The compound described by K2Cr3O9 crystallizes in the monoclinic P2_1/m space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 11-coordinate geometry to one O(3), one O(5), two equivalent O(1), three equivalent O(4), and four equivalent O(6) atoms. In the second K site, K(2) is bonded in a 6-coordinate geometry to one O(4), one O(7), two equivalent O(1), and two equivalent O(6) atoms. There are three inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form CrO6 octahedra that share corners with two equivalent Cr(2)O4 tetrahedra, corners with two equivalent Cr(3)O4 tetrahedra, and edges with two equivalent Cr(1)O6 octahedra. In the second Cr site, Cr(2) is bonded to one O(4), one O(5), and two equivalent O(1) atoms to form corner-sharing CrO4 tetrahedra. The corner-sharing octahedral tilt angles are 53°. In the third Cr site, Cr(3) is bonded to one O(2), one O(7), and two equivalent O(6) atoms to form corner-sharing CrO4 tetrahedra. The corner-sharing octahedral tilt angles are 48°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one K(1), one K(2), one Cr(1), and one Cr(2) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Cr(3) and two equivalent Cr(1) atoms. In the third O site, O(3) is bonded in a water-like geometry to one K(1) and two equivalent Cr(1) atoms. In the fourth O site, O(4) is bonded in a single-bond geometry to one K(2), three equivalent K(1), and one Cr(2) atom. In the fifth O site, O(5) is bonded in a single-bond geometry to one K(1) and one Cr(2) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one K(2), two equivalent K(1), and one Cr(3) atom. In the seventh O site, O(7) is bonded in a distorted single-bond geometry to one K(2) and one Cr(3) atom. is represented by the CIF file [CIF]
data_K2Cr3O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.003
_cell_length_b   8.226
_cell_length_c   9.462
_cell_angle_alpha   114.706
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   424.515
_cell_formula_units_Z   2
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
  K  K0  1  0.750  0.171  0.084  1.0
  K  K1  1  0.250  0.829  0.916  1.0
  K  K2  1  0.750  0.769  0.252  1.0
  K  K3  1  0.250  0.231  0.748  1.0
  Cr  Cr4  1  0.500  0.500  0.500  1.0
  Cr  Cr5  1  0.000  0.500  0.500  1.0
  Cr  Cr6  1  0.250  0.460  0.176  1.0
  Cr  Cr7  1  0.750  0.540  0.824  1.0
  Cr  Cr8  1  0.250  0.074  0.330  1.0
  Cr  Cr9  1  0.750  0.926  0.670  1.0
  O  O10  1  0.479  0.509  0.294  1.0
  O  O11  1  0.979  0.491  0.706  1.0
  O  O12  1  0.521  0.491  0.706  1.0
  O  O13  1  0.021  0.509  0.294  1.0
  O  O14  1  0.250  0.314  0.441  1.0
  O  O15  1  0.750  0.686  0.559  1.0
  O  O16  1  0.750  0.353  0.433  1.0
  O  O17  1  0.250  0.647  0.567  1.0
  O  O18  1  0.250  0.249  0.058  1.0
  O  O19  1  0.750  0.751  0.942  1.0
  O  O20  1  0.250  0.579  0.075  1.0
  O  O21  1  0.750  0.421  0.925  1.0
  O  O22  1  0.470  0.012  0.219  1.0
  O  O23  1  0.970  0.988  0.781  1.0
  O  O24  1  0.530  0.988  0.781  1.0
  O  O25  1  0.030  0.012  0.219  1.0
  O  O26  1  0.250  0.973  0.445  1.0
  O  O27  1  0.750  0.027  0.555  1.0
[/CIF]
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The compound described by K2Cr3O9 crystallizes in the monoclinic P2_1/m space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 11-coordinate geometry to one O(3), one O(5), two equivalent O(1), three equivalent O(4), and four equivalent O(6) atoms. In the second K site, K(2) is bonded in a 6-coordinate geometry to one O(4), one O(7), two equivalent O(1), and two equivalent O(6) atoms. There are three inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form CrO6 octahedra that share corners with two equivalent Cr(2)O4 tetrahedra, corners with two equivalent Cr(3)O4 tetrahedra, and edges with two equivalent Cr(1)O6 octahedra. In the second Cr site, Cr(2) is bonded to one O(4), one O(5), and two equivalent O(1) atoms to form corner-sharing CrO4 tetrahedra. The corner-sharing octahedral tilt angles are 53°. In the third Cr site, Cr(3) is bonded to one O(2), one O(7), and two equivalent O(6) atoms to form corner-sharing CrO4 tetrahedra. The corner-sharing octahedral tilt angles are 48°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one K(1), one K(2), one Cr(1), and one Cr(2) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Cr(3) and two equivalent Cr(1) atoms. In the third O site, O(3) is bonded in a water-like geometry to one K(1) and two equivalent Cr(1) atoms. In the fourth O site, O(4) is bonded in a single-bond geometry to one K(2), three equivalent K(1), and one Cr(2) atom. In the fifth O site, O(5) is bonded in a single-bond geometry to one K(1) and one Cr(2) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one K(2), two equivalent K(1), and one Cr(3) atom. In the seventh O site, O(7) is bonded in a distorted single-bond geometry to one K(2) and one Cr(3) atom. is represented by the CIF file [CIF]
data_K2Cr3O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.003
_cell_length_b   8.226
_cell_length_c   9.462
_cell_angle_alpha   114.706
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   424.515
_cell_formula_units_Z   2
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
  K  K0  1  0.750  0.171  0.084  1.0
  K  K1  1  0.250  0.829  0.916  1.0
  K  K2  1  0.750  0.769  0.252  1.0
  K  K3  1  0.250  0.231  0.748  1.0
  Cr  Cr4  1  0.500  0.500  0.500  1.0
  Cr  Cr5  1  0.000  0.500  0.500  1.0
  Cr  Cr6  1  0.250  0.460  0.176  1.0
  Cr  Cr7  1  0.750  0.540  0.824  1.0
  Cr  Cr8  1  0.250  0.074  0.330  1.0
  Cr  Cr9  1  0.750  0.926  0.670  1.0
  O  O10  1  0.479  0.509  0.294  1.0
  O  O11  1  0.979  0.491  0.706  1.0
  O  O12  1  0.521  0.491  0.706  1.0
  O  O13  1  0.021  0.509  0.294  1.0
  O  O14  1  0.250  0.314  0.441  1.0
  O  O15  1  0.750  0.686  0.559  1.0
  O  O16  1  0.750  0.353  0.433  1.0
  O  O17  1  0.250  0.647  0.567  1.0
  O  O18  1  0.250  0.249  0.058  1.0
  O  O19  1  0.750  0.751  0.942  1.0
  O  O20  1  0.250  0.579  0.075  1.0
  O  O21  1  0.750  0.421  0.925  1.0
  O  O22  1  0.470  0.012  0.219  1.0
  O  O23  1  0.970  0.988  0.781  1.0
  O  O24  1  0.530  0.988  0.781  1.0
  O  O25  1  0.030  0.012  0.219  1.0
  O  O26  1  0.250  0.973  0.445  1.0
  O  O27  1  0.750  0.027  0.555  1.0
[/CIF]
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