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Articles 61 - 90 of 230
Full-Text Articles in Physics
Structural Changes Of Pd-13 Upon Charging And Oxidation/Reduction, J. Ulises Reveles, A. M. Köster, P. Calaminici, S. N. Khanna
Structural Changes Of Pd-13 Upon Charging And Oxidation/Reduction, J. Ulises Reveles, A. M. Köster, P. Calaminici, S. N. Khanna
Physics Publications
First-principle generalized gradient corrected density functional calculations have been performed to study the stability of cationic and anionic Pd13 +/−, and neutral Pd13O2 clusters. It is found that while cationic Pd13 + favors a C s geometry similar to the neutral Pd13, both anionic Pd13 − and neutral Pd13O2 favor a compact ∼I h structure. A detailed analysis of the electronic structure shows that the stabilization of the delocalized 1P and 2P cluster orbitals, and the hybridization of the 1D orbitals with the oxygen atomic p orbitals …
Evolution Of Superhalogen Properties In Ptcln Clusters, Jorly Joseph, Kalpataru Pradhan, Purusottam Jena, Haopeng Wang, Xinxing Zhang, Yeon Jae Ko, Kit H. Bowen Jr.
Evolution Of Superhalogen Properties In Ptcln Clusters, Jorly Joseph, Kalpataru Pradhan, Purusottam Jena, Haopeng Wang, Xinxing Zhang, Yeon Jae Ko, Kit H. Bowen Jr.
Physics Publications
We have systematically calculated the ground state geometries, relative stability, electronic structure, and spectroscopic properties of PtCl n (n = 1–7) clusters. The bonding in these clusters is dominated by covalent interaction. In neutral clusters, chlorine atoms are chemically bound to Pt up to n = 5. However, in neutral PtCl6 and PtCl7 clusters, two of the chlorine atoms bind molecularly while the remaining bind as individual atoms. In the negative ions, this happens only in the case of PtCl7 cluster. The geometries of both neutral and anionic clusters can be considered as fragments of an …
Origin Of The Anomalous Magnetic Behavior Of The Fe13+ Cluster, M. Wu, A. K. Kandalam, G. L. Gutsev, Puru Jena
Origin Of The Anomalous Magnetic Behavior Of The Fe13+ Cluster, M. Wu, A. K. Kandalam, G. L. Gutsev, Puru Jena
Physics Publications
By using density functional theory, we show that the exceptionally low value of the total magnetic moment of Fe13+ observed in an experiment [Phys. Rev. Lett. 108, 057201 (2012)] is not due to antiferromagnetic coupling between the spins of the core and surface atoms as hypothesized but is due to the symmetry-driven quenching of the local spin moments of all atoms with the largest quenching observed for the central atom. Our study of Fe12+, Fe13+, Fe14+, and their neutral parents reveals that the total magnetic moment of Fe13+ decreases by 9μB with respect to that of neutral Fe13, …
Metallic And Molecular Orbital Concepts In Xmg8 Clusters, X = Be-F, Victor M. Medel, Arthur C. Reber, J. Ulises Reveles, Shiv N. Khanna
Metallic And Molecular Orbital Concepts In Xmg8 Clusters, X = Be-F, Victor M. Medel, Arthur C. Reber, J. Ulises Reveles, Shiv N. Khanna
Physics Publications
The electronic structure and stability of the XMg8 clusters (X = Be, B, C, N, O, and F) are studied using first principles theoretical calculations to understand the variation in bonding in heteroatomic clusters which mix simple divalent metals with main group dopants. We examine these progressions with two competing models, the first is a distorted nearly free electron gas model and the second is a molecular orbital picture examining the orbital overlap between the dopant and the cluster. OMg8 is found to be the most energetically stable cluster due to strong bonding of O with the Mg …
Temperature-Dependent Kelvin Probe Measurements Of Band Bending In P-Type Gan, M. Foussekis, J. D. Mcnamara, A. A. Baski, Michael A. Reshchikov
Temperature-Dependent Kelvin Probe Measurements Of Band Bending In P-Type Gan, M. Foussekis, J. D. Mcnamara, A. A. Baski, Michael A. Reshchikov
Physics Publications
The band bending in a Mg-doped, p-type GaN film grown by hydride vapor phase epitaxy was studied at various temperatures. At 295 K, the band bending in dark was calculated to be approximately −1.5 eV. However, when the sample was heated to 600 K for 1 h in dark before performing a measurement at 295 K, the calculated value of band bending in dark became about −2.0 eV. These results are explained by the fact that increasing the sample temperature exponentially increases the rate at which the band bending restores and allows for a more accurate value of band …
Adsorption Of Oxygen-Containing Functional Groups On Free And Supported Graphene Using Point Contact, Qian Wang, D. X. Ye, Y. Kawazoe, Puru Jena
Adsorption Of Oxygen-Containing Functional Groups On Free And Supported Graphene Using Point Contact, Qian Wang, D. X. Ye, Y. Kawazoe, Puru Jena
Physics Publications
First-principles electronic structure calculations based on spin-polarized density functional theory were carried out to study the adsorption of oxygen-containing functional groups -OH, -CHO, and -COOH on a two-dimensional (2D) infinite graphene sheet without edge states and defects. We find that the energy gain of adsorption can be significantly improved when the graphene sheet is supported via a point contact, a prototype for graphene sheet supported by catalysts, nanoparticles or nanopillars, or a surface with steps, edges, adatoms, or defects. This was modeled by placing a single atom of Fe, Co, and Ni under the graphene surface. Thus supported graphene not …
Lymph Node Characterization In Vivo Using Endoscopic Ultrasound Spectrum Analysis With Electronic Array Echo Endoscopes, Ronald Kumon, Aparna Repaka, Matthew Atkinson, Ashley L. Faulx, Richard C.K. Wong, Gerard A. Isenberg, Yi-Sing Hsiao, Madhu Sudhan Reddy Gudur, Cheri X. Deng, Amitabh Chak
Lymph Node Characterization In Vivo Using Endoscopic Ultrasound Spectrum Analysis With Electronic Array Echo Endoscopes, Ronald Kumon, Aparna Repaka, Matthew Atkinson, Ashley L. Faulx, Richard C.K. Wong, Gerard A. Isenberg, Yi-Sing Hsiao, Madhu Sudhan Reddy Gudur, Cheri X. Deng, Amitabh Chak
Physics Publications
Our purpose was to demonstrate the use of radiofrequency spectral analysis to distinguish between benign and malignant lymph nodes with data obtained using electronic array echo endoscopes, as we have done previously using mechanical echo endoscopes. In a prospective study, images were obtained from eight patients with benign-appearing lymph nodes and 11 with malignant lymph nodes, as verified by fine-needle aspiration. Midband fit, slope, intercept, correlation coefficient, and root-mean-square (RMS) deviation from a linear regression of the calibrated power spectra were determined and compared between the groups. Significant differences were observable for mean midband fit, intercept, and RMS deviation (t …
Magnetism Of Electrons In Atoms And Superatoms, Victor Medel, J. Ulises Reveles, Shiv N. Khanna
Magnetism Of Electrons In Atoms And Superatoms, Victor Medel, J. Ulises Reveles, Shiv N. Khanna
Physics Publications
The quantum states of electrons in small symmetric metallic clusters are grouped into shells similar to the electronic shells in free atoms, leading to the conceptual basis for defining superatoms. The filling of the electronic shells in clusters, however, do not follow Hund's rule and usually result in non-magnetic species. It is shown that by embedding a transition metal in group II atoms, one can stabilize superatoms with unpaired electronic supershells. We demonstrate this intriguing effect through electronic structure studies of MnSrn (n = 6-12) clusters within first principles generalized gradient calculations. The studies identify an unusually stable magnetic …
Quantum Spin Transport Through Magnetic Superatom Dimer (Cs8v-Cs8v), Lin Zhu, Shiv N. Khanna
Quantum Spin Transport Through Magnetic Superatom Dimer (Cs8v-Cs8v), Lin Zhu, Shiv N. Khanna
Physics Publications
Theoretical studies of the spin transport through a magnetic superatom dimer (Cs8V)-(Cs8V) have been carried out within a density functional theory combined with nonequilibrium Green's-function formalism. It is shown that the electronic transport is sensitive to the binding site as well as the contact distance between the dimer and the electrode, and that the conductance at zero bias exhibits an oscillatory behavior as a function of the contact distance. The conductance in ferromagnetic state shows an unusually high spin polarization that exceeds 80% at large separations. The I–V curve shows negative differential resistance for …
The Effects Of Diffusion On An Exonuclease/Nanopore-Based Dna Sequencing Engine, Joseph E. Reiner, Arvind Balijepalli, Joseph W. F. Robertson, Bryon S. Drown, Daniel L. Burden, John J. Kasianowicz
The Effects Of Diffusion On An Exonuclease/Nanopore-Based Dna Sequencing Engine, Joseph E. Reiner, Arvind Balijepalli, Joseph W. F. Robertson, Bryon S. Drown, Daniel L. Burden, John J. Kasianowicz
Physics Publications
Over 15 years ago, the ability to electrically detect and characterize individual polynucleotides as they are driven through a single protein ion channel was suggested as a potential method for rapidly sequencing DNA, base-by-base, in a ticker tape-like fashion. More recently, a variation of this method was proposed in which a nanopore would instead detect single nucleotides cleaved sequentially by an exonuclease enzyme in close proximity to one pore entrance. We analyze the exonuclease/nanopore-based DNA sequencing engine using analytical theory and computer simulations that describe nucleotide transport. The available data and analytical results suggest that the proposed method will be …
Structures And Photoelectron Spectroscopy Of Cu-N(Bo2)(M) - (N, M=1, 2) Clusters: Observation Of Hyperhalogen Behavior, Yuan Feng, Hong-Guang Xu, Weijun Zheng, Hongmin Zhao, Anil K. Kandalam, Puru Jena
Structures And Photoelectron Spectroscopy Of Cu-N(Bo2)(M) - (N, M=1, 2) Clusters: Observation Of Hyperhalogen Behavior, Yuan Feng, Hong-Guang Xu, Weijun Zheng, Hongmin Zhao, Anil K. Kandalam, Puru Jena
Physics Publications
The electronic structures of CuBO2 −, Cu(BO2)2 −, Cu2(BO2)−, and Cu2(BO2)2 − clusters were investigated using photoelectron spectroscopy. The measured vertical and adiabatic detachment energies of these clusters revealed unusual properties of Cu(BO2)2 cluster. With an electron affinity of 5.07 eV which is larger than that of its BO2 superhalogen (4.46 eV) building-block, Cu(BO2)2 can be classified as a hyperhalogen. Density functional theory based calculations were carried out to identify the ground stategeometries and study the …
Photoelectron Spectroscopic Study Of Iron-Pyrene Cluster Anions, Xiang Li, Kit H. Bowen Jr., Puru Jena, Anil K. Kandalam
Photoelectron Spectroscopic Study Of Iron-Pyrene Cluster Anions, Xiang Li, Kit H. Bowen Jr., Puru Jena, Anil K. Kandalam
Physics Publications
Iron-pyrene cluster anions, [Fem(pyrene)n]− (m = 1–2, n = 1–2) were studied in the gas phase by photoelectron spectroscopy, resulting in the determination of their electron affinity and vertical detachment energy values. Density functional theory calculations were also conducted, providing the structures and spin multiplicities of the neutral clusters and their anions as well as their respective electron affinity and vertical detachment energy values. The calculated magnetic moments of neutral Fe1(pyrene)1 and Fe2(pyrene)1 clusters suggest that a single pyrene molecule could be a suitable template on which to deposit …
Superhalogen Properties Of Cumcln Clusters: Theory And Experiment, Y. J. Ko, H. Wang, K. Pradhan, P. Koirala, A. K. Kandalam, K. H. Bowen, P. Jena
Superhalogen Properties Of Cumcln Clusters: Theory And Experiment, Y. J. Ko, H. Wang, K. Pradhan, P. Koirala, A. K. Kandalam, K. H. Bowen, P. Jena
Physics Publications
Using a combination of density functional theory and anion photoelectron spectroscopy experiment, we have studied the structure and electronic properties of CuCl n − (n = 1–5) and Cu2Cl n − (n = 2–5) clusters. Prominent peaks in the mass spectrum of these clusters occurring at n = 2, 3, and 4 in CuCl n − and at n = 3, 4, and 5 in Cu2Cl n − are shown to be associated with the large electron affinities of their neutral clusters that far exceed the value of Cl. While CuCl n(n …
Potential Candidates For Hyperhalogens: A Comparative Study Of Bo2, Alo2, And Vo3 Species, Kalpataru Pradhan, Purusottam Jena
Potential Candidates For Hyperhalogens: A Comparative Study Of Bo2, Alo2, And Vo3 Species, Kalpataru Pradhan, Purusottam Jena
Physics Publications
Recent work has shown that BO2 which is a superhalogen with an electron affinity of 4.46 eV, can be used as building block of a new class of molecules/clusters whose electron affinities can exceed that of BO2. This class of molecules was named hyperhalogens and the concept was illustrated by focusing on Au(BO2)2. Here we explore other superhalogens besides BO2 to see if they too can be used to form hyperhalogens. We have chosen to focus on AlO2 which is valence isoelectronic with BO2 as well as VO3 which …
Double Exchange Mediated Ferromagnetic Coupling Between Co Atoms In Dicobalt Complex, Kalpataru Pradhan, Purusottam Jena
Double Exchange Mediated Ferromagnetic Coupling Between Co Atoms In Dicobalt Complex, Kalpataru Pradhan, Purusottam Jena
Physics Publications
Realization of the full technological potential of molecular magnets requires a fundamental understanding of the origin of magnetic coupling in molecular systems. Using gradient corrected density functional theory and Cl as a ligand we show that the magnetic coupling between Co sites in a di-cobalt complex can be manipulated. While the ferromagnetic states of Co2Cl6 and Co2Cl7 are 0.07 eV and 0.20 eV lower in energy than their respective antiferromagnetic states, they are nearly degenerate in Co2Cl8. The origin of ferromagnetic coupling is explained using the double exchange model caused …
A Systematic Study Of Neutral And Charged 3d-Metal Trioxides And Tetraoxides, Kalpataru Pradhan, Gennady L. Gutsev, Charles A. Weatherford, Puru Jena
A Systematic Study Of Neutral And Charged 3d-Metal Trioxides And Tetraoxides, Kalpataru Pradhan, Gennady L. Gutsev, Charles A. Weatherford, Puru Jena
Physics Publications
Using density functional theory with generalized gradient approximation, we have performed a systematic study of the structure and properties of neutral and charged trioxides (MO3) and tetraoxides (MO4) of the 3d-metal atoms. The results of our calculations revealed a number of interesting features when moving along the 3d-metal series. (1) Geometrical configurations of the lowest total energy states of neutral and charged trioxides and tetraoxides are composed of oxo and/or peroxo groups, except for CuO3 − and ZnO3 − which possess a superoxo group, CuO4 + and ZnO4 + which possess two …
Extremely High Absolute Internal Quantum Efficiency Of Photoluminescence In Co-Doped Gan:Zn,Si, Michael A. Reshchikov, A. G. Willyard, A. Behrends, A. Bakin, A. Waag
Extremely High Absolute Internal Quantum Efficiency Of Photoluminescence In Co-Doped Gan:Zn,Si, Michael A. Reshchikov, A. G. Willyard, A. Behrends, A. Bakin, A. Waag
Physics Publications
We report on the fabrication of GaN co-doped with silicon and zinc by metalorganic vapor phase epitaxy and a detailed study of photoluminescence in this material. We observe an exceptionally high absolute internal quantum efficiency of blue photoluminescence in GaN:Zn,Si. The value of0.93±0.04 has been obtained from several approaches based on rate equations.
Sc-Phthalocyanine Sheet: Promising Material For Hydrogen Storage, Kun Lü, Jian Zhou, Le Zhou, Qian Wang, Qiang Sun, Puru Jena
Sc-Phthalocyanine Sheet: Promising Material For Hydrogen Storage, Kun Lü, Jian Zhou, Le Zhou, Qian Wang, Qiang Sun, Puru Jena
Physics Publications
It has been a long-standing dream to have high surface area materials with isolated and exposed transition-metal ions for hydrogen storage. The flexible synthesis procedure proposed recently by M. Abel, et al. [J. Am. Chem. Soc. 133, 1203 (2011)] and A. Sperl et al. [J. Am. Chem. Soc. 133, 11007 (2011)] provides a different pathway to achieve this goal. Using first-principles theory and grand canonical Monte Carlo simulation, we carry out a systematic study of 3d transition metals (Sc to Zn)-phthalocyanine porous sheets and find that Sc-phthalocyanine can store 4.6 wt. % hydrogen at 298 K and 100 …
Stability And Electronic Structure Of Bilayer Graphone, J. Zhou, Q. Wang, Q. Sun, Puru Jena
Stability And Electronic Structure Of Bilayer Graphone, J. Zhou, Q. Wang, Q. Sun, Puru Jena
Physics Publications
Stability, reconstruction, and electronic structure of a bilayer graphone have been studied, where the most stable configuration undergoes a (1×2)surface reconstruction. An energy barrier of 1.83 eV separates this structure from the nonbonded state. The stability of the reconstructed bilayer at room temperature is confirmed by both frequency calculation and molecular dynamics simulation. Unlike the graphone sheet, the bilayer graphone is nonmagnetic but remains metallic due to the existence of delocalized π orbital on the zigzag sp2carbon chains, which are stable against Peierls instability. The metallicity is also stable under gate external electric field.
Tuning The Band Gap And Magnetic Properties Of Bn Sheets Impregnated With Graphene Flakes, M. Kan, J. Zhou, Q. Wang, Q. Sun, Puru Jena
Tuning The Band Gap And Magnetic Properties Of Bn Sheets Impregnated With Graphene Flakes, M. Kan, J. Zhou, Q. Wang, Q. Sun, Puru Jena
Physics Publications
The BN sheet is a nonmagnetic wide-band-gap semiconductor. Using density functional theory, we show that these properties can be fundamentally altered by embedding graphene flakes. Not only do graphene flakes preserve the two-dimensional (2D) planar structure of the BN sheet, but by controlling their shape and size, unexpected electronic and magnetic properties also emerge. The electronic band structure can be tuned from a direct gap to an indirect gap, the energy gap can be further modulated by changing the bonding patterns, and both hole injecting or electron injecting can be achieved by tailoring the triangular embedding pattern. Furthermore, the Lieb …
Tunable And Abrupt Thermal Quenching Of Photoluminescence In High-Resistivity Zn-Doped Gan, Michael A. Reshchikov, Alexander A. Kvasov, Marilyn F. Bishop, Tom Mcmullen, Alexander Usikov, Vitali Soukhoveev, Vladimir A. Dmitriev
Tunable And Abrupt Thermal Quenching Of Photoluminescence In High-Resistivity Zn-Doped Gan, Michael A. Reshchikov, Alexander A. Kvasov, Marilyn F. Bishop, Tom Mcmullen, Alexander Usikov, Vitali Soukhoveev, Vladimir A. Dmitriev
Physics Publications
Tunable and abrupt thermal quenching of photoluminescence by increasing temperature has been observed for the blue band in high-resistivity Zn-doped GaN. The photoluminescence intensity dropped by several orders of magnitude within a few Kelvins, and the temperature at which that drop occurred could be tuned by changing the incident light intensity. Modeling the system with rate equations for competing electron-hole recombination flows through three defect species, one of which is a nonradiative deep donor, gives results consistent with these observations.
Closed-Shell To Split-Shell Stability Of Isovalent Clusters, Victor M. Medel, J. Ulises Reveles, A. C. Reber, Shiv N. Khanna, A. W. Castleman Jr.
Closed-Shell To Split-Shell Stability Of Isovalent Clusters, Victor M. Medel, J. Ulises Reveles, A. C. Reber, Shiv N. Khanna, A. W. Castleman Jr.
Physics Publications
Metallic clusters containing 2, 8, 18, and 20 electrons are now known to exhibit enhanced stability that can be reconciled because of filled 1S, 1P, 1D, and 2S electronic shells within a simplified confined nearly free electron (NFE) gas. Here, we present first-principles studies on three isovalent clusters, i.e., ZnMg8, CuMg8−, and AuMg8−, each with 18 valence electrons. All the clusters exhibit local energetic stability but with differing origins. Although the stability of ZnMg8 can be reconciled within the conventional confined NFE picture with filled 1S2, 1P6, and 1D10shells, CuMg8− and AuMg8− are shown to be stable despite the unfilled …
Impurity Complexes And Conductivity Of Ga-Doped Zno, D. O. Demchenko, B. Earles, H. Y. Liu, Vitaliy Avrutin, N. Izyumskaya, Ü. Özgür, Hadis Morkoç
Impurity Complexes And Conductivity Of Ga-Doped Zno, D. O. Demchenko, B. Earles, H. Y. Liu, Vitaliy Avrutin, N. Izyumskaya, Ü. Özgür, Hadis Morkoç
Physics Publications
Using hybrid functional theory together with experimental measurements, we investigate the influence of gallium impurities and their complexes on electrical properties of ZnO. In contrast to the behavior of isolated Ga impurities and native defects, the calculated formation energies of Ga complexes are consistent with our experimental data. We show that for high levels of Ga doping the acceptor behavior of GaZn-VZn and GaZn-Oi complexes explains the conductivity measurements and compensation levels in ZnO. The computed binding energies of these complexes are also consistent with the binding energies obtained from the measurements of the temperature dependence of carrier mobility. Our …
Electronic Structures And Bonding Of Graphyne Sheet And Its Bn Analog, Jian Zhou, Kun Lv, Qian Wang, X. S. Chen, Qiang Sun, Puru Jena
Electronic Structures And Bonding Of Graphyne Sheet And Its Bn Analog, Jian Zhou, Kun Lv, Qian Wang, X. S. Chen, Qiang Sun, Puru Jena
Physics Publications
Using density functional theory and generalized gradient approximation for exchange and correlation, we present theoretical analysis of the electronic structure of recently synthesized graphyne and its boron nitride analog (labeled as BN-yne). The former is composed of hexagonal carbon rings joined by C-chains, while the latter is composed of hexagonal BN rings joined by C-chains. We have explored the nature of bonding and energy band structure of these unique systems characterized by sp and sp 2 bonding. Both graphyne and BN-yne are found to be direct bandgap semiconductors. The bandgap can be modulated by changing the size of hexagonal ring …
Gas Phase Analogs Of Stable Sodium-Tin Zintl Ions: Anion Photoelectron Spectroscopy And Electronic Structure, W.-J. Zheng, O. C. Thomas, J. M. Nilles, K. H. Bowen Jr., A. C. Reber, S. N. Khanna
Gas Phase Analogs Of Stable Sodium-Tin Zintl Ions: Anion Photoelectron Spectroscopy And Electronic Structure, W.-J. Zheng, O. C. Thomas, J. M. Nilles, K. H. Bowen Jr., A. C. Reber, S. N. Khanna
Physics Publications
Mass spectrometry and photoelectron spectroscopy together with first principles theoretical calculations have been used to study the electronic and geometric properties of the following sodium-tin, cluster anion/neutral cluster combinations, (NanSn4)−/(NanSn4), n = 0–4 and (NaSnm)−/(NaSnm), m = 4–7. These synergistic studies found that specific Zintl anions, which are known to occur in condensed Zintl phases, also exist as stable moieties within free clusters. In particular, the cluster anion, (Na3Sn4)− is very stable and is characterized as (Na+) …
Interactions Of A Mn Atom With Halogen Atoms And Stability Of Its Half-Filled 3d-Shell, Kalpataru Pradhan, Gennady L. Gutsev, Charles A. Weatherford, Purusottam Jena
Interactions Of A Mn Atom With Halogen Atoms And Stability Of Its Half-Filled 3d-Shell, Kalpataru Pradhan, Gennady L. Gutsev, Charles A. Weatherford, Purusottam Jena
Physics Publications
Using density functional theory with hybrid exchange-correlation potential, we have calculated the geometrical and electronic structure, relative stability, and electron affinities of MnX ncompounds (n = 1–6) formed by a Mn atom and halogen atoms X = F, Cl, and Br. Our objective is to examine the extent to which the Mn–X interactions are similar and to elucidate if/how the half-filled 3d-shell of a Mn atom participates in chemical bonding as the number of halogen atoms increases. While the highest oxidation number of the Mn atom in fluorides is considered to be +4, the maximum …
Cooperative Effects In The Oxidation Of Co By Palladium Oxide Cations, Arthur C. Reber, Shiv N. Khanna, Eric C. Tyo, Christopher L. Harmon, A. W. Castleman Jr
Cooperative Effects In The Oxidation Of Co By Palladium Oxide Cations, Arthur C. Reber, Shiv N. Khanna, Eric C. Tyo, Christopher L. Harmon, A. W. Castleman Jr
Physics Publications
Cooperative reactivity plays an important role in the oxidation of CO to CO2 by palladium oxide cations and offers insight into factors which influence catalysis. Comprehensive studies including guided-ion-beam mass spectrometry and theoretical investigations reveal the reaction products and profiles of PdO2 + and PdO3 + with CO through oxygen radical centers and dioxygen complexes bound to the Pd atom. O radical centers are more reactive than the dioxygen complexes, and experimental evidence of both direct and cooperative CO oxidation with the adsorption of two CO molecules are observed. The binding of multiple electron withdrawing CO molecules …
Oxidation Of Pdn (N=1–7,10) Clusters Supported On Alumina/Nial(110), R. Robles, Shiv N. Khanna
Oxidation Of Pdn (N=1–7,10) Clusters Supported On Alumina/Nial(110), R. Robles, Shiv N. Khanna
Physics Publications
First-principles theoretical investigations on the oxidation of Pdn (n=1–7, 10) clusters deposited on alumina/NiAl(110) have been carried out using a gradient-corrected density-functional approach. Our studies indicate that the free Pdn clusters are compact and maintain their compact structures when deposited on the surface, undergoing only small relaxations of the Pd-Pd distance. The clusters bind to the surface via a pair of Pd atoms and with a binding energy of around 1.0 eV. Studies of oxidation through an O2molecule show that O2 occupies sites closer to the surface for Pd1, Pd4, Pd5, and Pd6 while, in other cases, the binding is …
Electronic And Magnetic Properties Of A Bn Sheet Decorated With Hydrogen And Fluorine, Jian Zhou, Qian Wang, Qiang Sun, Puru Jena
Electronic And Magnetic Properties Of A Bn Sheet Decorated With Hydrogen And Fluorine, Jian Zhou, Qian Wang, Qiang Sun, Puru Jena
Physics Publications
First-principles calculations based on density-functional theory reveal some unusual properties of BN sheet functionalized with hydrogen and fluorine. These properties differ from those of similarly functionalized graphene even though both share the same honeycomb structure. (1) Unlike graphene which undergoes a metal to insulator transition when fully hydrogenated, the band gap of the BN sheet significantly narrows when fully saturated with hydrogen. Furthermore, the band gap of the BN sheet can be tuned from 4.7 to 0.6 eV and the system can be a direct or an indirect semiconductor or even a half-metal depending on surface coverage. (2) Unlike graphene, …
Crystal Field Effects On The Reactivity Of Aluminum-Copper Cluster Anions, Patrick J. Roach, W. Hunter Woodward, Arthur C. Reber, Shiv N. Khanna, A. W. Castleman Jr.
Crystal Field Effects On The Reactivity Of Aluminum-Copper Cluster Anions, Patrick J. Roach, W. Hunter Woodward, Arthur C. Reber, Shiv N. Khanna, A. W. Castleman Jr.
Physics Publications
The limits and useful modifications of the jellium model are of great interest in understanding the properties of metallic clusters, especially involving bimetallic systems. We have measured the relative reactivity of CuAl−n clusters (n=11–34) with O2. An odd-even alternation is observed that is in accordance with spin-dependant etching, and CuAl−22is observed as a “magic peak.” The etching resistance of CuAl−22 is explained by an unusually large splitting of the 2D10 subshell that occurs because of a geometric distortion of the cluster that may also be understood as a crystal field splitting of the superatomic orbitals.