Buyukdagli Sahin
Department of Physics, Bilkent University, Ankara 06800, Turkey.
Phys Chem Chem Phys. 2022 Jun 8;24(22):13976-13987. doi: 10.1039/d2cp00853j.
We introduce a field-theoretic electrolyte model composed of structured solvent molecules and salt ions coupled by electrostatic and hard-core (HC) interactions. Within this explicit solvent framework, we characterize the salt-driven dielectric decrement by including salt-solvent correlations beyond weak-coupling (WC) electrostatics. The WC approximation of prior formalisms is relaxed by treating the salt charges a virial expansion. This virial approach enables the explicit inclusion of the many-body salt-solvent interactions, and directly leads to the experimentally observed linear decay of the electrolyte permittivity with added dilute salt. The permittivity formula emerging from our approach indicates that the reduction of the solvent permittivity is induced by the salt screening of the polarization charges suppressing the dielectric response of the solvent. By comparison with experiments, we also show that the salt-dressed permittivity formula can equally reproduce the attenuation of the electrolyte permittivity with rising temperature, the thermal decay of the dielectric decrement, and its intensification with the salt valency. In accordance with the observation of previous numerical simulations and implicit solvent theories, the consistent qualitative agreement of our theory with this wide range of experimental trends points out the electrostatic ion-solvent correlations as the primary mechanism behind the salt-induced dielectric decrement.
我们引入了一种场论电解质模型，该模型由结构化溶剂分子和盐离子组成，它们通过静电相互作用和硬核（HC）相互作用耦合。在这个明确的溶剂框架内，我们通过纳入超出弱耦合（WC）静电学的盐 - 溶剂相关性来表征盐驱动的介电常数降低。通过将盐电荷处理为维里展开，放宽了先前形式主义的WC近似。这种维里方法能够明确纳入多体盐 - 溶剂相互作用，并直接导致实验观察到的电解质介电常数随添加稀盐的线性衰减。我们方法中出现的介电常数公式表明，溶剂介电常数的降低是由极化电荷的盐屏蔽抑制溶剂的介电响应引起的。通过与实验比较，我们还表明盐修饰的介电常数公式同样可以再现电解质介电常数随温度升高的衰减、介电常数降低的热衰减以及其随盐价态的增强。与先前数值模拟和隐式溶剂理论的观察结果一致，我们的理论与这一系列广泛实验趋势的一致定性吻合表明，静电离子 - 溶剂相关性是盐诱导介电常数降低背后的主要机制。
