(2) is bonded to one Sr(2), three equivalent Sr(3), and one Cr(1) atom to form distorted NSr4Cr trigonal bipyramids that share  a cornercorner with one N(4)Sr6 octahedra, corners with two equivalent N(2)Sr4Cr trigonal bipyramids, edges with two equivalent N(4)Sr6 octahedra, and edges with two equivalent N(2)Sr4Cr trigonal bipyramids. The corner-sharing octahedral tilt angles are 9°. In the third N site, N(3) is bonded in a 5-coordinate geometry to one Sr(3), three equivalent Sr(5), and one Cr(1) atom. In the fourth N site, N(4) is bonded to one Sr(1), one Sr(3), two equivalent Sr(2), and two equivalent Sr(4) atoms to form NSr6 octahedra that share corners with three equivalent N(4)Sr6 octahedra,  a cornercorner with one N(2)Sr4Cr trigonal bipyramid,  an edgeedge with one N(4)Sr6 octahedra, and edges with two equivalent N(2)Sr4Cr trigonal bipyramids. The corner-sharing octahedral tilt angles range from 0-4°. is represented by the CIF file [CIF]
data_Sr9(CrN4)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   10.428
_cell_length_b   5.242
_cell_length_c   8.510
_cell_angle_alpha   90.000
_cell_angle_beta   68.616
_cell_angle_gamma   75.443
_symmetry_Int_Tables_number   1
_cell_volume   417.114
_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  0.000  0.500  0.500  1.0
  Sr  Sr1  1  0.080  0.960  0.759  1.0
  Sr  Sr2  1  0.920  0.040  0.241  1.0
  Sr  Sr3  1  0.651  0.674  0.448  1.0
  Sr  Sr4  1  0.349  0.326  0.552  1.0
  Sr  Sr5  1  0.827  0.587  0.991  1.0
  Sr  Sr6  1  0.173  0.413  0.009  1.0
  Sr  Sr7  1  0.608  0.196  0.827  1.0
  Sr  Sr8  1  0.392  0.804  0.173  1.0
  Cr  Cr9  1  0.384  0.808  0.803  1.0
  Cr  Cr10  1  0.616  0.192  0.197  1.0
  N  N11  1  0.229  0.886  0.985  1.0
  N  N12  1  0.771  0.114  0.015  1.0
  N  N13  1  0.368  0.816  0.610  1.0
  N  N14  1  0.632  0.184  0.390  1.0
  N  N15  1  0.551  0.725  0.819  1.0
  N  N16  1  0.449  0.275  0.181  1.0
  N  N17  1  0.073  0.464  0.756  1.0
  N  N18  1  0.927  0.536  0.244  1.0
[/CIF]
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The material structure described by Sr9(CrN4)2 crystallizes in the monoclinic C2/m space group. There are five inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a linear geometry to two equivalent N(4) atoms. In the second Sr site, Sr(2) is bonded to one N(2), two equivalent N(1), and two equivalent N(4) atoms to form distorted SrN5 trigonal bipyramids that share  a cornercorner with one Sr(3)N5 trigonal bipyramid, corners with two equivalent Sr(2)N5 trigonal bipyramids,  an edgeedge with one Sr(2)N5 trigonal bipyramid, edges with two equivalent Sr(3)N5 trigonal bipyramids, and edges with four equivalent Sr(4)N4 trigonal pyramids. In the third Sr site, Sr(3) is bonded to one N(3), one N(4), and three equivalent N(2) atoms to form distorted SrN5 trigonal bipyramids that share  a cornercorner with one Sr(2)N5 trigonal bipyramid, corners with two equivalent Sr(3)N5 trigonal bipyramids, corners with two equivalent Sr(4)N4 trigonal pyramids, edges with two equivalent Sr(2)N5 trigonal bipyramids, and edges with two equivalent Sr(3)N5 trigonal bipyramids. In the fourth Sr site, Sr(4) is bonded to two equivalent N(1) and two equivalent N(4) atoms to form SrN4 trigonal pyramids that share corners with two equivalent Sr(3)N5 trigonal bipyramids, corners with two equivalent Sr(4)N4 trigonal pyramids, edges with four equivalent Sr(2)N5 trigonal bipyramids, and  an edgeedge with one Sr(4)N4 trigonal pyramid. In the fifth Sr site, Sr(5) is bonded in a distorted square co-planar geometry to one N(1) and three equivalent N(3) atoms. Cr(1) is bonded in a trigonal planar geometry to one N(1), one N(2), and one N(3) atom. There are four inequivalent N sites. In the first N site, N(1) is bonded in a 6-coordinate geometry to one Sr(5), two equivalent Sr(2), two equivalent Sr(4), and one Cr(1) atom. In the second N site, N(2) is bonded to one Sr(2), three equivalent Sr(3), and one Cr(1) atom to form distorted NSr4Cr trigonal bipyramids that share  a cornercorner with one N(4)Sr6 octahedra, corners with two equivalent N(2)Sr4Cr trigonal bipyramids, edges with two equivalent N(4)Sr6 octahedra, and edges with two equivalent N(2)Sr4Cr trigonal bipyramids. The corner-sharing octahedral tilt angles are 9°. In the third N site, N(3) is bonded in a 5-coordinate geometry to one Sr(3), three equivalent Sr(5), and one Cr(1) atom. In the fourth N site, N(4) is bonded to one Sr(1), one Sr(3), two equivalent Sr(2), and two equivalent Sr(4) atoms to form NSr6 octahedra that share corners with three equivalent N(4)Sr6 octahedra,  a cornercorner with one N(2)Sr4Cr trigonal bipyramid,  an edgeedge with one N(4)Sr6 octahedra, and edges with two equivalent N(2)Sr4Cr trigonal bipyramids. The corner-sharing octahedral tilt angles range from 0-4°. is represented by the CIF file [CIF]
data_Sr9(CrN4)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   10.428
_cell_length_b   5.242
_cell_length_c   8.510
_cell_angle_alpha   90.000
_cell_angle_beta   68.616
_cell_angle_gamma   75.443
_symmetry_Int_Tables_number   1
_cell_volume   417.114
_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  0.000  0.500  0.500  1.0
  Sr  Sr1  1  0.080  0.960  0.759  1.0
  Sr  Sr2  1  0.920  0.040  0.241  1.0
  Sr  Sr3  1  0.651  0.674  0.448  1.0
  Sr  Sr4  1  0.349  0.326  0.552  1.0
  Sr  Sr5  1  0.827  0.587  0.991  1.0
  Sr  Sr6  1  0.173  0.413  0.009  1.0
  Sr  Sr7  1  0.608  0.196  0.827  1.0
  Sr  Sr8  1  0.392  0.804  0.173  1.0
  Cr  Cr9  1  0.384  0.808  0.803  1.0
  Cr  Cr10  1  0.616  0.192  0.197  1.0
  N  N11  1  0.229  0.886  0.985  1.0
  N  N12  1  0.771  0.114  0.015  1.0
  N  N13  1  0.368  0.816  0.610  1.0
  N  N14  1  0.632  0.184  0.390  1.0
  N  N15  1  0.551  0.725  0.819  1.0
  N  N16  1  0.449  0.275  0.181  1.0
  N  N17  1  0.073  0.464  0.756  1.0
  N  N18  1  0.927  0.536  0.244  1.0
[/CIF]
.