Corradini D, Gallo P, Buldyrev S V, Stanley H E
Center for Polymer Studies and Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA.
Phys Rev E Stat Nonlin Soft Matter Phys. 2012 May;85(5 Pt 1):051503. doi: 10.1103/PhysRevE.85.051503. Epub 2012 May 9.
Using discrete molecular dynamics simulations we study the relation between the thermodynamic and diffusive behaviors of a primitive model of aqueous solutions of hydrophobic solutes consisting of hard spheres in the Jagla particles solvent, close to the liquid-liquid critical point of the solvent. We find that the fragile-to-strong dynamic transition in the diffusive behavior is always coupled to the low-density-high-density liquid transition. Above the liquid-liquid critical pressure, the diffusivity crossover occurs at the Widom line, the line along which the thermodynamic response functions show maxima. Below the liquid-liquid critical pressure, the diffusivity crossover occurs when the limit of mechanical stability lines are crossed, as indicated by the hysteresis observed when going from high to low temperature and vice versa. These findings show that the strong connection between dynamics and thermodynamics found in bulk water persists in hydrophobic solutions for concentrations from low to moderate, indicating that experiments measuring the relaxation time in aqueous solutions represent a viable route for solving the open questions in the field of supercooled water.
我们使用离散分子动力学模拟，研究了在接近溶剂液-液临界点的Jagla粒子溶剂中，由硬球组成的疏水溶质水溶液原始模型的热力学行为与扩散行为之间的关系。我们发现，扩散行为中从脆弱到强烈的动力学转变总是与低密度到高密度的液体转变相关联。在液-液临界压力以上，扩散率交叉出现在Widom线上，沿着这条线热力学响应函数呈现最大值。在液-液临界压力以下，当跨越机械稳定性线的极限时发生扩散率交叉，这由从高温到低温以及反之亦然时观察到的滞后现象所表明。这些发现表明，在 bulk water 中发现的动力学与热力学之间的紧密联系在低至中等浓度的疏水溶液中依然存在，这表明测量水溶液中弛豫时间的实验是解决过冷水领域未解决问题的一条可行途径。
