Structural aspects of the Stokes-Einstein relation breakdown in high temperature melts

CH Li and YW Luan and XJ Han and JG Li, JOURNAL OF NON-CRYSTALLINE SOLIDS, 458, 107-117 (2017).

DOI: 10.1016/j.jnoncrysol.2016.12.025

Dynamical and structural properties of four Al-Fe melts (A(l100-x)Fe(x), x = 10, 20, 30, and 40) were calculated using molecular dynamics simulation over a wide temperature range. The dynamical results reveal that, a crossOver from Arrhenius to non-Arrhenius behavior occurs for ca-relaxation time Ta and shear viscosity ri bordered at T-x similar to 1.2T(L) (T-L the liquidus temperature). At T-x, we also found the breakdown of Stokes-Einstein relation and the rapid enhancement of dynamic heterogeneity. The structural results demonstrate that the fraction of icosahedral cluster increases with decreasing temperature, and the amplitude of increase has a significant shift at T-x. In order to facilitate a uniform description, local five-fold symmetry (LFFS) was selected to describe the development of various kinds of atomic clusters. It is seen that LFFS has an obvious change at T-x, implying a strong coupling between atomic dynamics, SER breakdown and liquid structure change. For the first time, the breakdown of SER is demonstrated to have a structure signature which could be characterized by LFFS. This work would be helpful in understanding the longstanding challenges of the dynamics-structure relationship in liquid metals. (C) 2016 Elsevier B.V. All rights reserved.

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