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Charge Effects (charge + effects)

Distribution by Scientific Domains
Physics and Astronomy50%

Selected Abstracts

Outlying Charge, Stability, Efficiency, and Algorithmic Enhancements in the Quantum-Mechanical Solvation Method, COSab-GAMESS

HELVETICA CHIMICA ACTA, Issue 12 2003
Laura
In this work, we present algorithmic modifications and extensions to our quantum-mechanical approach for the inclusion of solvent effects by means of molecule-shaped cavities. The theory of conductor-like screening, modified and extended for quantum-mechanical techniques, serves as the basis for our solvation methodology. The modified method is being referred to as COSab-GAMESS and is available within the GAMESS package. Our previous work has emphasized the implementation of this model by way of a distributed multipole approach for handling the effects of outlying charge. The method has been enabled within the framework of open- and closed-shell RHF and MP2. In the present work, we present a) a second method to handle outlying charge effects, b) algorithmic extensions to open- and closed-shell density-functional theory, second-derivative analysis, and reaction-path following, and c) enhancements to improve performance, convergence, and predictability. The method is now surtable for large molecular systems. New features of the enhanced continuum model are highlighted by means of a set of neutral and charged species. Computations on a series of structures with roughly the same molecular shape and volume provides an evaluation of cavitation effects. [source]

Baryon loading and the Weibel instability in gamma-ray bursts

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006
M. Fiore
ABSTRACT The dynamics of two counter-streaming electron,positron,ion unmagnetized plasma shells with zero net charge is analysed in the context of magnetic field generation in gamma-ray burst internal shocks due to the Weibel instability. The effects of large thermal motion of plasma particles, arbitrary mixture of plasma species and space charge effects are taken into account. We show that, although thermal effects slow down the instability, baryon loading leads to a non-negligible growth rate even for large temperatures and different shell velocities, thus guaranteeing the robustness and the occurrence of the Weibel instability for a wide range of scenarios. [source]

Monte Carlo simulation of surface charge effects in T-branch nanojunctions

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2008
T. González
Abstract We analyze the influence of the surface charge on the operation of ballistic T-branch junctions based on InAlAs/InGaAs layers by means of a semi-classical 2-D Monte Carlo simulator. A new self-consistent model in which the local value of the surface charge is dynamically adjusted depending on the surrounding carrier density is used in the calculations. The rectifying behaviour exhibited by these devices (down-bending shape of the output voltage VC as a function of the applied voltage VR = -VL =V) is found to be much influenced by the surface charge. A satisfactory agreement is achieved between simulated results and experimental measurements. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Computationally efficient expressions for the collision efficiency between electrically charged aerosol particles and cloud droplets

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 618 2006
S. N. Tripathi
Abstract A multiple factor parametrization is described to permit the efficient calculation of collision efficiency (E) between electrically charged aerosol particles and neutral cloud droplets in numerical models of cloud and climate. The four-parameter representation summarizes the results obtained from a detailed microphysical model ofE, which accounts for the different forces acting on the aerosol in the path of falling cloud droplets. The parametrization's range of validity is for aerosol particle radii of 0.4 to 10 ,m, aerosol particle densities of 1 to 2.0 g cm,3, aerosol particle charges from neutral to 100 elementary charges and drop radii from 18.55 to 142 , m. The parametrization yields values ofE well within an order of magnitude of the detailed model's values, from a dataset of 3978E values. Of these values 95% have modelled to parametrized ratios between 0.5 and 1.5 for aerosol particle sizes ranging between 0.4 and 2.0 , m, and about 96% in the second size range. This parametrization speeds up the calculation ofE by a factor of ,103 compared with the original microphysical model, permitting the inclusion of electric charge effects in numerical cloud and climate models. Copyright © 2006 Royal Meteorological Society [source]