First principle molecular dynamic simulation of the rapid solidification process of Ca50Mg20Cu30 alloy

Abstract

The rapid solidification processes of Ca50Mg20Cu30 liquid alloy have been simulated by first principle molecular dynamics simulation based on the density functional theory. The local structural evolution of the alloy is analysed using Honeycutt Andersen (HA) bond-type index and bond-angle distribution methods. The electronic properties of this amorphous solid are also studied. The simulated coordination numbers are very close to the theoretical values according to the efficient cluster packing model (ECP) model. The interaction between Ca-Cu atomic pairs is strongest in this alloy. The HA bond-type result shows that a large quantity of pentagonal bipyramids are formed in undercooled alloy liquid and become most common polyhedral local structures of the amorphous solid, which suppress the crystallization and increase the glass forming ability of Ca-Mg-Cu alloy. The bond-angle distribution indicates that the close packing of the three neighbor atoms and the pentagon configurations become the primary short range order (SRO) as temperature decreases. The electronic density demonstrates that the covalent bond of Ca-Mg, Ca-Cu, Mg-Cu, and Cu-Cu pairs is existed in this alloy. This chemical SRO also benefits the glass transition.