Bulletin of the American Physical Society
APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011; Dallas, Texas
Session W31: Energy Production & Distribution, Nuclear, Hydrogen, Bio and Infrastructure |
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Sponsoring Units: GERA Chair: Judy Pang, Oak Ridge National Laboratory Room: C145 |
Thursday, March 24, 2011 11:15AM - 11:27AM |
W31.00001: Phonon dynamics of UO$_{2}$ at high temperature J.W.L. Pang, A. Chernatynskiy, B.C. Larson, S.R. Phillpot, W.J.L. Buyers Inelastic neutron scattering and numerical simulations are being used to investigate the fundamental aspects of phonons and thermal transport in UO2 as part of a DOE-EFRC ``Center for Materials Science of Nuclear Fuel'' project. Understanding thermal transport associated with nuclear fuel environments requires a correct accounting for a wide range of phonon scattering processes, including anharmonic phonon-phonon, phonon-fission product, and phonon-defect cluster. Reactor and spallation neutron measurements of phonon dispersion, phonon linewidths and density of states in UO$_{2}$ at room and high temperature are in progress for direct comparison with atomic potential lattice-dynamics simulations of phonon dispersion, phonon group velocity, phonon linewidth, and phonon density of states. Direct comparisons between experimental measurements and numerical simulations in UO$_{2}$ as a function of temperature will be presented. [Preview Abstract] |
Thursday, March 24, 2011 11:27AM - 11:39AM |
W31.00002: An \textit{Ab Initio} Study of $\alpha $ --Pu Sarah C. Hernandez, Asok K. Ray Hybrid density functionals, which replace a fraction of density functional theory exchange with exact Hartree-Fock exchange has been used to study the electronic, geometric, and magnetic properties of $\alpha $ -- Pu. Different fractions of Hartree-Fock exchange have been used and the computations have been performed using the all-electron \underline {f}ull-\underline {p}otential \underline {l}inearized \underline {a}ugmented \underline {p}lane \underline {w}ave plus \underline {l}ocal \underline {o}rbitals basis method. Pu has been studied at the non-magnetic, ferromagnetic and anti-ferromagnetic configurations with spin-orbit coupling, orbital polarization, and \textit{full} geometry optimizations. The variations of the optimized lattice constants, magnetic moments, bulk moduli, density of states, and the degree of $5f $electron localization with the amount of Hartree -- Fock exchange will be reported. Results will be compared with those of $\delta $ -- Pu for which the performance of the hybrid functionals did \textit{not} seem superior to that of the pure density functionals.\footnote{R. Atta-Fynn and A. K. Ray, Europhys. Lett. 85, 27008 (2009).} [Preview Abstract] |
Thursday, March 24, 2011 11:39AM - 11:51AM |
W31.00003: Electron Correlation and Tranport Properties in Nuclear Fuel Materials Quan Yin, Kristjan Haule, Gabriel Kotliar, Sergey Savrasov, Warren Pickett Using first principle LDA+DMFT method, we conduct a systematic study on the correlated electronic structures and transport properties of select actinide carbides, nitrides, and oxides, many of which are nuclear fuel materials. Our results capture the metal--insulator Mott transition within the studied systems, and the appearance of the Zhang-Rice state in uranium dioxide. More importantly, by understanding the physics underlying their transport properties, we suggest ways to improve the efficiency of currently used fuels. [Preview Abstract] |
Thursday, March 24, 2011 11:51AM - 12:03PM |
W31.00004: Reaction Rate Measurement at the Californium User Facility (CUF) for unfolding the neutron spectrum Mohammad Hannan, Ruben Ortega Neutron Activation Analysis was used to determine Reaction Rate measurement of several activation detectors at the ORNL Californium User Facility (CUF). The irradiations were performed with 34 mg Cf$^{252}$ neutron source strength.. Ten source capsules $>$ 34 mg were positioned concentrically around a sample cavity. We have determined absolute activity per atom of 9 detectors: Au$^{197}$ (n,$\gamma )$ Au$^{198}$, Al$^{27}$(n,$\alpha )$Na$^{24}$, Al$^{27}$(n,p) Mg$^{27}$, Fe$^{56}$(n,p) Mn$^{5}$, Fe$^{54}$(n,p) Mn$^{54}$, In$^{115}$ (n,$\gamma )$In$^{116}$, Ti$^{46}$(n,p)Sc$^{46}$, Ni$^{60}$ (n,p) Co$^{60}$, Fe$^{58}$(n,$\gamma )$ Fe$^{59}$. The errors are within 1.5-8{\%} except Ni$^{60}$ and Fe$^{58}$ have errors of 46{\%} and 32 {\%}. These high errors may be attributed to the counting statistics. These reaction rate values will be used to unfold the neutron spectrum of the CUF using the MAXED 2000, a computer code for the de convolution of multi sphere neutron spectrometer data and the results are discussed. [Preview Abstract] |
Thursday, March 24, 2011 12:03PM - 12:15PM |
W31.00005: A first-principles investigation of III-V semiconductor-water interfaces for solar hydrogen production Brandon Wood, Tadashi Ogitsu, Eric Schwegler Photoelectrochemical devices promise sustainable hydrogen production using sunlight and water. Currently, the highest efficiency devices use III-V semiconductor photoelectrodes; however, stability of these materials under operating conditions remains an issue. In an effort to understand the chemical properties of the electrode-water interface, we have performed first-principles molecular dynamics simulations on model III-V surfaces in realistic aqueous environments. The structure, stability, and chemical activity of these surfaces are investigated, with the aim of understanding the reactive states precursory to photoexcitation and hydrogen evolution. Our results show that surface oxide nucleation is key to facilitating surface reactivity, and that the surface oxygen bonding arrangement is important for determining of the available pathways for water dissociation and corrosion. This points to the importance of III-V surface oxides as intermediates in the water-dissociation component of hydrogen evolution. Prepared by LLNL under Contract DE-AC52-07NA27344. [Preview Abstract] |
Thursday, March 24, 2011 12:15PM - 12:27PM |
W31.00006: Hydrogen Generation and Photoelectrochemical Effect of InGaN alloys Krishna Aryal, Bed Pantha, Rajendra Dahal, Jing Li, Jingyu Lin, Hongxing Jiang Generation of hydrogen gas, a clean source of energy with the highest conversion efficiency, via water splitting, using renewable resources has attracted tremendous research work in recent years. For producing hydrogen gas, a promising method using semiconductor materials is direct photoelectrolysis by solar water splitting. In$_{x}$Ga$_{1-x}$N alloys grown by metal organic chemical vapor deposition (MOCVD) are very promising candidates for water splitting because of their direct band gap which can be tuned to the entire solar spectrum through band gap engineering. It was found that n-GaN has a higher photocurrent density (J$_{ph})$ at zero bias, while an InGaN alloy provides much higher hydrogen generation rate (R$_{H})$ with a small external bias. R$_{H}$ of about 0.024 mL/min.cm$^{2}$ was obtained using an In$_{0.18}$Ga$_{0.82}$N as working electrode. The characteristics of time dependent J$_{ph}$ for a prolonged period of time (up to 7 days) showed higher chemical stability of the InGaN electrodes in aqueous solution of HBr. [Preview Abstract] |
Thursday, March 24, 2011 12:27PM - 12:39PM |
W31.00007: Sieving hydrogen based on its high compressibility Hangyan Chen, Deyan Sun, Xingao Gong, Zhifeng Liu Based on carbon nanotube intramolecular junction and a C60, a molecular sieve for hydrogen is presented. The small interspace between C60 and junction provides a size changeable channel for the permselectivity of hydrogen while blocking Ne and Ar. The sieving mechanism is due to the high compressibility of hydrogen. [Preview Abstract] |
Thursday, March 24, 2011 12:39PM - 12:51PM |
W31.00008: ABSTRACT WITHDRAWN |
Thursday, March 24, 2011 12:51PM - 1:03PM |
W31.00009: Combining micro-structures and micro-algae to increase lipid production for bio-fuel Saurabh Vyawahare, Emilly Zhu, Troy Mestler, Andr\'e Est\'evez-Torres, Robert Austin 3rd generation bio-fuels like lipid producing micro-algae are a promising source of energy that could replace our dependence on petroleum. However, until there are improvements in algae oil yields, and a reduction in the energy needed for processing, algae bio-fuels are not economically competitive with petroleum. Here, we describe our work combining micro-fabricated devices with micro-algae \textit{Neochloris oleoabundans}, a species first isolated on the sand dunes of Saudi Arabia. Inserting micro-algae of varying fitness into a landscape of micro-habitats allows us to evolve and select them based on a variety of conditions like specific gravity, starvation response and Nile Red fluorescence (which is a marker for lipid production). Hence, we can both estimate the production of lipids and generate conditions that allow the creation and isolation of algae which produce higher amounts of lipids, while discarding the rest. Finally, we can use micro-fabricated structures and flocculation to de-water these high lipid producing algae, reducing the need for expensive centrifugation and filtration. [Preview Abstract] |
Thursday, March 24, 2011 1:03PM - 1:15PM |
W31.00010: Structure and diffusion of furans and other cellulose-derived compounds in solvents via MD simulation Brooks Rabideau, Ahmed Ismail There is now a large push towards the development of energy sources that are both environmentally friendly and sustainable; with the conversion of cellulose derived from biomass into biofuels being one promising route. In this conversion, a variety of intermediary compounds have been identified, which appear critical to successful expansion of the process to an industrial scale. Here we examine the structure and diffusion of these furans and acids derived from cellulose within ionic liquids via molecular dynamic simulation. Ionic liquids have shown the ability to dissolve cellulose with certain `green' benefits over existing, conventional solvents. Specifically, we study the solvation properties of these chemicals by examining the pair correlation functions of solute with solvent, and by exploring the agglomeration and separation of these chemicals from the solvent as well as the hydrogen bonding between species. Additionally, we determine the diffusion constant of these compounds in ionic liquid and aqueous solvents. [Preview Abstract] |
Thursday, March 24, 2011 1:15PM - 1:27PM |
W31.00011: Molecular-dynamics study of proton transport near an ionomer-electrode interface Philip Taylor, Elshad Allahyarov Coarse-grained molecular-dynamics simulations have been used to study the behavior of an ionomer electrolyte in response to an induced current. We observe the changes in the distribution of charge concentration and local electrostatic field in the region near an electrode in contact with a Nafion-like ionomer. We have also analyzed how the morphology of the sulfonate clusters and the transport of water molecules depends on the current strength. In this study we insert protons at the electrode interface of the material and remove them at a plane some distance into the material. When a steady state is achieved we note the new charge distribution and average voltage difference between the faces of the simulation cell. We also note the change in distribution of water molecules within the material in response to the induced current of protons. We compare these results with those predicted by one-dimensional theoretical models. [Preview Abstract] |
Thursday, March 24, 2011 1:27PM - 1:39PM |
W31.00012: Origin of colossal ionic conductivity in YSZ/STO multilayers Timothy Pennycook, Mark Oxley, Matthew Beck, Javier Garcia-Barriocanal, Flavio Bruno, Carlos Leon, Jacobo Santamaria, Maria Varela, Stephen Pennycook, Sokrates Pantelides A colossal eight order of magnitude increase in the ionic conductivity of yttria- stabilized zirconia (YSZ) near room temperature was recently reported in YSZ/strontium titanate (STO) epitaxial heterostructures [1]. We present density functional theory results that explain the enhancement in terms of strain- and interface-induced disorder of the YSZ O-sublattice [2]. We further present experimental confirmation of O disorder using a combination of scanning transmission electron microscopy and electron energy loss spectroscopy. The O K-edge fine structure shows blurred-out features indicative of disorder [3]. Atomic-resolution elemental mapping clearly resolves the O sublattice in the STO but is blurred out in the YSZ, indicating disorder. This work is supported by DOE grant DE-FG02-09ER46554 and DOE Materials Sciences and Engineering Div. 1 J. Garcia-Barriocanal et al. Science 321, 676 (2008); 2 T.J. Pennycook et al., Phys. Rev. Lett. 104, 115901 (2010); 3 T.J. Pennycook et al., European Phys. J. [Preview Abstract] |
Thursday, March 24, 2011 1:39PM - 1:51PM |
W31.00013: Microscopic Understanding of Reactivity of Clinkers for Green Cement Engin Durgun, Hegoi Manzano, Roland J. M. Pellenq, Jeffrey C. Grossman Cement is the cause of up to 10 percent of global CO2 emissions, and yet, while it is one of the most common materials in use, we have remarkably little understanding of its microscopic properties. Toward this end, we use quantum mechanical simulations to examine the electronic properties and structure of cement crystals and to understand the surface reactivity of various clinker phases. Using these results, our aim is to clarify the mechanisms of cement dissolution, which is the initial stage of hydration and also one of the key processes that leads to the need for high temperature/energy manufacturing. As a first step we modeled the crystal structure of two major clinker phases, alite and belite and analyzed both electronic and mechanical properties. Next, we cleaved the clinker crystal in the simulation along different symmetry directions in order to obtain a prediction of the most stable surfaces. Dissolution occurs at the surface so accurate determination of the surface pattern is crucial. Using the computed surface energies, we can predict the full structure of the clinker nanocluster. This allows us to examine the interaction of water molecules with different nanocluster phases, in order to shed light on the dissolution mechanism and use this new understanding to predict possible novel routes for modifying and controlling the dissolution reactions. [Preview Abstract] |
Thursday, March 24, 2011 1:51PM - 2:03PM |
W31.00014: Comparison of Solar and Wind Power Output and Correlation with Real-Time Pricing Kathryn E. Hoepfl, Alvin D. Compaan, Andrew Solocha This study presents a method that can be used to determine the least volatile power output of a wind and solar hybrid energy system in which wind and solar systems have the same peak power. Hourly data for wind and PV systems in Northwest Ohio are used to show that a combination of both types of sustainable energy sources produces a more stable power output and would be more valuable to the grid than either individually. This method could be used to determine the ideal ratio in any part of the country and should help convince electric utility companies to bring more renewable generation online. This study also looks at real-time market pricing and how each system (solar, wind, and hybrid) correlates with 2009 hourly pricing from the Midwest Interconnect. [Preview Abstract] |
Thursday, March 24, 2011 2:03PM - 2:15PM |
W31.00015: Monte Carlo optimization of a matrix-based power-grid islanding algorithm Ibrahim Abou Hamad, Per Arne Rikvold, Svetlana V. Poroseva Spectral matrix methods are widely used for intelligent intentional islanding of power grids, the purposeful partitioning of a utility system to limit cascading disturbances. However, these methods may produce unbalanced islands of generators and loads when applied recursively. While some of the resulting islands have surplus generating capacity, others are deficient. We here implement a Monte Carlo simulated-annealing optimization procedure to load-balance the islands and increase their internal connectivity or modularity. After a matrix-based initial agglomeration of nearby loads and generators, Monte Carlo is used to redistribute loads among neighboring islands. The resulting network of islands is treated as a new network with the first-generation islands as the new nodes (``supergenerators'' and ``superloads''), and the same agglomeration and MC procedures are iteratively applied. We show here that combining matrix-based agglomeration and Monte Carlo methods results in well balanced, internally connected islands. [Preview Abstract] |
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