(Invited) Applications of the Reaxff Force Field for Identifying Reactive Properties for Complex Battery Materials and Interfaces

The ReaxFF method provides a highly transferable simulation method for atomistic scale simulations on chemical reactions at the nanosecond and nanometer scale. It
combines concepts of bond-order based potentials with a polarizable charge distribution. Since it initial development for hydrocarbons in 2001 [1], we have found that this concept
is transferable to applications to elements all across the periodic table, including all first row elements, metals, ceramics and ionic materials.
For all these elements and associated materials we have demonstrated that ReaxFF can accurately reproduce quantum mechanics-based structures, reaction energies and reaction barriers, enabling the method to predict reaction kinetics in complicated, multi-material environments at a relatively modest computational expense.
This presentation will describe the current concepts of the ReaxFF method, the current status of the various ReaxFF codes, including parallel implementations and recently developed new computational concepts, including grand canonical Monte Carlo and metadynamics options that enhance connectivity with experiment. Also, we will present and overview of recent applications to a range of materials of increasing complexity, with a particular focus on recent applications to battery anodes, cathodes and anode/electrolyte and cathode/electrolyte interfaces. This will specifically include ReaxFF development for Li/Si [2], Li/carbon [3], Li/sulfur [4] interfaces and electrolyte chemistry [5] and new method concepts that enable ReaxFF to include explicit electron or hole movement.

Figure caption: Snapshot from a ReaxFF molecular dynamics simulation of Li-migration in a carbon onion anode [3].

[1] van Duin, A. C. T., Dasgupta, S., Lorant, F., and Goddard, W. A., 2001. ReaxFF: A reactive force field for hydrocarbons. Journal of Physical Chemistry A 105, 9396-9409.

[2] Ostadhossein, A., Cubuk, E. D., Tritsaris, G. A., Kaxiras, E., Zhang, S., and van Duin, A. C. T., 2015. On the Lithium intercalation in Silicon Nanowires, Reactive Molecular Dynamics Simulation using ReaxFF Force Field. Phys. Chem. Chem. Phys. 17, 3832-3840.

[3] Raju, M., Ganesh, P., Kent, P. R. C., and van Duin, A. C. T., 2015. A Reactive Force Field study of Li/C Systems for Electrical Energy Storage. Journal of Computational and Theoretical Chemistry, published online , DOI: 10.1021/ct501027v

[4] Islam, M., Ostadhossein, A., Borodin, O., Yeates, A. T., Tipton, W. W., Hennig, R. G., Kumar, N., and van Duin, A. C. T., 2015. ReaxFF Molecular Dynamics Simulations on Lithiated Sulfur Cathode Materials Phys. Chem. Chem. Phys. 17, 3383-3393.

[5] Islam, M., Bryantsev, V. S., and van Duin, A. C. T., 2014. ReaxFF Reactive Force Field Simulations on the Influence of Teflon on Electrolyte Decomposition During Li/SWCNT Anode Discharge in Lithium Sulfur Batteries. Journal of the Electrochemical Society 161, E3009-E3014.