scholarly journals Modification of Bikerman model with specific ion sizes

2017 ◽  
Vol 5 (1) ◽  
pp. 142-149 ◽  
Author(s):  
Tzyy-Leng Horng ◽  
Ping-Hsuan Tsai ◽  
Tai-Chia Lin
Keyword(s):  
Steric Effect ◽  
Particle Distribution ◽  
Finite Size ◽  
Finite Size Effect ◽  
Ion Concentrations ◽  
Entropy Term ◽  
Direct Extension ◽  
Poisson Boltzmann ◽  
Ion Size ◽  
Forward Extension

Abstract Classical Poisson-Boltzman and Poisson-Nernst-Planck models can only work when ion concentrations are very dilute, which often mismatches experiments. Researchers have been working on the modification to include finite-size effect of ions, which is non-negelible when ion concentrations are not dilute. One of modified models with steric effect is Bikerman model, which is rather popular nowadays. It is based on the consideration of ion size by putting additional entropy term for solvent in free energy. However, ion size is non-specific in original Bikerman model, which did not consider specific ion sizes. Many researchers have worked on the extension of Bikerman model to have specific ion sizes. A direct extension of original Bikerman model by simply replacing the non-specific ion size to specific ones seems natural and has been acceptable to many researchers in this field.Herewe prove this straight forward extension, in some limiting situations, fails to uphold the basic requirement that ion occupation sites must be identical. This requirement is necessary when computing entropy via particle distribution on occupation sites.We derived a new modified Bikerman model for using specific ion sizes by fixing this problem, and obtained its modified Poisson-Boltzmann and Poisson-Nernst-Planck equations.

scholarly journals Review and Modification of Entropy Modeling for Steric Effects in the Poisson-Boltzmann Equation

Entropy ◽  
2020 ◽  
Vol 22 (6) ◽  
pp. 632
Author(s):  
Tzyy-Leng Horng
Keyword(s):  
Free Energy ◽  
Lattice Gas ◽  
Steric Effect ◽  
Mean Field ◽  
Boltzmann Distribution ◽  
Experimental Conditions ◽  
Ion Concentrations ◽  
Poisson Boltzmann ◽  
Poisson Boltzmann Equation ◽  
Ion Size

The classical Poisson-Boltzmann model can only work when ion concentrations are very dilute, which often does not match the experimental conditions. Researchers have been working on the modification of the model to include the steric effect of ions, which is non-negligible when the ion concentrations are not dilute. Generally the steric effect was modeled to correct the Helmholtz free energy either through its internal energy or entropy, and an overview is given here. The Bikerman model, based on adding solvent entropy to the free energy through the concept of volume exclusion, is a rather popular steric-effect model nowadays. However, ion sizes are treated as identical in the Bikerman model, making an extension of the Bikerman model to include specific ion sizes desirable. Directly replacing the ions of non-specific size by specific ones in the model seems natural and has been accepted by many researchers in this field. However, this straightforward modification does not have a free energy formula to support it. Here modifications of the Bikerman model to include specific ion sizes have been developed iteratively, and such a model is achieved with a guarantee that: (1) it can approach Boltzmann distribution at diluteness; (2) it can reach saturation limit as the reciprocal of specific ion size under extreme electrostatic conditions; (3) its entropy can be derived by mean-field lattice gas model.

A theoretical consideration of ion size effects on the electric double layer and voltammetry of nanometer-sized disk electrodes

2016 ◽  
Vol 193 ◽  
pp. 251-263 ◽  
Author(s):  
Yu Gao ◽  
Yuwen Liu ◽  
Shengli Chen
Keyword(s):  
Size Effect ◽  
Double Layer ◽  
Electric Double Layer ◽  
Finite Size ◽  
Finite Size Effect ◽  
The Poisson Equation ◽  
Electrochemical Interface ◽  
Disk Electrodes ◽  
Ion Size ◽  
Electrochemical Interfaces

Considering that an electric-double-layer (EDL) structure may significantly impact on the mass transport and charge transfer kinetics at the interfaces of nanometer-sized electrodes, while EDL structures could be altered by the finite sizes of electrolyte and redox ions, the possible effects of ion sizes on EDL structures and voltammetric responses of nanometer-sized disk (nanodisk) electrodes are investigated. Modified Boltzmann and Nernst–Planck (NP) equations, which include the influence of the finite ion volumes, are combined with the Poisson equation and modified Butler–Volmer equation to gain knowledge on how the finite sizes of ions and the nanometer sizes of electrodes may couple with each other to affect the structures and reactivities of a nanoscale electrochemical interface. Two typical ion radii, 0.38 nm and 0.68 nm, which could represent the sizes of the commonly used aqueous electrolyte ions (e.g., the solvated K+) and the organic electrolyte ions (e.g., the solvated TEA+) respectively, are considered. The finite size of ions can result in decreased screening of electrode charges, therefore magnifying EDL effects on the ion transport and the electron transfer at electrochemical interfaces. This finite size effect of ions becomes more pronounced for larger ions and at smaller electrodes as the electrode radii is larger than 10 nm. For electrodes with radii smaller than 10 nm, however, the ion size effect may be less pronounced with decreasing the electrode size. This can be explained in terms of the increased edge effect of disk electrodes at nanometer scales, which could relax the ion crowding at/near the outer Helmholtz plane. The conditions and situations under which the ion sizes may have a significant effect on the voltammetry of electrodes are discussed.

scholarly journals Horizon radiation reaction forces

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
Walter D. Goldberger ◽  
Ira Z. Rothstein
Keyword(s):  
Black Hole ◽  
Equations Of Motion ◽  
Finite Size ◽  
Radiation Reaction ◽  
Effective Field ◽  
Compact Objects ◽  
Finite Size Effect ◽  
Binary Black Holes ◽  
Dissipative Effects ◽  
Reaction Forces

Abstract Using Effective Field Theory (EFT) methods, we compute the effects of horizon dissipation on the gravitational interactions of relativistic binary black hole systems. We assume that the dynamics is perturbative, i.e it admits an expansion in powers of Newton’s constant (post-Minkowskian, or PM, approximation). As applications, we compute corrections to the scattering angle in a black hole collision due to dissipative effects to leading PM order, as well as the post-Newtonian (PN) corrections to the equations of motion of binary black holes in non-relativistic orbits, which represents the leading order finite size effect in the equations of motion. The methods developed here are also applicable to the case of more general compact objects, eg. neutron stars, where the magnitude of the dissipative effects depends on non-gravitational physics (e.g, the equation of state for nuclear matter).

scholarly journals Theoretical Investigation of the Size Effect on the Oxygen Adsorption Energy of Coinage Metal Nanoparticles

2021 ◽  
Author(s):  
Amir H. Hakimioun ◽  
Elisabeth M. Dietze ◽  
Bart D. Vandegehuchte ◽  
Daniel Curulla-Ferre ◽  
Lennart Joos ◽  
...  
Keyword(s):  
Particle Size ◽  
Size Effect ◽  
Adsorption Energy ◽  
Single Point ◽  
Finite Size ◽  
Geometry Optimization ◽  
Oxygen Adsorption ◽  
Finite Size Effect ◽  
Full Geometry Optimization ◽  
Coinage Metal

AbstractThis study evaluates the finite size effect on the oxygen adsorption energy of coinage metal (Cu, Ag and Au) cuboctahedral nanoparticles in the size range of 13 to 1415 atoms (0.7–3.5 nm in diameter). Trends in particle size effects are well described with single point calculations, in which the metal atoms are frozen in their bulk position and the oxygen atom is added in a location determined from periodic surface calculations. This is shown explicitly for Cu nanoparticles, for which full geometry optimization only leads to a constant offset between relaxed and unrelaxed adsorption energies that is independent of particle size. With increasing cluster size, the adsorption energy converges systematically to the limit of the (211) extended surface. The 55-atomic cluster is an outlier for all of the coinage metals and all three materials show similar behavior with respect to particle size. Graphic Abstract

scholarly journals Finite-size effect of critical penetration of Pearl vortices in narrow superconducting flat rings

2019 ◽  
Vol 125 (22) ◽  
pp. 223906 ◽  
Author(s):  
N. Kokubo ◽  
S. Okayasu ◽  
T. Nojima
Keyword(s):  
Size Effect ◽  
Finite Size ◽  
Finite Size Effect

scholarly journals EFFECTS OF LANGMUIR KINETICS ON TWO-LANE TOTALLY ASYMMETRIC EXCLUSION PROCESSES OF MOLECULAR MOTOR TRAFFIC

2007 ◽  
Vol 18 (09) ◽  
pp. 1483-1496 ◽  
Author(s):  
RUILI WANG ◽  
RUI JIANG ◽  
MINGZHE LIU ◽  
JIMING LIU ◽  
QING-SONG WU
Keyword(s):  
Finite Size ◽  
Exclusion Process ◽  
Mean Field Approximation ◽  
Open Boundary ◽  
Finite Size Effect ◽  
Open Boundary Conditions ◽  
Density Profiles ◽  
Lane Changing ◽  
Langmuir Kinetics ◽  
Changing Rate

In this paper, we study a two-lane totally asymmetric simple exclusion process (TASEP) coupled with random attachment and detachment of particles (Langmuir kinetics) in both lanes under open boundary conditions. Our model can describe the directed motion of molecular motors, attachment and detachment of motors, and free inter-lane transition of motors between filaments. In this paper, we focus on some finite-size effects of the system because normally the sizes of most real systems are finite and small (e.g., size ≤ 10 000). A special finite-size effect of the two-lane system has been observed, which is that the density wall moves left first and then move towards the right with the increase of the lane-changing rate. We called it the jumping effect. We find that increasing attachment and detachment rates will weaken the jumping effect. We also confirmed that when the size of the two-lane system is large enough, the jumping effect disappears, and the two-lane system has a similar density profile to a single-lane TASEP coupled with Langmuir kinetics. Increasing lane-changing rates has little effect on density profiles after the density reaches maximum. Also, lane-changing rate has no effect on density profiles of a two-lane TASEP coupled with Langmuir kinetics at a large attachment/detachment rate and/or a large system size. Mean-field approximation is presented and it agrees with our Monte Carlo simulations.

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