scholarly journals Relative Permittivity of Dipolar Model Fluids from Molecular Simulation and from the Co-Oriented Fluid Functional Equation for Electrostatic Interactions

2021 ◽  
Author(s):  
Kai Langenbach ◽  
Maximilian Kohns
Keyword(s):  
Functional Equation ◽  
Electric Fields ◽  
Relative Permittivity ◽  
Electrostatic Interactions ◽  
Equations Of State ◽  
Orientation Distribution ◽  
Theoretical Expression ◽  
Dipolar Fluids ◽  
Model Fluids ◽  
Dipolar Model

The relative permittivity of dipolar fluids is important in many industrial and scientific applications, e.g. whenever electrolytes or electromagnetic fields are present. For non-polarizable model molecules, it is directly linked to the mutual molecular orientation and thereby usually not accessible by equations of state. However, the recently developed Co-Oriented Fluid Functional Equation for Electrostatic interactions (COFFEE) allows for calculating the orientation distribution function of simple polar molecules and thereby establishes a connection between the thermodynamic behavior and the relative permittivity. In this article, we develop an expression to calculate the relative permittivity from the orientation distribution known from COFFEE. Furthermore, we calculate the relative permittivity of simple polar fluids using molecular simulations. We study the original Stockmayer fluid and the shifted Stockmayer fluid, in which the dipole is shifted away from the Lennard-Jones center along the dipole axis. For both fluids, different dipole strengths are investigated. The results from the theoretical expression from COFFEE are compared to the simulation data. Thereby, a possible link between polar equations of state and electric fields or electrolytes is developed.

scholarly journals Correction to “Relative Permittivity of Dipolar Model Fluids from Molecular Simulation and from the Co-Oriented Fluid Functional Equation for Electrostatic Interactions”

2021 ◽  
Author(s):  
Kai Langenbach ◽  
Maximilian Kohns
Keyword(s):  
Functional Equation ◽  
Molecular Simulation ◽  
Relative Permittivity ◽  
Electrostatic Interactions ◽  
Model Fluids ◽  
Dipolar Model

Correction to “Relative Permittivity of Dipolar Model Fluids from Molecular Simulation and from the Co-Oriented Fluid Functional Equation for Electrostatic Interactions”

Equations of State for Natural and Synthetic Rubber-Like Materials. I Unaccelerated Natural Soft Rubber

1943 ◽  
Vol 16 (2) ◽  
pp. 297-309 ◽  
Author(s):  
R. L. Anthony ◽  
R. H. Caston ◽  
Eugene Guth
Keyword(s):  
Thermal Expansion ◽  
Room Temperature ◽  
Equations Of State ◽  
Intermolecular Forces ◽  
Theoretical Expression ◽  
Total Force ◽  
Inversion Point ◽  
Synthetic Rubber ◽  
First Approximation ◽  
Direct Contrast

Abstract Summarizing, the following important conclusions may be drawn from these experiments on a typical unaccelerated soft gum compound. 1. The existence of the inversion point in the stress-temperature curves is shown to be due solely to ordinary volume thermal expansion, and may be eliminated by correcting for this thermal expansion. 2. The curves given in Figure 8a show that, for compounds of this type, the change of entropy with elongation accounts for more than 90 per cent of the total stress at room temperature, while the internal-energy contribution is less than 10 per cent and, to a first approximation, may be neglected. In other words, the retractive force is due almost entirely to the tendency of the extended rubber molecules to return to a less ordered curled-up state. This is in direct contrast to the elasticity exhibited by ordinary bodies, in which case elasticity is due to intermolecular forces. 3. The contribution of the entropy force to the total force is well represented by the theoretical expression of James and Guth. This agreement constitutes our main reason for interpreting the entropy force as being due to the kinetic motion of the rubber molecules.

scholarly journals Separation of water–ethanol solutions with carbon nanotubes and electric fields

2016 ◽  
Vol 18 (48) ◽  
pp. 33310-33319 ◽  
Author(s):  
Winarto Winarto ◽  
Daisuke Takaiwa ◽  
Eiji Yamamoto ◽  
Kenji Yasuoka
Keyword(s):  
Carbon Nanotubes ◽  
Electric Field ◽  
Electric Fields ◽  
Electrostatic Interactions ◽  
Water Molecules ◽  
Ordered Structure

Under an electric field, water prefers to fill CNTs over ethanol, and electrostatic interactions within the ordered structure of the water molecules determine the separation effects.

scholarly journals A Preorganized Electric Field Leads to Minimal Geometrical Reorientation in the Catalytic Reaction of Ketosteroid Isomerase

2020 ◽  
Author(s):  
Yufan Wu ◽  
Stephen Fried ◽  
Steven Boxer
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Ground State ◽  
Active Site ◽  
Electrostatic Interactions ◽  
Stark Effect ◽  
Structural Changes ◽  
Enzymatic Catalysis ◽  
Ketosteroid Isomerase ◽  
Computational Enzyme Design

<div><p>Electrostatic interactions play a pivotal role in enzymatic catalysis and are increasingly modeled explicitly in computational enzyme design; nevertheless, they are challenging to measure experimentally. Using vibrational Stark effect (VSE) spectroscopy, we have measured electric fields inside the active site of the enzyme ketosteroid isomerase (KSI). These studies have shown that these fields can be unusually large, but it has been unclear to what extent they specifically stabilize the transition state (TS) relative to a ground state (GS). In the following, we use crystallography and computational modeling to show that KSI’s intrinsic electric field is nearly perfectly oriented to stabilize the geometry of its reaction’s TS. Moreover, we find that this electric field adjusts the orientation of its substrate in the ground state so that the substrate needs to only undergo minimal structural changes upon activation to its TS. This work provides evidence that the active site electric field in KSI is preorganized to facilitate catalysis and provides a template for how electrostatic preorganization can be measured in enzymatic systems. <br></p></div>

scholarly journals Structure of Simple Dipolar Water-Like Fluids: Primitive Model and Hard Tetrahedra

2021 ◽  
Vol 9 ◽  
Author(s):  
I. Nezbeda
Keyword(s):  
Hydrogen Bonding ◽  
Short Range ◽  
Equations Of State ◽  
Dipole Interaction ◽  
Marginal Effect ◽  
Associating Fluids ◽  
Primitive Model ◽  
Bonding Structure ◽  
Bonding Interaction ◽  
Model Fluids

Dipolar versions of two qualitatively different types of simple short range model fluids which exhibit the phenomenon of hydrogen bonding and which could thus serve as a reference in equations of state for associating fluids have been considered: the primitive model of water descending from the TIP4P model and the fluid of hard tetrahedra. The hydrogen bonding structure exhibited by the latter model results from purely repulsive interactions whereas in the first model the “hydrogen bonding interaction” is explicitly incorporated in the model. Since the water molecules bear a strong dipole moment, the effect of the added dipole-dipole interaction on the structure of the two short-range models is therefore examined considering them both in the full and screened dipole-dipole modifications. It is found that the hydrogen bonding structure in the primitive model resulting from the site-site interactions is so strong that the additional dipole-dipole interaction has only a marginal effect on its structure and contributes thus only to the internal energy. On the contrary, even only a weak dipole-dipole interaction destroys the original hydrogen bonding structure of the hard tetrahedron fluid; to preserve it, a screened dipole-dipole interaction has to be used in the equation of state development.

Extended statistical associating fluid theory (SAFT) equations of state for dipolar fluids

AIChE Journal ◽  
2005 ◽  
Vol 51 (8) ◽  
pp. 2328-2342 ◽  
Author(s):  
Eirini K. Karakatsani ◽  
Theodora Spyriouni ◽  
Ioannis G. Economou
Keyword(s):  
Equations Of State ◽  
Statistical Associating Fluid Theory ◽  
Dipolar Fluids ◽  
Fluid Theory

scholarly journals The increase of thermionic currents from tungsten in strong electric fields

1928 ◽  
Vol 121 (787) ◽  
pp. 456-464 ◽  
Keyword(s):  
Experimental Investigation ◽  
External Field ◽  
Force Field ◽  
Work Function ◽  
Electric Fields ◽  
Experimental Verification ◽  
Image Force ◽  
Theoretical Expression ◽  
Electric Image ◽  
Strong Electric Fields

Schottky has pointed out that there should be an increase in thermionic currents above the saturation value with the application of strong electric fields. His theoretical expression is based on the assumption that an electron is prevented from escaping by the attraction of its electric image in the emitting wire, and that the external field neutralises part of this image force field. In the same paper he reports an approximate experimental verification of his theoretical law, though the details are lacking. Since that paper, reference has been made to this increase in current, and it has been applied as a correction in determining the thermionic work function. Becker and Mueller have discussed the problem, but apparently assume the correctness of Schottky’s expression. Under the circumstances it seemed that an experimental investigation was needed, all the more because Schottky’s theoretical expression seems open to question on certain points. Let us suppose that a single electron is escaping from a plane electrode, and that the image force alone is acting upon it.

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