Many methods had been proposed to process the β-silicon carbide, and the thermal oxidation-assisted polishing was considered as an efficient technique. The critical procedure in the thermal oxidation was absorption and diffusion process of the oxygen in the β-silicon carbide, especially in the asymmetric face. Therefore, the absorption and diffusion of the oxygen in the asymmetric face of the β-silicon carbide by born-oppenheimer molecular dynamics were studied. It could be observed from absorption and dissociation process of the O atom with the cell size that absorption of the oxygen in upper Si surface was fast, which was realized when the distance was smaller than 3Å. It could be observed from absorption and dissociation process of O atom with supercell size that absorption and oxidation for the Si surface was quickly, and steady oxide layer with silica was formed. On the contrary, absorption range of the C surface was smaller than that of the Si surface, and the surface recombination was more significant for the C surface. It could be calculated that the bond length of Si-O in the oxide layer was in the 1.65-1.77Å. The research products obtained in this study were propitious to reveal the mechanism in the thermal oxidation of asymmetric face of the β-silicon carbide with oxygen under ultra-high temperature.

Born-oppenheimer molecular dynamics is an effective method to analyze machining mechanism of some advanced manufacturing techniques, which was introduced to investigate the absorption of OH radical on different β-SiC surfaces in the reaction-sintered silicon carbide. During the plasma oxidation-assisted polishing of reaction-sintered silicon carbide, absorption of the OH radical in the SiC grains was one of the most important process, because hardness of the SiC grains was obviously higher than that of the Si grains. the born-oppenheimer molecular dynamics model to investigate the absorption process of the OH radical was constructed firstly, which could form the foundation for the further simulation and analysis. Secondly, absorption of the OH radicals in the Si-face, those in the C-face, and those in the asymmetric face were investigated successively, which included the absorption process and the oxide product. Finally, comparisons of the absorption of the OH radical in the different faces were conducted, which aimed to further understand the plasma oxidation-assisted polishing of reaction-sintered silicon carbide. Simulation result of born-oppenheimer molecular dynamics was propitious to promote the machining level of reaction-sintered silicon carbide and promote its practical application.