Cluster Calculation of B and A1 Impurities in Amorphous Silicon

1992 ◽  
Vol 291 ◽  
Author(s):  
J. A. Cogordan ◽  
L. E. Sansores ◽  
A. A. Valladares
Keyword(s):  
Molecular Structure ◽  
Geometry Optimization ◽  
Cluster Calculation ◽  
Molecular Electronic ◽  
Densities Of States ◽  
Electronic Wave Function ◽  
Contour Plots ◽  
Local Densities ◽  
Structure Calculations ◽  
Optimized Geometries

ABSTRACTWe report our results of molecular structure calculations for B and A1 impurities. From our unoptimized ab initio calculations, we found the molecular electronic wave function to be unstable for both impurities. This instability was removed through a geometry optimization process. Local densities of states (LDOS) were computed for the optimized geometries. They show a rise of a peak at the tail of the valence LDOS; this feature is due to p orbitals of B and Al. The contribution is slightly higher for B than for A1 impurities. Charge contour plots are presented.

scholarly journals Plutonium complexes in water: new approach to ab initio modeling

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Mikhail V. Ryzhkov ◽  
Andrei N. Enyashin ◽  
Bernard Delley
Keyword(s):  
Quantitative Estimation ◽  
Water Solution ◽  
Geometry Optimization ◽  
Model Potential ◽  
Water Dissociation ◽  
New Approach ◽  
Molecular Systems ◽  
Screening Model ◽  
Solvent Environment ◽  
Structure Calculations

Abstract Geometry optimization and the electronic structure calculations of Pu Z+ complexes (Z = 3–6) in water solution have been performed, within the framework of the DMol3 and Relativistic Discrete-Variational (RDV) methods. For the simulation of Pu Z+ molecular environment in aqueous solution we used 22 and 32 water molecules randomly distributed around cation. To model the effect of bulk solvent environment we used COSMO (Conductor-like Screening Model) potential for water (ε = 78.54). The obtained results showed that this approach allows the modeling of water dissociation and the formation of hydrolysis products. Our previously suggested scheme for the calculation of interaction energies between selected fragments of multi-molecular systems provides the quantitative estimation of the interaction strengths between plutonium in various oxidation states and each ligand in the first and second coordination shells in water solution.

Commentary on local densities of states, surface bonds and rate processes

1986 ◽  
Vol 318 (1541) ◽  
pp. 135-139 ◽  
Keyword(s):  
Electron Spectroscopy ◽  
Main Part ◽  
Catalytic Reactions ◽  
Solid Surfaces ◽  
Densities Of States ◽  
Rate Processes ◽  
Local Densities ◽  
Structure And Bonding ◽  
The Many

Although the main part of the title of this meeting is ‘ Studies of the surfaces of solids by electron spectroscopy’, the papers presented also cover some of the wider aspects of these studies, and I wish to pursue some of these here. I remark first that most of the systems studied by surface-sensitive spectroscopies are not technologically important, or even interesting in their own right. What makes them important and interesting is that the solids studied are, or are related to, catalysts, and the adsorbates studied are reactants, products or intermediates in important catalytic reactions. Consequently I ask the question: what is the relevance to catalysis of studies of structure, and bonding at solid surfaces? From among the many answers that might be given, I select two.

Electronic Structure of Epitaxial SiO2/Si(100) Interfaces

1989 ◽  
Vol 159 ◽  
Author(s):  
T. Motooka
Keyword(s):  
Tight Binding ◽  
Interface States ◽  
Photoelectron Spectra ◽  
Band Spectrum ◽  
Binding Model ◽  
Initial Oxidation ◽  
Recursion Method ◽  
Densities Of States ◽  
Local Densities ◽  
Gap States

ABSTRACTThe local densities of states (LDOS) of epitaxial SiO, layers on Si(100) surfaces have been calculated using the recursion method combined with the Harrison's universal tight-binding model. The interface states associated with strained epitaxial layers of β-cristobalite (√2×√2)R45° and tridymite (1010)<0001> || Si(100)<011> were examined. In the β-cristobalite layer, gap states due to the surface Si dangling bonds appeared while they were eliminated by H termination. In the tridymite layer, the interface states primarily composed of the surface Si back bonds appeared near the Si conduction band minimum. Comparing the calculated DOS with photoelectron spectra for initial oxidation processes of clean Si(100), it was found that the valence band spectrum from the initial oxide formed at ∼300°C resembled that of the β-cristobalite layer.

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