Abnormal breakdown of Stokes–Einstein relation in liquid aluminium  

作　　者：Chen-Hui Li Xiu-Jun Han Ying-Wei Luan Jian-Guo Li 李晨辉;韩秀君;栾英伟;李建国(Laboratory of Advanced Materials Solidification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China)

机构地区：Laboratory of Advanced Materials Solidification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

出　　处：《Chinese Physics B》2017年第1期333-343,共11页中国物理B（英文版）

基　　金：supported by the National Basic Research Program of China(Grant No.2011CB012900);the National Natural Science Foundation of China(Grant No.51171115);the Natural Science Foundation of Shanghai City,China(Grant No.10ZR1415700);the Research Fund for the Doctoral Program of Higher Education of China(Grant No.20100073120008);the Program for New Century Excellent Talents in Universities of China;partially supported by Alexander von Humboldt Foundation

摘　　要：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）, α（2,max）, increases at an accelerating rate as the temperature falls below Tx. The development of α（2,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.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）, α（2,max）, increases at an accelerating rate as the temperature falls below Tx. The development of α（2,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.

关 键 词：diffusion VISCOSITY dynamics heterogeneity local five-fold symmetry 

分 类 号：TG146.21[一般工业技术—材料科学与工程] TG111.4[金属学及工艺—金属材料]