Elucidating pore and surface features of soot nanoparticles using molecular dynamics simulations

Abstract

Understanding the surface and pore features of soot nanoparticles is important for predicting their behavior in combustion environments and atmospheric processes. Here, we present a novel computational framework combining reactive molecular dynamics simulations with detailed atomistic analysis to characterize the morphology of over 2000 incipient soot particles formed from acetylene pyrolysis at 1350–1800 K. The surface and pore features of these nanoparticles are explored directly using three-dimensional atomic surface mesh for the first time. The nanoparticles are found to have a highly irregular shape, with an average sphericity of 0.57 and a surface fractal dimension (D_S) of approximately 2.22, in excellent agreement with experimental data. The particles exhibit significant internal porosity (Φ≈0.22) dominated by micropores (≤2 nm). Micropores contribute to a very high specific surface area of approximately 2652. Three distinct pore types – tunnels, pockets, and isolated cavities – are identified in the incipient soot primary particles. The internal pore network is found to have a fractal dimension (D_VC) of approximately 2.15. Strong positive correlations between pore volume and surface area (R²≈0.70) are observed. The findings point to a complex and irregular external and internal structures of incipient soot nanoparticles and a complex pore network within them.