Using the adiabatic connection, we formulate the free energy in terms of the correlation function of a fictitious system, $h_λ({\bf r},{\bf r}')$, where $λ$ determines the interaction strength. To obtain $h_λ({\bf r},{\bf r}')$ we use the Ornstein-Zernike equation, and the two equations constitute a general liquid-state framework for treating inhomogeneous fluids. As the two equations do not form a closed set, an approximate closure relation is required and it determines a type of an approximation. In the present work we investigate the random phase approximation (RPA) closure. We determine that this approximation is identical to the variational Gaussian approximation derived within the framework of the field-theory. We then apply our generalized RPA approximation to the Gaussian core model and Coulomb charges.
A field theoretic representation of the classical partition function is derived for a system composed of a mixture of anisotropic and isotropic mobile charges that interact {\sl via} long range Coulomb and short range nematic interactions. The field theory is then solved on a saddle-point approximation level, leading to a coupled system of Poisson-Boltzmann and Maier-Saupe equations. Explicit solutions are finally obtained for a rod-like counterion-only system in proximity of a charged planar wall, generalizing the standard Gouy-Chapman results. The nematic order parameter profile, the counter…
We study the dependence of the surface tension of a fluid interface on the density profile of a third suspended phase. By means of an approximated model for the binary mixture and of a perturbative approach we derive close formulas for the free energy of the system and for the surface tension of the interface. Our results show a remarkable non-monotonous dependence of the surface tension on the peak of the density of the suspended phase. Our results also predict the local value of the surface tension in the case in which the density of the suspended phase is not homogeneous along the interface…
We propose a field-theoretical approach based on the thermodynamic perturbation theory and within it derive a grand thermodynamic potential of the inhomogeneous ionic fluid as a functional of electrostatic potential for an arbitrary reference fluid system. We obtain a modified Poisson-Boltzmann equation as the Euler-Lagrange equation for the obtained functional. Applying Noether's theorem to this functional, we derive a general mean-field expression for the stress tensor consistent with the respective modified Poisson-Boltzmann equation. We derive a general expression for the macroscopic force…
Definitions for a local pressure in an inhomogeneous fluid are considered for both equilibrium and local equilibrium states. Thermodynamic and mechanical (hydrodynamic) contexts are reconciled. Remaining problems and uncertainties are discussed.
Inhomogeneous fluid of penetrable-spheres: application of the random phase approximation
本工作的重点是将针对非均匀流体导出的无规相位近似(RPA)应用于可穿透球体[Frydel和Ma,Phys. Rev. E 93,062112(2016)]。随着可穿透球体随着相互作用的增加而转变为硬球体,它们为探索RPA、其缺点和局限性、弱耦合极限与强耦合极限提供了一个有趣的案例。本研究采取的两种方案是一个单组分和一个双组分流体与对称的相互作用。在后一种情况下,平均场的贡献被抵消,粒子相互作用的任何贡献都由相关性来解释。在这种情况下,RPA的准确性是某种程度上幸运地取消了错误的结果。
We have developed a field theory for strongly coupled Coulomb fluids, via introducing new functional--integral transformation of the electrostatic interaction energy. Our formalism not only reproduces the Lieb--Narnhofer lower bound, but also bridges logical gaps which previous approaches have involved.
The structure factor for electric field correlations in the two dimensional Coulomb fluid is simulated and compared to theories of the dielectric function. Singular changes in the structure factor occur at the BKT insulator to conductor transition, as well as at a higher temperature correlation transition between a poor electrolyte and perturbed Debye-Hückel fluid. Structure factors are found to differ in the canonical and grand canonical ensembles, with the poor electrolyte showing full ensemble inequivalence. We identify mechanisms of `underscreening' and `pinch point' scattering that are re…
A unified formulation of the density functional theory is constructed on the foundations of entropic inference in both the classical and the quantum regimes. The theory is introduced as an application of entropic inference for inhomogeneous fluids in thermal equilibrium. It is shown that entropic inference reproduces the variational principle of DFT when information about expected density of particles is imposed. In the classical regime, this process introduces a family of trial density-parametrized probability distributions, and consequently a trial entropy, from which the preferred one is fo…
Single-particle density matrix and superfluidity in the two-dimensional Bose Coulomb fluid
W. R. Magro和D. M. Ceperley [Phys. Rev. Lett. { \bf 73},826(1994)]已经表明,具有对数相互作用的荷电玻色子的二维流体的基态不是玻色凝聚的,而是在单粒子密度矩阵$ρ(r)$中表现出代数非对角阶。我们使用的流体动力学哈密顿表示的密度和相位算子,结合超流分数的$f$求和规则,重现这些结果,并延长评估的密度矩阵有限温度$T$。这种方法允许我们在没有凝聚物的情况下将液体视为超流体。我们发现:(i)非对角序来自相位涨落之间的相关性;(ii)超流密度$n_s(T)$决定了$ρ(r)$幂律衰减的指数。我们还发现,在长波长的单粒子能谱中的等离子体激元间隙随着$T$的增加而减小,并在超流性开始的临界温度处关闭。