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Articles 1 - 6 of 6
Full-Text Articles in Materials Science and Engineering
Sum Frequency Generation Vibrational Spectroscopy Of Pyridine Hydrogenation On Platinum Nanoparticles, Kaitlin M. Bratlie, Kyriakos Komvopoulos, Gabor A. Somorjai
Sum Frequency Generation Vibrational Spectroscopy Of Pyridine Hydrogenation On Platinum Nanoparticles, Kaitlin M. Bratlie, Kyriakos Komvopoulos, Gabor A. Somorjai
Kaitlin M. Bratlie
Pyridine hydrogenation in the presence of a surface monolayer consisting of cubic Pt nanoparticles stabilized by tetradecyltrimethylammonium bromide (TTAB) was investigated by sum frequency generation (SFG) vibrational spectroscopy using total internal reflection (TIR) geometry. TIR-SFG spectra analysis revealed that a pyridinium cation (C5H5NH+) forms during pyridine hydrogenation on the Pt nanoparticle surface, and the NH group in the C5H5NH+ cation becomes more hydrogen bound with the increase of the temperature. In addition, the surface coverage of the cation decreases with the increase of the temperature. An important contribution of this study is the in situ identification of reaction intermediates adsorbed …
Low-Energy Antiphase Boundaries, Degenerate Superstructures, And Phase Stability In Frustrated Fcc Ising Model And Ag-Au Alloys, Nikolai A. Zarkevich, Teck L. Tan, Lin-Lin Wang, Duane D. Johnson
Low-Energy Antiphase Boundaries, Degenerate Superstructures, And Phase Stability In Frustrated Fcc Ising Model And Ag-Au Alloys, Nikolai A. Zarkevich, Teck L. Tan, Lin-Lin Wang, Duane D. Johnson
Duane D. Johnson
An Ising model exhibits zero-energy antiphase boundaries (APBs) and frustration on close-packed face-centered cubic (fcc) and triangular lattices. The frustration results in degenerate structures and chains of long-period superstructures forming a quasicontinuous ground-state “hull” in the formation energy versus composition (c) diagram. In alloys, a nonzero but small APB energy yields a c-dependent reduction in this degeneracy that affects the phase diagram topology and range of the two-phase coexistence. Using density functional theory combined with cluster expansions (CEs), we study Ag-Au alloys as a prototype and find the effective cluster interactions (dominated by nearest-neighbor pairs), predict energetics of millions of …
Grain Growth And Texture Development In Lithium Fluoride Thin Films, Hakkwan Kim, Alexander H. King
Grain Growth And Texture Development In Lithium Fluoride Thin Films, Hakkwan Kim, Alexander H. King
Alexander H. King
We have studied grain-growth and texture development in polycrystalline lithium fluoride thin films using dark-field transmission electron microscopy. We demonstrate that we can isolate the size distribution of 〈111〉 surface normal grains from the overall size distribution, based on simple and plausible assumptions about the texture. The {111} texture formation and surface morphology were also observed by x-ray diffraction and atomic force microscopy, respectively. The grain-size distributions become clearly bimodal as the annealing time increases, and we deduce that the short-time size distributions are also a sum of two overlapping peaks. The smaller grain-size peak in the distribution corresponds to …
Predicting Enthalpies Of Molecular Substances: Application To Libh4, Nikolai A. Zarkevich, Duane D. Johnson
Predicting Enthalpies Of Molecular Substances: Application To Libh4, Nikolai A. Zarkevich, Duane D. Johnson
Duane D. Johnson
For molecular substances exhibiting harmonic and nonharmonic vibrations, we present a first-principles approach to predict enthalpy differences between phases at finite temperatures, including solid-solid and melting. We apply it to the complex hydride LiBH4. Using ab initio molecular dynamics, we predict a structure for the high-T solid phase of lithium borohydride, and we propose an approximation to account for nonharmonic vibrations. We then predict the enthalpy changes for solid-solid transition, melting, and an H-storage reaction, all in agreement with experiment.
(Crcl3)3@2[C4mim][Ome]—Molecular Cluster-Type Chromium(Iii) Chloride Stabilized In A Salt Matrix, Bert Mallick, Harald Kierspel, Anja V. Mudring
(Crcl3)3@2[C4mim][Ome]—Molecular Cluster-Type Chromium(Iii) Chloride Stabilized In A Salt Matrix, Bert Mallick, Harald Kierspel, Anja V. Mudring
Anja V. Mudring
In [C4mim]2[CrCl3]3[OMe]2 molecular (CrCl3)3 units are embedded in a salt matrix of [C4mim][OMe]. This structural subunit can be viewed as a trapped molecular polymorph of CrCl3. Experimental and theoretical investigations indicate that, in contrast to bulk CrCl3, metal−metal bonds are formed at low temperatures.
Seven-Coordinate Ruthenium Atoms Sequestered In Praseodymium Clusters In The Chloride {Rupr3}Cl3, Nina Hermann, Anja V. Mudring, Gerd Meyer
Seven-Coordinate Ruthenium Atoms Sequestered In Praseodymium Clusters In The Chloride {Rupr3}Cl3, Nina Hermann, Anja V. Mudring, Gerd Meyer
Anja V. Mudring
The first example for an endohedral transition-metal atom (Ru) sequestered in a seven-coordinate surrounding of rare-earth metal atoms (Pr) has been found for {RuPr3}Cl3. The monocapped trigonal prisms of Pr atoms share two rectangular faces, forming a zigzag chain with Ru−Ru distances of 308 pm. Intracluster bonding is dominated by Ru−Pr bonding with very little Ru−Ru bonding.