• JoAS-159-205866-

On the reactive coagulation of incipient soot nanoparticles

Authors: Dingyu Hou, Laura Pascazio, Jacob W. Martin, Yuxin Zhou, Markus Kraft*, and Xiaoqing You

Reference: Journal of Aerosol Science 159, 205866, (2022)

  • 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.

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