The initial chemical reactants of part A were selected based on the existing knowledge from both quantum chemistry and experimental studies . All six reactants shown in Fig. are mixed with equal ratio (200 molecules per species) and the density of the system is 0.25 g/cm 3 in order to speed up the process. MD simulations under the NVT ensemble were performed with the time step of 0.1fs in a cubic box with the side length of 50.81Å. Berendsen thermostat was used to control the temperature at 1750K. A total of 1ns reactive MD simulations (100ps per trajectory for a total of 10 trajectories). Fig. shows reaction paths that produce monocyclic (benzene and phenyl) and bicyclic (naphthalene and indene) PAHs predicted by the simulations. Reaction path 1 shows the formation of the benzene with butadienyl and acetylene being the reactants. The whole process took about 50ps. In fact, this reaction path has been confirmed by time-of-flight mass spectrometry previously. . Paths 2 and 3 are two reaction paths that generate the phenyl radical. Path 4 is the so-called C-C bond scission pathway (48) of forming a naphthalene from two five-membered rings (C5H5 and C5H4), which took about 90ps to complete. Of interest is one new reaction path discovered in the current simulation (path 5). In this path, a carbon chain was firstly formed and then converted to an indene by the closure and the subsequently abstraction of a hydrogen atom.