Be2Tb2O5 crystallizes in the tetragonal P4/mmm space group. Be(1) is bonded to one O(2) and four equivalent O(1) atoms to form distorted BeO5 square pyramids that share corners with five equivalent Be(1)O5 square pyramids and faces with four equivalent Tb(2)O12 cuboctahedra. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded in a body-centered cubic geometry to eight equivalent O(1) atoms. In the second Tb site, Tb(2) is bonded to four equivalent O(2) and eight equivalent O(1) atoms to form TbO12 cuboctahedra that share corners with four equivalent Tb(2)O12 cuboctahedra, faces with four equivalent Tb(2)O12 cuboctahedra, and faces with eight equivalent Be(1)O5 square pyramids. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to two equivalent Be(1), two equivalent Tb(1), and two equivalent Tb(2) atoms. In the second O site, O(2) is bonded in a linear geometry to two equivalent Be(1) and four equivalent Tb(2) atoms.
Be2Tb2O5 crystallizes in the tetragonal P4/mmm space group. Be(1) is bonded to one O(2) and four equivalent O(1) atoms to form distorted BeO5 square pyramids that share corners with five equivalent Be(1)O5 square pyramids and faces with four equivalent Tb(2)O12 cuboctahedra. The Be(1)-O(2) bond length is 1.58 Å. All Be(1)-O(1) bond lengths are 1.83 Å. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded in a body-centered cubic geometry to eight equivalent O(1) atoms. All Tb(1)-O(1) bond lengths are 2.35 Å. In the second Tb site, Tb(2) is bonded to four equivalent O(2) and eight equivalent O(1) atoms to form TbO12 cuboctahedra that share corners with four equivalent Tb(2)O12 cuboctahedra, faces with four equivalent Tb(2)O12 cuboctahedra, and faces with eight equivalent Be(1)O5 square pyramids. All Tb(2)-O(2) bond lengths are 2.56 Å. All Tb(2)-O(1) bond lengths are 2.62 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to two equivalent Be(1), two equivalent Tb(1), and two equivalent Tb(2) atoms. In the second O site, O(2) is bonded in a linear geometry to two equivalent Be(1) and four equivalent Tb(2) atoms.