Abnormal breakdown of Stokes–Einstein relation in liquid aluminium

• Published in: 中国物理B：英文版 2017 (1), p.337-347
• Main Author: 李晨辉 韩秀君 栾英伟 李建国
• Format: Article
• Language: English
• ISSN: 1674-1056; 2058-3834

We present the results of systematic molecular dynamics simulations of pure aluminium melt with a well-accepted embedded atom potential. The structure and dynamics were calculated over a wide temperature range, and the calculated results（including the pair correlation function, self-diffusion coefficient, and viscosity） agree well with the available experimental observations. The calculated data were used to examine the Stokes–Einstein relation（SER）. The results indicate that the SER begins to break down at a temperature Tx（1090 K） which is well above the equilibrium melting point（912.5 K）.This high-temperature breakdown is confirmed by the evolution of dynamics heterogeneity, which is characterised by the non-Gaussian parameter α2（t）. The maximum value of α 2（t）, α2,max, increases at an accelerating rate as the temperature falls below Tx. The development of α2,max was found to be related to the liquid structure change evidenced by local fivefold symmetry. Accordingly, we suggest that this high-temperature breakdown of SER has a structural origin. The results of this study are expected to make researchers reconsider the applicability of SER and promote greater understanding of the relationship between dynamics and structure.