Armstrong Jeff, Bresme Fernando
Department of Chemistry, Imperial College, London SW7 2AZ, United Kingdom.
Department of Chemistry, Norwegian University of Science and Technology, Trondheim, Norway.
Phys Rev E Stat Nonlin Soft Matter Phys. 2015 Dec;92(6):060103. doi: 10.1103/PhysRevE.92.060103. Epub 2015 Dec 30.
Temperature gradients polarize water, a nonequilibrium effect that may result in significant electrostatic fields for strong thermal gradients. Using nonequilibrium molecular dynamics simulations, we show that the thermal polarization features a significant dependence with temperature that ultimately leads to an inversion phenomenon, whereby the polarization field reverses its sign at a specific temperature. Temperature inversion effects have been reported before in the Soret coefficient of aqueous solutions, where the solution changes from thermophobic to thermophilic at specific temperatures. We show that a similar inversion behavior is observed in pure water. Microscopically, the inversion is the result of a balance of dipolar and quadrupolar contributions and the strong temperature dependence of the quadrupolar contribution, which is determined by the thermal expansion of the liquid.
温度梯度使水极化，这是一种非平衡效应，对于强热梯度可能会产生显著的静电场。通过非平衡分子动力学模拟，我们表明热极化对温度有显著依赖性，最终导致一种反转现象，即在特定温度下极化场会反转其符号。之前在水溶液的索雷特系数中已报道过温度反转效应，在特定温度下溶液从热疏性变为热亲性。我们表明在纯水中也观察到类似的反转行为。从微观角度来看，这种反转是偶极和四极贡献平衡以及四极贡献强烈温度依赖性的结果，而四极贡献由液体的热膨胀决定。
