Mg2Gd2O5 crystallizes in the tetragonal P4/mmm space group. Mg(1) is bonded to one O(2) and four equivalent O(1) atoms to form MgO5 square pyramids that share corners with five equivalent Mg(1)O5 square pyramids and faces with four equivalent Gd(2)O12 cuboctahedra. There are two inequivalent Gd sites. In the first Gd site, Gd(1) is bonded in a body-centered cubic geometry to eight equivalent O(1) atoms. In the second Gd site, Gd(2) is bonded to four equivalent O(2) and eight equivalent O(1) atoms to form GdO12 cuboctahedra that share corners with four equivalent Gd(2)O12 cuboctahedra, faces with four equivalent Gd(2)O12 cuboctahedra, and faces with eight equivalent Mg(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 Mg(1), two equivalent Gd(1), and two equivalent Gd(2) atoms. In the second O site, O(2) is bonded in a distorted linear geometry to two equivalent Mg(1) and four equivalent Gd(2) atoms.
Mg2Gd2O5 crystallizes in the tetragonal P4/mmm space group. Mg(1) is bonded to one O(2) and four equivalent O(1) atoms to form MgO5 square pyramids that share corners with five equivalent Mg(1)O5 square pyramids and faces with four equivalent Gd(2)O12 cuboctahedra. The Mg(1)-O(2) bond length is 1.90 Å. All Mg(1)-O(1) bond lengths are 1.97 Å. There are two inequivalent Gd sites. In the first Gd site, Gd(1) is bonded in a body-centered cubic geometry to eight equivalent O(1) atoms. All Gd(1)-O(1) bond lengths are 2.44 Å. In the second Gd site, Gd(2) is bonded to four equivalent O(2) and eight equivalent O(1) atoms to form GdO12 cuboctahedra that share corners with four equivalent Gd(2)O12 cuboctahedra, faces with four equivalent Gd(2)O12 cuboctahedra, and faces with eight equivalent Mg(1)O5 square pyramids. All Gd(2)-O(2) bond lengths are 2.76 Å. All Gd(2)-O(1) bond lengths are 2.93 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to two equivalent Mg(1), two equivalent Gd(1), and two equivalent Gd(2) atoms. In the second O site, O(2) is bonded in a distorted linear geometry to two equivalent Mg(1) and four equivalent Gd(2) atoms.