Structural Complexity in Metallic Glasses: Unveiling the Mechanisms and Motifs of Glass Formation from Molecular Dynamics Simulations

Metallic glasses (MG) are renowned for their exceptional mechanical properties, including high strength, corrosion resistance, and ease of processing. These properties stem from their amorphous atomic structures and the presence of both regular and distorted five-fold icosahedral motifs, which vary in proportion and connectivity. Despite extensive research, the relationship between structural complexity, motif connectivity, and material properties remains elusive.

In this study, we employ molecular dynamics simulations to investigate the atomic-scale dynamics of glass formation, focusing on the emergence of distinct motifs with varying connectivities. We analyze MG samples of different compositions (Fe_xZr_100-x, Co_xZr_100-x, Cu_xZr_100-x) and explore the formation and "freezing in" of distinct regions during melt-quench simulations. We evaluate the dynamical trajectories to identify features associated with regions that quickly freeze and those that retain liquid-like character for prolonged time. We track the distribution of atomic diffusivities and their evolution as the disordered structure solidifies, observing that several regions linked to connected sequences of icosahedra exhibit liquid-like ionic transport down to low temperatures. This analysis sheds light on the mechanisms of glass formation and their relationship to structural motifs and atomic-scale diffusion.