BaNb2Fe2O9 crystallizes in the orthorhombic Fmm2 space group. Ba(1) is bonded to four equivalent O(1) and eight equivalent O(4) atoms to form BaO12 cuboctahedra that share corners with four equivalent Ba(1)O12 cuboctahedra, faces with four equivalent Ba(1)O12 cuboctahedra, and faces with eight equivalent Nb(1)O6 octahedra. Nb(1) is bonded to one O(1), one O(2), and four equivalent O(4) atoms to form NbO6 octahedra that share corners with five equivalent Nb(1)O6 octahedra and faces with four equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 4-12°. Fe(1) is bonded in a 5-coordinate geometry to one O(2) and four equivalent O(3) atoms. There are four inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Ba(1) and two equivalent Nb(1) atoms to form a mixture of corner and edge-sharing OBa4Nb2 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the second O site, O(2) is bonded in a linear geometry to one Nb(1) and one Fe(1) atom. In the third O site, O(3) is bonded to four equivalent Fe(1) atoms to form a mixture of distorted corner and edge-sharing OFe4 trigonal pyramids. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ba(1) and two equivalent Nb(1) atoms.
BaNb2Fe2O9 crystallizes in the orthorhombic Fmm2 space group. Ba(1) is bonded to four equivalent O(1) and eight equivalent O(4) atoms to form BaO12 cuboctahedra that share corners with four equivalent Ba(1)O12 cuboctahedra, faces with four equivalent Ba(1)O12 cuboctahedra, and faces with eight equivalent Nb(1)O6 octahedra. There are a spread of Ba(1)-O(1) bond distances ranging from 2.78-2.84 Å. There are four shorter (2.81 Å) and four longer (2.86 Å) Ba(1)-O(4) bond lengths. Nb(1) is bonded to one O(1), one O(2), and four equivalent O(4) atoms to form NbO6 octahedra that share corners with five equivalent Nb(1)O6 octahedra and faces with four equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 4-12°. The Nb(1)-O(1) bond length is 2.22 Å. The Nb(1)-O(2) bond length is 1.92 Å. There are two shorter (1.94 Å) and two longer (2.06 Å) Nb(1)-O(4) bond lengths. Fe(1) is bonded in a 5-coordinate geometry to one O(2) and four equivalent O(3) atoms. The Fe(1)-O(2) bond length is 1.81 Å. All Fe(1)-O(3) bond lengths are 2.09 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Ba(1) and two equivalent Nb(1) atoms to form a mixture of corner and edge-sharing OBa4Nb2 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the second O site, O(2) is bonded in a linear geometry to one Nb(1) and one Fe(1) atom. In the third O site, O(3) is bonded to four equivalent Fe(1) atoms to form a mixture of distorted corner and edge-sharing OFe4 trigonal pyramids. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ba(1) and two equivalent Nb(1) atoms.