  A systematic density functional theory (DFT)+U study is conducted to
investigate the electron correlation and spin-orbit coupling (SOC) effects in
US3 and USe3. Our calculations reveal that inclusion of the U term is essential
to get energy band gaps for them, indicating the strong correlation effects for
uranium 5f electrons. Taking consideration of the SOC effect results in small
reduction on the electronic band gaps of US3 and USe3, but largely changes the
energy band shapes around the Fermi energy. As a result, US3 has a direct band
gap while USe3 has an indirect one. Our calculations predict that both US3 and
USe3 are antiferromagnetic insulators, in agreement with corresponding
experimental results. Based on our DFT+U calculations, we systematically
present the ground-state electronic, mechanical, and Raman properties for US3
and USe3.
