Atomic structure evolution and its correlation with the kinetic fragility of liquid tantalum during cooling

摘要

The evolution of atomic structures and its correlation with the kinetic fragility of liquid tantalum (Ta) during cooling were investigated through molecular dynamics simulations. Pair distribution function, angular distribution function, and largest standard cluster analysis were used to characterize the atomic configurations in the Ta metal system. Results revealed that canonical Kasper clusters with a coordination number of >= 12 play a critical role in the formation of Ta monoatomic metallic glasses. Similar to the pattern observed in many multi-component metallic glass-forming liquids, the three-stage evolution pattern of the self-diffusion coefficient could be observed during cooling. The fragile-to-strong (F-S) transition temperature of liquid Ta is identified to be Tf-s approximate to 1.18 T-g. The possible structural reason for the strong-to-fragile liquid transition is correlated with the formation of abundant Kasper medium-range orders (MROs) and their zigzag competition with the loose configurations in liquid regions. The F-S transition is attributed to the success of MROs in the competition and their subsequent rapid growth.