Pressure-driven densification and connectivity in a CuZr metallic glass

Metallic glasses (MGs) exhibit exceptional strength, elasticity, and corrosion resistance due to their disordered atomic structure, with Cu-Zr alloys serving as widely studied model systems. External pressure can significantly modify glass formation, atomic packing, and mechanical response by altering short-range order (SRO), medium-range order (MRO), and the glass transition temperature. While previous studies have reported pressure-induced crystallization or reductions in icosahedral ordering at high pressures, the present work shows that moderate external pressures (<10 GPa) enhance dense atomic packing without triggering crystallization. In particular, pressure increases the glass transition temperature and promotes the formation and interconnectivity of icosahedra-like structures, strengthening the amorphous backbone of the glass.

Molecular dynamics simulations were performed on a ${\text{Cu}}_{64}{\text{Zr}}_{36}$ metallic glass obtained by cooling the liquid under external pressures ranging from 0 to 10 GPa. Structural evolution was characterized using radial distribution functions, Voronoi polyhedra analysis, and network connectivity analysis. SRO was quantified through populations of icosahedra-like (solid-like), transition, and liquid-like polyhedra, revealing a pressure-induced increase in solid-like and transition polyhedra and a reduction in liquid-like environments. MRO was examined via 2-atom, 3-atom, and 4-atom connections and the interconnectivity of icosahedra-like networks, showing enhanced face-sharing connectivity and increased network cohesion at higher pressures. Elastic moduli were calculated from the stiffness tensor and were found to increase with pressure, consistent with the formation of denser atomic packings and a more mechanically stable glass structure.