Eu2Al2O5 crystallizes in the tetragonal P4/mmm space group. There are two inequivalent Eu sites. In the first Eu site, Eu(1) is bonded in a body-centered cubic geometry to eight equivalent O(1) atoms. In the second Eu site, Eu(2) is bonded to four equivalent O(2) and eight equivalent O(1) atoms to form EuO12 cuboctahedra that share corners with four equivalent Eu(2)O12 cuboctahedra, faces with four equivalent Eu(2)O12 cuboctahedra, and faces with eight equivalent Al(1)O5 square pyramids. Al(1) is bonded to one O(2) and four equivalent O(1) atoms to form AlO5 square pyramids that share corners with five equivalent Al(1)O5 square pyramids and faces with four equivalent Eu(2)O12 cuboctahedra. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to two equivalent Eu(1), two equivalent Eu(2), and two equivalent Al(1) atoms. In the second O site, O(2) is bonded in a distorted linear geometry to four equivalent Eu(2) and two equivalent Al(1) atoms.
Eu2Al2O5 crystallizes in the tetragonal P4/mmm space group. There are two inequivalent Eu sites. In the first Eu site, Eu(1) is bonded in a body-centered cubic geometry to eight equivalent O(1) atoms. All Eu(1)-O(1) bond lengths are 2.55 Å. In the second Eu site, Eu(2) is bonded to four equivalent O(2) and eight equivalent O(1) atoms to form EuO12 cuboctahedra that share corners with four equivalent Eu(2)O12 cuboctahedra, faces with four equivalent Eu(2)O12 cuboctahedra, and faces with eight equivalent Al(1)O5 square pyramids. All Eu(2)-O(2) bond lengths are 2.67 Å. All Eu(2)-O(1) bond lengths are 2.81 Å. Al(1) is bonded to one O(2) and four equivalent O(1) atoms to form AlO5 square pyramids that share corners with five equivalent Al(1)O5 square pyramids and faces with four equivalent Eu(2)O12 cuboctahedra. The Al(1)-O(2) bond length is 1.82 Å. All Al(1)-O(1) bond lengths are 1.91 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to two equivalent Eu(1), two equivalent Eu(2), and two equivalent Al(1) atoms. In the second O site, O(2) is bonded in a distorted linear geometry to four equivalent Eu(2) and two equivalent Al(1) atoms.