Prediction of Glass-Forming Ability and Atomic-Level Structure of the Al--Zr--Pd Metallic Glasses by Molecular Dynamics Simulations

For the Al--Zr--Pd system, an interatomic potential was constructed under the formulism named long-range smoothed second-moment approximation of tight-binding, and proved to be realistic. Applying the constructed Al--Zr--Pd potentials, molecular dynamics simulations were carried out to compare the relative stability of crystalline solid solution versus its disordered counterpart, over the entire composition triangle. The simulations not only reveal that the origin of metallic glass formation is the crystalline lattice collapsing while the solute concentrations exceed critical values, but also determine a hexagonal composition region, within which the metallic glass formation is energetically favored. Moreover, the driving forces for amorphization, i.e., the energy differences between the crystalline solid solutions and disordered states were derived from the simulations. From the derived driving forces, an optimized composition area was located and within the area metallic glass is more readily to be formed as well as more stable than other alloys in the system. For the atomic-level structure, the coordinate numbers of two profiles with compositions across the optimized amorphous alloy were analyzed by the Voronoi tessellation method, showing significant changing in atomic configurations upon crystal-to-amorphous structural transformation.