Coarse-grained chemical reaction model

We have developed a methodology for including effects of chemical reactions in coarse-grained computer simulations such as those that use the united atom approximation. The new coarse-grained chemical reaction model (CGCRM) adopts the philosophy of kinetic Monte Carlo approaches and includes a probabilistic element to predicting when reactions occur, thus obviating the need for a chemically correct interaction potential. The CGCRM uses known chemical reactions along with their probabilities and exothermicities for a specific material in order to assess the effect of chemical reactions on a physical process of interest. The reaction event in the simulation is implemented by removing the reactant molecules from the simulation and replacing them with product molecules. The position of the product molecules is carefully adjusted to make sure that the total energy change of the system corresponds to the reaction exothermicity. The CGCR model has been applied to simulations of laser irradiation of chlorobenzene at fluences such that there is ablation or massive removal of material. Two simulations, one for photothermal ablation and one for photochemical ablation, are compared to each other and to experimental data. In the photothermal simulation, all the laser energy goes into heat. In the photochemical simulation, the photon cleaves the C-Cl bond creating two radicals that can undergo subsequent abstraction and radical-radical recombination reactions.