Molecular dynamics simulations of critically percolated, cluster-packed structure in Zr–Al–Ni bulk metallic glass

Abstract

We have studied the local atomic arrangements of a Zr0.60Al0.15Ni0.25 bulk metallic glass (BMG) with molecular dynamics (MD) simulations based on a plastic crystal model (PCM). We have utilized features of orientationally disordered state of a molecule in plastic crystals. A Zr0.618Al0.146Ni0.236 alloy with an approximated composition to the Zr0.60Al0.15Ni0.25 has been created using MD–PCM from a Zr0.73Ni0.27 glassy alloy that possesses critically percolated Ni atoms. The MD–PCM dealt with icosahedral and tetrahedral clusters with 13 and five atoms, respectively, with a Ni, Al, or Zr atom at each center site of the clusters. After the Zr0.73Ni0.27 glassy alloy had been created with monatomic MD simulation by quenching from a liquid, the Zr and Ni atoms in the Zr0.73Ni0.27 glassy alloy were replaced with randomly oriented icosahedral and tetrahedral clusters, respectively. Subsequently, structural relaxation was performed after adjusting the density to that of the Zr0.618Al0.146Ni0.236 alloy. Total pair-distribution and interference functions revealed that the Zr0.618Al0.146Ni0.236 alloys created with MD–PCM exhibit the characteristics of a non-crystalline phase. Further, Voronoi polyhedra analysis revealed that the Ni-centered polyhedral clusters used as initial atomic arrangements for MD–PCM tend to reproduce the features of the conventional MD results. The origin of the excellent glass-forming ability of the Zr0.618Al0.146Ni0.236 alloy is attributed to the critically percolated cluster-packed structure.