Statistical field theory for polar fluids

Abstract

Using a variational field-theoretic approach, we derive a theory for polar fluids. The theory naturally accounts for the reaction field without resorting to the cavity construct and leads to a simple formula for the dielectric constant in terms of the molecular dipole moment and density. We apply our formula to calculate the dielectric constants of nonpolarizable liquid models for more than a hundred small molecules without using any adjustable parameters. Our formula predicts dielectric constants of these nonpolarizable liquid models more accurately than the Onsager theory and previous field-theoretic dielectric theories, as demonstrated by the closer agreement to the simulation results. The general theory also yields the free energy, which can describe the response of polar fluids under applied electric fields.

Like dissolves like: A first-principles theory for predicting liquid miscibility and mixture dielectric constant

“…In terms of the polarization ˆ P (r) , the electrostatic energy of the fluid is (12) where T(r) = −∇∇(1/4 0 |r|) is the dipole-dipole interaction tensor. A detailed discussion of the relevant mathematical properties of T(r) has been presented in our earlier work in (12). Particularly useful is the Fourier transform of T(r) given by ~ T (k ) = kk /  0 k 2 .…”

“…Their discussions of liquid miscibility focused on nonpolar liquids (i.e., without permanent dipoles) and the comparisons to experimental data involved the use of adjustable parameters. Furthermore, their work used a bare one-loop expansion, which we have shown to give less accurate predictions on the dielectric constant of polar liquids than our renormalized Gaussian fluctuation theory (12). Instead of the one-loop expansion, we use a variational method to account for the reaction field effects.…”

A Simple Explicit-Solvent Model of Polyampholyte Phase Behaviors and Its Ramifications for Dielectric Effects in Biomolecular Condensates

“…To address the generality of this putative principle, we have also developed corresponding field-theory formulations for polyampholytes with a polar solvent modeled as permanent or polarizable dipoles that are treated explicitly in the theory. Similar permanent − and polarizable , dipole models were used to study dielectric properties of polar solutions − and the effect of electric field on phase stability of charged polymers, but these have not been applied to tackle the question at hand. Here we find that the trend of phase behaviors predicted using RPA of our field-theory formulation regarding explicit versus implicit solvent are in agreement with that obtained by explicit-chain simulations, suggesting that a compensation between more favorable polyampholyte–polar-solvent electrostatic interactions in a high-ϵ r dilute phase and more favorable effective interpolyampholyte electrostatic interactions in a low-ϵ r condensed phase is a rather robust feature of polyampholyte LLPS systems.…”

Statistical theory of fluids with a complex electric structure: Application to solutions of soft-core dipolar particles

“…One can especially stress, among others, a number of macromolecules (such as proteins, polypeptides and betaines) that have some important applications and under certain conditions acquire a large dipole moment ( 100 − 1000 D) [14][15][16][17][18][19][20][21][22] . However, in order to describe theoretically the electrostatic interactions between such big dipolar macromolecules, it is incorrect to model them as the point-like dipoles (or even dipolar hard spheres) similar to polar molecules in the theory of simple dipolar fluids [23][24][25][26][27][28][29][30][31][32][33][34][35] due to a very big dipole length (∼ 1 − 20 nm). Instead, it is necessary to consider a dipolar molecule as a set of charged centers (sites), separated by a fixed or fluctuating distance 36 .…”