The crystal structure described by Ca2Nb2CrO8 crystallizes in the triclinic P-1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 5-coordinate geometry to one O(7), two equivalent O(5), two equivalent O(6), and two equivalent O(8) atoms. In the second Ca site, Ca(2) is bonded in a 8-coordinate geometry to one O(2), one O(8), two equivalent O(5), two equivalent O(6), and two equivalent O(7) atoms. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(3), one O(5), one O(6), and one O(8) atom. In the second Nb site, Nb(2) is bonded to one O(1), one O(2), one O(4), one O(5), one O(6), and one O(7) atom to form distorted NbO6 octahedra that share corners with four equivalent Cr(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-53°. Cr(1) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted CrO6 octahedra that share corners with four equivalent Nb(2)O6 octahedra and edges with two equivalent Cr(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-53°. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Nb(1), one Nb(2), and one Cr(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Ca(2), one Nb(1), one Nb(2), and one Cr(1) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Nb(1) and two equivalent Cr(1) atoms. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Nb(2) and two equivalent Cr(1) atoms. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to two equivalent Ca(1), two equivalent Ca(2), one Nb(1), and one Nb(2) atom. In the sixth O site, O(6) is bonded in a 6-coordinate geometry to two equivalent Ca(1), two equivalent Ca(2), one Nb(1), and one Nb(2) atom. In the seventh O site, O(7) is bonded to one Ca(1), two equivalent Ca(2), and one Nb(2) atom to form a mixture of distorted corner and edge-sharing OCa3Nb trigonal pyramids. In the eighth O site, O(8) is bonded to one Ca(2), two equivalent Ca(1), and one Nb(1) atom to form a mixture of distorted corner and edge-sharing OCa3Nb trigonal pyramids. is represented by the CIF file [CIF]
data_Ca2Nb2CrO8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.495
_cell_length_b   6.465
_cell_length_c   10.024
_cell_angle_alpha   106.169
_cell_angle_beta   91.646
_cell_angle_gamma   91.559
_symmetry_Int_Tables_number   1
_cell_volume   341.672
_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
  Ca  Ca0  1  0.244  0.884  0.422  1.0
  Ca  Ca1  1  0.256  0.466  0.582  1.0
  Ca  Ca2  1  0.756  0.116  0.578  1.0
  Ca  Ca3  1  0.744  0.534  0.418  1.0
  Nb  Nb4  1  0.255  0.026  0.772  1.0
  Nb  Nb5  1  0.251  0.271  0.226  1.0
  Nb  Nb6  1  0.745  0.974  0.228  1.0
  Nb  Nb7  1  0.749  0.729  0.774  1.0
  Cr  Cr8  1  0.243  0.650  0.001  1.0
  Cr  Cr9  1  0.757  0.350  0.999  1.0
  O  O10  1  0.927  0.027  0.854  1.0
  O  O11  1  0.587  0.213  0.145  1.0
  O  O12  1  0.073  0.973  0.146  1.0
  O  O13  1  0.413  0.787  0.855  1.0
  O  O14  1  0.435  0.266  0.881  1.0
  O  O15  1  0.088  0.415  0.109  1.0
  O  O16  1  0.565  0.734  0.119  1.0
  O  O17  1  0.912  0.585  0.891  1.0
  O  O18  1  0.507  0.875  0.633  1.0
  O  O19  1  0.999  0.252  0.369  1.0
  O  O20  1  0.657  0.461  0.629  1.0
  O  O21  1  0.841  0.839  0.370  1.0
  O  O22  1  0.343  0.539  0.371  1.0
  O  O23  1  0.159  0.161  0.630  1.0
  O  O24  1  0.001  0.748  0.631  1.0
  O  O25  1  0.493  0.125  0.367  1.0
[/CIF]
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The crystal structure described by Ca2Nb2CrO8 crystallizes in the triclinic P-1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 5-coordinate geometry to one O(7), two equivalent O(5), two equivalent O(6), and two equivalent O(8) atoms. In the second Ca site, Ca(2) is bonded in a 8-coordinate geometry to one O(2), one O(8), two equivalent O(5), two equivalent O(6), and two equivalent O(7) atoms. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(3), one O(5), one O(6), and one O(8) atom. In the second Nb site, Nb(2) is bonded to one O(1), one O(2), one O(4), one O(5), one O(6), and one O(7) atom to form distorted NbO6 octahedra that share corners with four equivalent Cr(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-53°. Cr(1) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted CrO6 octahedra that share corners with four equivalent Nb(2)O6 octahedra and edges with two equivalent Cr(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-53°. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Nb(1), one Nb(2), and one Cr(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Ca(2), one Nb(1), one Nb(2), and one Cr(1) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Nb(1) and two equivalent Cr(1) atoms. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Nb(2) and two equivalent Cr(1) atoms. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to two equivalent Ca(1), two equivalent Ca(2), one Nb(1), and one Nb(2) atom. In the sixth O site, O(6) is bonded in a 6-coordinate geometry to two equivalent Ca(1), two equivalent Ca(2), one Nb(1), and one Nb(2) atom. In the seventh O site, O(7) is bonded to one Ca(1), two equivalent Ca(2), and one Nb(2) atom to form a mixture of distorted corner and edge-sharing OCa3Nb trigonal pyramids. In the eighth O site, O(8) is bonded to one Ca(2), two equivalent Ca(1), and one Nb(1) atom to form a mixture of distorted corner and edge-sharing OCa3Nb trigonal pyramids. is represented by the CIF file [CIF]
data_Ca2Nb2CrO8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.495
_cell_length_b   6.465
_cell_length_c   10.024
_cell_angle_alpha   106.169
_cell_angle_beta   91.646
_cell_angle_gamma   91.559
_symmetry_Int_Tables_number   1
_cell_volume   341.672
_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
  Ca  Ca0  1  0.244  0.884  0.422  1.0
  Ca  Ca1  1  0.256  0.466  0.582  1.0
  Ca  Ca2  1  0.756  0.116  0.578  1.0
  Ca  Ca3  1  0.744  0.534  0.418  1.0
  Nb  Nb4  1  0.255  0.026  0.772  1.0
  Nb  Nb5  1  0.251  0.271  0.226  1.0
  Nb  Nb6  1  0.745  0.974  0.228  1.0
  Nb  Nb7  1  0.749  0.729  0.774  1.0
  Cr  Cr8  1  0.243  0.650  0.001  1.0
  Cr  Cr9  1  0.757  0.350  0.999  1.0
  O  O10  1  0.927  0.027  0.854  1.0
  O  O11  1  0.587  0.213  0.145  1.0
  O  O12  1  0.073  0.973  0.146  1.0
  O  O13  1  0.413  0.787  0.855  1.0
  O  O14  1  0.435  0.266  0.881  1.0
  O  O15  1  0.088  0.415  0.109  1.0
  O  O16  1  0.565  0.734  0.119  1.0
  O  O17  1  0.912  0.585  0.891  1.0
  O  O18  1  0.507  0.875  0.633  1.0
  O  O19  1  0.999  0.252  0.369  1.0
  O  O20  1  0.657  0.461  0.629  1.0
  O  O21  1  0.841  0.839  0.370  1.0
  O  O22  1  0.343  0.539  0.371  1.0
  O  O23  1  0.159  0.161  0.630  1.0
  O  O24  1  0.001  0.748  0.631  1.0
  O  O25  1  0.493  0.125  0.367  1.0
[/CIF]
.