BaNb2Fe2O9 crystallizes in the orthorhombic Cmc2_1 space group. Ba(1) is bonded to four equivalent O(1), four equivalent O(4), and four equivalent O(5) 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), two equivalent O(4), and two equivalent O(5) 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 4-14°. Fe(1) is bonded in a 5-coordinate geometry to one O(2) and four equivalent O(3) atoms. There are five inequivalent O sites. In the first O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ba(1) and two equivalent Nb(1) atoms. In the second O site, O(1) is bonded to four equivalent Ba(1) and two equivalent Nb(1) atoms to form a mixture of edge and corner-sharing OBa4Nb2 octahedra. The corner-sharing octahedral tilt angles range from 1-2°. In the third O site, O(2) is bonded in a linear geometry to one Nb(1) and one Fe(1) atom. In the fourth O site, O(3) is bonded to four equivalent Fe(1) atoms to form a mixture of distorted edge and corner-sharing OFe4 trigonal pyramids. In the fifth O site, O(4) is bonded in a distorted linear geometry to two equivalent Ba(1) and two equivalent Nb(1) atoms.
BaNb2Fe2O9 crystallizes in the orthorhombic Cmc2_1 space group. Ba(1) is bonded to four equivalent O(1), four equivalent O(4), and four equivalent O(5) 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 two shorter (2.77 Å) and two longer (2.85 Å) Ba(1)-O(1) bond lengths. There are two shorter (2.82 Å) and two longer (2.89 Å) Ba(1)-O(4) bond lengths. There are two shorter (2.77 Å) and two longer (2.84 Å) Ba(1)-O(5) bond lengths. Nb(1) is bonded to one O(1), one O(2), two equivalent O(4), and two equivalent O(5) 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 4-14°. The Nb(1)-O(1) bond length is 2.21 Å. The Nb(1)-O(2) bond length is 1.92 Å. There is one shorter (1.93 Å) and one longer (2.07 Å) Nb(1)-O(4) bond length. There is one shorter (1.93 Å) and one longer (2.07 Å) Nb(1)-O(5) bond length. 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. There are a spread of Fe(1)-O(3) bond distances ranging from 2.09-2.11 Å. There are five inequivalent O sites. In the first O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ba(1) and two equivalent Nb(1) atoms. In the second O site, O(1) is bonded to four equivalent Ba(1) and two equivalent Nb(1) atoms to form a mixture of edge and corner-sharing OBa4Nb2 octahedra. The corner-sharing octahedral tilt angles range from 1-2°. In the third O site, O(2) is bonded in a linear geometry to one Nb(1) and one Fe(1) atom. In the fourth O site, O(3) is bonded to four equivalent Fe(1) atoms to form a mixture of distorted edge and corner-sharing OFe4 trigonal pyramids. In the fifth O site, O(4) is bonded in a distorted linear geometry to two equivalent Ba(1) and two equivalent Nb(1) atoms.