Extracting double layer charge density distributions using the method of moments

1994 ◽  
Vol 22 (3) ◽  
pp. 278-280
Author(s):  
K.E. Lonngren ◽  
P.V. Schwartz ◽  
Er Wei Bai ◽  
W.C. Theisen ◽  
R.L. Merlino ◽  
...  
Keyword(s):  
Charge Density ◽  
Double Layer ◽  
Method Of Moments ◽  
Layer Charge ◽  
Density Distributions

Electric condensation of divalent counterions by humic acid nanoparticles

2016 ◽  
Vol 13 (1) ◽  
pp. 76 ◽  
Author(s):  
Herman P. van Leeuwen ◽  
Raewyn M. Town
Keyword(s):  
Humic Acid ◽  
Charge Density ◽  
Double Layer ◽  
Ion Pairs ◽  
Ion Pairing ◽  
Counterion Condensation ◽  
Counterion Binding ◽  
Satisfactory Description ◽  
Poisson Boltzmann ◽  
Very High

Environmental context Humic acids are negatively charged soft nanoparticles that play a governing role in the speciation of many ionic and molecular compounds in the environment. The charge density in the humic acid nanoparticle can be very high and the binding of divalent cations such as Ca2+ appears to go far beyond traditional ion pairing or Poisson–Boltzmann electrostatics. A two-state approach, combining counterion condensation in the intraparticulate double layer and classical Donnan partitioning in the bulk of the particle, provides a satisfactory description of the physicochemical speciation. Abstract Experimental data for divalent counterion binding by soil humic acid nanoparticles are set against ion distributions as ensuing from continuous Poisson–Boltzmann electrostatics and a two-state condensation approach. The results demonstrate that Poisson–Boltzmann massively underestimates the extent of binding of Ca2+ by humic acid, and that electric condensation of these counterions within the soft nanoparticulate body must be involved. The measured stability of the Ca2+–humic acid associate is also much greater than that predicted for ion pairing between single Ca2+ ions and monovalent negative humic acid sites, which also points to extensive electrostatic cooperativity within the humic acid particle. At sufficiently high pH, the charge density inside the humic acid entity may indeed become so high that the bulk particle attains a very high and practically flat potential profile throughout. At this limit, all the intraparticulate Ca2+ is at approximately the same electrostatic potential and the status of individual ion pairs has become immaterial. A two-state model, combining counterion condensation in the charged intraparticulate part of the double layer at the particle–medium interface and Donnan partitioning in the uncharged bulk of the humic acid particle, seems to lead the way to adequate modelling of the divalent counterion binding for various particle sizes and different ionic strengths.

scholarly journals Rich p -type-doping phenomena in boron-substituted silicene systems

2020 ◽  
Vol 7 (12) ◽  
pp. 200723
Author(s):  
Hai Duong Pham ◽  
Wu-Pei Su ◽  
Thi Dieu Hien Nguyen ◽  
Ngoc Thanh Thuy Tran ◽  
Ming-Fa Lin
Keyword(s):  
Charge Transfer ◽  
Fermi Level ◽  
Charge Density ◽  
Electronic Properties ◽  
First Principles ◽  
Chemical Environment ◽  
First Principles Calculations ◽  
Density Distributions ◽  
Essential Properties ◽  
P Type

The essential properties of monolayer silicene greatly enriched by boron substitutions are thoroughly explored through first-principles calculations. Delicate analyses are conducted on the highly non-uniform Moire superlattices, atom-dominated band structures, charge density distributions and atom- and orbital-decomposed van Hove singularities. The hybridized 2 p z –3 p z and [2s, 2 p x , 2 p y ]–[3s, 3 p x , 3 p y ] bondings, with orthogonal relations, are obtained from the developed theoretical framework. The red-shifted Fermi level and the modified Dirac cones/ π bands/ σ bands are clearly identified under various concentrations and configurations of boron-guest atoms. Our results demonstrate that the charge transfer leads to the non-uniform chemical environment that creates diverse electronic properties.

scholarly journals Charge density distributions and electron scattering form factors of 25Mg, 27Al and 29Si nuclei

2019 ◽  
Vol 14 (30) ◽  
pp. 129-135
Author(s):  
Lubna Abduljabbar Mahmood
Keyword(s):  
Charge Density ◽  
Explicit Form ◽  
Electron Scattering ◽  
Ground State ◽  
Density Operator ◽  
Form Factors ◽  
Body Density ◽  
Density Distributions ◽  
Tail Part

An effective two-body density operator for point nucleon systemfolded with the tenser force correlations( TC's), is produced and usedto derive an explicit form for ground state two-body charge densitydistributions (2BCDD's) applicable for 25Mg, 27Al and 29Si nuclei. It isfound that the inclusion of the two-body TC's has the feature ofincreasing the central part of the 2BCDD's significantly and reducingthe tail part of them slightly, i.e. it tends to increase the probability oftransferring the protons from the surface of the nucleus towards itscenteral region and consequently makes the nucleus to be more rigidthan the case when there is no TC's and also leads to decrease the1/ 2r 2 of the nucleus. It is also found that the effect of the TC's and theeffect of increasing the values of  on the 2BCDD's, elasticelectron scattering form factors and r2 1/ 2 are in the same directionfor all considered nuclei.

scholarly journals Preparation of hectorite-like swelling silicate with controlled layer charge density

2008 ◽  
Vol 116 (1360) ◽  
pp. 1309-1313 ◽  
Author(s):  
Makoto OGAWA ◽  
Takayuki MATSUTOMO ◽  
Tomohiko OKADA
Keyword(s):  
Charge Density ◽  
Layer Charge

Charge density studies on methylene blue – a potential anti-Alzheimer agent

2018 ◽  
Vol 73 (2) ◽  
pp. 99-108 ◽  
Author(s):  
Peter Luger ◽  
Birger Dittrich ◽  
Leonard Benecke ◽  
Hannes Sterzel
Keyword(s):  
Methylene Blue ◽  
Charge Density ◽  
Molecular Electrostatic Potential ◽  
Positive Charge ◽  
Atomic Charges ◽  
Charge Densities ◽  
Density Distributions ◽  
Atomic Properties ◽  
Counter Ions ◽  
Medical Interest

AbstractMotivated by the medical interest in methylene blue as potential anti-Alzheimer agent, the charge densities of three salt structures containing the methylene blue cation with nitrate (as dihydrate), chloride (as pentahydrate) and thiocyanate counter-ions were generated by application of the invariom formalism and examined. The so-obtained charge density distributions were analyzed using the QTAIM formalism to yield bond topological and atomic properties. The atomic charges on the methylene blue cation indicate a delocalized charge distribution; only a small positive charge on the sulfur atom was found. Electrostatic potentials mapped onto iso-surfaces of electron density for the cations, and for the methylene blue cations with anions, were compared. The effect of hydrogen disorder on the molecular electrostatic potential was investigated for the thiocyanate structure.

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