BaEu2Mn2O7 crystallizes in the tetragonal I4/mmm space group. Ba(1) is bonded to four equivalent O(1) and eight equivalent O(3) 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 four equivalent O(3) and five equivalent O(2) atoms. Mn(1) is bonded to one O(1), one O(2), and four 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 0-6°. There are three inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Ba(1) and two equivalent Mn(1) atoms to form distorted OBa4Mn2 octahedra that share corners with two equivalent O(2)Eu5Mn octahedra, corners with four equivalent O(1)Ba4Mn2 octahedra, corners with sixteen equivalent O(3)Ba2Eu2Mn2 octahedra, edges with four equivalent O(1)Ba4Mn2 octahedra, and faces with eight equivalent O(3)Ba2Eu2Mn2 octahedra. The corner-sharing octahedral tilt angles range from 0-61°. In the second O site, O(2) is bonded to five equivalent Eu(1) and one Mn(1) atom to form distorted OEu5Mn octahedra that share  a cornercorner with one O(1)Ba4Mn2 octahedra, corners with four equivalent O(2)Eu5Mn octahedra, corners with twelve equivalent O(3)Ba2Eu2Mn2 octahedra, edges with eight equivalent O(2)Eu5Mn octahedra, and faces with four equivalent O(3)Ba2Eu2Mn2 octahedra. The corner-sharing octahedral tilt angles range from 0-52°. In the third O site, O(3) 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 four equivalent O(1)Ba4Mn2 octahedra, corners with six equivalent O(2)Eu5Mn octahedra, corners with eight equivalent O(3)Ba2Eu2Mn2 octahedra, edges with three equivalent O(3)Ba2Eu2Mn2 octahedra, faces with two equivalent O(1)Ba4Mn2 octahedra, faces with two equivalent O(2)Eu5Mn octahedra, and faces with four equivalent O(3)Ba2Eu2Mn2 octahedra. The corner-sharing octahedral tilt angles range from 0-61°.
BaEu2Mn2O7 crystallizes in the tetragonal I4/mmm space group. Ba(1) is bonded to four equivalent O(1) and eight equivalent O(3) 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 2.75 Å. All Ba(1)-O(3) bond lengths are 2.86 Å. Eu(1) is bonded in a 9-coordinate geometry to four equivalent O(3) and five equivalent O(2) atoms. All Eu(1)-O(3) bond lengths are 2.50 Å. There is one shorter (2.33 Å) and four longer (2.77 Å) Eu(1)-O(2) bond lengths. Mn(1) is bonded to one O(1), one O(2), and four 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 0-6°. The Mn(1)-O(1) bond length is 2.00 Å. The Mn(1)-O(2) bond length is 1.97 Å. All Mn(1)-O(3) bond lengths are 1.95 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Ba(1) and two equivalent Mn(1) atoms to form distorted OBa4Mn2 octahedra that share corners with two equivalent O(2)Eu5Mn octahedra, corners with four equivalent O(1)Ba4Mn2 octahedra, corners with sixteen equivalent O(3)Ba2Eu2Mn2 octahedra, edges with four equivalent O(1)Ba4Mn2 octahedra, and faces with eight equivalent O(3)Ba2Eu2Mn2 octahedra. The corner-sharing octahedral tilt angles range from 0-61°. In the second O site, O(2) is bonded to five equivalent Eu(1) and one Mn(1) atom to form distorted OEu5Mn octahedra that share  a cornercorner with one O(1)Ba4Mn2 octahedra, corners with four equivalent O(2)Eu5Mn octahedra, corners with twelve equivalent O(3)Ba2Eu2Mn2 octahedra, edges with eight equivalent O(2)Eu5Mn octahedra, and faces with four equivalent O(3)Ba2Eu2Mn2 octahedra. The corner-sharing octahedral tilt angles range from 0-52°. In the third O site, O(3) 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 four equivalent O(1)Ba4Mn2 octahedra, corners with six equivalent O(2)Eu5Mn octahedra, corners with eight equivalent O(3)Ba2Eu2Mn2 octahedra, edges with three equivalent O(3)Ba2Eu2Mn2 octahedra, faces with two equivalent O(1)Ba4Mn2 octahedra, faces with two equivalent O(2)Eu5Mn octahedra, and faces with four equivalent O(3)Ba2Eu2Mn2 octahedra. The corner-sharing octahedral tilt angles range from 0-61°.