Development of a Transferable ReaxFF Parameter Set for Carbon- And Silicon-Based Solid Systems

The performance of carbon- and silicon-based solid lubricants is strongly affected by the tribochemical reactions, especially with hydrogen and oxygen. Even though understanding and unveiling these reaction dynamics are important to improve performance, these insights are difficult to be obtained by experiments. Molecular dynamics simulation using the reactive force field (ReaxFF) provides a way to study the detailed reaction dynamics at the atomic scale; however, there is no available ReaxFF parameter set which is able to handle all of the desired properties and tribochemical reactions regarding carbon- and silicon-based materials. Here, we succeed to develop a ReaxFF parameter set for the H/C/N/O/Si system which covers most of the current research targets on the carbon/silicon-based solid lubricants using the simulated annealing algorithm to fit with the first-principles calculations. This developed parameter set is able to well describe the chemical reactions of carbon- and silicon-based solids with conventional environmental reactants such as water, H₂, and O₂ molecules. Furthermore, to validate the developed parameters, oxidation processes of SiC and Si₃N₄ in oxygen atmosphere are simulated and compared to the experimental results, showing good agreement. This well-trained ReaxFF parameter set is expected to benefit future studies on the tribochemical reactions and friction/wear mechanisms of carbon- and silicon-based lubricating systems.