Mao Qian, Hou Dingyu, Luo Kai H, You Xiaoqing
Center for Combustion Energy, Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Energy and Power Engineering , Tsinghua University , Beijing 100084 , China.
Department of Mechanical Engineering , University College London , Torrington Place , London WC1E 7JE , U.K.
J Phys Chem A. 2018 Nov 8;122(44):8701-8708. doi: 10.1021/acs.jpca.8b07102. Epub 2018 Oct 30.
This work presents a dynamic and kinetic study on the dimerization of polycyclic aromatic hydrocarbon (PAH) molecules and radicals under flame conditions using reactive force field (ReaxFF) molecular dynamics (MD) simulations. The accuracy of the ReaxFF force field is evaluated through comparing with quantum chemistry (QC) calculations of the barrier heights and species concentrations of PAHs reacting with H and OH radicals. A series of homobinary collisions between PAH molecules/radicals are performed to reveal the influence of temperature, molecular size, PAH composition, and the number of radical sites on the dynamics and kinetics of PAH dimerization. Instead of directly forming the strong covalent bonds, the majority of the binary collisions between PAH radicals are bound with weak intermolecular interactions. Effects of oxygen on PAH radical dimerization are also investigated, which indicates that the oxygenated PAH radicals are less likely to contribute to soot nucleation. In addition, the temperature, PAH characteristic, and radical site dependent collision efficiency for PAH radical-radical combinations is extracted from this study.
本研究利用反应力场（ReaxFF）分子动力学（MD）模拟，对火焰条件下多环芳烃（PAH）分子和自由基的二聚反应进行了动力学和动态学研究。通过与PAH与H和OH自由基反应的势垒高度和物种浓度的量子化学（QC）计算结果进行比较，评估了ReaxFF力场的准确性。进行了一系列PAH分子/自由基之间的同二元碰撞，以揭示温度、分子大小、PAH组成和自由基位点数量对PAH二聚反应动力学和动态学的影响。PAH自由基之间的大多数二元碰撞并非直接形成强共价键，而是通过弱分子间相互作用结合。还研究了氧对PAH自由基二聚反应的影响，结果表明氧化的PAH自由基对烟灰成核的贡献较小。此外，本研究还提取了PAH自由基-自由基组合的温度、PAH特性和自由基位点相关的碰撞效率。
