Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session T8: Onsager Prize, Nicholson Medal, Apker Award, Davisson-Germer Prize |
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Sponsoring Units: DCMP Chair: Warren Pickett, University of California, Davis Room: 414/415 |
Wednesday, March 18, 2009 2:30PM - 3:06PM |
T8.00001: Nicholson Medal Talk: Hydrodynamic Turbulence Invited Speaker: This talk will be an introduction on hydrodynamic turbulence to a non-specialist audience. It will summarize the essential developments in the field, and only modest emphasis will be placed on the speaker's own work. Hydrodynamic turbulence may be said to have begun as a subject of scientific study with Osborne Reynolds' classical paper towards the end of the nineteenth century, but it is a subject of great interest in the 21st century. The intent is to highlight the principal accomplishments in a way that draws attention to their connections to other areas of physics, where possible. [Preview Abstract] |
Wednesday, March 18, 2009 3:06PM - 3:42PM |
T8.00002: Lar Onsager Prize Talk: An Exactly solvable model for Strontium Copper Borate: Mott Hubbard Physics on an Archimedean Lattices Invited Speaker: An exactly solvable model of spin half particles on a certain 2-dimensional frustrated lattice hasĀ been recently realized in the compound $SrCu_2(BO_3)_2$, and other similar systems have been found more recently. These systems appear to be ideal testing grounds for contemporary theoretical ideas on the role of correlations and frustration in Mott Hubbard systems. In this talk I will summarize the work on these systems emphasizing their role in testing key concepts. [Preview Abstract] |
Wednesday, March 18, 2009 3:42PM - 4:18PM |
T8.00003: LeRoy Apker Award Talk: Electronics at the Nanoscale: Graphene, Carbon Nanotubes, and Single-Molecule Devices Invited Speaker: Low-dimensional nanostructures are emerging as model systems for fundamental studies of quantum transport, as well as promising candidates for novel post-silicon electronic devices incorporating quantum size effects. Key examples of these include few-layer graphene, carbon nanotubes, polymer nanofibers, and even single molecules. In this talk, I will summarize my work combining experimental and computational tools to study, control, and apply molecular nanomaterials of low dimensionality -- using scanning probe microscopy techniques to study electronic phenomena in few-layer graphene and carbon nanotubes, as well as to elucidate the structure of biochemically-functionalized carbon nanotubes; using computer simulations to investigate key electronic properties of single-molecule transistors; and demonstrating a straightforward chemical technique by which samples of few-layer graphene can be etched along their crystallographic directions, potentially enabling the creation of a variety of new graphene-based nanostructures. [Preview Abstract] |
Wednesday, March 18, 2009 4:18PM - 4:54PM |
T8.00004: Davisson-Germer Prize Talk: Hydrogen storage in nanoporous materials Invited Speaker: To develop a hydrogen-based energy technology, several classes of materials are being considered to achieve the DOE targets for gravimetric and volumetric hydrogen densities for hydrogen storage, including liquids (e.g. ammonium borohydrides), clathrate structures, complex metal hydrides, nanostructured (e.g. carbon) an nanoporous materials. Fundamental studies are necessary to determine the ultimate hydrogen capacity of each system. Nanoporous Metal-organic Framework (MOF) materials are promising candidates for hydrogen storage because the chemical nature and size of their unit cell can be tailored to weakly attract and incorporate H$_{2}$ molecules, with good volumetric and mass density. In this talk, we consider the structure M$_{2}$(BDC)$_{2}$(TED), where M is a metal atom (Zn, Ni, Cu), BDC is benzenedicarboxylate and TED triethylenediamine, to determine the location and interaction of H$_{2}$ molecules within the MOF. These compounds are isostructural and crystallize in the tetragonal phase (space group P4/ncc), they construct 3D porous structures with relatively large pore size ($\sim $7-8 A\r{ }), pore volume ($\sim $0.63-0.84 cc/g) and BET surface area ($\sim $1500-1900 m$^{2}$/g). At high pressures (300-800 psi), the perturbation of the H-H stretching mode can be measured with IR absorption spectroscopy, showing a 35 cm$^{-1}$ redshift from the unperturbed ortho (4155 cm$^{-1}$ ) and para (4161 cm$^{-1}$ ) frequencies. Using a newly developed non empirical van der Waals DFT method vdW-DFT),\footnote{J.Y. Lee, D.H. Olson, L. Pan, T.J. Emge, J. Li, Adv. Func. Mater. 17, 1255 (2007)} it can be shown that the locus of the deepest H$_{2}$ binding positions lies within to types of narrow channels. The energies of the most stable binding sites, as well as the number of such binding sites, are consistent with the values obtained from experimental adsorption isotherms, and heat of adsorption) data.\footnote{M. Dion, H. Ryberg, E. Schroder, D. C. Langreth, B.I. Lundqvist, Phys. Rev. Lett. 92, 246401 (2004).} Importantly, the calculated shift of the H-H stretch is $\sim $-30 cm$^{-1}$ at the strongest binding points of the two channels, suggesting that the combination of IR and vdW-DFT gives a consistent and accurate picture of H$_{2}$ binding in MOF structures. These methods can therefore provide the fundamental information necessary to guide synthesis for improving H$_{2}$ uptake and release. [Preview Abstract] |
Wednesday, March 18, 2009 4:54PM - 5:30PM |
T8.00005: Davisson-Germer Prize Talk: Surface vibrations of adsorbates on Si(111): From small clusters to infinite lattices Invited Speaker: Organic functionalization of semiconductor surfaces is a growing research area that offers the possibility of molecular level control of surface features and tailored electronic properties. In this work, quantum chemical cluster calculations are used in conjunction with surface vibrational spectroscopy to determine the structures of functionalized Si(111) surfaces. Interestingly, the interpretation of these spectra even for simple adsorbates is not straightforward. In the limit of high coverage, most calculations using small cluster models lack the long range coupling of the real surface that is required to make definitive assignments. In order to understand the relationship between clusters and infinite periodic vibrations, we have investigated the geometries and harmonic vibrational frequencies of the methyl, acetylenyl, methylacetylenyl, hydrogen, deuterium and chlorine functionalized Si(111) surfaces. From a careful analysis of these systems, we have derived a technique where the collective vibrational modes corresponding to the vibrations of the infinite periodic system can be derived from relatively small cluster models. The calculated frequencies are in good agreement with available experimental values and yield novel insights about the coupling between low frequency adsorbate frequencies and surface phonons. The efficacy of this approach for surfaces of varying adsorbate coverage and the prediction of novel frequency shifts will be discussed along with more complex systems. [Preview Abstract] |
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