Bulletin of the American Physical Society
Joint Spring 2010 Meeting of the Texas Sections of the APS, AAPT, and SPS
Volume 55, Number 3
Thursday–Saturday, March 18–20, 2010; Austin, Texas
Session F3: Condensed Matter Physics II |
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Room: Robert Lee Moore Hall 7.104 |
Friday, March 19, 2010 3:15PM - 3:27PM |
F3.00001: Zr Doping Effects on LiFePO4 with Carbon Coating for Lithium-Ion Batteries Travis Neeley, Jacob Hill, Jessica Burk, Kenny Swatzel, Yamin Chowdhury, Gan Liang, Hui Fang LiFePO4 cathode materials doped with various percentages of Zr on the Fe site are synthesized using both the solution and ball milling methods. The effects of carbon coating on the Fe site with various Zr doping percentages will be discussed versus non-coated material doped at the same percentages. X-ray diffraction, cyclic voltammetry, and constant current charge/discharge measurements are employed to characterize the structural, electronic, and electrochemical properties of the samples. The effects caused by Zr doping on Fe site sintered at various temperatures will be discussed and presented. [Preview Abstract] |
Friday, March 19, 2010 3:27PM - 3:39PM |
F3.00002: W Doping Effects on LiFePO4 Cathode Materials with Carbon Coating for Lithium-Ion Batteries Jacob Hill, Travis Neeley, Jessica Burk, Kenneth Swatzel III, Yamin Chowdhury, Hui Fang, Gan Liang The effects of doping on Fe site of LiFeP4 cathode materials with varying concentrations of W and with carbon coating, synthesized by ball milling method, will be presented. Results of W doping without carbon coating will also be shown. X-ray diffraction, cyclic voltammetry, and constant current charge/discharge measurements are employed to characterize the structural, electronic, and electro chemical properties of the samples. [Preview Abstract] |
Friday, March 19, 2010 3:39PM - 3:51PM |
F3.00003: Preparation and characterization of Li$_{1-3x}$Cr$_{x}$FePO$_{4}$ cathode materials for lithium ion batteries Jessica Burk, Kenneth Swatzel, Jacob Hill, Travis Neeley, Yamin Chowdhury, Hui Fang, Gan Liang Cr-doped LiFePO$_{4}$ cathode materials have been synthesized by solid-state reaction method and characterized by and specific capacity, synchrotron-based in-situ energy dispersive x-ray diffraction (EDXRD), and x-ray absorption (XAS) measurements. It is found that with the increase of the concentration of the doped-Cr, the specific capacity decreases. The specific capacity decreases with increasing charge/discharge rate. XAS result shows that Cr in the cathode materials is in trivalent state. The in-situ EDXRD measurement on Cr-doped LiFePO$_{4}$ coin cell batteries shows that EDXRD is an excellent technique for studying internal layer structure and chemical reactions in Li-ion batteries with thick metallic walls. [Preview Abstract] |
Friday, March 19, 2010 3:51PM - 4:03PM |
F3.00004: Femtosecond Electron Diffraction and Shadow Imaging David McPherson Using femtosecond electron pulses as an imaging tool, we can probe ultrafast dynamics by taking snapshots at different time delays. By using femtosecond electron diffraction (FED), we can examine structural dynamics at the atomic level in real time, and study the structure-function correlation. Additionally, femtosecond electron shadow imaging (FESI) can explore the dynamics of laser induced plasmas off the surfaces of conductors, semiconductors, and insulators. Project as part of a Research Experience for Undergraduates program funded by the National High Magnetic Field Laboratory, Florida State University and the National Science Foundation under supervision of Jianming Cao, PhD., Florida State University. [Preview Abstract] |
Friday, March 19, 2010 4:03PM - 4:15PM |
F3.00005: Ab-initio Density Functional Theory Based Study of Adsorption of No on Pt, Pd and Ir Surfaces Churna Bhandari Among many chemical by-products released from combustion engines and other industrial processes, NO is one of the most harmful components which causes significant pollution to the environment. To minimize this effect and produce pollutionless energy, one needs an efficient catalyst which can change it into some other harmless forms. To study the catalytic behavior of metals, a powerful tool so called DFT is implemented. In this talk, I will mainly discuss the adsorption behavior of NO on the clean Pt, Pd and Ir surfaces studied on the basis of time independent DFT calculation. [Preview Abstract] |
Friday, March 19, 2010 4:15PM - 4:27PM |
F3.00006: Rippling of Graphene Maria Moura, Rebecca Thompson-Flagg, Michael Marder Experiments found that free standing, single-layer graphene sheets display ripples [1]. Here we show that graphene can develop ripples as a consequence of adsorbed molecules sitting on random sites. The adsorbates cause the bonds between the carbon atoms to lengthen slightly. Static buckles then result from a mechanism like the one that leads to buckling of leaves. Ripples caused by roughly 20\% coverage of adsorbates are consistent with experimental observation. We show why this mechanism is more likely to explain ripples than are thermal fluctuations or the Mermin-Wagner theorem (previously invoked [2]). This work was recently published [3]. \\[4pt] [1] J. C. Meyer, A. K. Geim, M. I. Katsnelson, K. S. Novoselov, T. J. Booth, and S. Roth, Nature, 446, 60 (2007). \\[0pt] [2] A. Fasolino, J. H. Los, and M. I. Katsnelson, Nature Materials, 6, 858, (2007). \\[0pt] [3] R. Thompson-Flagg, M. J. B. Moura, and M. Marder, EPL, 85, 46002 (2009). [Preview Abstract] |
Friday, March 19, 2010 4:27PM - 4:39PM |
F3.00007: Ba$_8$Ga$_{16}$Sn$_{30}$ type-I clathrate NMR lineshape simulations Sergio Y. Rodriguez, Xiang Zheng, Laziz Saribaev, Joseph H. Ross, Jr. Semiconductor clathrates consist of Si, Ge or Sn networks containing guest atoms. Clathrates have gained considerable attention due to their potential for thermoelectric device application. To understand the Ga substitutional configuration and Ga-Ga bonding, we calculated Ga NMR lineshapes for type-I Ba$_8$Ga$_{16}$Sn$_{30}$. The results were obtained by calculating Electric Field Gradients (EFG) for different Ga framework occupation. To obtain the EFG's we used $ab$ $initio$ methods with the Generalized Gradient Approximation for the exchange-correlation term as implemented in the WIEN2k code. These were compared with our experimental NMR lineshapes. By x-ray-absorption fine structure technique simulations it had previously being suggested that the number of Ga-Ga bonds was between 4 and 5. Our results showed that this number should be lower due to the mismatch between the experimental and simulated NMR lineshapes. Furthermore it was obtained that Ga-Ga bonds on 16$i$ adjacent sites are not energetically favorable. EFG's corresponding to such configurations are also extremely large and do not agree with our measured NMR lineshapes. On the other hand we found good agreement between the measured lineshapes and the configuration with the lowest computed energy. This work was supported by Robert A. Welch Foundation (Grant A-1526). [Preview Abstract] |
Friday, March 19, 2010 4:39PM - 4:51PM |
F3.00008: ABSTRACT WITHDRAWN |
Friday, March 19, 2010 4:51PM - 5:03PM |
F3.00009: Band Structure of Delta-Doped STO Guru Khalsa, Rafi Bistritzer, Allan MacDonald Recently there has been much progress towards controlling two-dimensional electron systems in complex oxides, in particular SrTiO3. There are, at present, no tools for quantitative modeling of these systems. Because of the low filling in these materials, the k.p method allows for many simplifications. In this talk, I will discuss our recent progress towards quantitative modeling of delta-doped SrTiO3 quantum wells. [Preview Abstract] |
Friday, March 19, 2010 5:03PM - 5:15PM |
F3.00010: A DFT study on Molybdenum/di-Sulfide-Cobalt/Sulfide interface to understand the promotion effect in nano-structured catalytical materials Manuel Ramos, Gilles Berhaut, Brenda Torres, Domingo Ferrer, Rusell Chianelli Previous studies done to understand promotion effect and structure/function in unsupported catalyst show that d-electrons plays an important role promoting catalytical active sites at the edges of MoS$_{2}$ forming so-called CoMoS phase. Information about how Co-Mo acted together is under discussion still and has been approached by meaning of Density Functional Theory (DFT) indicating that hydrodesulfurization takes place at the MoS$_{2}$ edge when promoted with Co, several technical papers reports lattice parameter, particle size, crystallographic structure and promotion by meaning of STM on MoS$_{2}$/Au. We present here most recent results on DFT calculations using CASTEP for MoS$_{2}$/Co nano-structure in order to explain promotion effect as observed by High Resolution TEM on MoS$_{2}$/Co nano-structured materials.\textit{(Authors dedicated this research work to: }\textbf{\textit{Edward I. Stiefel}}\textit{ for his immense contributions to the field of transition metal catalysis while at ExxonMobil research labs.).} [Preview Abstract] |
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