Ba2Fe3AlO7 crystallizes in the triclinic P1 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 9-coordinate geometry to one O(2), two equivalent O(1), two equivalent O(4), and four equivalent O(6) atoms. In the second Ba site, Ba(2) is bonded in a 5-coordinate geometry to one O(3), two equivalent O(1), and two equivalent O(7) atoms. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(4), one O(5), one O(6), and two equivalent O(2) atoms to form distorted FeO5 trigonal bipyramids that share  a cornercorner with one Fe(2)O4 tetrahedra, corners with two equivalent Al(1)O4 tetrahedra, corners with two equivalent Fe(1)O5 trigonal bipyramids, and  an edgeedge with one Al(1)O4 tetrahedra. In the second Fe site, Fe(2) is bonded to one O(5), one O(7), and two equivalent O(3) atoms to form distorted FeO4 tetrahedra that share corners with two equivalent Fe(2)O4 tetrahedra, corners with three equivalent Al(1)O4 tetrahedra, and  a cornercorner with one Fe(1)O5 trigonal bipyramid. In the third Fe site, Fe(3) is bonded in a distorted T-shaped geometry to one O(6), one O(7), and two equivalent O(1) atoms. Al(1) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form AlO4 tetrahedra that share corners with three equivalent Fe(2)O4 tetrahedra, corners with two equivalent Fe(1)O5 trigonal bipyramids, and  an edgeedge with one Fe(1)O5 trigonal bipyramid. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to two equivalent Ba(1), two equivalent Ba(2), and two equivalent Fe(3) atoms. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Ba(1), two equivalent Fe(1), and one Al(1) atom. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Ba(2), two equivalent Fe(2), and one Al(1) atom. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to two equivalent Ba(1), one Fe(1), and one Al(1) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Fe(1), one Fe(2), and one Al(1) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to four equivalent Ba(1), one Fe(1), and one Fe(3) atom. In the seventh O site, O(7) is bonded in a 2-coordinate geometry to two equivalent Ba(2), one Fe(2), and one Fe(3) atom.
Ba2Fe3AlO7 crystallizes in the triclinic P1 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 9-coordinate geometry to one O(2), two equivalent O(1), two equivalent O(4), and four equivalent O(6) atoms. The Ba(1)-O(2) bond length is 2.67 Å. There is one shorter (2.73 Å) and one longer (2.75 Å) Ba(1)-O(1) bond length. There is one shorter (2.85 Å) and one longer (3.09 Å) Ba(1)-O(4) bond length. There are a spread of Ba(1)-O(6) bond distances ranging from 2.84-3.15 Å. In the second Ba site, Ba(2) is bonded in a 5-coordinate geometry to one O(3), two equivalent O(1), and two equivalent O(7) atoms. The Ba(2)-O(3) bond length is 2.71 Å. There is one shorter (2.72 Å) and one longer (2.75 Å) Ba(2)-O(1) bond length. There is one shorter (2.77 Å) and one longer (2.84 Å) Ba(2)-O(7) bond length. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(4), one O(5), one O(6), and two equivalent O(2) atoms to form distorted FeO5 trigonal bipyramids that share  a cornercorner with one Fe(2)O4 tetrahedra, corners with two equivalent Al(1)O4 tetrahedra, corners with two equivalent Fe(1)O5 trigonal bipyramids, and  an edgeedge with one Al(1)O4 tetrahedra. The Fe(1)-O(4) bond length is 1.89 Å. The Fe(1)-O(5) bond length is 2.16 Å. The Fe(1)-O(6) bond length is 1.97 Å. There is one shorter (1.98 Å) and one longer (2.06 Å) Fe(1)-O(2) bond length. In the second Fe site, Fe(2) is bonded to one O(5), one O(7), and two equivalent O(3) atoms to form distorted FeO4 tetrahedra that share corners with two equivalent Fe(2)O4 tetrahedra, corners with three equivalent Al(1)O4 tetrahedra, and  a cornercorner with one Fe(1)O5 trigonal bipyramid. The Fe(2)-O(5) bond length is 1.99 Å. The Fe(2)-O(7) bond length is 2.05 Å. There is one shorter (2.02 Å) and one longer (2.15 Å) Fe(2)-O(3) bond length. In the third Fe site, Fe(3) is bonded in a distorted T-shaped geometry to one O(6), one O(7), and two equivalent O(1) atoms. The Fe(3)-O(6) bond length is 1.97 Å. The Fe(3)-O(7) bond length is 1.92 Å. There is one shorter (1.98 Å) and one longer (2.77 Å) Fe(3)-O(1) bond length. Al(1) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form AlO4 tetrahedra that share corners with three equivalent Fe(2)O4 tetrahedra, corners with two equivalent Fe(1)O5 trigonal bipyramids, and  an edgeedge with one Fe(1)O5 trigonal bipyramid. The Al(1)-O(2) bond length is 1.81 Å. The Al(1)-O(3) bond length is 1.76 Å. The Al(1)-O(4) bond length is 1.83 Å. The Al(1)-O(5) bond length is 1.79 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to two equivalent Ba(1), two equivalent Ba(2), and two equivalent Fe(3) atoms. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Ba(1), two equivalent Fe(1), and one Al(1) atom. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Ba(2), two equivalent Fe(2), and one Al(1) atom. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to two equivalent Ba(1), one Fe(1), and one Al(1) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Fe(1), one Fe(2), and one Al(1) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to four equivalent Ba(1), one Fe(1), and one Fe(3) atom. In the seventh O site, O(7) is bonded in a 2-coordinate geometry to two equivalent Ba(2), one Fe(2), and one Fe(3) atom.