BaEu2Mn2O7 crystallizes in the orthorhombic Cmcm space group. Ba(1) is bonded to four equivalent O(1), four equivalent O(3), and four 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 Mn(1)O6 octahedra. Eu(1) is bonded in a 9-coordinate geometry to two equivalent O(1), two equivalent O(3), and five equivalent O(2) atoms. Mn(1) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(3) atoms to form MnO6 octahedra that share corners with five equivalent Mn(1)O6 octahedra and faces with four equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 2-13°. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ba(1), two equivalent Eu(1), and two equivalent Mn(1) atoms to form distorted OBa2Eu2Mn2 octahedra that share corners with two equivalent O(1)Ba2Eu2Mn2 octahedra, corners with four equivalent O(4)Ba4Mn2 octahedra,  an edgeedge with one O(1)Ba2Eu2Mn2 octahedra, faces with two equivalent O(1)Ba2Eu2Mn2 octahedra, and faces with two equivalent O(4)Ba4Mn2 octahedra. The corner-sharing octahedral tilt angles range from 59-60°. In the second O site, O(2) is bonded in a 6-coordinate geometry to five equivalent Eu(1) and one Mn(1) atom. In the third O site, O(3) is bonded in a 6-coordinate geometry to two equivalent Ba(1), two equivalent Eu(1), and two equivalent Mn(1) atoms. In the fourth O site, O(4) is bonded to four equivalent Ba(1) and two equivalent Mn(1) atoms to form distorted OBa4Mn2 octahedra that share corners with four equivalent O(4)Ba4Mn2 octahedra, corners with eight equivalent O(1)Ba2Eu2Mn2 octahedra, edges with four equivalent O(4)Ba4Mn2 octahedra, and faces with four equivalent O(1)Ba2Eu2Mn2 octahedra. The corner-sharing octahedral tilt angles range from 0-60°.
BaEu2Mn2O7 crystallizes in the orthorhombic Cmcm space group. Ba(1) is bonded to four equivalent O(1), four equivalent O(3), and four 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 Mn(1)O6 octahedra. All Ba(1)-O(1) bond lengths are 2.84 Å. All Ba(1)-O(3) bond lengths are 2.99 Å. There are a spread of Ba(1)-O(4) bond distances ranging from 2.74-2.91 Å. Eu(1) is bonded in a 9-coordinate geometry to two equivalent O(1), two equivalent O(3), and five equivalent O(2) atoms. Both Eu(1)-O(1) bond lengths are 2.53 Å. Both Eu(1)-O(3) bond lengths are 2.51 Å. There are a spread of Eu(1)-O(2) bond distances ranging from 2.35-3.13 Å. Mn(1) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(3) atoms to form MnO6 octahedra that share corners with five equivalent Mn(1)O6 octahedra and faces with four equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 2-13°. The Mn(1)-O(2) bond length is 2.05 Å. The Mn(1)-O(4) bond length is 2.00 Å. Both Mn(1)-O(1) bond lengths are 2.00 Å. Both Mn(1)-O(3) bond lengths are 2.00 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ba(1), two equivalent Eu(1), and two equivalent Mn(1) atoms to form distorted OBa2Eu2Mn2 octahedra that share corners with two equivalent O(1)Ba2Eu2Mn2 octahedra, corners with four equivalent O(4)Ba4Mn2 octahedra,  an edgeedge with one O(1)Ba2Eu2Mn2 octahedra, faces with two equivalent O(1)Ba2Eu2Mn2 octahedra, and faces with two equivalent O(4)Ba4Mn2 octahedra. The corner-sharing octahedral tilt angles range from 59-60°. In the second O site, O(2) is bonded in a 6-coordinate geometry to five equivalent Eu(1) and one Mn(1) atom. In the third O site, O(3) is bonded in a 6-coordinate geometry to two equivalent Ba(1), two equivalent Eu(1), and two equivalent Mn(1) atoms. In the fourth O site, O(4) is bonded to four equivalent Ba(1) and two equivalent Mn(1) atoms to form distorted OBa4Mn2 octahedra that share corners with four equivalent O(4)Ba4Mn2 octahedra, corners with eight equivalent O(1)Ba2Eu2Mn2 octahedra, edges with four equivalent O(4)Ba4Mn2 octahedra, and faces with four equivalent O(1)Ba2Eu2Mn2 octahedra. The corner-sharing octahedral tilt angles range from 0-60°.