The inception mechanism of PAH radicals is investigated with our NN model. We find that the physical interaction enhances chemical nucleation, and such enhancement is observed for clusters of π-and σradicals, which is distinct from the dimer. It is also found that PAH radicals can produce soot particles at flame temperatures (1500 K), and the particle morphology is strongly affected by PAH size. For PAH radicals of 374 Da, a core-shell soot particle with a disordered core and outer shell of stacked PAHs is observed, and similar structures are also observed in HRTEM experiments. These results suggest that physically stabilized soot inception of PAH radicals larger than 200 Da is a potential nucleation mechanism.