THEORETICAL STUDY ON STRUCTURAL AND MECHANICAL PROPERTIES OF SINGLE LANTHANUM AND SAMARIUM ATOMS DOPED NBX2 (X= S, SE) MONOLAYER

Abstract

Pure NbX₂ (X=S, Se) exhibits remarkable mechanical and electronic properties; many electromechanical applications may come from chemically doping it with heteroatoms. The goal is to tune the atomic lattice and, in turn, modulate the structural properties of NbX₂ (X=S, Se)  – that may also affect the mechanical responses of the NbX₂ (X=S, Se)  monolayer. Particularly essential for both practical applications and fundamental interests is to characterize the effect of chemical doping on the mechanical properties of NbX₂ (X=S, Se). Here we report NbX₂ (X=S, Se)  can maintain a large fraction of its pure strength and stiffness after substituting RE (La and Sm) for Nb atoms. Counter-intuitively, RE doping can ameliorate the brittle nature of the original lattice by deflecting the cracks and enabling damage-tolerant behaviors. We further offer a direct mapping between the Raman spectra and the measured mechanical performances that can show the relationship between doping structure and mechanical properties of NbX₂ (X=S, Se) . This work offers important implications for the rational design of NbX₂ (X=S, Se) -based systems that require chemical modifications and also utilize the mechanics of NbX₂ (X=S, Se).