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Investigations of Thermochemistry and the Kinetics of H Atom Radical Reactions

Description: The thermochemistry of several species, and the kinetics of various H atom radical reactions relevant to atmospheric and combustion chemistry were investigated using ab initio theoretical techniques and the flash photolysis / resonance fluorescence technique. Using ab initio quantum mechanical calculations up to the G3 level of theory, the C-H bond strengths of several alkanes were calculated. The bond strengths were calculated using two working reactions. From the results, it is apparent that … more
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Date: December 2002
Creator: Peebles, Lynda Renee
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Evolution of the Surface Science of Catalysis from Single Crystals to Metal Nanoparticles under Pressure

Description: Vacuum studies of metal single crystal surfaces using electron and molecular beam scattering revealed that the surface atoms relocate when the surface is clean (reconstruction) and when it is covered by adsorbates (adsorbate induced restructuring). It was also discovered that atomic steps and other low coordination surface sites are active for breaking chemical bonds (H-H, O=O, C-H, C=O and C-C) with high reaction probability. Investigations at high reactant pressures using sum frequency genera… more
Date: March 6, 2008
Creator: Somorjai, Gabor A. & Park, Jeong Y.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Symmetry reduction of (delta)-plutonium: an electronic-structure effect

Description: Using first-principles density-functional theory calculations, we show that the anomalously large anisotropy of {sigma}-plutonium is a consequence of greatly varying bond-strengths between the 12 nearest neighbors. Employing the calculated bond strengths, we expand the tenants of classical crystallography by incorporating anisotropy of chemical bonds, which yields a structure with the monoclinic space group Cm for {delta}-plutonium rather than face-centered cubic Fm{bar 3}m. The reduced space g… more
Date: November 16, 2005
Creator: Moore, K; Soderlind, P; Schwartz, A & Laughlin, D
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Cerocene Revisited: The Electronic Structure of and Interconversion Between Ce2(C8H8)3 and Ce(C8H8)2

Description: New synthetic procedures for the preparation of Ce(cot)2, cerocene, from [Li(thf)4][Ce(cot)2], and Ce2(cot)3 in high yield and purity are reported. Heating solid Ce(cot)2 yields Ce2(cot)3 and COT while heating Ce2(cot)3 with an excess of COT in C6D6 to 65oC over four months yields Ce(cot)2. The solid state magnetic susceptibility of these three organocerium compounds shows that Ce(cot)2 behaves as a TIP (temperature independent paramagnet) over the temperature range of 5-300 K, while that of Ce… more
Date: February 2, 2009
Creator: Walter, Marc D.; Booth, Corwin H.; Lukens, Wayne W. & Andersen, Richard A.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Delocalization and hybridization enhance the magnetocaloric effect in Ni2Mn0.75Cu0.25Ga

Description: In view of the looming energy crisis facing our planet, attention increasingly focuses on materials potentially useful as a basis for energy saving technologies. The discovery of giant magnetocaloric (GMC) compounds - materials that exhibit especially large changes in temperature as the externally applied magnetic field is varied - is one such compound 1. These materials have potential for use in solid state cooling technology as a viable alternative to existing gas based refrigeration technolo… more
Date: November 26, 2008
Creator: Roy, Sujoy; Blackburn, E.; Valvidares, S. M.; Fitzsimmons, M. R.; Vogel, Sven C.; Khan, M. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Novel Methods for Binding Disparate Materials

Description: This project was intended to advance the science of surface bonding in order to provide the functionality demanded by target fabrication requirements, as well as similar needs in other fields of importance to LLNL. We have developed and demonstrated a very powerful capability, i.e. 'single molecule force spectroscopy', that allows the strength of individual chemical bonds to be measured. This project focused on long chain molecules that are covalently bound to surfaces on one end and have compl… more
Date: February 13, 2006
Creator: McElfresh, M W; Rudd, R E; Ratto, T V & Langry, K C
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Detonation of Meta-stable Clusters

Description: We consider the energy accumulation in meta-stable clusters. This energy can be much larger than the typical chemical bond energy (~;;1 ev/atom). For example, polymeric nitrogen can accumulate 4 ev/atom in the N8 (fcc) structure, while helium can accumulate 9 ev/atom in the excited triplet state He2* . They release their energy by cluster fission: N8 -> 4N2 and He2* -> 2He. We study the locus of states in thermodynamic state space for the detonation of such meta-stable clusters. In partic… more
Date: May 31, 2008
Creator: Kuhl, Allen; Kuhl, Allen L.; Fried, Laurence E.; Howard, W. Michael; Seizew, Michael R.; Bell, John B. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Modeling local chemistry in the presence of collective phenomena.

Description: Confinement within the nanoscale pores of a zeolite strongly modifies the behavior of small molecules. Typical of many such interesting and important problems, realistic modeling of this phenomena requires simultaneously capturing the detailed behavior of chemical bonds and the possibility of collective dynamics occurring in a complex unit cell (672 atoms in the case of Zeolite-4A). Classical simulations alone cannot reliably model the breaking and formation of chemical bonds, while quantum met… more
Date: January 1, 2005
Creator: Chandross, Michael Evan & Modine, Normand Arthur
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Chemical Bonding, Interfaces and Defects in Hafnium Oxide/Germanium Oxynitride Gate Stacks on Ge (100)

Description: Correlations among interface properties and chemical bonding characteristics in HfO{sub 2}/GeO{sub x}N{sub y}/Ge MIS stacks were investigated using in-situ remote nitridation of the Ge (100) surface prior to HfO{sub 2} atomic layer deposition (ALD). Ultra thin ({approx}1.1 nm), thermally stable and aqueous etch-resistant GeO{sub x}N{sub y} interfaces layers that exhibited Ge core level photoelectron spectra (PES) similar to stoichiometric Ge{sub 3}N{sub 4} were synthesized. To evaluate GeO{sub … more
Date: October 31, 2008
Creator: Oshima, Yasuhiro; /Stanford U., Materials Sci. Dept.; Sun, Yun; /SLAC, SSRL; Kuzum, Duygu; U., /Stanford et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Surface-Enhanced Raman Spectroscopy with High Spatial Resolution

Description: The identification of individual molecules and the determination of how these interact with their local environment are critical steps toward a better understanding of complex organic systems. Optical detection techniques have always played a key role in the nondestructive and noninvasive analysis of complex materials. Until recently, however, optical microscopy has lacked the sensitivity to study processes on the molecular scale. This has changed with the recent development of new schemes that… more
Date: February 4, 2003
Creator: Huser, T R
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

A self-consistent MoD-WM/MM structural refinement method: characterization of hydrogen bonding in the orytricha nova G-1uar

Description: This paper generalizes the MoD-QM/MM hybrid method, developed for ab initio computations of protein electrostatic potentials [Gasc6n, l.A.; Leung, S.S.F.; Batista, E.R.; Batista, V.S. J. Chem. Theory Comput. 2006,2, 175-186], as a practical algorithm for structural refinement of extended systems. The computational protocol involves a space-domain decomposition scheme for the formal fragmentation of extended systems into smaller, partially overlapping, molecular domains and the iterative self-co… more
Date: January 1, 2008
Creator: Batista, Enrique R; Newcomer, Micharel B; Raggin, Christina M; Gascon, Jose A; Loria, J Patrick & Batista, Victor S
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Thermal expansion and decomposition of jarosite: a high-temperature neutron diffraction study

Description: The structure of deuterated jarosite, KFe{sub 3}(SO{sub 4}){sub 2}(OD){sub 6}, was investigated using time-of-flight neutron diffraction up to its dehydroxylation temperature. Rietveld analysis reveals that with increasing temperature, its c dimension expands at a rate {approx}10 times greater than that for a. This anisotropy of thermal expansion is due to rapid increase in the thickness of the (001) sheet of [Fe(O,OH){sub 6}] octahedra and [SO{sub 4}] tetrahedra with increasing temperature. Fi… more
Date: January 1, 2009
Creator: Xu, Hongwu; Zhao, Yusheng; Vogel, Sven C; Hickmott, Donald D; Daemen, Luke L & Hartl, Monika A
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Ductility Enhancement of Molybdenum Phase by Nano-sizedd Oxide Dispersions

Description: The present research is focused on ductility enhancement of molybdenum (Mo) alloys by adding nano-sized oxide particles to the alloy system. The research approach includes: (1) determination of microscopic mechanisms responsible for the macroscopic ductility enhancement effects through atomistic modeling of the metal-ceramic interface; (2) subsequent computer simulation-aided optimization of composition and nanoparticle size of the dispersion for improved performance; (3) synthesis and characte… more
Date: July 31, 2008
Creator: Kang, Bruce
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Next-Generation Photon Sources for Grand Challenges in Science and Energy

Description: The next generation of sustainable energy technologies will revolve around transformational new materials and chemical processes that convert energy efficiently among photons, electrons, and chemical bonds. New materials that tap sunlight, store electricity, or make fuel from splitting water or recycling carbon dioxide will need to be much smarter and more functional than today's commodity-based energy materials. To control and catalyze chemical reactions or to convert a solar photon to an elec… more
Date: May 1, 2009
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Miniaturized Mid-Infrared Sensor Technologies

Description: Fundamental vibrational and rotational modes associated with most inorganic and organic molecules are spectroscopically accessible within the mid-infrared (MIR; 3-20 {micro}m) regime of the electromagnetic spectrum. The interaction between MIR photons and organic molecules provides particularly sharp transitions, which - despite the wide variety of organic molecules - provide unique MIR absorption spectra reflecting the molecularly characteristic arrangement of chemical bonds within the probed … more
Date: August 16, 2007
Creator: Kim, S.; Young, C. & Mizaikoff, B.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

CHEMISTRY OF SO2 AND DESOX PROCESSES ON OXIDE NANOPARTICLES.

Description: On bulk stoichiometric oxides, SO{sub 2} mainly reacts with the O centers to form SO{sub 3} or SO{sub 4} species that decompose at elevated temperatures. Adsorption on the metal cations occurs below 300 K and does not lead to cleavage of the S-O bonds. In bulk oxides, the occupied cation bands are too stable for effective bonding interactions with the LUMO of SO{sub 2}. The effects of quantum confinement on the electronic properties of oxide nanoparticles and the structural defects that usually… more
Date: June 30, 2006
Creator: Rodriguez, J. A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Uranium (VI)Bis(imido) chalcogenate complexes:synthesis and density functional theory analysis

Description: Bis(imido) uranium(VI) trans- and cis-dichalcogenate complexes with the general formula U(NtBu)2(EAr)2(OPPh3)2 (EAr = O-2-tBuC6H4, SPh, SePh, TePh) and U(NtBu)2(EAr)2(R2bpy) (EAr = SPh, SePh, TePh) (R2bpy = 4,4'-disubstituted-2,2'-bipyridyl, R = Me, tBu) have been prepared. This family of complexes includes the first reported monodentate selenolate and tellurolate complexes of uranium(VI). Density functional theory calculations show that covalent interactions in the U-E bond increase in the tra… more
Date: January 1, 2009
Creator: Spencer, Liam P.; Batista, Enrique R.; Boncella, James M.; Yang, Ping & Scott, Brian L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Interplay of metal-allyl and metal-metal bonding in dimolybdenum allyl complexes

Description: Addition of PMe{sub 3} to Mo{sub 2}(allyl){sub 4} afforded Mo{sub 2}(allyl){sub 4}(PMe{sub 3}){sub 2}, in which two of the allyl groups adopt an unprecedented {mu}{sub 2{sup -}}{eta}{sup 1}, {eta}{sup 3} bonding mode; theoretical studies elucidate the role sof the {sigma}- and {pi}-donor ligands in the interplay of metal-allyl and metal-metal bonding.
Date: January 1, 2008
Creator: John, Kevin D.; Martin, Richard L.; Obrey, Steven J. & Scott, Brian L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Theory for dynamical self arrest and gelation in microemulsions and the block copolymer systems

Description: The main purpose of this work is to investigate the glassy behavior of microemulsions and block copolymers. The origin of glassy behavior in microemulsions and block copolymers is frustration due to a competition between short-range interaction and long range interaction. According to the charge frustrated Ising model, the competition between ferromagnetic interaction and antiferromagnetic interaction is the origin of frustration in microemulsions. The competition between entropic effects and s… more
Date: May 1, 2005
Creator: Wu, Sangwook
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries Government Documents Department
open access

Final Report

Description: The research funded by this grant yielded 20 papers with the P.I as the main author or a co-author. In this report, a brief outline of the completed projects is given.
Date: September 1, 2004
Creator: Cioslowski,J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Ultrafast x-ray science at the Advanced Light Source

Description: Our scientific understanding of the static or time-averaged structure of condensed matter on the atomic scale has been dramatically advanced by direct structural measurements using x-ray techniques and modern synchrotron sources. Of course the structure of condensed matter is not static, and to understanding the behavior of condensed matter at the most fundamental level requires structural measurements on the time scale on which atoms move. The evolution of condensed-matter structure, via the m… more
Date: November 25, 2000
Creator: Schoenlein, R. W.; Chin, A. H.; Chong, H. H. W.; Falcone, R. W.; Glover, T. E.; Heimann, P. A. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

The Kinetics of Dissociations of Aluminum - Oxygen Bonds in Aqueous Complexes - An NMR Study

Description: OAK B262 The Kinetics of Dissociations of Aluminum--Oxygen Bonds in Aqueous Complexes--An NMR Study. In this project we determined rates and mechanisms of Al(III)-O bond rupture at mineral surfaces and in dissolved aluminum complexes. We then compared the experimental results to simulations in an attempt to predict rate coefficients. Most of the low-temperature reactions that are geochemically important involve a bonded atom or molecule that is replaced with another. We probe these reactions at… more
Date: September 3, 2003
Creator: Casey, Dr. William
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Laser-Induced Fluorescence Detection in High-Throughput Screening of Heterogeneous Catalysts and Single Cells Analysis

Description: Laser-induced fluorescence detection is one of the most sensitive detection techniques and it has found enormous applications in various areas. The purpose of this research was to develop detection approaches based on laser-induced fluorescence detection in two different areas, heterogeneous catalysts screening and single cell study. First, we introduced laser-induced imaging (LIFI) as a high-throughput screening technique for heterogeneous catalysts to explore the use of this high-throughput s… more
Date: May 1, 2001
Creator: Su, Hui
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries Government Documents Department
open access

Laser-Induced Fluorescence Detection in High-Throughput Screening of Heterogeneous Catalysts and Single Cells Analysis

Description: Laser-induced fluorescence detection is one of the most sensitive detection techniques and it has found enormous applications in various areas. The purpose of this research was to develop detection approaches based on laser-induced fluorescence detection in two different areas, heterogeneous catalysts screening and single cell study. First, the author introduced laser-induced imaging (LIFI) as a high-throughput screening technique for heterogeneous catalysts to explore the use of this high-thro… more
Date: May 25, 2001
Creator: Su, Hui
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries Government Documents Department
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