Ba2YTlSn2O7 crystallizes in the tetragonal P4/mmm space group. Ba(1) is bonded in a 5-coordinate geometry to one O(3) and four equivalent O(1) atoms. Y(1) is bonded in a body-centered cubic geometry to eight equivalent O(2) atoms. Tl(1) is bonded in a linear geometry to two equivalent O(1) atoms. Sn(1) is bonded to one O(1) and four equivalent O(2) atoms to form corner-sharing SnO5 square pyramids. There are three inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Ba(1), one Tl(1), and one Sn(1) atom to form a mixture of distorted corner and edge-sharing OBa4TlSn octahedra. The corner-sharing octahedral tilt angles range from 0-12°. In the second O site, O(2) is bonded in a distorted see-saw-like geometry to two equivalent Y(1) and two equivalent Sn(1) atoms. In the third O site, O(3) is bonded in a linear geometry to two equivalent Ba(1) atoms.
Ba2YTlSn2O7 crystallizes in the tetragonal P4/mmm space group. Ba(1) is bonded in a 5-coordinate geometry to one O(3) and four equivalent O(1) atoms. The Ba(1)-O(3) bond length is 2.45 Å. All Ba(1)-O(1) bond lengths are 3.01 Å. Y(1) is bonded in a body-centered cubic geometry to eight equivalent O(2) atoms. All Y(1)-O(2) bond lengths are 2.55 Å. Tl(1) is bonded in a linear geometry to two equivalent O(1) atoms. Both Tl(1)-O(1) bond lengths are 2.76 Å. Sn(1) is bonded to one O(1) and four equivalent O(2) atoms to form corner-sharing SnO5 square pyramids. The Sn(1)-O(1) bond length is 2.05 Å. All Sn(1)-O(2) bond lengths are 2.14 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Ba(1), one Tl(1), and one Sn(1) atom to form a mixture of distorted corner and edge-sharing OBa4TlSn octahedra. The corner-sharing octahedral tilt angles range from 0-12°. In the second O site, O(2) is bonded in a distorted see-saw-like geometry to two equivalent Y(1) and two equivalent Sn(1) atoms. In the third O site, O(3) is bonded in a linear geometry to two equivalent Ba(1) atoms.