Sorbonne Université, CNRS, Institut des Nanosciences de Paris, INSP, UMR 7588, 4 place Jussieu, 75005 Paris, France.
Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA.
Phys Rev E. 2019 Nov;100(5-1):052145. doi: 10.1103/PhysRevE.100.052145.
We investigate ionic criticality on the basis of a specially devised spherical model that accounts both for Coulomb and nonionic forces in binary systems. We show in detail here the consequences of the entanglement of density and charge correlation functions G_{NN} and G_{ZZ} on criticality and screening. We also show on this soluble model how, because of electroneutrality, the long-range Coulomb interactions do not change the universality class of criticality in the model driven primarily by sufficiently attractive nonionic interactions. Near criticality, G_{NN} and G_{ZZ} are fully decoupled in charge symmetric systems. However, in more realistic nonsymmetric models, charge and density fluctuations couple in leading order so that the charge and density correlation lengths diverge asymptotically in a similar way. Similarly, the Stillinger-Lovett sum rule, which characterizes a conducting fluid, is violated at criticality in nonsymmetric models when the critical-point density-decay exponent η vanishes. In addition, if quantum effects are accounted for semiclassically by incorporating algebraically decaying interactions, G_{ZZ} decays only as a power law in the whole phase space, contrary to the usually expected exponential Debye screening. We expect these results on this soluble toy model to be general and to reveal general mechanisms ruling ionic criticality.
我们基于一个特殊设计的球形模型来研究离子临界点，该模型同时考虑了二元体系中的库仑力和非离子力。在这里，我们详细展示了密度和电荷相关函数 G_{NN} 和 G_{ZZ} 的缠结对临界点和屏蔽的影响。我们还在这个可解模型上展示了，由于电中性，主要由足够吸引人的非离子相互作用驱动的模型中的临界点的普遍性类别不会因长程库仑相互作用而改变。在临界点附近，在电荷对称系统中，G_{NN} 和 G_{ZZ} 完全解耦。然而，在更现实的非对称模型中，电荷和密度涨落在主导阶次上耦合，因此电荷和密度相关长度以相似的方式渐近发散。同样，当临界点密度衰减指数 η 消失时，Stillinger-Lovett 求和规则（表征导电流体）在非对称模型中违反临界点。此外，如果通过包含指数衰减相互作用半经典地考虑量子效应，那么在整个相空间中，G_{ZZ} 仅按幂律衰减，这与通常预期的指数 Debye 屏蔽相反。我们期望这个可解模型的这些结果是普遍的，并揭示出支配离子临界点的一般机制。
