稠密电解质中的结构与动力学相变
Structural and Dynamical Crossovers in Dense Electrolytes
AI总结：
研究通过分子动力学模拟揭示了高浓度电解质中结构与动力学相变的机制，发现离子-溶剂耦合对屏蔽和动力学行为有显著影响。
摘要：
静电相互作用从根本上决定了电解质的结构和传输性质。然而，在高浓度电解质中，静电和立体排斥相关性，以及离子-溶剂耦合，导致了复杂的行为，如欠屏蔽，尽管有大量理论研究，仍难以解释。通过分子动力学模拟原始电解质，包括有和无空间填充溶剂粒子，我们阐明了随着盐浓度增加出现的结构和动力学相变及其联系。显式溶剂电解质表现出从电荷主导稀释态到密度主导浓缩态的屏蔽转变，伴随离子自扩散和离子对寿命的动力学相变。这些动力学相变表现出明显的不连续性，不同于屏蔽相变的平滑变化，后者起源于短程离子-反离子结构。显著增长的离子簇导致只有在更高浓度时才会出现渗透相变，而结构和动力学相变的出现主要与局部离子配对或小聚集体有关。结构和动力学行为均对离子-溶剂耦合敏感：隐式溶剂电解质表现出在两个电荷主导态之间的屏蔽转变，伴随不同的动力学行为。最后，我们证明扩散校正的离子对寿命提供了一种连贯的描述符，将离子结构和动力学联系起来，适用于电解质系统。
英文摘要：
Electrostatic interactions fundamentally govern the structure and transport of electrolytes. In concentrated electrolytes, however, electrostatic and steric correlations, together with ion-solvent coupling, give rise to complex behavior, such as underscreening, that remains challenging to explain despite extensive theoretical effort. Using molecular dynamics simulations of primitive electrolytes with and without space-filling solvent particles, we elucidate the structural and dynamical crossovers and their connection that emerge with increasing salt concentration. Explicit-solvent electrolytes exhibit a screening transition from a charge-dominated dilute regime to a density-dominated concentrated regime, accompanied by dynamical crossovers in ion self-diffusion and ion-pair lifetimes. These dynamical crossovers display a marked discontinuity, unlike the smoother variation of the screening crossover, which originates from short-range ion-counterion structures. The pronounced growth of ionic clusters leads to a percolation transition only at higher concentrations, whereas the onset of the structural and dynamical crossovers is associated primarily with local ion pairing or small aggregates. Both structural and dynamical behaviors are found to depend sensitively on ion-solvent coupling: implicit-solvent electrolytes exhibit a screening transition between two charge-dominated regimes, accompanied by qualitatively distinct dynamical behavior. Finally, we demonstrate that the diffusion-corrected ion-pair lifetime provides a consistent descriptor linking ionic structure and dynamics across electrolyte systems.
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