Generation of viable nanocrystalline structures using the melt-cool method: the influence of force field selection

Abstract

ABSTRACT The influence of force field selection on the formation of nanocrystalline structures of pure copper using the Melt-Cool method within Molecular Dynamics (MD) was investigated. This is of utmost importance since the use of MD to investigate nanocrystalline materials is critical due to the ability to study on the appropriate length scale. The Melt-Cool simulation method involves annealing the starting single crystal structure to temperatures exceeding the melting point of the material, followed by rapid quenching and equilibration to room temperature. The heating and rapid quenching allows for the mixture of atoms to randomised orientations with realistic microstructures and randomised defects, such as interstitial or vacancy atoms. Due to the requirement of the mathematical model (force field) to predict the nanocrystalline structure, the influence of force field selection is of paramount importance – a major gap found in currently available literature. The current investigation was performed in two phases: initial investigation to understand influence of force field parameterisation on formation of nanocrystalline structures, followed with an investigation to enhance predictions of mechanical properties of nanocrystalline copper found in currently available literature. The initial phase demonstrated a clear dependence on force field selection for the formation of viable nanocrystalline structures. The second phase demonstrated that the most accurate force field for mechanical properties may not be the ideal selection for use with the Melt-Cool method. The most ideal force field selection when performing the Melt-Cool method with the goal of obtaining accurate mechanical properties for pure copper was determined.