Development and validation of a ReaxFF potential for hydrocarbon cracking reactions on Co and Fe-doped aluminosilicate catalysts

The objective of this Phase-I research effort is to develop a force field (FF) based reactive molecular dynamics (MD) simulation program to understand hydrocarbon cracking catalysis on well-defined aluminosilicate systems and on Fe- and Co-doped catalysts. Full dynamical description of the catalyst/fuel interface requires a computational method that is a number of magnitudes faster than the quantum mechanical (QM) based approach but retains the quality of QM-results for reaction energies and reaction barriers. Force field (FF) based approaches can provide the computational speed required to perform molecular dynamics (MD) simulations on systems sizes sufficiently large to describe the full chemistry of the catalyst/fuel interface. The research effort invested in Phase-I will establish and validate ReaxFF parameters for the aluminosilicate and Co- and Fe-doped aluminosilicate systems and their interactions with a hydrocarbon feedstock. These validated parameters will then be used during Phase-II research effort for an extensive MD-based study to map out the mechanisms and rates of the cracking reaction for (a) various pressures and temperatures, (b) different composition of the hydrocarbon feedstock, and (c) varying dopant concentration and location. BENEFIT: The development of a force field (FF) based reactive molecular dynamics (MD) simulation program to understand hydrocarbon cracking catalysis for high-heat sink fuels will play a key role in the research and development of scramjet engines. The proposed software will be capable of performing nanosecond-scale MD-simulations on large (>>1000 atoms), and the development of parallel ReaxFF will enable application to systems >1,000,000 atoms. Hence, the development of this software will enable researchers in educational, industry, and DoD research facilities to study the full complexity of a dynamic catalyst/fuel interface for a range of applications from propulsion/energy to materials. Groups that have an interest in ReaxFF include Exxon (fuel chemistry and catalysis), Lockheed Martin (carbon nanotube enforced polymers), CFDRC (catalyzed canbon nanotube growth), Intel (catalyzed carbon nanotube growth), Seiko-Epson (SiO2/Si interfaces), and Nissan (diamond-like carbon materials). Spectral Energies will work with our partners at Penn State and the Air Force Research Laboratory to ensure that the results of this work enable the development of advanced engine technology, as described in the work for Phase II, as well as follow-on Phase III activities.