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arXiv 1102.3337cond-mat.softcond-mat.stat-mechphysics.bio-ph
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非理想体系中的离子相变

Ionic phase transitions in non-ideal systems

Kyle J. Welch, Fred Gittes

摘要:

我们建立了一个明确可解的朗道平均场论,用于研究由二价和一价反离子相对浓度驱动的受限或固定离子的体积相变。这种相变已经在离子凝胶中被广泛研究,其中该机制依赖于网络的自吸引或弹性。我们发现在水溶液中离子的非理想行为理论上可以在没有自吸引或弹性网络的情况下驱动相变。我们用类似于德拜-休克尔的幂律活动或关联自由能来表示非理想性,并保留机械自排斥以避免由于非理想项而导致的失控崩溃。在这个模型中,我们发现了一个连续的线的气-液型临界点,连接一个纯粹的单价,二价敏感的临界点在一个极端与二价,单价敏感的临界点在其他。朗道泛函的另一种表示处理第二种情况。我们包括一个公式的电势,这可能是一个方便的代理临界变化的体积。我们相对简单的平均场公式可能有助于探索离子检测技术和生物渗透控制等领域的可调临界灵敏度。

英文摘要:

We construct an explicitly solvable Landau mean-field theory for volume phase transitions of confined or fixed ions driven by relative concentrations of divalent and monovalent counterions. Such phase transitions have been widely studied in ionic gels, where the mechanism relies on self-attraction or elasticity of a network. We find here that non-ideal behavior of ions in aqueous solution can in theory drive phase transitions without a self-attracting or elastic network. We represent non-ideality by a Debye-Hückel-like power-law activity, or correlation free energy, and retain a mechanical self-repulsion to avoid runaway collapse due to the non-ideal term. Within this model we find a continuous line of gas-liquid-type critical points, connecting a purely monovalent, divalent-sensitive critical point at one extreme with a divalent, monovalent-sensitive critical point at the other. An alternative representation of the Landau functional handles the second case. We include a formula for electrical potential, which may be a convenient proxy for critically varying volume. Our relatively simple mean-field formulation may facilitate explorations of tunable critical sensitivity in areas such as ion detection technology and biological osmotic control.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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