Tl2SeO4 crystallizes in the orthorhombic P2_12_12_1 space group. There are two inequivalent Tl sites. In the first Tl site, Tl(1) is bonded in a 1-coordinate geometry to one O(2) atom. In the second Tl site, Tl(2) is bonded in a 3-coordinate geometry to one O(1), one O(2), and one O(3) atom. Se(1) is bonded in a tetrahedral geometry to one O(1), one O(2), one O(3), and one O(4) atom. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Tl(2) and one Se(1) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one Tl(1), one Tl(2), and one Se(1) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Tl(2) and one Se(1) atom. In the fourth O site, O(4) is bonded in a single-bond geometry to one Se(1) atom.
Tl2SeO4 crystallizes in the orthorhombic P2_12_12_1 space group. There are two inequivalent Tl sites. In the first Tl site, Tl(1) is bonded in a 1-coordinate geometry to one O(2) atom. The Tl(1)-O(2) bond length is 2.74 Å. In the second Tl site, Tl(2) is bonded in a 3-coordinate geometry to one O(1), one O(2), and one O(3) atom. The Tl(2)-O(1) bond length is 2.66 Å. The Tl(2)-O(2) bond length is 2.82 Å. The Tl(2)-O(3) bond length is 2.72 Å. Se(1) is bonded in a tetrahedral geometry to one O(1), one O(2), one O(3), and one O(4) atom. The Se(1)-O(1) bond length is 1.66 Å. The Se(1)-O(2) bond length is 1.66 Å. The Se(1)-O(3) bond length is 1.67 Å. The Se(1)-O(4) bond length is 1.66 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Tl(2) and one Se(1) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one Tl(1), one Tl(2), and one Se(1) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Tl(2) and one Se(1) atom. In the fourth O site, O(4) is bonded in a single-bond geometry to one Se(1) atom.