Title: Connectivity-based parallel replica dynamics method for simulating chemically reactive systems using ReaxFF reactive force field method
Presenter: Sumathy Raman
Affiliation: ExxonMobil Research and Engineering, Annandale, NJ 08801
Co-authors: Kaushik Joshi and A.C.T. van Duin
Affiliation: Pennsylvania State University, University Park, PA 16801
Abstract: Many chemical reactions have relatively high activation energies putting them beyond the time-scale of the conventional molecular dynamics (MD) algorithms at modest temperatures. One way of tackling this time-scale issue is to perform the MD simulations at elevated temperatures using the reactive force field methods such as ReaxFF 1. However, elevated temperatures favor entropically favored reactions thereby changing the product distribution compared to low temperature chemistry. In order to capture the low temperature chemistry in atomic scale simulations, we implemented parallel replica dynamics (PRD) method 2 together with reactive force field and developed a new “event detection scheme” that allows us to simulate longer timescales, essentially up to a microsecond. In the newly developed event detection scheme, events are identified using a near-neighbor list accounting for a change in connectivity to any atom. The presentation will cover the implementation and results from the PRD simulations on pyrolysis of n-heptene, hexadecane and kerogen fragment at different densities and highlight some of the challenges in achieving a high parallelization efficiency with PRD and suggest opportunities for its improvement.
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 Voter, A., 1998, “Parallel replica method for dynamics of infrequent events”, Physical Review B, 57, 985