A Microscopic Theory of a Single Hydrogen Centre in a Magnesium Crystal

1992 ◽  
Vol 47 (6) ◽  
pp. 733-747
Author(s):  
M. Gnirßt ◽  
F. Wahl
Keyword(s):  
Harmonic Approximation ◽  
Microscopic Theory ◽  
Electronic System ◽  
Energy Difference ◽  
Electronic Energy ◽  
Host Lattice ◽  
System A ◽  
Metal Crystal ◽  
Lattice Problem ◽  
Storage Energy

AbstractA microscopic theory of a single hydrogen center embedded in a magnesium crystal is presented. Starting with a many-particle Schrödinger equation, an adiabatic decoupling yields in an electronic system a protonic system and a host lattice system. The storage energy is defined to consist of an electronic part and lattice contributions. The electronic problem is treated with the help of a special energy difference procedure developed by Wahl et al. This procedure is applied in a higher approximation to calculate the electronic energy difference eigenvalue between a metal crystal with and without a hydrogen impurity. The lattice problem is treated in the classical harmonic approximation.

Foundations of a Theory Concerning Hydrogen Centres in Metals

1984 ◽  
Vol 39 (6) ◽  
pp. 524-536
Author(s):  
F. Wahl ◽  
R. Duscher ◽  
K. Göbel ◽  
J. K. Maichle
Keyword(s):  
Electronic System ◽  
Host Lattice ◽  
Quantum Mechanical ◽  
Many Body ◽  
Lattice Contribution ◽  
Theoretical Methods ◽  
System A ◽  
Metal Crystal ◽  
The Many ◽  
Storage Energy

The present work is an attempt to treat hydrogen storage in metals with the aid of field theoretical methods. Starting with the many-body Schrödinger equation, an adiabatic decomposition yields an electronic system, a protonic system and a host lattice system. We define a storage energy consisting of a lattice contribution and an electronic part. The latter one will be evaluated by The New Tamm-Dancoff (NTD) procedure. This formalism is a method to compute differences of eigenvalues in quantum mechanical problems. As an example we derive a one-particle equation describing a single hydrogen atom in a metal crystal.

A Higher Order Approximation for the Electronic Structure of Hydrogen in Metals

1986 ◽  
Vol 41 (12) ◽  
pp. 1381-1398
Author(s):  
K. Göbel ◽  
F. Wahl
Keyword(s):  
Order Approximation ◽  
Energy Eigenvalue ◽  
Energy Difference ◽  
Electronic Energy ◽  
Host Lattice ◽  
Higher Order ◽  
Logarithmic Singularities ◽  
Special Case ◽  
Storage Energy ◽  
Coulomb Potentials

A functional energy difference method based on first principles is used to calculate the electronic contribution to the storage energy of hydrogen impurities in metals. That electronic problem is treated in a higher order approximation which means considering the coupling between one-electron wavefunctions and three-particle amplitudes. A formalism is presented to eliminate all higher order correlations and to reduce the whole system to a one-particle Schrödinger equation with the help of a suitable G reen’s function. The resulting one-electron eigenvalue problem contains some logarithmic singularities due to the fact that there is no gap between occupied and unoccupied electron states in the band structure of a metal. In an electron gas model a convergent theory is reached by an improvement of the Green’s function leading to a screening of the long-range Coulomb potentials. The result is a complicated non-linear algebraic eigenvalue equation which is solved numerically for the special case of a single hydrogen perturbation in a magnesium crystal. The solution shows the influence of higher order electron correlations on the electronic energy eigenvalue of an interstitial hydrogen centre plot as a function of host lattice distortions.

Electronic Structure of a Single Hydrogen Centre in Magnesium Crystals

1985 ◽  
Vol 40 (5) ◽  
pp. 433-438
Author(s):  
R. Duscher ◽  
J. K. Maichle
Keyword(s):  
Electronic Structure ◽  
Density Distribution ◽  
Electron Density Distribution ◽  
Energy Difference ◽  
Electronic Energy ◽  
Hexagonal Structure ◽  
Metal Crystal ◽  
Nearest Neighbours ◽  
The Difference ◽  
Radial Electron Density Distribution

In the present work, the problem “hydrogen storage in metals” is treated with the aid of the so-called New Tamm-Dancoff (NTD) procedure. We employ this method in lowest approximation for the evaluation of the electronic energy difference eigenvalue between a metal crystal with and without hydrogen centre. As an example we use Magnesium with hexagonal structure. For this system we calculate the difference eigenvalue with dependence on the displacement of the nearest neighbours and next nearest neighbours of the hydrogen centre, respectively. Finally we calculate the radial electron density distribution in the environment of the proton.

A Microscopic Theory of a SingleHydrogen Centre in Niobium

1988 ◽  
Vol 43 (11) ◽  
pp. 914-922
Author(s):  
K. Hau ◽  
P. Frodl ◽  
F. Sommer ◽  
F. Wahl
Keyword(s):  
Experimental Data ◽  
Microscopic Theory ◽  
Energy Difference ◽  
Electronic Energy ◽  
Heat Of Solution ◽  
Electronic Density ◽  
Nearest Neighbours ◽  
Dipole Force ◽  
Electronic Density Distribution ◽  
Good Agreement

Abstract A microscopic theory of a single hydrogen centre embedded in a Niobium crystal lattice is given. The electronic structure is investigated on the basis of a special energy difference procedure devel­oped by Wahl et al. This procedure, here applied in its lowest approximation, yields the change in the electronic energy and electronic density distribution due to the embedded hydrogen atom. From these quantities, the dipole force tensor, the displacement of the ions close to the interstitial (nearest and next nearest neighbours) and the heat of solution are calculated. The computed results show good agreement with experimental data.

Computational studies of ice defects

2003 ◽  
Vol 81 (1-2) ◽  
pp. 325-332 ◽  
Author(s):  
P LM Plummer
Keyword(s):  
Defect Formation ◽  
Structural Evolution ◽  
Energy Difference ◽  
Electronic Energy ◽  
Energy Structure ◽  
Defect Site ◽  
And Migration ◽  
Dynamics Simulations ◽  
Small Clusters ◽  
Structure Calculations

Continuing our investigations of the energetics associated with defect formation and migration, both ab initio energy-structure calculations and molecular dynamics simulations are carried out on small clusters of water molecules containing one or more defects in hydrogen bonding. Previous studies in this series have identified structures containing defects that are stable at 0 K or that are transition states between such structures. However, results from this laboratory and elsewhere have shown that the energy required for the production or migration of a defect is more complex than merely the energy difference between the static structures. Cooperative motion of neighbors to the defect site can either increase or decrease the energy involved to produce or annihilate the defect. Thus, experimental measurements associated with the energy of defects in ice can differ substantially from those calculated using static models. By increasing the complexity of the model, the studies described in this report attempt to more realistically simulate a defect-containing ice system. The types of defects studied include ion and ion-pair defects. The initial structures are energetically stable — minima on the electronic energy surface — and contain one or more kinds of defects. Since the means and amount of energy injection can alter the migration path, the energy is introduced into the system in a variety of ways. The structural evolution of the ice system is then monitored as a function of time. PACS Nos.: 82.20Wt, 82.20Kh, 82.30Rs

scholarly journals On the Modeling of Automotive Security: A Survey of Methods and Perspectives

2020 ◽  
Vol 12 (11) ◽  
pp. 198
Author(s):  
Jingjing Hao ◽  
Guangsheng Han
Keyword(s):  
Electronic System ◽  
Intelligent Transport System ◽  
Car Industry ◽  
Industry Chain ◽  
Intelligent Transport ◽  
New Methods ◽  
System A ◽  
Automotive Electronic ◽  
Security Models ◽  
Security Modeling

As the intelligent car-networking represents the new direction of the future vehicular development, automotive security plays an increasingly important role in the whole car industry chain. On condition that the accompanying problems of security are proofed, vehicles will provide more convenience while ensuring safety. Security models can be utilized as tools to rationalize the security of the automotive system and represent it in a structured manner. It is essential to improve the knowledge about security models by comparing them besides proposing new methods. This paper aims to give a comprehensive introduction to the topic of security models for the Intelligent Transport System (ITS). A survey of the current methodologies for security modeling is conducted and a classification scheme is subsequently proposed. Furthermore, the existing framework and methods to build automotive security models are broadly examined according to the features of automotive electronic system. A number of fundamental aspects are defined to compare the presented methods in order to comprehend the automotive security modeling in depth.

Assessment of a Strategy for Optimum Control of Ignition Advance Angle

1988 ◽  
Vol 202 (1) ◽  
pp. 1-8 ◽  
Author(s):  
R S Quayle ◽  
S R Bhot
Keyword(s):  
Combustion Engine ◽  
Electronic System ◽  
Open Loop ◽  
Operating Conditions ◽  
Ignition Timing ◽  
System A ◽  
Engine Design ◽  
Peak Cylinder Pressure ◽  
Crank Angle ◽  
Inlet Manifold

The control of ignition timing in an internal combustion engine can improve fuel consumption. Electronic control implemented in software with a microprocessor has advantages over conventional mechanical systems. An open-loop electronic system, while incorporating an optimum profile against inlet manifold vacuum and speed, cannot readily adjust for wear. The optimum crank angle at which the peak cylinder pressure occurs has been found to be reasonably constant for a particular engine design irrespective of operating conditions. This paper presents a discussion of the use of this parameter as a measurand for a closed-loop ignition timing system. A discussion is presented of the control strategy used and results demonstrate the ability of the strategy to maintain constant the peak pressure position.

Effect of Ni concentration on optical properties of rocksalt CdS system (A DFT + U study)

2018 ◽  
Vol 32 (25) ◽  
pp. 1850280 ◽  
Author(s):  
M. Junaid Iqbal Khan ◽  
Zarfishan Kanwal ◽  
M. Nauman Usmani ◽  
Masood Yousef ◽  
Perveen Akhtar ◽  
...  
Keyword(s):  
Optical Properties ◽  
Optical Absorption ◽  
Fermi Surface ◽  
Optical Sensors ◽  
Dopant Concentration ◽  
Host Lattice ◽  
Computational Approach ◽  
Slight Variation ◽  
Ni Doping ◽  
System A

Present study is a computational approach focused on optical properties of Ni-doped rocksalt CdS system under PBE-GGA and GGA + U approximations. Investigation of optical properties of CdS:Ni system by fixing supercell size and increasing dopant concentration is a focus of study. Cd atoms are substituted by Ni atoms and optical properties show significant change for higher Ni concentration. Redshift in optical absorption is observed as dopant concentration is increased. Interaction of Ni and S atoms and localization of d-states are inspected near the conduction band minima or Fermi surface. GGA + U absorption plots show slight variation with increase in energy values. Ni-doping in CdS host lattice enhances its opto-electronic properties which extend its applications in optical sensors, optical and similar devices.

On the Electronic Structure of Metal Hydrides I. Exposition of a Many-Electron Theory

1979 ◽  
Vol 34 (12) ◽  
pp. 1373-1384
Author(s):  
F. Wahl ◽  
G. Baumann
Keyword(s):  
Order Approximation ◽  
Energy Difference ◽  
Host Lattice ◽  
Hydrogen Atoms ◽  
Electron Theory ◽  
First Order ◽  
Structure Of Metal ◽  
Self Consistent ◽  
First Order Approximation ◽  
Dynamical Potential

Abstract We present the concept of a many-electron theory for the calculation of the energy difference between an undisturbed metallic host lattice and a crystal disturbed by stored hydrogen atoms. With the help of an elimination procedure a multidimensional system of equations is reduced to a one-particle Schrödinger equation for the electron of the hydrogen. The interaction with the electrons of the metal is then described by a dynamical potential depending on the state of the electron itself. A first order approximation with static screening is discussed and then generalized to a self-consistent calculation of one-electron functions which are used as a basis for expansions.

scholarly journals Novel Methodology for Arbitration of Talented Students using an Electronic System: A Higher Education Perspective

2019 ◽  
Vol 14 (21) ◽  
pp. 250
Author(s):  
Asim Seedahmed Ali Osman ◽  
Faizal Khan
Keyword(s):  
Higher Education ◽  
Electronic System ◽  
Development Stages ◽  
Complete Development ◽  
System A ◽  
Simple Interface ◽  
Talented Students ◽  
Electronic Administration

Arbitration of Talented Students System (ATSS) provides a simple interface for Arbitrator and students to add the talent and evaluate it. It can be used by educational institutes or colleges to evaluate the talented students easily. This methodology depends on ten criteria that are used by arbitrator to evaluate the talent to increasing productivity and efficiency, and also reduce the time and effort in arbitration talent. The proposed methodology allows talented students to follow his talent using a code which is generated automatically by the system. The administrator of the system can accept/reject the talent depending on arbitrator evaluation and his notes. This paper describes all the benefits of the system. It also gives idea about the complete development stages of the system and adapting of the system in the Shaqra University and its impact on the working by developing performance and supporting university in its orientation towards electronic administration.

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