Hydrogen-induced structural transition in single layer ReS ₂

Abstract By performing density functional theory-based calculations, we investigate how structural, electronic and mechanical properties of single layer ReS ₂ can be tuned upon hydrogenation of its surfaces. It is found that a stable, fully hydrogenated structure can be obtained by formation of strong S-H bonds. The optimized atomic structure of ReS ₂ H ₂ is considerably different than that of the monolayer ReS ₂ which has a distorted-1T phase. By performing phonon dispersion calculations, we also predict that the Re ₂ -dimerized 1T structure (called 1T { }^{{Re}₂} ) of the ReS ₂ H ₂ is dynamically stable. Unlike the bare ReS ₂ the 1T { }^{{Re}₂} –ReS ₂ H ₂ structure which is formed by breaking the Re ₄ clusters into separated Re ₂ dimers, is an indirect-gap semiconductor. Furthermore, mechanical properties of the 1T { }^{{Re}₂} phase in terms of elastic constants, in-plane stiffness ( C ) and Poisson ratio ( ν ) are investigated. It is found that full hydrogenation not only enhances the flexibility of the single layer ReS ₂ crystal but also increases anisotropy of the elastic constants.