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Electron Number (electron + number)

Distribution by Scientific Domains

Physics and Astronomy	50%
Chemistry	50%

Selected Abstracts

On the applicability of the HSAB principle through the use of improved computational schemes for chemical hardness evaluation

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 7 2004
Mihai V. Putz
Abstract Finite difference schemes, named Compact Finite Difference Schemes with Spectral-like Resolution, have been used for a less crude approximation of the analytical hardness definition as the second-order derivative of the energy with respect to the electron number. The improved computational schemes, at different levels of theory, have been used to calculate global hardness values of some probe bases, traditionally classified as hard and soft on the basis of their chemical behavior, and to investigate the quantitative applicability of the HSAB principle. Exchange acid-base reactions have been used to test the HSAB principle assuming the reaction energies as a measure of the stabilization of product adducts. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 994,1003, 2004 [source]

Full counting statistics for electron number in quantum dots

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2008
Yasuhiro Utsumi
Abstract Measurements of the average current and its fluctuations (noise) have been powerful tools to study the quantumtransport in mesoscopic systems. Recently it became possible to measure the probability distribution of current, ,full counting statistics' (FCS), by using quantum point-contact charge-detectors. Motivated by recent experiments, we developed the FCS theory for the joint probability distribution of the current and the electron number inside quantum dots (QDs). We show that a non-Gaussian exponential distribution appears when there is no dot state close to the lead chemical potentials. We show that the measurement of the joint probability distribution of current and electron number would reveal nontrivial correlations, which reflect the asymmetry of tunnel barriers. We also show that for increasing strength of tunneling, the quantum fluctuations of charge qualitatively change the probability distribution of the electron number. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Sense the Electrons that Come and Go

CHEMPHYSCHEM, Issue 1 2004
Daniël Vanmaekelbergh Prof. Dr.
Electron tunneling dynamics: This highlight outlines how fluctuations in the electron number of a semiconductor quantum dot, connected to a source and drain electrode by tunneling barriers (see green circuit in the picture) and capacitively coupled to a gate electrode (black), can be measured by an independent single electron transistor (gray circuit). This allows to probe the tunneling dynamics between the quantum dot and the source and drain electrodes in the (green) quantum dot circuit with microsecond time resolution. [source]

Occupation numbers for atomic shells in direct space bounded by the maxima of the one-electron potential

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 6 2001
M. Kohout
Abstract Atomic shells defined as wells of the one-electron potential bounded by successive maxima of this electron density function give reasonable electron numbers for the occupation of shells with empty d orbitals. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 83: 324,331, 2001 [source]

The Hubbard model extended by nearest-neighbor Coulomb and exchange interaction on a cubic cluster , rigorous and exact results

ANNALEN DER PHYSIK, Issue 6 2010
R. Schumann
The Hubbard model on a cube was revisited and extended by both nearest-neighbor Coulomb correlation W and nearest-neighbor Heisenberg exchange J. The complete eigensystem was computed exactly for all electron occupancies and all model parameters ranging from minus infinity to plus infinity. For two electrons on the cluster the eigensystem is given in analytical form. For six electrons and infinite on-site correlation U we determinded the groundstate and the groundstate energy of the pure Hubbard model analytically. For fixed electron numbers we found a multitude of ground state level crossings depending on the various model parameters. Furthermore the groundstates of the pure Hubbard model in dependence on a magnetic field h coupled to the spins are shown for the complete U-h plane. The critical magnetic field, where the zero spin groundstate breaks down is given for four and six electrons. Suprisingly we found parameter regions, where the ground state spin does not depend monotonously on J in the extended model. For the cubic cluster gas, i.e. an ensemble of clusters coupled to an electron bath, we calculated the density n (,, T, h) and the thermodynamical density of states from the grand potential. The ground states and the various spin-spin correlation functions are studied for both attractive and repulsive values of the three interaction constants. We determined the various anomalous degeneration lines, where n (,, T = 0, h = 0) shows steps higher than one, since in this parameter regions exotic phenomena as phase separation are to expect in extended models. For the cases where these lines end in triple points, i.e. groundstates of three different occupation numbers are degenerated, we give the related parameter values. Regarding the influence of the nn-exchange and the nn-Coulomb correlation onto the anomalous degeneration we find both lifting and inducing of degeneracies depending on the parameter values. [source]