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Linear scaling algorithms: Progress and promise

Description: The goal of this laboratory-directed research and development (LDRD) project was to develop a new and efficient electronic structure algorithm that would scale linearly with system size. Since the start of the program this field has received much attention in the literature as well as in terms of focused symposia and at least one dedicated international workshop. The major success of this program is the development of a unique algorithm for minimization of the density functional energy which re… more
Date: August 1, 1996
Creator: Stechel, E. B.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Charge Accumulation at a Threading Edge Dislocation in GaN

Description: We have performed Monte Carlo calculations to determine the charge accumulation on threading edge dislocations in GaN as a function of the dislocation density and background dopant density. Four possible core structures have been examined, each of which produces defect levels in the gap and may therefore act as electron or hole traps. Our results indicate that charge accumulation, and the resulting electrostatic interactions, can change the relative stabilities of the different core structures.… more
Date: January 20, 1999
Creator: Leung, K.; Stechel, E. B. & Wright, A. F.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Auger spectroscopy and electronically-stimulated surface processes

Description: Electronic excitations in adsorbate layers stimulate desorption and dissociation of adsorbed molecules as well as chemical reactions between adsorbates. The highest-probability stimulated processes produce neutral desorbates and determine how surface composition is altered by electron or photon radiation. A basic understanding has emerged, due largely to laser resonance-enhanced multi-photon ionization (REMPI) experiments, which provide quantum-state resolution of the gas-phase products. Auger … more
Date: January 1, 1991
Creator: Jennison, D. R.; Burns, A. R. & Stechel, E. B.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Optical properties of fractal nanocomposites

Description: Optical prossesses in nanostructured fractal composites are shown to be strongly enhanced. The enhancement occurs because of a localization of dipolar eigenmodes in subwavelength areas.
Date: December 31, 1994
Creator: Markel, V. A.; Kim, W.; Armstrong, R.; Shalaev, V. & Stechel, E. B.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Chemisorbed-molecule potential-energy surfaces and electronically- stimulated processes

Description: Three topics illustrate some central physics of processes produced by UV-laser and low-energy electron stimulation. First, a multi-dimensional ground-state potential energy surface (PES) for NH{sub 3}: Pd(111), computed using ab initio local-density functional theory, allows dramatically different dynamics depending on poorly-known excited-state forces. We use quantum-resolved experimental data to argue that stimulated desorption is dominated by a direct path off the surface, following placemen… more
Date: March 1, 1994
Creator: Jennison, D. R.; Stechel, E. B.; Burns, A. R. & Li, S. Y.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Unconstrained and Constrained Minimization, Linear Scaling, and the Grassmann Manifold: Theory and Applications

Description: An unconstrained minimization algorithm for electronic structure calculations using density functional for systems with a gap is developed to solve for nonorthogonal Wannier-like orbitals in the spirit of E. B. Stechel, A. R. Williams, and P. J. Feibelman, Phys. Rev. B 49, 10,008 (1994). The search for the occupied sub-space is a Grassmann conjugate gradient algorithm generalized from the algorithm of A. Edelman, T.A. Arias, and S. T. Smith, SIAM J. on Matrix Anal. Appl. 20, 303 (1998). The gra… more
Date: July 19, 2000
Creator: Raczkowski, David; Fong, C. Y.; Schultz, Peter A.; Lippert, Ross A. & Stechel, E. B.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

The electronic transport mechanism in amorphous tetrahedrally-coordinated carbon films

Description: The electronic transport mechanism in tetrahedrally coordinated amorphous carbon was investigated using measurements of stress relaxation, thermal evolution of electrical conductivity, and temperature dependent conductivity measurements. Stress relaxation measurements were used to determine the change in 3-fold coordinated carbon concentration, and the electrical conductivity was correlated to this change. It was found that the conductivity was exponentially proportional to the change in 3-fold… more
Date: February 1, 1998
Creator: Sullivan, J. P.; Friedmann, T. A.; Dunn, R. G.; Stechel, E. B. & Schultz, P. A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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