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arXiv 1402.6527cond-mat.soft
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电解质溶液中润湿转变的顺序

Order of wetting transitions in electrolyte solutions

Ingrid Ibagon, Markus Bier, S. Dietrich

摘要:

对于在稀电解质溶液中靠近带电壁的润湿膜,我们给出了它们的有效界面电位的解析表达式。这些表达式的分析呈现的条件下,相应的润湿过渡可以是一阶或二阶。在平均场论中,我们考虑两种模型,一种是短程的,另一种是长程的溶剂-溶剂和溶剂-壁相互作用。分析结果以透明的方式揭示了电解质溶液中的润湿转变,该转变发生在远离其临界点(即,体相关长度小于德拜长度的一半)总是一级的。相反,润湿转变接近溶剂的本体临界点(即,体相关长度大于德拜长度)表现出与纯的相同的润湿行为,即,无盐、溶剂。如果无盐溶剂由长程溶剂-溶剂以及长程溶剂-壁相互作用控制并且表现出临界润湿性,则添加盐可导致发生离子诱导的第一级薄-厚转变,其先于无盐溶剂的后续连续润湿。

英文摘要:

For wetting films in dilute electrolyte solutions close to charged walls we present analytic expressions for their effective interface potentials. The analysis of these expressions renders the conditions under which corresponding wetting transitions can be first- or second-order. Within mean field theory we consider two models, one with short- and one with long-ranged solvent-solvent and solvent-wall interactions. The analytic results reveal in a transparent way that wetting transitions in electrolyte solutions, which occur far away from their critical point (i.e., the bulk correlation length is less than half of the Debye length) are always first-order if the solvent-solvent and solvent-wall interactions are short-ranged. In contrast, wetting transitions close to the bulk critical point of the solvent (i.e., the bulk correlation length is larger than the Debye length) exhibit the same wetting behavior as the pure, i.e., salt-free, solvent. If the salt-free solvent is governed by long-ranged solvent-solvent as well as long-ranged solvent-wall interactions and exhibits critical wetting, adding salt can cause the occurrence of an ion-induced first-order thin-thick transition which precedes the subsequent continuous wetting as for the salt-free solvent.

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