Development and Application of a ReaxFF Reactive Force Field for Ni-Doped MoS₂

The properties of MoS₂ can be tuned or optimized through doping. In particular, Ni doping has been shown to improve the performance of MoS₂ for various applications, including catalysis and tribology. To enable investigation of Ni-doped MoS₂ with reactive molecular dynamics simulations, we developed a new ReaxFF force field to describe this material. The force field parameters were optimized to match a large set of density functional theory (DFT) calculations of 2H-MoS₂ doped with Ni, at four different sites (Mo-substituted, S-substituted, octahedral intercalation, and tetrahedral intercalation), under uniaxial, biaxial, triaxial, and shear strain. The force field was evaluated by comparing ReaxFF- and DFT-relaxed structural parameters, the tetrahedral/octahedral energy difference in doped 2H, energies of doped 1H and 1T monolayers, and doped 2H structures with vacancies. We demonstrated the application of the force field with reactive simulations of sputtering deposition and annealing of Ni-doped MoS₂ films. Results show that the developed force field can successfully model the phase transition of Ni-doped MoS₂ from amorphous to crystalline. The newly developed force field can be used in subsequent investigations to study the properties and behavior of Ni-doped MoS₂ using reactive molecular dynamics simulations.