On the reactive coagulation of incipient soot nanoparticles
- Reactive MD simulations have been performed to study the coagulation efficiency η of incipient soot nanoparticles at T ≥ 1500 K.
- Head-on coagulation efficiency η has been determined based on hundreds of MD simulated trajectories.
- σ-radicals on soot surface have been found to mildly enhance η by ~10% through C-C bond formation between the nanoclusters.
In this work, we studied the coagulation process of two PAH clusters with diameter ~2 nm using reactive molecular dynamics (MD) simulations. To describe the coagulation process quantitatively, the distance between the center of mass (COM) of the two PAH clusters, as well as the inter-cluster potential energy and kinetic energy of the COM of the clusters were calculated. Head-on coagulation efficiencies (η) of two PAH clusters at typical flame temperatures where soot inception is most likely to occur, i.e., 1500 K-2000 K, were determined based on hundreds of MD simulated trajectories. Our simulation results showed that η decreases with increasing temperature, which is mainly due to the increased kinetic energy of atoms within the PAH clusters at higher temperature. In addition, introduction of surface σ-radical site fraction in the range of 0.01 to 0.1 can only moderately improve η by ~10% by forming carbon–carbon bonds between the two coagulating clusters, which suggests η of incipient soot nanoparticles with surface σ-radicals in high temperature flame regions is very low even if with reactive coagulation taken into consideration.
- Access the article at the publisher: DOI: 10.1016/j.jaerosci.2021.105866
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