First-principles calculations to investigate the effects of strain, electric field, and atom impurity on the electronic and magnetic properties of RuX2 (X = S, Se) nanosheets.

An experimental group (Angew. Chem., Int. Ed., 2021, 60, 7013-7017) has recently demonstrated the synthesis of two-dimensional (2D) RuSe2, which was shown to hold promise for hydrogen evolution due to enhanced HER performance. Herein, we studied the effects of external factors (strain, electric field, and atom adsorption) on the electronic and magnetic properties of T'-RuX2 (X = S, Se) sheets using DFT+U calculations. The estimated carrier effective mass results show that electrons are heavier than holes for T'-RuX2 sheets. The band-gap increases when the bi-axial strain increases from -5% to -1% (-5% to 1%) for T'-RuS2(RuSe2) and then decreases beyond these strain points. We found that the T'-RuX2 sheets exhibit a semiconductor to metal transition under a maximum electric field strength of 10 V nm-1. It is revealed that the magnetic moment can be achieved in T'-RuX2via adsorption of Li, Na, and K atoms. The findings show that the AFM state is the preferred magnetic ground state for T'-RuS2 with adsorbed Li and Na, whereas FM is the magnetic ground state for the remaining atm-RuX2 systems. Interestingly, an indirect to direct transition of the band-gap for T'-RuS2 with adsorbed K was found whereas the remaining T'-RuX2 with adsorbed Li, Na and K atoms showed either half-metallic or metallic electronic properties. Our results can extend the application of T'-RuX2 sheets in actuating, optoelectronic and spintronic fields.