Solid-state amorphization observed in the equilibrium-immiscible Cu-Re system by molecular dynamics simulations.

ABSTRACT

Assisted by ab initio calculations, an n-body Cu-Re potential is first constructed for the equilibrium-immiscible Cu-Re system under the second moment approximation of a tight-binding scheme. The proven realistic Cu-Re potential is then applied to perform the molecular dynamics simulations using the Cu-Re sandwich model. The simulations reveal that the interfacial free energy stored in the Cu/Re interfaces plays an important role in facilitating the spontaneous solid-state amorphization and that the amorphous interlayer grows in a layer-by-layer mode featuring an asymmetric behavior, i.e., the growth of the amorphous interlayer advances faster toward the Cu lattice than toward the Re direction. It is also found that with increasing the simulation time, the growth speed of the amorphous interlayer gradually slows down and eventually becomes zero when the interlayer reaches a thickness of about 1.47 nm. Interestingly, according to a recently proposed thermodynamic and kinetic model, the maximum thickness of the growing amorphous layer is limited by the available interfacial free energy and in the Cu-Re system, it is estimated to be around 1.35 nm, which is comparable with that observed from the simulations.