Chen Sow-Hsin, Mallamace Francesco, Mou Chung-Yuan, Broccio Matteo, Corsaro Carmelo, Faraone Antonio, Liu Li
Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, 02139, USA.
Proc Natl Acad Sci U S A. 2006 Aug 29;103(35):12974-8. doi: 10.1073/pnas.0603253103. Epub 2006 Aug 18.
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) approximately equals 235 K. In particular, the dynamical parameters of water can be measured down to 180 K, approaching the suggested glass transition temperature T(g) approximately equals 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 approximately 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.
通过将水限制在极窄的纳米孔中，使得液体无法冻结，就有可能在远低于其均匀成核温度(T(H))（约等于235K）的情况下探究其性质。特别是，水的动力学参数可以测量到180K，接近所提出的玻璃化转变温度(T(g))（约等于165K）。在此，我们展示了从核磁共振和准弹性中子散射光谱学获得的实验证据，证明了输运性质（自扩散系数和平均平移弛豫时间）存在明确的解耦，这意味着斯托克斯 - 爱因斯坦关系的失效。我们进一步表明，这种非单调解耦反映了最近在约225K观察到的动态转变的特征，该转变发生在被称为脆弱和强的两种动力学行为之间，这是液态水氢键结构变化的结果。
