Dielectric Constant Of Polar Liquids Research Articles

Dielectric Susceptibility of Water in the Interface.

It has long been anticipated that dielectric constants of polar liquids are reduced in the interfacial layer. Recent experiments and computer simulations support these expectations. A strong reduction of the dielectric constant is found in the direction perpendicular to a planar substrate, while the parallel response is bulk-like. This Perspective highlights recent theoretical calculations and simulations with an eye on relating them to properties observable in the laboratory. The average interface dielectric constant computed from simulations connects to thin films experiments, but this cannot be extended to screening of charges. In contrast to dielectric theories where a single dielectric constant gauges both the polarization energy and screening, these two signatures of dielectric polarization diverge on the molecular scale. The reduction of the dielectric constant of water in thin films is currently viewed as a combined effect of geometric confinement imposed by the substrate and the reconstruction of water hydrogen bonds in the surface layer.

First principle determination of dielectric constant of polar liquids by the extended RISM theory with the bridge diagrams concerning dipole-dipole interactions

The extended RISM (XRISM) theory with a new closure relation is proposed. The new equation incorporates the chain sum of the dipole-dipole interactions into XRISM as the bridge diagrams (Dipole Bridge: DB) in its closure relation. The new theory reproduces the dielectric constant of polar liquids without using phenomenological parameters, but with a parameter which reflects the effect of short-range correlation onto the dipole-dipole interaction between the two molecules. The parameter is essentially universal in dipolar liquids including water. The computational algorithm to solve the XRISM-DB equation is identical to that of XRISM, so that all the programs developed for XRISM can be transferred to the new equation by adding few lines which define the screening constant concerning the dipole-dipole interaction.

Uncertainties in the static dielectric constants computed from molecular dynamics simulations

In this work, the uncertainties in the dielectric constants of polar liquids, computed using molecular dynamics (MD) simulations, are compared for two different calculations schemes. Expressions of the uncertainty are derived for the external field method, and compared with those of the fluctuation method. Significant differences in their the system size dependence were found. In addition, alternative calculation procedures are proposed. The individual contributions of different parts of the system to the electric susceptibility, and their corresponding uncertainties, are also studied. Additionally, the effects of the sampling frequency on the uncertainties are analyzed. MD simulations of pure liquid water (SPC/E) at 298.15 K and 1 bar were performed in order to corroborate the obtained results. In such conditions, the best estimate of the dielectric constant obtained in this study is 70.46 ± 0.31.

Computing the Kirkwood g-Factor by Combining Constant Maxwell Electric Field and Electric Displacement Simulations: Application to the Dielectric Constant of Liquid Water.

In his classic 1939 paper, Kirkwood linked the macroscopic dielectric constant of polar liquids to the local orientational order as measured by the g-factor (later named after him) and suggested that the corresponding dielectric constant at short-range is effectively equal to the macroscopic value just after "a distance of molecular magnitude" [ Kirkwood, J. Chem. Phys., 1939, 7, 911 ]. Here, we show a simple approach to extract the short-ranged Kirkwood g-factor from molecular dynamics (MD) simulation by superposing the outcomes of constant electric field E and constant electric displacement D simulations [ Zhang and Sprik, Phys. Rev. B: Condens. Matter Mater. Phys., 2016, 93, 144201 ]. Rather than from the notoriously slow fluctuations of the dipole moment of the full MD cell, the dielectric constant can now be estimated from dipole fluctuations at short-range, accelerating the convergence. Exploiting this feature, we computed the bulk dielectric constant of liquid water modeled in the generalized gradient approximation (PBE) to density functional theory and found it to be at least 40% larger than the experimental value.

JACS AT 125

RETURN TO ISSUEPREVNewsNEXTJACS AT 125AN ELECTRIC MOMENTCorrection of Debye theory to predict dielectric constants of polar liquids had far-reaching effectCELIA HENRYCite this: Chem. Eng. News 2003, 81, 46, 70Publication Date (Print):November 17, 2003Publication History Published online13 November 2010Published inissue 17 November 2003https://doi.org/10.1021/cen-v081n046.p070Copyright © 2003 AMERICAN CHEMICAL SOCIETYArticle Views10Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (542 KB) SUBJECTS:Molecules Get e-Alerts

Ultrafast dielectric relaxation response of polar liquids

In this paper we calculate the complex dielectric constant of polar liquids for microwave and far-infrared range of frequencies. We use the formalism of extended irreversible thermodynamics (EIT) to obtain the autocorrelation function of the polarization vector. To this end, we introduce the local variation of the polarization flow as an independent variable, which allows for the description of collective interacting effects into the formalism. The results obtained here are compared with previous work in the so-called three-variable theory based on the Mori-Zwanzig projection operator technique. This comparison provides an interpretation of EIT in terms of a microscopic theory from which the role of the new independent variable can be established. Using the result of the complex dielectric constant presented here, we show that the fitting of experimental data in polar fluids can be improved in the far infrared frequencies.

A theory of electric polarisation in liquids: II. Polar liquids

In the frame of a theory previously developed by the author for non-polar liquids, the static dielectric constant of polar liquids is described through a new formula without adjustable parameters, valid for spherical molecules carrying a mathematical dipole. The application of the formula to 20 polar liquids shows that the dipole moments resulting from the theory are satisfactorily compared with those deduced from vapour phase data. The agreement obtained in this way between theory and experiment is better than that obtained through the analogous Onsager's formula.

Universal nomograms for measurement of UHF dielectric constants of polar liquids

Universal nomograms for measurement of UHF dielectric constants of polar liquids

A calculation of the complex dielectric constant of a polar liquid by the librating molecule method

The dielectric constant of polar liquids is calculated by assuming a model of the molecule which describes its interaction with the electric field and by introducing means of calculating certain averages demanded by the statistical mechanical theory. In this paper we make a calculation for the time-dependent case which parallels the approach of Onsager. The model is introduced at the beginning, and the average torque on a molecule due to the local field is found by solving quasistatically the problem of a polarizable dipole performing small librations in a cavity in a continuum having a complex dielectric constant. The result of the calculation predicts a non-exponential decay of the macroscopic polarization. The results are compared with the treatment of similar type by Scaife, and with treatments by means of the Kubo theory of non-equilibrium statistical mechanics. These latter allow the introduction of the model at a late stage in the calculation, as in the theories of Kirkwood, Frohlich and Buckingham on the static case. Such a treatment, as carried out by Glarum, and a modification of it by the authors are considered. It is found that the results of the present paper show a certain agreement with the results of Scaife and with the authors' modification of the treatment of Glarum.

Dielectric Constant of Polar Liquids at High Field Strengths

A critical examination is given of a simplifying assumption made in an earlier calculation of the functional dependence of the integral dielectric constant of polar liquids on the applied field. It was assumed in this calculation that, for the cavity and reaction fields at all field strengths the usual expressions for low field strengths could be employed. It was pointed out that this simplification is plausible if the static dielectric constant is large compared with the optical dielectric constant. In the present note it is shown that, if it is postulated that the reaction field alone retains its conventional value, then the cavity field is appreciably increased by dielectric saturation. In the case of water the effect is equivalent to an increase of the external field by about 10 percent; a modified relation between the field and the dielectric constant is suggested. The alteration of the reaction field as a result of saturation, and the effect of this modification on the dielectric constant, are also examined.

Influence of molecular shape on the dielectric constant of polar liquids

Influence of molecular shape on the dielectric constant of polar liquids

A contribution to the theory of the dielectric constant of polar liquids

Some simplifications used in Onsager's theory on the dielectric constant of pure liquids are considered. At first, instead of a spherical, an ellipsoidal shape of the molecules is attempted and the cavity field and reaction field of a dipole are computed in this case. It appears that the reaction field of a dipole in an ellipsoidal cavity is smaller than the reaction field in a spherical cavity of the same volume if the longest axis is in the direction of the dipole. In the case that the shortest axis is in the direction of the dipole, the reaction field is greater than in a spherical cavity. Also a discussion on the radius of the cavity is given. A model is assumed in which for the polarisability effects the continuous environment begins at a distance equal to the radius of the molecules while for the influance of the dipolar interaction the continuous environment begins at twice as great a distance.

The Cavity Resonator Method of Measuring the Dielectric Constants of Polar Liquids in the Centimetre Band

A method is described of determining the refractive index n of a polar liquid in the centimetre band by measuring the resonance curve of an H01 resonator with an axial capillary of liquid. An independent value of κ is required. The method has been tried out on water at 21° c. Three independent measurements gave n=6.25, 6.30, 6.35, so that the method is capable of ±1% accuracy.

The Dielectric Constants of Polar Liquids.

The Dielectric Constants of Polar Liquids.

Free Volumes and Free Angle Ratios of Molecules in Liquids

The free volume is defined as the total integral over that part of the potential energy of the molecule in the liquid which is due to thermal displacements of the center of gravity of the molecule from its equilibrium position. The free angle is the corresponding integral over angular displacements of the molecule. The free volume, Vf is related to the velocity of sound, u, in the liquid by u(liquid)=u (gas) (V/Vf)13.This equation is used to derive a formula connecting the sound velocity in the liquid with its thermal conductivity. The quantity, RT/p exp (ΔH/RT), gives the product of the free angle ratio and the free volume, rather than the free volume itself. Here p is the vapor pressure and ΔH is the heat of vaporization. The free volumes from sound velocities agree with those determined by independent methods. Specific heats, entropies of vaporization, the spectroscopic observations of Cartwright, and the differences between sound velocity, free volumes and the function RT/p ×exp (ΔH/RT) are examined from the point of view of restricted rotation of the molecules in liquids. Lack of free rotation of molecules suffices to explain the abnormalities of the liquids examined. The dielectric constants of polar liquids are interpreted assuming restricted rotation and the following formula is derived: μl2μg−2=1−((1−cos θ1)/2)2,where μl is the apparent dipole moment of the molecule in the liquid, μg is the dipole moment as determined from measurements in the gas phase, and θ1, is the polar angle related to the free angle ratio, δ2, by δ2=(1−cos θ1)/2.The concept of restricted rotation of the molecules in the liquid accounts satisfactorily for the observed dielectric polarizations of water and methyl alcohol.

The dielectric constant of dipole liquids

The half empirical formula for the dielectric constant of polar liquids, found by van Arkel and Snoek has been arrived at, starting from Onsagers theory of the reaction field.