ReaxFF-molecular dynamics simulations of non-oxidative and non-catalyzed thermal decomposition of methane at high temperatures

Abstract

Incomplete combustion of carbon based materials produces fine, carbon rich particles. Controlled manufacturing of very pure carbon nanoparticles (Carbon Black) can be achieved by, for example, thermal decomposition of gaseous precursors like acetylene and methane. Molecular dynamics simulations of hydrocarbon growth after non-catalyzed thermal decomposition of methane were carried out in order to understand the impact of the thermal decomposition reaction of methane on the formation of large hydrocarbon molecules. A reactive force field (ReaxFF) was employed to model the interactions of the involved hydrocarbons. The decomposition of 150 methane molecules was investigated at different system temperatures and system densities. Formation of molecular hydrogen, a broad range of hydrocarbons and carbon dimers from decomposed methane was observed above a temperature of 2500 K. The basic reactions are in agreement with existing models of thermal decomposition of methane. An increasing variety of hydrocarbons is observed with increasing temperature. The largest molecules formed within 1 ns of simulation time at 3500 K contain enough carbon atoms to form ring structures. Ring formation is observed in one case.

The effect of time step, thermostat, and strain rate on ReaxFF simulations of mechanical failure in diamond, graphene, and carbon nanotube

“…Fracture occurs at higher stresses and strains for the highest strain rates. For the three slower strain rates, the mechanical response of the system is essentially converged, indicating that nothing is gained by the use of a strain rate below 2.2 ns 21 .…”

“…In this work, deformation simulations were performed with strain rates spanning four orders of magnitude to identify the maximum reliable rate for each material. The slowest strain rate tested was 0.022 ns 21 . For graphene, deformations in both directions (zigzag and armchair) were simulated.…”

“…ReaxFF has been shown to accurately describe a wide range of carbon‐based systems . Additionally, ReaxFF has been used to study a variety of inorganic materials including silicon and silicon oxide systems, BiMoO x , magnesium hydride systems, aluminum and aluminum oxides, platinum, and lithium .…”

“…ReaxFF has been shown to accurately describe a wide range of carbon-based systems. [8,[16][17][18][19][20][21][22][23][24][25][26][27][28][29] Additionally, ReaxFF has been used to study a variety of inorganic materials including silicon and silicon oxide systems, [30,31] BiMoO x , [32] magnesium hydride systems, [33] aluminum and aluminum oxides, [34] platinum, [35] and lithium. [36] ReaxFF has also been used to investigate fracture properties of materials such as silicon, [30,37] graphyne, [38,39] graphene, [22,29] and Fe/Ni/Al.…”

Extracting the mechanisms and kinetic models of complex reactions from atomistic simulation data

“…Despite the advances in identifying reaction species and rates from simulation data, [12][13][14][15][16][17][18][19][20][21][22][23][24] there is no established method for obtaining reaction mechanisms that can be used directly for engineering (kinetic) modeling. In a recent work by Döntgen et al, [18] a method for identifying reaction species and elementary reactions was proposed.…”