7th International Conference on Matter and Radiation at Extremes (ICMRE2024)

Metallic glasses (MGs), as a synthetic glass system, have attracted extensive attention not only due to their superior properties to conventional crystalline metals but also as simple atomic glass model systems for fundamental studies of glasses in general. With non-directional metallic bonds, MGs were initially believed to possess an atomic structure resembling that of a random close packing of hard spheres. Recently, it has been gradually recognized that detailed chemical interaction between different elements, namely the complex electronic structures, could play a critical even dominant role in determining the atomic structures and properties of MGs. By applying pressure, some MGs show interesting amorphous-to-amorphous transitions (polyamorphism), which were clarified to arise from changes in electronic structures rather than their already very high coordination numbers. These MGs usually involve elements with pressure-sensitive electronic structures, such as rare earth elements with 4f electrons. Therefore, not surprisingly, in previous high-pressure experiments, the MGs systems consisting of only transition metals, such as the prototype Zr-Cu binary MGs, pressure-induced polyamorphism has not been observed. X-ray diffraction (XRD) patterns taken under high pressure typically retained a similar profile to that at ambient pressure, i.e., the entire pattern shifts elastically with pressure. In contrast, replacing Cu with another neighboring transition metal with near identical atomic size, Ni, our studies surprisingly reveal a pressure-induced local structural crossover in the Zr-Ni binary MG. The atomic structure of this Zr-Ni MG is studied up to 40 GPa by in situ high-pressure synchrotron XRD experiment. In situ high-pressure resistance measurement and molecular dynamics simulation reveal that the pressure-induced electronic structure changes account for the unusual structural crossover. The findings offer a new MG system to explore the relationship between composition (chemistry) and glass atomic structures and properties from an electronic structure point of view.

high pressure,metallic glass,synchrotron x-ray diffraction,electronic structure