Solvent-induced ion clusters generate long-ranged double-layer forces at high ionic strengths.

IF 2.9 3区 化学 Q3 CHEMISTRY, PHYSICAL
Soft Matter Pub Date : 2025-06-23 DOI:10.1039/d5sm00027k
David Ribar, Clifford E Woodward, Jan Forsman
{"title":"Solvent-induced ion clusters generate long-ranged double-layer forces at high ionic strengths.","authors":"David Ribar, Clifford E Woodward, Jan Forsman","doi":"10.1039/d5sm00027k","DOIUrl":null,"url":null,"abstract":"<p><p>Recent experimental results by the surface force apparatus (SFA) have identified a dramatic deviation from previously established theories of simple electrolytes. This deviation, referred to as anomalous underscreening, suggests that the range of electrostatic interactions increase upon a further addition of salt, beyond some threshold concentration (usually about 1 M). In this theoretical work, we explore an extension of the restricted primitive model (RPM) wherein a short-ranged pair potential of mean force (sPMF) is added to the usual Coulombic interactions so as to mimic changes of the hydration as two ions approach one another. The strength of this potential is adjusted so that the modified RPM saturates at a realistic concentration level (within a range 4-7 M, typical to aqueous 1 : 1 salts). We utilise grand canonical simulations to establish surface forces predicted by the model and compare them directly with SFA data. We explore different sPMF models, which in all cases display significant clustering at concentrations above about 1 M. In these models, we find significant double-layer repulsion at separations that significantly exceed those expected from standard RPM predictions. We do not, however, observe an increase of the screening length with salt concentration, but rather that this screening length seemingly saturates at a (rather high) value. The simulated long-ranged interactions are shown to correlate with ion cluster formation, implicating the important role of accompanying cluster-cluster interactions. In particular, steric interactions between clusters (manifested in density-density correlations) are quite relevant in these systems.</p>","PeriodicalId":103,"journal":{"name":"Soft Matter","volume":" ","pages":""},"PeriodicalIF":2.9000,"publicationDate":"2025-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Soft Matter","FirstCategoryId":"92","ListUrlMain":"https://doi.org/10.1039/d5sm00027k","RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"CHEMISTRY, PHYSICAL","Score":null,"Total":0}
引用次数: 0

Abstract

Recent experimental results by the surface force apparatus (SFA) have identified a dramatic deviation from previously established theories of simple electrolytes. This deviation, referred to as anomalous underscreening, suggests that the range of electrostatic interactions increase upon a further addition of salt, beyond some threshold concentration (usually about 1 M). In this theoretical work, we explore an extension of the restricted primitive model (RPM) wherein a short-ranged pair potential of mean force (sPMF) is added to the usual Coulombic interactions so as to mimic changes of the hydration as two ions approach one another. The strength of this potential is adjusted so that the modified RPM saturates at a realistic concentration level (within a range 4-7 M, typical to aqueous 1 : 1 salts). We utilise grand canonical simulations to establish surface forces predicted by the model and compare them directly with SFA data. We explore different sPMF models, which in all cases display significant clustering at concentrations above about 1 M. In these models, we find significant double-layer repulsion at separations that significantly exceed those expected from standard RPM predictions. We do not, however, observe an increase of the screening length with salt concentration, but rather that this screening length seemingly saturates at a (rather high) value. The simulated long-ranged interactions are shown to correlate with ion cluster formation, implicating the important role of accompanying cluster-cluster interactions. In particular, steric interactions between clusters (manifested in density-density correlations) are quite relevant in these systems.

溶剂诱导的离子团簇在高离子强度下产生长距离的双层力。
最近由表面力装置(SFA)的实验结果已经确定了与先前建立的简单电解质理论的巨大偏差。这种偏差被称为异常筛选不足,表明静电相互作用的范围随着盐的进一步添加而增加,超过某个阈值浓度(通常约为1m)。在这项理论工作中,我们探索了限制原始模型(RPM)的扩展,其中在通常的库仑相互作用中加入了短程平均力对势(sPMF),以模拟两个离子相互接近时水合作用的变化。调整该电位的强度,使修改后的RPM达到一个实际的浓度水平(在4-7 M范围内,典型的1:1水盐)。我们利用大规范模拟来建立由模型预测的表面力,并将其与SFA数据直接进行比较。我们探索了不同的sPMF模型,这些模型在所有情况下都显示出浓度高于1m的显著聚类。在这些模型中,我们发现在分离处显著的双层排斥明显超过标准RPM预测的预期。然而,我们没有观察到筛选长度随着盐浓度的增加而增加,而是这个筛选长度似乎在一个(相当高的)值上饱和。模拟的远程相互作用显示与离子簇的形成相关,暗示伴随的簇-簇相互作用的重要作用。特别是,团簇之间的空间相互作用(表现为密度-密度相关性)在这些系统中非常相关。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
求助全文
约1分钟内获得全文 求助全文
来源期刊
Soft Matter
Soft Matter 工程技术-材料科学:综合
CiteScore
6.00
自引率
5.90%
发文量
891
审稿时长
1.9 months
期刊介绍: Soft Matter is an international journal published by the Royal Society of Chemistry using Engineering-Materials Science: A Synthesis as its research focus. It publishes original research articles, review articles, and synthesis articles related to this field, reporting the latest discoveries in the relevant theoretical, practical, and applied disciplines in a timely manner, and aims to promote the rapid exchange of scientific information in this subject area. The journal is an open access journal. The journal is an open access journal and has not been placed on the alert list in the last three years.
×
引用
GB/T 7714-2015
复制
MLA
复制
APA
复制
导出至
BibTeX EndNote RefMan NoteFirst NoteExpress
×
提示
您的信息不完整,为了账户安全,请先补充。
现在去补充
×
提示
您因"违规操作"
具体请查看互助需知
我知道了
×
提示
确定
请完成安全验证×
copy
已复制链接
快去分享给好友吧!
我知道了
右上角分享
点击右上角分享
0
联系我们:info@booksci.cn Book学术提供免费学术资源搜索服务,方便国内外学者检索中英文文献。致力于提供最便捷和优质的服务体验。 Copyright © 2023 布克学术 All rights reserved.
京ICP备2023020795号-1
ghs 京公网安备 11010802042870号
Book学术文献互助
Book学术文献互助群
群 号:604180095
Book学术官方微信