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- ALUMINUM CLUSTERS; BUILDING-BLOCKS; SHELL STRUCTURE; SUPERATOMS; REACTIVITY; GEOMETRY; MODEL; ATOMS (1)
- BORON-NITRIDE; MOLECULES (1)
- BUILDING-BLOCKS; CLUSTERS; DISTORTIONS; WIRES (1)
- CHEMICAL FUNCTIONALIZATION; STABILITY; DEFECTS (1)
- DENSITY-FUNCTIONAL CALCULATIONS; ELECTRON-AFFINITIES; AB-INITIO; ANIONS X; PHOTOELECTRON-SPECTROSCOPY; PLATINUM FLUORIDES; BR; CL; STABILITY; COMPLEXES (1)
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- GENERALIZED GRADIENT APPROXIMATION; TRANSITION-METAL CLUSTERS; DENSITY-FUNCTIONAL THEORY; IRON CLUSTERS; IONIZATION-POTENTIALS; NICKEL CLUSTERS; ENERGIES; MOLECULES; EXCHANGE; MOMENTS (1)
- IRREVERSIBLE ELECTRICAL BREAKDOWN; BETA-CYCLODEXTRIN; PROTEIN NANOPORE; MEMBRANE CHANNEL; PORE; MOLECULE; DYNAMICS; GENOME; IDENTIFICATION; DEVICE (1)
- METAL-CLUSTERS; PALLADIUM CLUSTERS; COPPER CLUSTERS; JELLIUM MODEL; PD; OXYGEN; OXIDATION; MAGNETISM; ISOMERS; OPTIMIZATION (1)
- RECOMBINATION; LUMINESCENCE (1)
- ROOM-TEMPERATURE (1)
- SCANNING-TUNNELING-MICROSCOPY; INITIO MOLECULAR-DYNAMICS; SATURATED SI(100) SURFACE; TOTAL-ENERGY CALCULATIONS; WAVE BASIS-SET; AB-INITIO; ELASTIC PROPERTIES; SPECTROSCOPY; ADSORPTION; H/SI(001) (1)
- SIMPLE METAL-CLUSTERS; ALUMINUM CLUSTERS; BUILDING-BLOCKS; SHELL STRUCTURE; JELLIUM MODEL; REACTIVITY; TRANSITION; STABILITY; APPROXIMATION; OPTIMIZATION (1)
- SURFACE; EPITAXY (1)
- TEMPERATURE-DEPENDENCE; ACCEPTOR; LUMINESCENCE; EMISSION; DONOR (1)
Articles 1 - 14 of 14
Full-Text Articles in Physics
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 …
Two-Step Thermal Quenching Of Photoluminescence In Zn-Doped Gan, Michael A. Reshchikov
Two-Step Thermal Quenching Of Photoluminescence In Zn-Doped Gan, Michael A. Reshchikov
Physics Publications
We observed tunable two-step thermal quenching of photoluminescence in high-resistivity Zn-doped GaN. The characteristic temperatures of the first and second steps increase with increasing excitation intensity. The effect is explained within a phenomenological model involving shallow donors, nonradiative deep donors, and two types of acceptors.
Tuning Magnetic Properties Of Graphene Nanoribbons With Topological Line Defects: From Antiferromagnetic To Ferromagnetic, Min Kan, Jian Zhou, Qiang Sun, Qiang Wang, Yoshiyuki Kawazoe, Puru Jena
Tuning Magnetic Properties Of Graphene Nanoribbons With Topological Line Defects: From Antiferromagnetic To Ferromagnetic, Min Kan, Jian Zhou, Qiang Sun, Qiang Wang, Yoshiyuki Kawazoe, Puru Jena
Physics Publications
Zigzag-edged graphene nanoribbons are antiferromagnetic in cross-edge coupling and unsuitable for spintronics applications. Two new strategies of tuning antiferromagnetism (AFM) to ferromagnetism (FM) in graphene nanoribbons are introduced through topological line defects composed of pentagonal and octagonal rings, and their ability to induce magnetic transition is probed by using density functional theory. The resulting exchange energy is found to be large enough for ferromagnetism to be observed at room temperature. Both strategies are experimentally feasible, and the results suggest that defect engineering may provide a novel path to manipulate the magnetic properties of graphene nanoribbons.
Determination Of The Absolute Internal Quantum Efficiency Of Photoluminescence In Gan Co-Doped With Si And Zn, M. A. Reshchikov, M. Foussekis, J. D. Mcnamara, A. Behrends, A. Bakin, A. Waag
Determination Of The Absolute Internal Quantum Efficiency Of Photoluminescence In Gan Co-Doped With Si And Zn, M. A. Reshchikov, M. Foussekis, J. D. Mcnamara, A. Behrends, A. Bakin, A. Waag
Physics Publications
The optical properties of high-quality GaN co-doped with silicon and zinc are investigated by using temperature-dependent continuous-wave and time-resolved photoluminescence measurements. The blue luminescence band is related to the ZnGa acceptor in GaN:Si,Zn, which exhibits an exceptionally high absolute internal quantum efficiency (IQE). An IQE above 90% was calculated for several samples having different concentrations of Zn. Accurate and reliable values of the IQE were obtained by using several approaches based on rate equations. The concentrations of the ZnGa acceptors and free electrons were also estimated from the photoluminescence measurements.
Electrical Transition Of (3,3) Carbon Nanotube On Patterned Hydrogen Terminated Si(001)-2 X 1 Driven By Electric Field, Bikash C. Gupta, Shyamal Konar, Puru Jena
Electrical Transition Of (3,3) Carbon Nanotube On Patterned Hydrogen Terminated Si(001)-2 X 1 Driven By Electric Field, Bikash C. Gupta, Shyamal Konar, Puru Jena
Physics Publications
Structure, energetics, and electrical properties of (3,3) carbon nanotube(CNT) supported on patterned hydrogen terminated Si(001): 2 × 1 surface are studied using density functional theory. Our investigation reveals that an otherwise metallic (3,3) CNT when supported becomes semiconducting with a band gap of ≈0.5 eV due to its strong interaction with the surface. During adsorption, Si-C bonds form at the interface and charges transfer from Si surface to CNT. The Si-C bonds at the interface are partially covalent and partially ionic in nature. Under the application of an external electric field, the bandgap of the supported CNT reduces to zero, …
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 …
Ferromagnetism In Li Doped Zno Nanoparticles: The Role Of Interstitial Li, Saif Ullah Awan, S. K. Hasanain, Massimo F. Bertino, G. Hassnain Jaffari
Ferromagnetism In Li Doped Zno Nanoparticles: The Role Of Interstitial Li, Saif Ullah Awan, S. K. Hasanain, Massimo F. Bertino, G. Hassnain Jaffari
Physics Publications
ZnO nanoparticles doped with Li (Zn1−yLiyO, y ≤ 0.1) have been investigated with emphasis on the correlation between their magnetic, electronic, and structural properties. In particular, defects such as interstitial Li and Zn atoms, substitutional Li atoms, and oxygen vacancies have been identified by X-ray photoelectron spectroscopy(XPS) and their respective roles in stabilization of the magnetic moment are discussed. X-ray diffraction(XRD) and XPS give clear evidence of Li presence at both substitutional and interstitial sites. XPS studies further show that the amount of substitutional Li defects (Lizn) and interstitial Li defects (Lii) …
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 …
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 …
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, …
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 …
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 …