Direct correspondence between liquid and glass polymorphism in densely packed metallic alloys

Liquid and glass are two closely related disordered states of matter. Whether each can exhibit two or more structurally distinct yet chemically identical forms have been debated for decades and the relationship between polymorphism in equilibrium liquids and that in non-equilibrium glasses remains elusive. Here, we address these long-standing issues in two prototype glass-forming metallic alloys using in situ high-pressure high-temperature synchrotron X-ray diffraction in diamond anvil cells. We identify distinct liquids above their melting temperatures and corresponding glasses formed upon melt quenching at different pressures, as evidenced by reproducible discontinuous changes in multiple diffraction-derived structural descriptors. Comprehensive structural and compositional characterizations consistently demonstrate that the recovered samples are fully amorphous and chemically homogeneous glasses. By continuously monitoring the formation and transformation pathways with in situ structural probes, our study provides compelling experimental evidence for the more general existence of liquid and glass polymorphism in densely packed metallic alloy systems.