| First-principles based atomic-level simulations can be used to develop realistic models of gas-surface chemistry and gas-phase chemistry, or to inform or validate the existing ones. A mechanism-based finite rate catalytic wall boundary condition for use in reacting flow simulation is presented. The input parameters of this model are the reaction rates kr of each elementary one-step process, including molecular and atomic adsorption. Therefore, ReaxFF Molecular Dynamics (MD) simulations of O2 adsorption on a platinum (111) surface are presented and compared to the existing experimental and computational results in the literature. Furthermore, the surface state of a catalyst strongly affects its performance. Grand Canonical Monte Carlo simulations are used to study oxygen coverage on Pt(111) exposed to molecular oxygen at certain pressure and temperature conditions. The results compare well with the available experimental and first-principles data. Finally, full-scale MD simulations of normal shock waves in dilute and rarefied argon are presented, and are critically compared to similar Direct Simulation Monte Carlo (DSMC) calculations as well as experiments. For very dilute gases, a novel Event-Driven/Time-Driven algorithm is developed to speed up the MD simulation of rarefied gases using realistic spherically symmetric soft potentials. This technique could pave the way for the application of much more refined and expensive interatomic potentials (potentially ab initio) to MD simulations of nonequilibrium flow features in rarefied gases, involving vibrational excitation and chemical reactivity. |
