Stokes-Einstein-Debye failure in molecular orientational diffusion: exception or rule?
Stokes-Einstein-Debye failure in molecular orientational diffusion: exception or rule?
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DOI：
10.1021/jp5012457
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发表时间：
2014-04
期刊：
影响因子：
--
通讯作者：
D. Turton;K. Wynne
中科院分区：
文献类型：
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作者：
D. Turton;K. Wynne
斯托克斯-爱因斯坦-德拜（SED）表达式通常用于将取向分子扩散率定量地与粘度联系起来。然而，众所周知，爱因斯坦方程是从流体动力学理论推导出来的，用于布朗粒子在均匀流体中的扩散，并且分子扩散的SED崩溃和失败的例子并不罕见。在这里，使用光学克尔效应光谱测量盐酸胍在水中的溶液和二硫化碳与十六烷的混合物的取向扩散，我们表明，这两个对比系统各自显示出明显的例外的SED关系，并询问它是否是合理的，期望分子扩散是一个简单的函数的粘度。
The Stokes-Einstein-Debye (SED) expression is used routinely to relate orientational molecular diffusivity quantitatively to viscosity. However, it is well-known that Einstein's equations are derived from hydrodynamic theory for the diffusion of a Brownian particle in a homogeneous fluid and examples of SED breakdown and failure for molecular diffusion are not unusual. Here, using optical Kerr-effect spectroscopy to measure orientational diffusion for solutions of guanidine hydrochloride in water and mixtures of carbon disulfide with hexadecane, we show that these two contrasting systems each show pronounced exception to the SED relation and ask if it is reasonable to expect molecular diffusion to be a simple function of viscosity.