TlBeAsO4 crystallizes in the orthorhombic Pna2_1 space group. Be(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form BeO4 tetrahedra that share corners with four equivalent As(1)O4 tetrahedra. Tl(1) is bonded in a 2-coordinate geometry to one O(1) and one O(4) atom. As(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form AsO4 tetrahedra that share corners with four equivalent Be(1)O4 tetrahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Be(1), one Tl(1), and one As(1) atom. In the second O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Be(1) and one As(1) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Be(1) and one As(1) atom. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to one Be(1), one Tl(1), and one As(1) atom.
TlBeAsO4 crystallizes in the orthorhombic Pna2_1 space group. Be(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form BeO4 tetrahedra that share corners with four equivalent As(1)O4 tetrahedra. The Be(1)-O(1) bond length is 1.66 Å. The Be(1)-O(2) bond length is 1.63 Å. The Be(1)-O(3) bond length is 1.65 Å. The Be(1)-O(4) bond length is 1.64 Å. Tl(1) is bonded in a 2-coordinate geometry to one O(1) and one O(4) atom. The Tl(1)-O(1) bond length is 2.66 Å. The Tl(1)-O(4) bond length is 2.69 Å. As(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form AsO4 tetrahedra that share corners with four equivalent Be(1)O4 tetrahedra. The As(1)-O(1) bond length is 1.71 Å. The As(1)-O(2) bond length is 1.72 Å. The As(1)-O(3) bond length is 1.71 Å. The As(1)-O(4) bond length is 1.73 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Be(1), one Tl(1), and one As(1) atom. In the second O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Be(1) and one As(1) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Be(1) and one As(1) atom. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to one Be(1), one Tl(1), and one As(1) atom.