The compound described by BaCaCeNbO6 crystallizes in the orthorhombic P222 space group. There are four inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to four equivalent O(1), four equivalent O(2), and four equivalent O(3) atoms to form BaO12 cuboctahedra that share faces with four equivalent Ce(1)O6 octahedra and faces with four equivalent Nb(1)O6 octahedra. In the second Ba site, Ba(2) is bonded to four equivalent O(4), four equivalent O(5), and four equivalent O(6) atoms to form BaO12 cuboctahedra that share faces with four equivalent Ce(1)O6 octahedra and faces with four equivalent Nb(1)O6 octahedra. In the third Ba site, Ba(3) is bonded in a distorted body-centered cubic geometry to four equivalent O(2) and four equivalent O(6) atoms. In the fourth Ba site, Ba(4) is bonded in a distorted body-centered cubic geometry to four equivalent O(1) and four equivalent O(6) atoms. There are four inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a square co-planar geometry to four equivalent O(5) atoms. In the second Ca site, Ca(2) is bonded in a distorted square co-planar geometry to four equivalent O(4) atoms. In the third Ca site, Ca(3) is bonded in a square co-planar geometry to four equivalent O(2) atoms. In the fourth Ca site, Ca(4) is bonded in a rectangular see-saw-like geometry to four equivalent O(3) atoms. Ce(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form CeO6 octahedra that share corners with six equivalent Nb(1)O6 octahedra,  a faceface with one Ba(1)O12 cuboctahedra, and  a faceface with one Ba(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 21-32°. Nb(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form NbO6 octahedra that share corners with six equivalent Ce(1)O6 octahedra,  a faceface with one Ba(1)O12 cuboctahedra, and  a faceface with one Ba(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 21-32°. There are six inequivalent O sites. In the first O site, O(5) is bonded in a 3-coordinate geometry to one Ba(2), one Ca(1), one Ce(1), and one Nb(1) atom. In the second O site, O(6) is bonded in a 5-coordinate geometry to one Ba(2), one Ba(3), one Ba(4), one Ce(1), and one Nb(1) atom. In the third O site, O(1) is bonded in a 4-coordinate geometry to one Ba(1), one Ba(4), one Ce(1), and one Nb(1) atom. In the fourth O site, O(2) is bonded in a 3-coordinate geometry to one Ba(1), one Ba(3), one Ca(3), one Ce(1), and one Nb(1) atom. In the fifth O site, O(3) is bonded in a 3-coordinate geometry to one Ba(1), one Ca(4), one Ce(1), and one Nb(1) atom. In the sixth O site, O(4) is bonded in a 3-coordinate geometry to one Ba(2), one Ca(2), one Ce(1), and one Nb(1) atom. is represented by the CIF file [CIF]
data_BaCaCeNbO6
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.452
_cell_length_b   8.509
_cell_length_c   8.463
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   608.652
_cell_formula_units_Z   4
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
  Ba  Ba0  1  0.000  0.000  0.000  1.0
  Ba  Ba1  1  0.500  0.500  0.500  1.0
  Ba  Ba2  1  0.500  0.000  0.500  1.0
  Ba  Ba3  1  0.000  0.000  0.500  1.0
  Ca  Ca4  1  0.000  0.500  0.500  1.0
  Ca  Ca5  1  0.500  0.500  0.000  1.0
  Ca  Ca6  1  0.500  0.000  0.000  1.0
  Ca  Ca7  1  0.000  0.500  0.000  1.0
  Ce  Ce8  1  0.749  0.745  0.755  1.0
  Ce  Ce9  1  0.251  0.255  0.755  1.0
  Ce  Ce10  1  0.251  0.745  0.245  1.0
  Ce  Ce11  1  0.749  0.255  0.245  1.0
  Nb  Nb12  1  0.248  0.257  0.246  1.0
  Nb  Nb13  1  0.752  0.743  0.246  1.0
  Nb  Nb14  1  0.752  0.257  0.754  1.0
  Nb  Nb15  1  0.248  0.743  0.754  1.0
  O  O16  1  0.015  0.212  0.272  1.0
  O  O17  1  0.985  0.788  0.272  1.0
  O  O18  1  0.985  0.212  0.728  1.0
  O  O19  1  0.015  0.788  0.728  1.0
  O  O20  1  0.294  0.020  0.200  1.0
  O  O21  1  0.294  0.980  0.800  1.0
  O  O22  1  0.706  0.980  0.200  1.0
  O  O23  1  0.706  0.020  0.800  1.0
  O  O24  1  0.200  0.304  0.015  1.0
  O  O25  1  0.800  0.304  0.985  1.0
  O  O26  1  0.200  0.696  0.985  1.0
  O  O27  1  0.800  0.696  0.015  1.0
  O  O28  1  0.482  0.305  0.203  1.0
  O  O29  1  0.518  0.695  0.203  1.0
  O  O30  1  0.518  0.305  0.797  1.0
  O  O31  1  0.482  0.695  0.797  1.0
  O  O32  1  0.204  0.487  0.300  1.0
  O  O33  1  0.204  0.513  0.700  1.0
  O  O34  1  0.796  0.513  0.300  1.0
  O  O35  1  0.796  0.487  0.700  1.0
  O  O36  1  0.282  0.223  0.481  1.0
  O  O37  1  0.718  0.223  0.519  1.0
  O  O38  1  0.282  0.777  0.519  1.0
  O  O39  1  0.718  0.777  0.481  1.0
[/CIF]
.
The compound described by BaCaCeNbO6 crystallizes in the orthorhombic P222 space group. There are four inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to four equivalent O(1), four equivalent O(2), and four equivalent O(3) atoms to form BaO12 cuboctahedra that share faces with four equivalent Ce(1)O6 octahedra and faces with four equivalent Nb(1)O6 octahedra. In the second Ba site, Ba(2) is bonded to four equivalent O(4), four equivalent O(5), and four equivalent O(6) atoms to form BaO12 cuboctahedra that share faces with four equivalent Ce(1)O6 octahedra and faces with four equivalent Nb(1)O6 octahedra. In the third Ba site, Ba(3) is bonded in a distorted body-centered cubic geometry to four equivalent O(2) and four equivalent O(6) atoms. In the fourth Ba site, Ba(4) is bonded in a distorted body-centered cubic geometry to four equivalent O(1) and four equivalent O(6) atoms. There are four inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a square co-planar geometry to four equivalent O(5) atoms. In the second Ca site, Ca(2) is bonded in a distorted square co-planar geometry to four equivalent O(4) atoms. In the third Ca site, Ca(3) is bonded in a square co-planar geometry to four equivalent O(2) atoms. In the fourth Ca site, Ca(4) is bonded in a rectangular see-saw-like geometry to four equivalent O(3) atoms. Ce(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form CeO6 octahedra that share corners with six equivalent Nb(1)O6 octahedra,  a faceface with one Ba(1)O12 cuboctahedra, and  a faceface with one Ba(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 21-32°. Nb(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form NbO6 octahedra that share corners with six equivalent Ce(1)O6 octahedra,  a faceface with one Ba(1)O12 cuboctahedra, and  a faceface with one Ba(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 21-32°. There are six inequivalent O sites. In the first O site, O(5) is bonded in a 3-coordinate geometry to one Ba(2), one Ca(1), one Ce(1), and one Nb(1) atom. In the second O site, O(6) is bonded in a 5-coordinate geometry to one Ba(2), one Ba(3), one Ba(4), one Ce(1), and one Nb(1) atom. In the third O site, O(1) is bonded in a 4-coordinate geometry to one Ba(1), one Ba(4), one Ce(1), and one Nb(1) atom. In the fourth O site, O(2) is bonded in a 3-coordinate geometry to one Ba(1), one Ba(3), one Ca(3), one Ce(1), and one Nb(1) atom. In the fifth O site, O(3) is bonded in a 3-coordinate geometry to one Ba(1), one Ca(4), one Ce(1), and one Nb(1) atom. In the sixth O site, O(4) is bonded in a 3-coordinate geometry to one Ba(2), one Ca(2), one Ce(1), and one Nb(1) atom. is represented by the CIF file [CIF]
data_BaCaCeNbO6
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.452
_cell_length_b   8.509
_cell_length_c   8.463
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   608.652
_cell_formula_units_Z   4
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
  Ba  Ba0  1  0.000  0.000  0.000  1.0
  Ba  Ba1  1  0.500  0.500  0.500  1.0
  Ba  Ba2  1  0.500  0.000  0.500  1.0
  Ba  Ba3  1  0.000  0.000  0.500  1.0
  Ca  Ca4  1  0.000  0.500  0.500  1.0
  Ca  Ca5  1  0.500  0.500  0.000  1.0
  Ca  Ca6  1  0.500  0.000  0.000  1.0
  Ca  Ca7  1  0.000  0.500  0.000  1.0
  Ce  Ce8  1  0.749  0.745  0.755  1.0
  Ce  Ce9  1  0.251  0.255  0.755  1.0
  Ce  Ce10  1  0.251  0.745  0.245  1.0
  Ce  Ce11  1  0.749  0.255  0.245  1.0
  Nb  Nb12  1  0.248  0.257  0.246  1.0
  Nb  Nb13  1  0.752  0.743  0.246  1.0
  Nb  Nb14  1  0.752  0.257  0.754  1.0
  Nb  Nb15  1  0.248  0.743  0.754  1.0
  O  O16  1  0.015  0.212  0.272  1.0
  O  O17  1  0.985  0.788  0.272  1.0
  O  O18  1  0.985  0.212  0.728  1.0
  O  O19  1  0.015  0.788  0.728  1.0
  O  O20  1  0.294  0.020  0.200  1.0
  O  O21  1  0.294  0.980  0.800  1.0
  O  O22  1  0.706  0.980  0.200  1.0
  O  O23  1  0.706  0.020  0.800  1.0
  O  O24  1  0.200  0.304  0.015  1.0
  O  O25  1  0.800  0.304  0.985  1.0
  O  O26  1  0.200  0.696  0.985  1.0
  O  O27  1  0.800  0.696  0.015  1.0
  O  O28  1  0.482  0.305  0.203  1.0
  O  O29  1  0.518  0.695  0.203  1.0
  O  O30  1  0.518  0.305  0.797  1.0
  O  O31  1  0.482  0.695  0.797  1.0
  O  O32  1  0.204  0.487  0.300  1.0
  O  O33  1  0.204  0.513  0.700  1.0
  O  O34  1  0.796  0.513  0.300  1.0
  O  O35  1  0.796  0.487  0.700  1.0
  O  O36  1  0.282  0.223  0.481  1.0
  O  O37  1  0.718  0.223  0.519  1.0
  O  O38  1  0.282  0.777  0.519  1.0
  O  O39  1  0.718  0.777  0.481  1.0
[/CIF]
.