Abstract
A new quaternary uranium (V) selenide, Ba 8 PdU 2 Se 12 (Se 2) 2 , has been synthesized by reaction of elements at 1173 K. A single-crystal X-ray diffraction study shows that the compound crystallizes in a new structure type with two formula units in space group D 1 2 2 h −Pnnm of the orthorhombic crystal system with cell constants of a = 9.490(1), b = 12.240(2), and c = 13.780(3) Å. Its crystal structure consists of [PdU 2 Se 12 12− ] units where U atoms are coordinated to six Se atoms in octahedral geometry and Pd atoms are coordinated to four Se atoms in square-planar geometry. These [PdU 2 Se 12 12− ] units are separated by Ba to result in a salt-like crystal structure. This compound also contains Se 2 2− dimers that are part of Ba coordination polyhedra. The formula charge balances as (Ba 2+) 8 (Pd 2+)(U 5+) 2 (Se 2−) 12 (Se 2 2−) 2. Theoretical calculations predict antiferromagnetic semiconducting behavior for this compound with a band gap of 1.6 eV. Temperature-dependent four-probe resistivity measurements on single crystal confirm semiconducting nature with an activation energy of 0.18(1) eV.