A Molecular Dynamics Simulation Framework for an Al+Fe 2 O 3 Reactive Metal Powder Mixture
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A Molecular Dynamics Simulation Framework for an Al+Fe2O3 Reactive Metal Powder Mixture
Vikas Tomar and Min Zhou The George W Woodruff School of Mechanical Engineering Georgia Institute of Technology Atlanta, Georgia 30332, U.S.A. ABSTRACT This work focuses on the development of a classical molecular dynamics (MD) framework that can be used to analyze the quasi-static strength, elastic-constants, and dynamic strength of nanostructured Fe2O3+Al reactive metal powder (NRMP) mixtures. An interatomic potential is developed for the Fe2O3+Al NRMP system, accounting for the behavior of Al, Fe, Fe-Al intermetallics, Fe2O3, and Al2O3. This potential can be regarded as a generalization and combination of several existing potentials for the individual components in the system. The potential incorporates electronegativity equalization to account for pressure-induced phase transformation. In addition, the parameter set of the potential is capable of predicting the elastic properties of components over a range of 0 - 900 K. INTRODUCTION Molecular level modeling and characterization using classical molecular dynamics (MD) can provide vital input for the desired nano-construction of advanced materials. The most important input required for a classical MD analysis is a phenomenological description of the interatomic interactions. This description is calibrated by ab initio and/or experimental values of material properties at a specific temperature and pressure. Interatomic potentials fitted to properties at a specific temperature and pressure have been shown to perform satisfactorily over a range of temperatures and pressures [1, 2]. The current work focuses on the development of a classical MD framework that can be used to characterize the behavior of a nanostructured Fe2O3+Al reactive metal powder (NRMP) thermite mixture. The potential should also be able to describe the pressure-induced structural changes, and it should predict the system properties over a range of temperature. The primary interest is to use this potential to analyze nanoscopic morphological characteristics that affect the elastic constants, quasi-static strength, and dynamic strength as functions of applied loading with and without the possibility of phase transformation. The MD model must account for the behavior of the products of the Fe2O3+Al thermite reaction as well as that of the reactants. The interatomic potential proposed here meets this requirement by providing a unified description for the reactants (Fe2O3 and Al), the products (Al2O3 and Fe) and the Al-Fe intermetallics. The potential incorporates electronegativity equalization to update the charges of atoms according to changes in their environment during pressure-induced deformation. The parameters for the potential obtained by fitting to the properties at room temperature (300 K) are shown to predict the system properties over a temperature range of 0 K to 900 K. The potential is expected to provide a reasonable account of the pressure-induced mechanochemical deformation of the NRMP mixt
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