Generation of amorphous carbon models using liquid quench method: A reactive molecular dynamics study

Abstract Using molecular dynamics simulations with a reactive force field ( ReaxFF) , we generate models of amorphous carbon ( a-C ) at a wide range of densities (from 0.5 g/cc to 3.2 g/cc) via the ‘liquid-quench’ method. A systematic study is undertaken to characterize the structural features of the resulting a-C models as a function of carbon density and liquid quench simulation conditions: quench rate, type of quench (linear or exponential), annealing time and size of simulation box. The structural features of the models are investigated in terms of pair correlation functions, bond-angles, pore-size distribution and carbon hybridization content. Further, the influence of quench conditions on hybridization/graphitization is investigated for different stages of the simulation. We observe that the structural features of generated a-C models agree well with similar models reported in literature. We find that in the low-density regime, size effects play an important role in determining the pore size distribution and the structures are predominantly anisotropic. Whereas, at densities larger than 1.0 g/cc, the structures are space-filling and differences exist only in terms of carbon hybridization. The rate of structural evolution (pore size and hybridization) during the quench process is observed to be dependent on the quench type, rate and the annealing time.