Melting Point and\nCrystal Growth Kinetics of Metals\nand Metal Oxides Using Reactive Force Fields: The Case of Aluminum\nand Alumina

Alumina and aluminum\nare strategic materials employed in energy\napplications, with metal aluminum being interesting in phase change\nmaterial applications. Therefore, the theoretical description of the\nthermophysical properties of these materials represents an important\nobjective. Here, we investigate the liquid–solid coexistence\nproperties of aluminum and alumina using a state-of-the-art reactive\nforce field (ReaxFF) and molecular dynamics simulations. Aluminum\nfeatures ultrafast crystal growth, which enables the direct determination\nof its melting temperature via direct coexistence simulations (858\n± 2 K). However, at standard pressure, alumina is easily trapped\nin a glass state, preventing the application of the direct coexistence\nmethod. We demonstrate that direct coexistence can be used at high\npressures above 2 GPa, where alumina features a higher melting temperature,\nand the liquid–solid interface exhibits enhanced dynamics.\nOur approach opens a route to obtain the melting temperature of ReaxFF\nalumina at standard pressure (1670 ± 10 K) and, more generally,\na viable method for calculating the melting point of metal oxides\nvia direct coexistence simulations. We further investigated the dynamics\nof crystal growth of the solid–liquid aluminum and alumina\ninterfaces.