Molecular Dynamics Simulations of Gas Molecule Bombardments onto the Graphite Surface
Molecular Dynamics Simulations Gas Molecule Bombardments Graphite Surface;
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In order to understand the fundamental essence in the erosion of graphite by hot gas molecules, in this study we investigate the mechanical properties of a single layer of graphite (e.g. graphene) at high temperatures. The stress-strain curve describes that the stiffness of the graphene decreases with increase in temperature. The strength of graphene at 2400 K is 60% less than the strength of graphene at 300 K. The high-temperature behavior of graphene and the bombardment of H2 CO2 and H2O on graphene are simulated using molecular dynamics (MD) simulations. This work is also concentrated to determine the sublimation temperature of graphene for smaller and smaller heating rates. The bond breaking and bond forming phenomenon can be clearly observed with Reactive Empirical Bond Order (REBO) potential. But in this work a modified cut-off function (Rmin = Rmax = 2.0 Å) of the REBO potential is used. The bombardment of gas molecules is carried out for different temperatures ranging between 300 K and 3000 K, by keeping the kinetic energy of incident particle constant. Until 2400 K, both H2O and CO2 molecules are reflected back from the surface. However, at a critical temperature i.e., 2700 K and beyond, the bombardment of gas molecules begins to break the C-C bond in the graphene. As the temperature increases, the graphene is destroyed quickly. In order to obtain an equilibrated structure of graphene above 3000 K, the cutoff parameter is adjusted to Rmin = 1.95 Å and Rmax = 2.0 Å. And the bombardment simulations are performed at near sublimation temperatures like 5000 K, 5200 K, 5400 K and 5500 K for H2, CO2 and H2O using the REBO potential with the newly modified cut-off distance. The gas molecules are bombarded as a single molecule and as a group containing 16 molecules and their performance is analysed. This study shows that the graphene can be a strongest material even at very high temperature.