Structure, Thermodynamics, and Raman Spectroscopy of Rhenium-Doped Bulk MoS2 from First Principles

Doping MoS2 with Re is known to alter the electronic, structural, and tribological properties. Re-doped MoS2 has been previously mainly studied in the monolayer or few-layer form but can also be relevant for applications in the many-layer or bulk form. In this work, we use density functional theory to explore the structure, phase stability, and Raman spectrum of bulk Re-doped MoS2. We consider the possibility of the Re dopant existing at different locations and provide experimentally distinguishable characteristics of the most likely sites: Mo substitution and tetrahedral (t-) intercalation. We demonstrate and benchmark a general approach to calculate Raman spectra of doped materials with metallic densities of states by using atomic Raman tensors from the pristine material. Upon applying this method to the metallic Re-doped structures, we find characteristic shifts in the Raman-active peaks depending on the Re dopant position: red shifts in both A1g and E2g1 peaks in the t-intercalated case versus a red shift for A1g and a blue shift (sometimes accompanied by a smaller red-shifted peak) for E2g1 peaks in the Mo-substituted case, which can be used to identify the dopant sites in experimental samples. We analyze the interactions giving rise to these shifts.