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Reactive Molecular Dynamics of Nucleation of incipient soot particles from PAHs


Nucleation of incipient soot particles from polycyclic aromatic hydrocarbons (PAHs) is a long-standing, unsolved problem.The multiscale and multi-physics presents a formidable challenge to any experimental technique, numerical simulation or theory. Recently, researchers at CCE, in collaboration with colleagues in The Pennsylvania State University, USA and University College London, UK have developed state-of-the-artReaxFF molecular dynamics simulations to investigate the dynamic processes of soot inception from a variety of PAHs. The aims are toreveal the mechanisms of PAH dimerization and nascent soot inception, andidentify the key influencing parameters.Three distinctive regimes of nucleation are found with increasing temperature. At low temperatures,soot particles are comprised of PAHs in stacks through physical nucleation;at moderate temperatures, PAHs cannot nucleate to soot particles due to weak physical and chemical driving forces; At high temperatures, soot particles instacked structures with ‘carbon bridge’ and fullerene-like structures are formed via chemical nucleation[1]. In addition, a model has been constructed to predict PAH dimerization with any PAH characteristics, concentration or temperature[2].

Snapshots of key stages of PAH fragmentation and soot inception from circumcorenene monomers in path A and path B [1]. Cyan and white spheres represent carbon and hydrogen atoms, respectively. Important carbon and hydrogen atoms are highlighted by orange and yellow.

[1] Mao Q, van Duin ACT, Luo KH. Formation of incipient soot particles from polycyclic aromatic hydrocarbons : A ReaxFF molecular dynamics study. Carbon 2017;121:380–8.

[2] Mao Q, Ren Y, Luo KH, van Duin ACT. Dynamics and Kinetics of Reversible Homo-molecular Dimerization of Polycyclic Aromatic Hydrocarbons. J Chem Phys 2017;147:244305.

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