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Energy barriers for point-defect reactions in 3C-SiC

Physical Review B 2013年第5期88卷 054105-054105页

作者： Ming-Jie Zheng Narasimhan Swaminathan Dane Morgan Izabela Szlufarska Materials Science and Engineering Department University of Wisconsin-Madison Madison Wisconsin USA Department of Mechanical Engineering Indian Institute of Technology Madras Chennai 600036 India Material Science Program University of Wisconsin-Madison Madison Wisconsin USA

Energy barriers of the key annealing reactions of neutral and charged point defects in SiC are calculated with ab initio density functional theory methods. In order to effectively search for the lowest energy migration paths the preliminary path is first established based on ab initio molecular dynamics (AIMD) simulations. The energy barrier of each hop is then calculated via climbing image nudged elastic band methods for paths guided by the AIMD simulations. The final paths and barriers are determined by comparing different pathways. The annealing reactions have important implications in understanding the amorphization, recovery, and other aspects of the radiation response of SiC. The results are compared with the literature data and experimental results on SiC recovery and amorphization. We propose that the C interstitial and Si antisite annealing reaction may provide a critical barrier that governs both the recovery stage III and amorphization processes.

关键词： SILICON carbide AB initio methods (Quantum mechanics) MOLECULAR dynamics AMORPHIZATION SIMULATED annealing (Mathematics)

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Tunable optical antennas enabled by the phase transition in vanadium dioxide

Tunable optical antennas enabled by the phase transition in ...

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作者： Earl, Stuart K. James, Timothy D. Davis, Timothy J. McCallum, Jeffrey C. Marvel, Robert E. Haglund Jr., Richard F. Roberts, Ann School of Physics University of Melbourne VIC 3010 Australia Australian National Fabrication Facility Clayton VIC 3168 Australia CSIRO Material Science and Engineering Private Bag 33 Clayton VIC 3168 Australia Interdisciplinary Materials Science Program Vanderbilt University Nashville TN 37235 United States Department of Physics and Astronomy Vanderbilt University Nashville TN 37325 United States

Optical antennas, subwavelength metallic structures resonating at visible frequencies, are a relatively new branch of antenna technology being applied in science, technology and medicine. Dynamically tuning the resonances of these antennas would increase their range of application and offer potential increases in plasmonic device efficiencies. Silver nanoantenna arrays were fabricated on a thin film of the phase change material vanadium dioxide (VO2) and the resonant wavelength of these arrays was modulated by increasing the temperature of the substrate above the critical temperature (approximately 68°C). Depending on the array, wavelength modulation of up to 110 nm was observed. ©2013 Optical Society of America.

关键词： Vanadium dioxide

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Tactile Feedback Display with Spatial and Temporal Resolutions (vol 3, 2521, 2013)

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SCIENTIFIC REPORTS 2013年第2013期3卷 2521-2521页

作者： Vishniakou, Siarhei Lewis, Brian W. Niu, Xiaofan Kargar, Alireza Sun, Ke Kalajian, Michael Park, Namseok Yang, Muchuan Jing, Yi Brochu, Paul Sun, Zhelin Li, Chun Truong Nguyen Pei, Qibing Wang, Deli Department of Electrical and Computer Engineering University of California - San Diego CA 92093 California Institute of Telecommunication and Information Technology University of California - San Diego CA 92093 Material Science Program University of California - San Diego CA 92093 Department of Material Science and Engineering University of California - Los Angeles CA 90095 These authors contributed equally to this work.

We report the electronic recording of the touch contact and pressure using an active matrix pressure sensor array made of transparent zinc oxide thin-film transistors and tactile feedback display using an array of diaphragm actuators made of an interpenetrating polymer elastomer network. Digital replay, editing and manipulation of the recorded touch events were demonstrated with both spatial and temporal resolutions. Analog reproduction of the force is also shown possible using the polymer actuators, despite of the high driving voltage. The ability to record, store, edit, and replay touch information adds an additional dimension to digital technologies and extends the capabilities of modern information exchange with the potential to revolutionize physical learning, social networking, e-commerce, robotics, gaming, medical and military applications.

关键词： ZINC oxide ACTUATORS POLYMERS SOCIAL networks PRESSURE transducers

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Angular-Momentum-Dependent Orbital-Free Density Functional Theory

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Physical Review Letters 2013年第6期111卷 066402-066402页

作者： Youqi Ke Florian Libisch Junchao Xia Lin-Wang Wang Emily A. Carter Department of Mechanical and Aerospace Engineering Program in Applied and Computational Mathematics and Andlinger Center for Energy and the Environment Princeton University Princeton New Jersey 08544 USA Material Science Division Lawrence Berkeley National Laboratory Berkeley California 94720 USA

Orbital-free (OF) density functional theory (DFT) directly solves for the electron density rather than the wave function of many electron systems, greatly simplifying and enabling large scale first principles simulations. However, the required approximate noninteracting kinetic energy density functionals and local electron-ion pseudopotentials severely restrict the general applicability of conventional OFDFT. Here, we present a new generation of OFDFT called angular-momentum-dependent (AMD)-OFDFT to harness the accuracy of Kohn-Sham DFT and the simplicity of OFDFT. The angular momenta of electrons are explicitly introduced within atom-centered spheres so that the important ionic core region can be accurately described. In addition to conventional OF total energy functionals, we introduce a crucial nonlocal energy term with a set of AMD energies to correct errors due to the kinetic energy density functional and the local pseudopotential. We find that our AMD-OFDFT formalism offers substantial improvements over conventional OFDFT, as we show for various properties of the transition metal titanium.

关键词： DENSITY functional theory ELECTRON density KINETIC energy PSEUDOPOTENTIAL method TRANSITION metal compounds ELECTRON-ion collisions

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Selective enrichment and sensitive detection of candidate disease biomarker using a novel surfactant-coated magnetic nanoparticles

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IOP Conference Series: materials science and engineering 2014年第1期64卷

作者： R Y Capangpangan M A C dela Rosa C H Chang W C Wang J Peng S J Shih M H Chiang D L Tzou C C Lin Y J Chen Department of Chemistry National Tsing Hua University Hsinchu Taiwan Molecular Science and Technology Taiwan International Graduate Program Taiwan contributed equally to this work Department of Chemistry National Taiwan University Taipei Taiwan Nanoscience and Technology Program Taiwan International Graduate Program Taiwan En Hou Polymer Chemical Ind. Co. Ltd. Taiwan Department of Material Science and Engineering National Taiwan University of Science and Technology Taipei Taiwan Institute of Chemistry Academia Sinica Taipei Taiwan To whom any correspondence should be addressed

In this study, novel surfactant-coated magnetic nanoparticles were synthesized and evaluated for enrichment performance towards the sensitive detection of disease biomarkers. Surfactants with phosphate ester groups (RD35A and RD66) were used as a coating to reduce aggregation and to enhance the nanoparticle dispersion. Importantly, sensitive enrichment of the target proteins using the antibody-functionalized magnetic nanoparticles (Ab@MNP) was obtained, with a five-fold increase in recovery compared to uncoated magnetic nanoparticles. Similarly, phosphopeptide enrichment using the NTA@MNP in standard samples showed that the nanoparticles could selectively enrich phosphorylated peptides.

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Advanced characterization techniques for nanoparticles for cancer research: Applications of SEM and NanoSIMS for locating au nanoparticles in cells

Advanced characterization techniques for nanoparticles for c...

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2013 MRS Spring Meeting

作者： Kempen, Paul J. Hitzman, Chuck Sasportas, Laura S. Gambhir, Sanjiv S. Sinclair, Robert Department of Material Science and Engineering Stanford University 496 Lomita Mall Stanford CA 94305-4034 United States Stanford Nanocharacterization Laboratory Stanford University 476 Lomita Mall Stanford CA 94305-4035 United States Molecular Imaging Program at Stanford Department of Radiology Stanford University 318 Campus Drive Stanford CA 94305-5427 United States

The ability of nano secondary ion mass spectrometry (NanoSIMS) to locate and analyze Raman active gold core nanoparticles (R-AuNPs) in a biological system is compared with the standard analysis using the scanning electron microscope (SEM). The same cell with R-AuNPs on and inside the macrophage was analyzed with both techniques to directly compare them. SEM analysis showed a large number of nanoparticles within the cell. Subsequent NanoSIMS analysis showed fewer R-AuNPs with lower spatial resolution. SEM was determined to be superior to NanoSIMS for the analysis of inorganic nanoparticles in complex biological systems. Copyright © materials Research Society 2013.

关键词： Scanning electron microscopy

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The Fragmentation of Al-W Granular Composites Under Explosive Loading

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MRS Online Proceedings Library 2013年第1期1521卷 1-6页

作者： Karl L. Olney Po-Hsun Chiu Vitali F. Nesterenko David J. Benson Chris Braithwaite Adam Collins David Williamson Francesca McKenzie Department of Mechanical and Aerospace Engineering University of California San Diego USA Material Science and Engineering program University of California San Diego USA Department of Structural Engineering University of California San Diego USA Fracture and Shock Physics SMF Group Department of Physics Cavendish Laboratory Cambridge United Kingdom Imperial College London Institute of Shock Physics London United Kingdom

Small scale explosively driven fragmentation experiments have been performed on Aluminum (Al)-Tungsten (W) granular composite rings processed using cold isostatic compression of Al and W powders with a particle size of 4-30 microns. Fragments collected from the experiments had a maximum size of the order of a few hundred micrometers. This is a dramatic reduction in the fragment size when compared to the 1-10 mm typical for a homogeneous material such as solid aluminum under similar loading conditions. Numerical simulations of the experiment were performed to elucidate the mechanisms of fragmentation that were responsible for this shift in fragmentation size scales. Simulations were performed with a significantly stronger explosive driver to examine how the mechanisms of fragmentation change when the detonation pressure increases.

关键词： energetic material simulation shock loading

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The fragmentation of Al-W granular composites under explosive loading

The fragmentation of Al-W granular composites under explosiv...

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2012 MRS Fall Meeting

作者： Olney, Karl L. Chiu, Po-Hsun Nesterenko, Vitali F. Benson, David J. Braithwaite, Chris Collins, Adam Williamson, David McKenzie, Francesca Department of Mechanical and Aerospace Engineering University of California San Diego San Diego CA United States Material Science and Engineering Program University of California San Diego San Diego CA United States Department of Structural Engineering University of California San Diego San Diego CA United States Fracture and Shock Physics Department of Physics Cavendish Laboratory Cambridge CB3 0HE United Kingdom Institute of Shock Physics Imperial College London South Kensington Campus London SW7 2AZ United Kingdom

ISBN: (纸本)9781632661111

Small scale explosively driven fragmentation experiments have been performed on Aluminum (Al)-Tungsten (W) granular composite rings processed using cold isostatic compression of A1 and W powders with a particle size of 4-30 microns. Fragments collected from the experiments had a maximum size of the order of a few hundred micrometers. This is a dramatic reduction in the fragment size when compared to the 1-10 mm typical for a homogeneous material such as solid aluminum under similar loading conditions. Numerical simulations of the experiment were performed to elucidate the mechanisms of fragmentation that were responsible for this shift in fragmentation size scales. Simulations were performed with a significantly stronger explosive driver to examine how the mechanisms of fragmentation change when the detonation pressure increases. © 2013 materials Research Society.

关键词： Binary alloys

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Origin of Overstretching Transitions in Single-Stranded Nucleic Acids

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Physical Review Letters 2013年第18期111卷 188302-188302页

作者： Zackary N. Scholl Mahir Rabbi David Lee Laura Manson Hanna S-Gracz Piotr E. Marszalek Program in Computational Biology and Bioinformatics Duke University Durham North Carolina 27708 USA Department of Mechanical Engineering and Materials Science Center for Biologically Inspired Materials and Material Systems Duke University Durham North Carolina 27708 USA Department of Molecular and Structural Biochemistry North Carolina State University Raleigh North Carolina 27708 USA

We combined single-molecule force spectroscopy with nuclear magnetic resonance measurements and molecular mechanics simulations to examine overstretching transitions in single-stranded nucleic acids. In single-stranded DNA and single-stranded RNA there is a low-force transition that involves unwinding of the helical structure, along with base unstacking. We determined that the high-force transition that occurs in polydeoxyadenylic acid single-stranded DNA is caused by the cooperative forced flipping of the dihedral angle formed between four atoms, O5’-C5’-C4’-C3’ (γ torsion), in the nucleic acid backbone within the canonical B-type helix. The γ torsion also flips under force in A-type helices, where the helix is shorter and wider as compared to the B-type helix, but this transition is less cooperative than in the B type and does not generate a high-force plateau in the force spectrums of A-type helices. We find that a similar high-force transition can be induced in polyadenylic acid single-stranded RNA by urea, presumably due to disrupting the intramolecular hydrogen bonding in the backbone. We hypothesize that a pronounced high-force transition observed for B-type helices of double stranded DNA also involves a cooperative flip of the γ torsion. These observations suggest new fundamental relationships between the canonical structures of single-and double-stranded DNA and the mechanism of their molecular elasticity.

关键词： NUCLEAR magnetic resonance spectroscopy SINGLE-stranded DNA NUCLEOTIDE sequence DEOXYRIBOSE ATOMIC force microscopy

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Terahertz Emission From Graphene-Coated InP (100) Surface

Terahertz Emission From Graphene-Coated InP (100) Surface

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Conference on Lasers and Electro-Optics Pacific Rim

作者： Y. Sano M. Tabata K. Salek I. Kawayama M. Wang R. Vajtai J. Kono P. M. Ajayan M. Tonouchi Institute of Laser Engineering Osaka University NanoJapan Program and Department of Electrical and Computer Engineering Rice University Department of Mechanical Engineering and Material Science Rice University

We observed THz radiation from the graphene-coated InP (100) surface and found the drastic change of the waveforms of THz radiation with time, which cannot be explained by the simple absorption of graphene.

ISBN: (纸本)9781467364744

关键词： Chemical vapor deposition Emission Femtosecond pulses Surfaces Thin films Ti:sapphire lasers

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