Effect of Fe–O ReaxFF on Liquid Iron Oxide Properties Derived from Reactive Molecular Dynamics

Abstract

As iron powder nowadays attracts research attention as a carbon-free, circular energy carrier, molecular dynamics (MD) simulations can be used to better understand the mechanisms of liquid iron oxidation at elevated temperatures. However, prudence must be practiced in the selection of a reactive force field. This work investigates the influence of currently available reactive force fields (ReaxFFs) on a number of properties of the liquid iron–oxygen (Fe–O) system derived (or resulting) from MD simulations. Liquid Fe–O systems are considered over a range of oxidation degrees Z O , which represents the molar ratio of O/(O + Fe), with 0 < Z O < 0.6 and at a constant temperature of 2000 K, which is representative of the combustion temperature of micrometric iron particles burning in air. The investigated properties include the minimum energy path, system structure, (im)miscibility, transport properties, and the mass and thermal accommodation coefficients. The properties are compared to experimental values and thermodynamic calculation results if available. Results show that there are significant differences in the properties obtained with MD using the various ReaxFF parameter sets. Based on the available experimental data and equilibrium calculation results, an improved ReaxFF is required to better capture the properties of a liquid Fe–O system.

Investigation of Iron Nanoparticle Oxidation under External Electrostatic Fields Using Reactive Molecular Dynamics

“…Figure shows the diffusion of an oxygen atom from one octahedral interstitial site to an adjacent site passing through a tetrahedral site. Overall, the MEPs obtained with the three ReaxFF parameter sets under consideration and without an external electric field are in agreement with the study of Thijs et al The energy barrier of the oxygen migration obtained from DFT computations has been reported in the literature and ranges between 11.07 and 13.84 kcal/mol. − On the contrary, ReaxFF-2010 predicts a MEP with negative energies. The inability of ReaxFF-2010 to capture this reaction has also been noted by Huang et al Interestingly, ReaxFF-2010 (ox) predicts an appropriate MEP, with a positive energy barrier.…”

“…The bond order is computed based on the interatomic distance of a pair of elements. Note that none of the commonly used ReaxFF parameter sets can capture all physical properties of Fe–O systems, as recently demonstrated by Thijs et al In the present work, two reactive force fields are used, namely ReaxFF-2010 and ReaxFF-2016, which can predict with satisfactory accuracy the adsorption, miscibility, and burn time compared to other ReaxFF parameter sets . For the former, two versions have been proposed as discussed in Aryanpour et al: one including interactions between Fe, H, and O elements, called ReaxFF-2010 (full), and one with interactions between Fe and O elements only, called ReaxFF-2010 (oxides).…”

Quantifying reaction rates in methane oxidation: atomistic simulations at high temperature

“…Furthermore, another primary advantage of reactive molecular dynamics lies in their capacity to simulate systems across a broad spectrum of conditions, encompassing extreme temperatures and pressures that pose a challenge to replicate in laboratory settings [17]. Rismiller et al [18] employed ReaxFF MD to investigate the waterassisted liquefaction of lignocellulose biomass at temperatures ranging from 1250 to 2000 K; Thijs et al [19] also used ReaxFF MD to study the properties of liquid iron/oxygen systems under extreme conditions like those encountered during the combustion of micrometric iron particles. Ibrahim et al [20] performed reactive molecular dynamics simulations to optimize water desalination efficiency using graphene membranes.…”