]]> Wed, 24 Apr 2013 17:13:00 -0400 http://www.ornl.gov/~pk7/publications/hybriddensity_1.html Submitted to Physical Review B (2013)

]]> Thu, 4 Apr 2013 15:35:00 -0400 http://www.ornl.gov/~pk7/publications/polaronictran_1.html Submitted (2013)

]]> Thu, 18 Apr 2013 11:59:00 -0400 http://www.ornl.gov/~pk7/publications/trustworthypr_1.html Nature 493 314 (2013)

News and Views on Booth et al.'s article "Towards and exact description of electronic wavefunctions in real solids".

The effect of changes in morphology and surface hydroxyl species upon thermal treatment of zirconia on the oxidation activity of Au/ZrO2 catalyst was studied. We observed using transmission Fourier transform infrared (FTIR) spectroscopy progressive changes in the presence of monodentate (type I), bidentate (type II) and hydrogen bridged species (type III) for each of the thermally treated (85 to 500 °C) supports consisting of bare zirconia and Au/ZrO2 catalysts. Furthermore, structural changes in zirconia were accompanied by an increase in crystal size (7 to 58 nm) and contraction of the supports porosity (SSA 532 to 7 m2 g−1) with increasing thermal treatment. Deposition of gold nanoparticles under similar preparation conditions on different thermally treated zirconia resulted in changes in the mean gold cluster size, ranging from 3.7 to 5.6 nm. Changes in the surface hydroxyl species, support structure and size of the gold centers are important parameters responsible for the observed decrease (>90%) in CO conversion activity for the Au/ZrO2 catalysts. Density functional theory calculations provide evidence of increased CO binding to Au nanoclusters in the presence of surface hydroxyls on zirconia, which increases charge transfer at the perimeter of the gold nanocluster on zirconia support. This further helps in reducing a model CO-oxidation reaction barrier in the presence of surface hydroxyls. This work demonstrates the need to understand the structure–activity relationship of both the support and active particles for the design of catalytic materials.

]]> Wed, 24 Apr 2013 10:58:00 -0400 http://www.ornl.gov/~pk7/publications/solvent-type-_1.html Submitted to JACS (2013)

]]> Thu, 28 Mar 2013 12:15:00 -0400 http://www.ornl.gov/~pk7/publications/tuningfromhal_1.html Submitted (2013)

]]> Wed, 24 Apr 2013 10:58:00 -0400 http://www.ornl.gov/~pk7/publications/structureandg_1.html Journal of Physics: Condensed Matter 25 014011 (2012)

Quasi one-dimensional YSi2 nanostructures are formed via self-assembly on the Si(100) surface. These epitaxial nanowires are metastable and their formation strongly depends on the growth parameters. Here, we explore the various stages of yttrium silicide formation over a range of metal coverages and growth temperatures, and establish a rudimentary phase diagram for these novel and often coexisting nanophases. In addition to previously identified stoichiometric wires, we identify several new nanowire systems. These nanowires exhibit a variety of surface reconstructions, which sometimes coexist on a single wire. From a comparison of scanning tunneling microcopy images, tunneling spectra, and first-principles density functional theory calculations, we determine that these surface reconstructions arise from local orderings of yttrium vacancies. Nanowires often agglomerate into nanowire bundles, the thinnest of which are formed by single wire pairs. The calculations show that such bundles are energetically favored compared to well-separated single wires. Thicker bundles are formed at slightly higher temperature. They extend over several microns, forming a robust network of conducting wires that could possibly be employed in nanodevice applications.

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