BaLa2O4 crystallizes in the monoclinic C2/c space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 6-coordinate geometry to one O(2), one O(4), one O(5), one O(6), and two equivalent O(3) atoms. In the second Ba site, Ba(2) is bonded in a trigonal planar geometry to one O(6) and two equivalent O(3) atoms. There are three inequivalent La sites. In the first La site, La(1) is bonded to one O(2), one O(4), one O(5), one O(6), and two equivalent O(3) atoms to form a mixture of face and corner-sharing LaO6 octahedra. The corner-sharing octahedral tilt angles range from 29-32°. In the second La site, La(2) is bonded to one O(2), one O(4), one O(5), one O(7), and two equivalent O(1) atoms to form a mixture of distorted face, corner, and edge-sharing LaO6 octahedra. The corner-sharing octahedra are not tilted. In the third La site, La(3) is bonded in a 6-coordinate geometry to one O(2), one O(4), one O(5), one O(7), and two equivalent O(1) atoms. There are seven inequivalent O sites. In the first O site, O(1) is bonded to two equivalent La(2) and two equivalent La(3) atoms to form distorted OLa4 tetrahedra that share corners with two equivalent O(2)BaLa3 tetrahedra, corners with two equivalent O(5)BaLa3 tetrahedra,  an edgeedge with one O(2)BaLa3 tetrahedra,  an edgeedge with one O(5)BaLa3 tetrahedra, and edges with two equivalent O(1)La4 tetrahedra. In the second O site, O(2) is bonded to one Ba(1), one La(1), one La(2), and one La(3) atom to form distorted OBaLa3 tetrahedra that share corners with two equivalent O(5)BaLa3 tetrahedra, corners with two equivalent O(1)La4 tetrahedra,  an edgeedge with one O(5)BaLa3 tetrahedra, and  an edgeedge with one O(1)La4 tetrahedra. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Ba(2), two equivalent Ba(1), and two equivalent La(1) atoms. In the fourth O site, O(4) is bonded in a distorted see-saw-like geometry to one Ba(1), one La(1), one La(2), and one La(3) atom. In the fifth O site, O(5) is bonded to one Ba(1), one La(1), one La(2), and one La(3) atom to form distorted OBaLa3 tetrahedra that share corners with two equivalent O(2)BaLa3 tetrahedra, corners with two equivalent O(1)La4 tetrahedra,  an edgeedge with one O(2)BaLa3 tetrahedra, and  an edgeedge with one O(1)La4 tetrahedra. In the sixth O site, O(6) is bonded in a 5-coordinate geometry to one Ba(2), two equivalent Ba(1), and two equivalent La(1) atoms. In the seventh O site, O(7) is bonded in a distorted square co-planar geometry to two equivalent La(2) and two equivalent La(3) atoms.
BaLa2O4 crystallizes in the monoclinic C2/c space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 6-coordinate geometry to one O(2), one O(4), one O(5), one O(6), and two equivalent O(3) atoms. The Ba(1)-O(2) bond length is 2.69 Å. The Ba(1)-O(4) bond length is 2.75 Å. The Ba(1)-O(5) bond length is 2.67 Å. The Ba(1)-O(6) bond length is 3.04 Å. There is one shorter (2.98 Å) and one longer (3.14 Å) Ba(1)-O(3) bond length. In the second Ba site, Ba(2) is bonded in a trigonal planar geometry to one O(6) and two equivalent O(3) atoms. The Ba(2)-O(6) bond length is 2.61 Å. Both Ba(2)-O(3) bond lengths are 2.62 Å. There are three inequivalent La sites. In the first La site, La(1) is bonded to one O(2), one O(4), one O(5), one O(6), and two equivalent O(3) atoms to form a mixture of face and corner-sharing LaO6 octahedra. The corner-sharing octahedral tilt angles range from 29-32°. The La(1)-O(2) bond length is 2.47 Å. The La(1)-O(4) bond length is 2.53 Å. The La(1)-O(5) bond length is 2.53 Å. The La(1)-O(6) bond length is 2.37 Å. Both La(1)-O(3) bond lengths are 2.36 Å. In the second La site, La(2) is bonded to one O(2), one O(4), one O(5), one O(7), and two equivalent O(1) atoms to form a mixture of distorted face, corner, and edge-sharing LaO6 octahedra. The corner-sharing octahedra are not tilted. The La(2)-O(2) bond length is 2.62 Å. The La(2)-O(4) bond length is 2.46 Å. The La(2)-O(5) bond length is 2.54 Å. The La(2)-O(7) bond length is 2.29 Å. There is one shorter (2.40 Å) and one longer (2.47 Å) La(2)-O(1) bond length. In the third La site, La(3) is bonded in a 6-coordinate geometry to one O(2), one O(4), one O(5), one O(7), and two equivalent O(1) atoms. The La(3)-O(2) bond length is 2.35 Å. The La(3)-O(4) bond length is 2.35 Å. The La(3)-O(5) bond length is 2.35 Å. The La(3)-O(7) bond length is 3.06 Å. There is one shorter (2.48 Å) and one longer (2.54 Å) La(3)-O(1) bond length. There are seven inequivalent O sites. In the first O site, O(1) is bonded to two equivalent La(2) and two equivalent La(3) atoms to form distorted OLa4 tetrahedra that share corners with two equivalent O(2)BaLa3 tetrahedra, corners with two equivalent O(5)BaLa3 tetrahedra,  an edgeedge with one O(2)BaLa3 tetrahedra,  an edgeedge with one O(5)BaLa3 tetrahedra, and edges with two equivalent O(1)La4 tetrahedra. In the second O site, O(2) is bonded to one Ba(1), one La(1), one La(2), and one La(3) atom to form distorted OBaLa3 tetrahedra that share corners with two equivalent O(5)BaLa3 tetrahedra, corners with two equivalent O(1)La4 tetrahedra,  an edgeedge with one O(5)BaLa3 tetrahedra, and  an edgeedge with one O(1)La4 tetrahedra. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Ba(2), two equivalent Ba(1), and two equivalent La(1) atoms. In the fourth O site, O(4) is bonded in a distorted see-saw-like geometry to one Ba(1), one La(1), one La(2), and one La(3) atom. In the fifth O site, O(5) is bonded to one Ba(1), one La(1), one La(2), and one La(3) atom to form distorted OBaLa3 tetrahedra that share corners with two equivalent O(2)BaLa3 tetrahedra, corners with two equivalent O(1)La4 tetrahedra,  an edgeedge with one O(2)BaLa3 tetrahedra, and  an edgeedge with one O(1)La4 tetrahedra. In the sixth O site, O(6) is bonded in a 5-coordinate geometry to one Ba(2), two equivalent Ba(1), and two equivalent La(1) atoms. In the seventh O site, O(7) is bonded in a distorted square co-planar geometry to two equivalent La(2) and two equivalent La(3) atoms.