Development of a Reactive Force Field for Iron-Oxyhydroxide Systems

We adopt a classical force field methodology. ReaxFF, which is able to reproduce chemical reactions, and train its parameters or the thermodynamics of iron oxides as well as energetics of a few iron redox reactions. Two parametrizations are developed, and their results are compared with quantum calculations or experimental measurements. In addition to training, two test cases arc considered: the lattice parameters of a selected set of iron minerals, and the molecular dynamics simulation of a model for alpha-FeOOH (goethite)-water interaction. Reliability and limitations of the developed force fields in predicting structure and energetics are discussed.