The violation of the Stokes-Einstein relation in supercooled water
The violation of the Stokes-Einstein relation in supercooled water
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DOI：
10.1073/pnas.0603253103
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发表时间：
2006-08-29
影响因子：
11.1
通讯作者：
Liu, Li
中科院分区：
文献类型：
--
作者：
Chen, Sow-Hsin;Mallamace, Francesco;Liu, Li
通过将水限制在纳米孔中，使液体不能冻结，就有可能在接近235K的均匀成核温度T-H以下探索水的性质。特别是，水的动力学参数可以测量到180K，接近建议的玻璃转变温度T-g，接近165K。我们提供了从核磁共振和准弹性中子散射谱获得的实验证据，证明了输运性质(自扩散系数和平均平移弛豫时间)的明确解耦，这意味着斯托克斯-爱因斯坦关系的破裂。我们进一步表明，这种非单调的去耦合反映了最近观察到的在225K附近的两种动力学行为之间的动态交叉的特征，这是液态水的氢键结构改变的结果。
By confining water in nanopores, so narrow that the liquid cannot freeze, it is possible to explore its properties well below its homogeneous nucleation temperature T-H approximate to 235 K. In particular, the dynamical parameters of water can be measured down to 180 K, approaching the suggested glass transition temperature T-g approximate to 165 K. Here we present experimental evidence, obtained from Nuclear Magnetic Resonance and Quasi-Elastic Neutron Scattering spectroscopies, of a well defined decoupling of transport properties (the self-diffusion coefficient and the average translational relaxation time), which implies the breakdown of the Stokes-Einstein relation. We further show that such a non-monotonic decoupling reflects the characteristics of the recently observed dynamic crossover, at approximate to 225 K, between the two dynamical behaviors known as fragile and strong, which is a consequence of a change in the hydrogen bond structure of liquid water.