Electronic structure, defect properties, and hydrogen storage capacity of 2H-WS2: A first-principles study

Abstract

First-principles calculations based on density functional theory (DFT) have been performed for layered 2H tungsten disulphide (WS2) with the aim to find its possible applications in opto-electronic and hydrogen storage devices. To study opto-electronic features of WS2, we solve the Bethe-Salpeter-Equation (BSE) on top of the standard self consistent GW quasiparticle (QP) calculations. These calculations capture the excitonic effects which originate near the edge of conduction band, shows good agreement with the available measured data. The suitability of WS2 as a prospective material for hydrogen storage were predicted by using the Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional. We have explored the effect of interstitial hydrogen and H2 molecules insertion on the structural stability of WS2 in detail. The hydrogen atom charge states dependent stability was studied in the context of formation energy. Our calculations suggest that interstitial hydrogen can act as a deep donor whereas H2 molecule exhibits more stability. The diffusion energy of H2 molecule from one hollow site to the nearest in-plane hollow site has been calculated using transition state theory. Finally, ab−initio molecular-dynamics (AIMD) calculations are carried out for WS2 consisting of 16H2 molecules that ensures its structural stability at temperatures 300, 500, and 1000 K. Present predictions show that this material may be utilize for hydrogen storage due to expected high hydrogen density.