Phase transition behaviors of Al nanoparticles with low oxidation degree: A molecular dynamics study

Abstract

In this study, the ReaxFF reactive force field is applied to simulate the melting and annealing behaviors of aluminum (Al) nanoparticles (ANP) by molecular dynamics (MD) simulations. Potential energy, specific heat and FCC lattice number are used to study the thermal behavior of the entire phase transition process. First, the melting and solidification process of 3[Formula: see text]nm cubic Al and Al2O3 models under constant-pressure/temperature ensemble (NPT) system was simulated without boundary, and the steady-state simulation was discussed at specific temperature points. The non-boundary simulation proved the effectiveness of the Reaxff reactive force field for ANP phase transition simulations. It is confirmed that the physical properties of Al and Al2O3 could be effectively reflected in the MD simulations. ANP with low oxidation degree cannot be completely ignored in engineering applications. The existence of oxide layer hinders the annealing behavior. Therefore, this study also carried out an additional simulation process of 6 nm ANP and its oxide particles in canonical ensemble (NVT). Those obtained results show that a small amount of oxide layer can greatly change the thermal properties of ANP. If the surface of ANP is isolated, then its melting point could be increased by at least 30[Formula: see text]K.