Electron correlation and spin-orbit coupling effects in US3 and USe3.

A systematic density functional theory (DFT)+U study is conducted to investigate the electron correlation and spin-orbit coupling (SOC) effects in US(3) and USe(3). 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 US(3) and USe(3), but largely changes the energy band shapes around the Fermi energy. As a result, US(3) has a direct band gap while USe(3) has an indirect one. Our calculations predict that both US(3) and USe(3) 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 US(3) and USe(3).