A fully integrated Kinetic Monte Carlo/Molecular Dynamics approach for the simulation of soot precursor growth

The emphasis in this paper is on presenting a new methodology, together with some illustrative applications, for the study of polycyclic aromatic hydrocarbon polymerization leading to soot, widely recognized as a very important and challenging combustion problem. The new code, named fully integrated Kinetic Monte Carlo/Molecular Dynamics (KMC/MD), places the two simulation procedures on an equal footing and involves alternating between KMC and MD steps during the simulation. The KMC/MD simulations are used in conjunction with high-level quantum chemical calculations. With traditional kinetic rates and dealing with the growth of particles, it is often necessary to perform a lumping procedure in which much atomic-scale information is lost. Our KMC/MD approach is designed to preserve atomic-scale structure: a single particle evolves in time with real three-dimensional structure (bonds, bond angles, dihedral angles). In this paper, the methodology is illustrated by a sample simulation of high molecular mass compound growth in an environment (T, H, H2, naphthalene, and acenaphthylene concentrations) of a low-pressure laminar premixed benzene/oxygen/argon flame with an equivalence ratio of 1.8. The use of this approach enables the investigation of the physical (e.g., porosity, density, sphericity) as well as chemical (e.g., H/C, aromatic moieties, number of cross-links) properties.