Developing eReaxFF Force Fields for Peroxide and Radical Chemistry in the Contexts of Polymer Dielectric Breakdown and Oxidative Damage Induced by Reactive Oxygen Species
Open Access
Author:
Penrod, Katheryn Anne
Graduate Program:
Chemistry
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
June 16, 2021
Committee Members:
Benjamin Lear, Major Field Member Gerald Knizia, Co-Chair & Dissertation Advisor Edward O'Brien, Major Field Member Adri van Duin, Co-Chair & Dissertation Advisor Philip Bevilacqua, Program Head/Chair Kristen Fichthorn, Outside Unit, Field & Minor Member
Keywords:
ReaxFF eReaxFF MD polymer dielectric power cable ROS DNA oxidation redox radical peroxide chemistry simulation
Abstract:
By exploiting the relationship between bond length and bond order, reactive force fields can simulate chemical reactions without the full expense of QM calculations. In particular, the reactive force field (ReaxFF) method provides a reasonable description of reaction chemistry and equilibrium geometries for a wide range of molecules. Electronic effects in ReaxFF are treated implicitly in the bonded interaction terms, which has proven insufficient for determination of electron affinities (EAs) and ionization potentials (IPs) for many chemical species. Consequently, ReaxFF struggles to model redox reactions, which are characterized by direct transfer of electron(s). The eReaxFF method expands the basic framework of standard ReaxFF to incorporate explicit electron particles. In eReaxFF, nuclei are treated as point charges while electrons are represented as Gaussian waves bearing a -1 charge. The fundamental difference is that in eReaxFF, the valency and number of lone-pair electrons of an atom are modified based on its proximity to the explicit electrons. In this way, eReaxFF achieves a more accurate description of charge transfer in reactive environments than standard ReaxFF. In this dissertation, the existing eReaxFF description for polyethylene systems is expanded using Constrained Density Functional Theory (C-DFT) as a supplement to standard DFT calculations. Furthermore, a new application of eReaxFF is introduced in Chapter 3, where DNA oxidative damage induced by reactive oxygen species (ROS) is explored.