ReaxFF MD simulations of graphitization of intact and O,N-doped amorphous carbon

Abstract

Understanding the impact of heteroatom doping on the structural evolution and graphitization of amorphous carbon is essential for the development of carbon-based anode materials. However, the underlying mechanisms remain poorly understood. In this study, molecular dynamics simulations employing reactive force field (ReaxFF) were systematically conducted to analyze the effects of temperature and oxygen (O) and nitrogen (N) heteroatom doping on the graphitization behavior of amorphous carbon. The simulations were performed within a temperature range of 2000 K to 6000 K, with doping ratios of 0.3%, 5%, and 10%. The analysis focused on factors such as sp²/sp³ hybrid carbon content, ring structure distribution, radial distribution function (RDF), and coordination number. The results demonstrated that the annealing temperatures range of 3500 K ~ 4000 K and the heteroatom doping ratios of 0.3% oxygen and 5% nitrogen can significantly promote the graphitization of amorphous carbon, and higher temperature disrupted the layered structure. Meanwhile, the higher presence of O/N in the system during the graphitization of amorphous carbon did not guarantee their rich doping. This study contributes to a molecular level of understanding of how heteroatom doping influences the graphitization behavior of amorphous carbon and provides insight into the proper control of temperature and the presence of doping sources in order to manipulate the morphology of the carbon materials.