Department of Chemistry, Indian Institute of Technology-Delhi, New Delhi 110016, India.
J Chem Phys. 2011 Jan 7;134(1):014502. doi: 10.1063/1.3521488.
The regime of validity of Rosenfeld excess entropy scaling of diffusivity and viscosity is examined for two tetrahedral, network-forming ionic melts (BeF(2) and SiO(2)) using molecular dynamics simulations. With decrease in temperature, onset of local caging behavior in the diffusional dynamics is shown to be accompanied by a significant increase in the effect of three-body and higher-order particle correlations on the excess entropy, diffusivity, ionic conductivity, and entropy-transport relationships. The signature of caging effects on the Rosenfeld entropy scaling of transport properties is a distinctly steeper dependence of the logarithm of the diffusivity on the excess entropy in ionic melts. This is shown to be true also for a binary Lennard-Jones glassformer, based on available results in the literature. Our results suggest that the onset of a landscape-influenced regime in the dynamics is correlated with this characteristic departure from Rosenfeld scaling. The breakdown of the Nernst-Einstein relation in the ionic melts can also be correlated with the emerging cooperative dynamics.
用分子动力学模拟研究了两个四面体型、形成网络的离子熔体（BeF2和 SiO2）的扩散系数和粘度罗森菲尔德过剩熵标度的有效范围。随着温度的降低，在扩散动力学中局部笼状行为的出现伴随着三体和更高阶粒子相关性对过剩熵、扩散系数、离子电导率和熵输运关系的影响显著增加。笼状效应对输运性质的罗森菲尔德熵标度的特征是，离子熔体中扩散系数的对数对过剩熵的依赖性明显更陡峭。这也适用于基于文献中可用结果的二元 Lennard-Jones 玻璃形成体。我们的结果表明，动力学中受景观影响的范围的出现与这种偏离罗森菲尔德标度的特征有关。离子熔体中能斯特-爱因斯坦关系的破裂也可以与新兴的协同动力学相关联。
