A ReaxFF Force Field for 2D-WS₂ and Its Interaction with Sapphire

Abstract

We present a new ReaxFF reactive force field parameter set enabling large-scale computational synthesis and characterization of 2D-WS 2 , guided by an extensive quantum mechanical data set on both periodic and nonperiodic systems and validated against ADF-STEM experiments. This potential is designed to capture the most essential features of a WS 2 thin film, such as the 2H → 1T displacive phase transition, S-vacancy migration, and the energetics of various point and line defects, e.g., ripplocations in a WS 2 monolayer, thus enabling cost-effective simulations supporting phase and defect engineering of 2D-WS 2 . Additionally, the new ReaxFF description accurately describes the nucleation of a finite 1T phase on the 2H basal plane or edges, the rotational and translational grain boundaries, and the coupled effect of chemical potential and edge stability on the formation of S-and W-oriented grain boundaries. Because the epitaxial relationship between the substrate and 2D flakes plays a key role in controlling the growth direction and thus the crystal quality of a 2D film, this potential is trained further for the WS 2 /sapphire interface and therefore can provide valuable insights into the morphological changes observed in a coalesced WS 2 grown film on sapphire.

Recent Advances in 2D Material Theory, Synthesis, Properties, and Applications

“…Therefore, ReaxFF molecular dynamics (MD) simulations are highly effective in capturing detailed chemical events, reaction pathways, and product formation during gas-phase and gas/condensed phase simulations, for systems up to ≈10 6 atoms and for time scales not accessible to first-principles based techniques. This ReaxFF potential can simulate the nucleation and growth and intercalation of 2D materials, which involves both gas-phase and surface interactions, as a function of local chemical environment, helping in predicting effective growth protocol. − It features vdW interactions which particularly enables the simulation of multilayer vdW hetero- and homostructures. , Additionally, ReaxFF provides thermodynamic and kinetic insight into fundamental solid-phase phenomena observed in 2D materials such as atomic intercalation, grain boundary (GB), defect formation and diffusion, stress induced lattice distortions, morphological evolution of 2D domains as a function of local chemical environment during the growth. Also, ReaxFF differs from the so-called “first generation” reactive force fields such as Tersoff , and Brenner by applying a significantly longer-ranged bond-order relationship, which makes it possible to achieve accurate reaction kinetics.…”

Aqueous Stability of Metal–Organic Frameworks Using ReaxFF-Based Metadynamics Simulations

“…Due to the transferability of the ReaxFF parameters across different materials, ReaxFF is capable of modeling complex systems involving multiple phases in contact with one another. In particular, ReaxFF has been employed to simulate chemical reactions in various porous materials, e.g., graphene and graphene oxide, , tungsten disulfide (WS2), covalent–organic frameworks (COF), and metal–organic frameworks (MOFs). , In this work, we extend the ReaxFF force field for Zn/N/C/H/O, which has been applied to the study of ZIF-4, ZIF-62, and ZIF-77, , to other ZIFs and MOF-177 to simulate the water stability of various MOFs.…”

Patterning two‐dimensional semiconductors with thermal etching

“…To simulate the effects of existing holes or defects, perfect WS 2 and WS 2 bilayers with defects were modeled by a 20 × 20 × 1 supercell. Interactions between atoms were described by the ReaxFF force field 44 . The static electric interactions were described by Coulombs low by describing atoms as point charge particles.…”