摘要
With sufficiently high cooling rates,liquids will cross their equilibrium melting temperatures and can be maintained in a metastable undercooled state before solidifying.Studies of undercooled liquids reveal several intriguing dynamic phenomena and because explicit connections between liquid structure and liquids dynamics are difficult to identify,it remains a major challenge to capture the underlying structural link to these phenomena.Ab initio molecular dynamics(AIMD)simulations are yet especially powerful in providing atomic-scale details otherwise not accessible in experiments.Through the AIMD-based study of Cr additions in Al-based liquids,we evidence for the first time a close relationship between the decoupling of component diffusion and the emergence of dynamic heterogeneities in the undercooling regime.In addition,we demonstrate that the origin of both phenomena is related to a structural heterogeneity caused by a strong interplay between chemical short-range order(CSRO)and local fivefold topology(ISRO)at the short-range scale in the liquid phase that develops into an icosahedral-based medium-range order(IMRO)upon undercooling.Finally,our findings reveal that this structural signature is also captured in the temperature dependence of partial pair-distribution functions which opens up the route to more elaborated experimental studies.
基金
the CINES and IDRIS under Project N°INP2227/72914 as well as PHYNUM CIMENT for computational resources
performed within the framework of the Centre of Excellence of Multifunctional Architectured Materials“CEMAM”n°ANR-10-LABX-44-01 funded by the“Investments for the Future”Program.
