Polarization force on a charged particulate in a nonuniform plasma

S. Hamaguchi and R. T. Farouki, Phys. Rev. E 49, 4430, 199

On the Interaction of Charged Particles with Plasma

The last several years have seen great activity in the study of the properties of the free electron gas or plasma, An electronic plasma is understood to mean an assembly of electrons which may be regarded as nearly free in their response to a disturbance. The assembly is assumed to be electrically neutral on the whole, due to a stationary positive charge background which will be assumed uniform in density. These electrons interact with each other via the longrange coulomb potential. Due to the nature of this interaction, the system exhibits a very interesting collective behavior which evinces itself in the existence of plasma oscillations

Some heavy doping effects in silicon

In this thesis the theoretical and experimental concentration and temperature dependent band gap narrowing in uncompensated n-type silicon is studied. Electron-electron and electron-impurity interaction energies are used to calculate the theoretical band gap narrowing in the plasmon-pole approximation. These reveal an increase of 14 meV in the band gap narrowing at 300 K for a donor concentration of 3.10(^19) cm(^-3) above the zero temperature value of 95 meV. For higher concentrations the degeneracy deepens and the zero and finite temperature band gap narrowing curves converge. Localized states in the band gap resulting from local fluctuations in the electron-impurity interaction, a result of the random position of the impurities, are also considered. When the analysis includes the effect on the host band of the electron-impurity interactions calculated above the resulting density of states in the band tail of uncompensated silicon is found to be ten times smaller than is usually imagined. Using published values for the minority carrier mobility both the band gap narrowing and the minority carrier lifetime are experimentally determined in the buried n-type layer of an Integrated Injection Logic transistor. The transport factor in the base of a parasitic pnp transistor formed by the p-type substrate, buried layer and p-type Integrated Injection Logic transistors base region is calculated by monitoring the substrate current density and minority carrier injection into the buried layer. A range of temperatures from 200 K to 400 K are used to determine the temperature dependence of the minority carrier mobility in the buried layer (T(^0)). A band gap narrowing of (100 ± 15) meV) and minority carrier lifetime of (30 ± 10) ns are measured for the buried layer (2.4.10(^19) cm(^-3))

Electron density and pair correlation functions in metals

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Large-scale parallelised boundary element method electrostatics for biomolecular simulation

Large-scale biomolecular simulations require a model of particle interactions capable of incorporating the behaviour of large numbers of particles over relatively long timescales. If water is modelled as a continuous medium then the most important intermolecular forces between biomolecules can be modelled as long-range electrostatics governed by the Poisson- Boltzmann Equation (PBE). We present a linearised PBE solver called the "Boundary Element Electrostatics Program"(BEEP). BEEP is based on the Boundary Element Method (BEM), in combination with a recently developed O(N) Fast Multipole Method (FMM) algorithm which approximates the far-�field integrals within the BEM, yielding a method which scales linearly with the number of particles. BEEP improves on existing methods by parallelising the underlying algorithms for use on modern cluster architectures, as well as taking advantage of recent progress in the �field of GPGPU (General Purpose GPU) Programming, to exploit the highly parallel nature of graphics cards. We found the stability and numerical accuracy of the BEM/FMM method to be highly dependent on the choice of surface representation and integration method. For real proteins we demonstrate the critical level of surface detail required to produce converged electrostatic solvation energies, and introduce a curved surface representation based on Point-Normal G1-continuous triangles which we �find generally improves numerical stability compared to a simpler surface constructed from planar triangles. Despite our improvements upon existing BEM methods, we �find that it is not possible to directly integrate BEM surface solutions to obtain intermolecular electrostatic forces. It is, however, practicable to use the total electrostatic solvation energy calculated by BEEP to drive a Monte-Carlo simulation

Interface electronic structure

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