Center for Computing Research (CCR)
Center for Computing Research (CCR)

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Surface effects in semiconductor interstitial formation energies

Sandia journal manuscript; Not yet accepted for publication

Wills, Ann E.; Wixom, Ryan R.

In this work, we examine the formation energies of interstitials in semiconductors obtained with four different pure functionals. Explicitely we investigate three silicon self-interstitials. All functionals give the same trend among those interstitials; the lowest energy being for formation of the <110>-split, somewhat higher energy for the formation of the hexagonal interstitial, while highest energy among the three is obtained for the meta-stable tetragonal configuration. However, the value for the formation energy for a specific interstitial differs substantially in calculations using different functionals. It is shown that the main contribution to these differences is stemming from the functionals different surface intrinsic errors. We also discuss the puzzle that the values obtained with the surface intrisic error free AM05 functional (Armiento and Mattsson, Phys. Rev. B 72, 085108 (2006)) gives values substantially lower than Quantum Monte Carlo results

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TYPE Journal Article YEAR 2007
OSTI

Macro-meso-microsystems integration in LTCC : LDRD report

Rohde, Steven B.; Okandan, Murat; Pfeifer, Kent B.; De Smet, Dennis; Patel, Kamlesh; Ho, Clifford K.; Nordquist, Christopher D.; Walker, Charles; Rohrer, Brandon R.; Buerger, Stephen P.; Turner, Timothy; Wroblewski, Brian W.

Low Temperature Cofired Ceramic (LTCC) has proven to be an enabling medium for microsystem technologies, because of its desirable electrical, physical, and chemical properties coupled with its capability for rapid prototyping and scalable manufacturing of components. LTCC is viewed as an extension of hybrid microcircuits, and in that function it enables development, testing, and deployment of silicon microsystems. However, its versatility has allowed it to succeed as a microsystem medium in its own right, with applications in non-microelectronic meso-scale devices and in a range of sensor devices. Applications include silicon microfluidic ''chip-and-wire'' systems and fluid grid array (FGA)/microfluidic multichip modules using embedded channels in LTCC, and cofired electro-mechanical systems with moving parts. Both the microfluidic and mechanical system applications are enabled by sacrificial volume materials (SVM), which serve to create and maintain cavities and separation gaps during the lamination and cofiring process. SVMs consisting of thermally fugitive or partially inert materials are easily incorporated. Recognizing the premium on devices that are cofired rather than assembled, we report on functional-as-released and functional-as-fired moving parts. Additional applications for cofired transparent windows, some as small as an optical fiber, are also described. The applications described help pave the way for widespread application of LTCC to biomedical, control, analysis, characterization, and radio frequency (RF) functions for macro-meso-microsystems.

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TYPE SAND Report YEAR 2007
DOIOSTI

3D optical sectioning with a new hyperspectral confocal fluorescence imaging system

Haaland, David M.; Sinclair, Michael B.; Jones, Howland D.T.; Timlin, Jerilyn A.; Bachand, George D.; Sasaki, Darryl Y.; Davidson, George S.; Van Benthem, Mark H.

A novel hyperspectral fluorescence microscope for high-resolution 3D optical sectioning of cells and other structures has been designed, constructed, and used to investigate a number of different problems. We have significantly extended new multivariate curve resolution (MCR) data analysis methods to deconvolve the hyperspectral image data and to rapidly extract quantitative 3D concentration distribution maps of all emitting species. The imaging system has many advantages over current confocal imaging systems including simultaneous monitoring of numerous highly overlapped fluorophores, immunity to autofluorescence or impurity fluorescence, enhanced sensitivity, and dramatically improved accuracy, reliability, and dynamic range. Efficient data compression in the spectral dimension has allowed personal computers to perform quantitative analysis of hyperspectral images of large size without loss of image quality. We have also developed and tested software to perform analysis of time resolved hyperspectral images using trilinear multivariate analysis methods. The new imaging system is an enabling technology for numerous applications including (1) 3D composition mapping analysis of multicomponent processes occurring during host-pathogen interactions, (2) monitoring microfluidic processes, (3) imaging of molecular motors and (4) understanding photosynthetic processes in wild type and mutant Synechocystis cyanobacteria.

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TYPE SAND Report YEAR 2007
DOIOSTIDOIOSTI

Supercomputer and cluster performance modeling and analysis efforts:2004-2006

Ang, James A.; Vaughan, Courtenay T.; Barnette, Daniel W.; Benner, Robert E.; Doerfler, Douglas W.; Ganti, Anand; Phelps, Sue C.; Rajan, Mahesh; Stevenson, Joel O.; Scott, Ryan T.

This report describes efforts by the Performance Modeling and Analysis Team to investigate performance characteristics of Sandia's engineering and scientific applications on the ASC capability and advanced architecture supercomputers, and Sandia's capacity Linux clusters. Efforts to model various aspects of these computers are also discussed. The goals of these efforts are to quantify and compare Sandia's supercomputer and cluster performance characteristics; to reveal strengths and weaknesses in such systems; and to predict performance characteristics of, and provide guidelines for, future acquisitions and follow-on systems. Described herein are the results obtained from running benchmarks and applications to extract performance characteristics and comparisons, as well as modeling efforts, obtained during the time period 2004-2006. The format of the report, with hypertext links to numerous additional documents, purposefully minimizes the document size needed to disseminate the extensive results from our research.

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TYPE SAND Report YEAR 2007
DOIDOIOSTIOSTI

Algebraic multilevel preconditioners for nonsymmetric PDEs on stretched grids

Lecture Notes in Computational Science and Engineering

Sala, Marzio; Lin, Paul T.; Shadid, John N.; Tuminaro, Raymond S.

We report on algebraic multilevel preconditioners for the parallel solution of linear systems arising from a Newton procedure applied to the finite-element (FE) discretization of the incompressible Navier-Stokes equations. We focus on the issue of how to coarsen FE operators produced from high aspect ratio elements.

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TYPE Conference YEAR 2007
ScopusOSTI
Results 11401–11450 of 12,511
Results 11401–11450 of 12,511
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