Open Access. Powered by Scholars. Published by Universities.®
- Discipline
- Keyword
-
- ELECTRONIC-STRUCTURE (11)
- APPROXIMATION (10)
- AB-INITIO (9)
- CLUSTERS (8)
- PHOTOELECTRON-SPECTROSCOPY (8)
-
- ATOMS (7)
- MOLECULES (7)
- ANIONS (6)
- IONIZATION ENERGIES (6)
- SPECTROSCOPY (6)
- STABILITY (6)
- AUGMENTED-WAVE METHOD (5)
- BINDING-ENERGIES (5)
- DENSITY (5)
- ENERGY (5)
- GAS-PHASE (5)
- IONS (5)
- DECKER SANDWICH (4)
- DENSITY-FUNCTIONAL THEORY (4)
- METAL-BENZENE COMPLEXES (4)
- SANDWICH CLUSTERS (4)
- Acoustics (3)
- BASIS-SETS (3)
- COMPLEXES (3)
- COUPLED-CLUSTER (3)
- ELECTRON-AFFINITIES (3)
- GOLD (3)
- NEGATIVE-IONS (3)
- SHELL STRUCTURE (3)
- TRANSITION-METAL DIATOMICS (3)
Articles 151 - 180 of 230
Full-Text Articles in Physics
Structure And Stability Of Co-N(Pyridine)(M)(-) Clusters: Absence Of Metal Inserted Structures, B. Douglas Edmonds, A. K. Kandalam, S. N. Khanna, X. Li, A. Grubisic, I. Khanna, K. H. Bowen
Structure And Stability Of Co-N(Pyridine)(M)(-) Clusters: Absence Of Metal Inserted Structures, B. Douglas Edmonds, A. K. Kandalam, S. N. Khanna, X. Li, A. Grubisic, I. Khanna, K. H. Bowen
Physics Publications
A synergistic approach combining the experimental photoelectron spectroscopy and theoretical electronic structure studies is used to probe the geometrical structure and the spin magnetic moment of Con(pyridine)−m clusters. It is predicted that the ground state of Co(pyridine)− is a structure where the Co atom is inserted in a CH bond. However, the insertion is marked by a barrier of 0.33eV that is not overcome under the existing experimental conditions resulting in the formation of a structure where Co occupies a site above the pyridine plane. For Co2(pyridine)−, a ground-state structure is predicted in which the Co2 diametric moiety is inserted …
Hydrogen Storage And The 18-Electron Rule, Boggavarapu Kiran, Anil K. Kandalam, Puru Jena
Hydrogen Storage And The 18-Electron Rule, Boggavarapu Kiran, Anil K. Kandalam, Puru Jena
Physics Publications
We show that the 18-electron rule can be used to design new organometallic systems that can store hydrogen with large gravimetric density. In particular, Ti containing organic molecules such as C4H4, C5H5, and C8H8 can store up to 9wt% hydrogen, which meets the Department of Energy target for the year 2015. More importantly, hydrogen in these materials is stored in molecular form with an average binding energy of about 0.55eV∕H2 molecule, which is ideal for fast kinetics. Using molecular orbitals we have analyzed the maximum number of H2 molecules that can be adsorbed as well as the nature of their …
Gold As Hydrogen: Structural And Electronic Properties And Chemical Bonding In Si3au3+/0/- And Comparisons To Si3h3+/0/-, Boggavarapu Kiran, Xi Li, Hua-Jin Zhai, Lai-Sheng Wang
Gold As Hydrogen: Structural And Electronic Properties And Chemical Bonding In Si3au3+/0/- And Comparisons To Si3h3+/0/-, Boggavarapu Kiran, Xi Li, Hua-Jin Zhai, Lai-Sheng Wang
Physics Publications
A single Au atom has been shown to behave like H in its bonding to Si in several mono- and disilicon gold clusters. In the current work, we investigate the Au∕H analogy in trisilicon gold clusters, Si3Au+∕0∕−3. Photoelectron spectroscopy and density functional calculations are combined to examine the geometric and electronic structure of Si3Au−3. We find that there are three isomers competing for the ground state of Si3Au−3 as is the case for Si3H−3. Extensive structural searches show that the potential energy surfaces of the trisilicon gold clusters (Si3Au−3, Si3Au3, and Si3Au+3) are similar to those of the corresponding silicon …
Subpicosecond Time-Resolved Raman Studies Of Field-Induced Transient Transport In An Inxga1−Xas-Based P-I-N Semiconductor Nanostructure, K. T. Tsen, Juliann G. Kiang, D. K. Ferry, Hadis Morkoç
Subpicosecond Time-Resolved Raman Studies Of Field-Induced Transient Transport In An Inxga1−Xas-Based P-I-N Semiconductor Nanostructure, K. T. Tsen, Juliann G. Kiang, D. K. Ferry, Hadis Morkoç
Physics Publications
Electron transient transport in an InxGa1−xAs-based (x=0.53) p-i-nnanostructure under the application of an electric field has been studied by time-resolvedRaman spectroscopy on a subpicosecond time scale and at T=300K. The experimental results reveal the time evolution of the electron distribution function and electron drift velocity with subpicosecond time resolution. These experimental results are compared with those of both InP-based and GaAs-based p-i-nnanostructures and provide a consistent understanding and better insight of electron transient transport phenomena in semiconductors.
Clustering Of Cr In Gan Nanotubes And The Onset Of Ferrimagnetic Order, Q. Wang, Q. Sun, Puru Jena, Y. Kawazoe
Clustering Of Cr In Gan Nanotubes And The Onset Of Ferrimagnetic Order, Q. Wang, Q. Sun, Puru Jena, Y. Kawazoe
Physics Publications
A comprehensive theoretical study of the structure and magnetic properties of Cr-doped GaN nanotubes yields some interesting and unexpected results: (1) A single wall GaN nanotube constructed from the GaN wurtzite crystal relaxes to a carbon-like zigzag SWNT structure and remains stable at 300K, while a multiwall GaN nanotube retains its original wurtzite form. (2) Cr atoms prefer to form clusters and the underlying magnetism depends on the degree of clustering. (3) The coupling between two Cr atoms mediated by the neighboring N is ferromagnetic, but changes to ferrimagnetic as the cluster grows. These results are based on spin polarized …
Structural, Electronic, And Chemical Properties Of Multiply Iodized Aluminum Clusters, N. O. Jones, J. Ulises Reveles, S. N. Khanna, D. E. Bergeron, P. J. Roach, A. W. Castleman Jr.
Structural, Electronic, And Chemical Properties Of Multiply Iodized Aluminum Clusters, N. O. Jones, J. Ulises Reveles, S. N. Khanna, D. E. Bergeron, P. J. Roach, A. W. Castleman Jr.
Physics Publications
The electronic structure, stability, and reactivity of iodized aluminum clusters, which have been investigated via reactivity studies, are examined by first-principles gradient corrected density functional calculations. The observed behavior of Al13I−x and Al14I−x clusters is shown to indicate that for x⩽8, they consist of compact Al−13 and Al++14 cores, respectively, demonstrating that they behave as halogen- or alkaline earthlike superatoms. For x>8, the Al cores assume a cagelike structure associated with the charging of the cores. The observed mass spectra of the reacted clusters reveal that Al13I−x species are more stable for even x while Al14I−x exhibit enhanced stability …
Strong Suppression Of The Yellow Luminescence In C-Doped Gan In Air Ambient, Michael A. Reshchikov
Strong Suppression Of The Yellow Luminescence In C-Doped Gan In Air Ambient, Michael A. Reshchikov
Physics Publications
The authors observed a drastic reduction of the yellow luminescence (YL) intensity in carbon-doped semi-insulating GaN in air or oxygen ambient as compared to the intensity in vacuum. The YL intensity dropped about 300 times while the exciton emission remained almost unchanged. The authors assume that the donor-acceptor-pair transitions involving a gallium vacancy complex in a thin near-surface region cause the strong YL. Oxygen molecules or ions induce the surface states acting as a very efficient channel of nonradiative recombination. The results indicate that carbon may not be involved in the acceptor responsible for the YL band in GaN:C.
Midinfrared Intersubband Absorption In Znxcd1−Xse/Znx′Cdy′Mg1−X′−Y′Se Multiple Quantum Well Structures, H. Lu, A. Shen, M. C. Tamargo, C. Y. Song, H. C. Liu, S. K. Zhang, R. R. Alfano, M. Muñoz
Midinfrared Intersubband Absorption In Znxcd1−Xse/Znx′Cdy′Mg1−X′−Y′Se Multiple Quantum Well Structures, H. Lu, A. Shen, M. C. Tamargo, C. Y. Song, H. C. Liu, S. K. Zhang, R. R. Alfano, M. Muñoz
Physics Publications
The authors report the observation of intersubband absorption in ZnxCd(1−x)Se/Znx′Cdy′Mg(1−x′−y′)Semultiple quantum wells. Lattice-matched samples were grown by molecular beam epitaxy on InP (001) substrates. Photoluminescence measurements indicate that the samples have excellent material quality. The peak absorption wavelengths measured by Fourier transform infrared spectroscopy are 3.99 and 5.35μm for two samples with ZnxCd(1−x)Se well widths of 28 and 42Å, respectively. These values fall within the 3–5μm wavelength range, which is of interest for midinfrared intersubband devices, such as quantum cascade lasers and quantum well infrared photodetectors. Their experimental results fit well with theoretical predictions based on the envelope function approximation. …
Determination Of Acceptor Concentration In Gan From Photoluminescence, Michael A. Reshchikov
Determination Of Acceptor Concentration In Gan From Photoluminescence, Michael A. Reshchikov
Physics Publications
The concentration of the acceptor responsible for the yellow luminescence (YL) band at about 2.2eV in GaN is determined from photoluminescence. The YL band intensity increases linearly with excitation power density and partially saturates above some critical value. The dependence is quantitatively described within a phenomenological model accounting for recombination statistics in GaN layer and saturation of acceptors with photogenerated holes. The incomplete saturation of the YL intensity at high excitation intensities is explained by gradual saturation of acceptors at different distances from the sample surface. The identity of deep and shallow acceptors in GaN is discussed.
Dehydrogenation Mechanism In Catalyst-Activated Mgh2, S. Li, Puru Jena, R. Ahuja
Dehydrogenation Mechanism In Catalyst-Activated Mgh2, S. Li, Puru Jena, R. Ahuja
Physics Publications
A small amount of Nb2O5 catalyst is known to substantially improve the desorption thermodynamics and kinetics of MgH2. Using density functional theory in combination with ab initio molecular dynamics simulation, we provide theoretical understanding of the mechanism of dehydrogenation in Nb doped MgH2. We show that the substitution of Nb at the Mg site followed by the clustering of H around Nb is a likely pathway for hydrogen desorption. We also find that dehydrogenation from the vicinity of Mg vacancies is exothermic. However, the vacancies are not likely to play a significant role in hydrogen desorption due to their high …
Electronic Counting Rules For The Stability Of Metal-Silicon Clusters, J. Ulises Reveles, Shiv N. Khanna
Electronic Counting Rules For The Stability Of Metal-Silicon Clusters, J. Ulises Reveles, Shiv N. Khanna
Physics Publications
First principles electronic structure calculations have been carried out to examine the stability of cationic, neutral, and anionic MSi15, MSi16, and MSi17 (M=Sc, Ti, and V) clusters. ScSi16−, TiSi16, and VSi16+ are found to be particularly stable in agreement with recent experiments. It is shown that the enhanced stability can be reconciled within a model where each Si atom coordinated to the metal contributes one electron to the valence pool. Clusters where the total number of valence electrons obtained by summing one electron from each Si site coordinated to metal atom and the valence electrons of the metal attain 20 …
Ferromagnetism In Al1−Xcrxn Thin Films By Density Functional Calculations, Q. Wang, A. K. Kandalam, Q. Sun, Puru Jena
Ferromagnetism In Al1−Xcrxn Thin Films By Density Functional Calculations, Q. Wang, A. K. Kandalam, Q. Sun, Puru Jena
Physics Publications
We report the results of a theoretical study of magnetic coupling between Cr atoms doped in bulk AlN as well as AlN (112¯0) thin films having wurtzite structure. The calculations are based on density fuctional theory with the generalized gradient approximation to the exchange and correlation potential. In the thin film, modeled by a slab of finite thickness, Cr atoms are found to cluster around N on the surface layer and couple ferromagnetically. The results for the Cr-doped AlN crystal are similar, namely, Cr atoms cluster around N and couple ferromagnetically. In the thin film, the preference of Cr to …
Vacancy-Mediated Hydrogen Desorption In Naalh4, C. Moysés Araújo, S. Li, R. Ahuja, Puru Jena
Vacancy-Mediated Hydrogen Desorption In Naalh4, C. Moysés Araújo, S. Li, R. Ahuja, Puru Jena
Physics Publications
First-principles calculations based on density functional theory are carried out to understand the mechanisms responsible for hydrogen desorption from Ti-doped sodium-alanate (NaAlH4). While the energy needed to remove a hydrogen atom from NaAlH4 with Ti substituted either at the Na site or at Al site is found to be significantly lower than that from the pristine NaAlH4, the presence of Na vacancies is shown to play an even larger role: It is not only an order of magnitude smaller than that from Ti-doped sodium-alanate, but the removal of hydrogen associated with a Na vacancy is exothermic with respect to formation …
Ab Initio Study Of Ferromagnetism In Ga1−Xcrxn Thin Films, Qin Wang, Q. Sun, Puru Jena, J. Z. Yu, R. Note, Y. Kawazoe
Ab Initio Study Of Ferromagnetism In Ga1−Xcrxn Thin Films, Qin Wang, Q. Sun, Puru Jena, J. Z. Yu, R. Note, Y. Kawazoe
Physics Publications
Electronic structure and magnetic properties of Ga1-xCrxN thin films are studied using the gradient corrected density functional method and a supercell slab model. Calculations are carried out by varying the concentration of doped Cr atoms and the sites they occupy. Cr atoms are found to prefer to reside on the surface sites and cluster around N as Mn atoms do. However, unlike Mn-doped GaN, Cr-doped GaN is found to be ferromagnetic for all concentrations studied. The calculated ferromagnetism is in agreement with recent experimental observations.
Evolution Of The Electronic Structure Of Be Clusters, V. Cerowski, B. K. Rao, S. K. Khanna, P. Jena, Soh Ishii, Kaoru Ohno, Yoshiyuki Kawazoe
Evolution Of The Electronic Structure Of Be Clusters, V. Cerowski, B. K. Rao, S. K. Khanna, P. Jena, Soh Ishii, Kaoru Ohno, Yoshiyuki Kawazoe
Physics Publications
Using a modified symbiotic genetic algorithm approach and many-body interatomic potential derived from first principles, we have calculated equilibrium geometries and binding energies of the ground-state and low-lying isomers of Be clusters containing up to 41 atoms. Molecular-dynamics study was also carried out to study the frequency of occurrence of the various geometrical isomers as these clusters are annealed during the simulation process. For a selected group of these clusters, higher-energy isomers were more often found than their ground-statestructures due to large catchment areas. The accuracy of the above ground-stategeometries and their corresponding binding energies were verified by carrying out …
Effects Of Hydrogen On The Morphology And Electrical Properties Of Gan Grown By Plasma-Assisted Molecular-Beam Epitaxy, Y. Dong, R. M. Feenstra, D. W. Greve, J. C. Moore, M. D. Sievert, A. A. Baski
Effects Of Hydrogen On The Morphology And Electrical Properties Of Gan Grown By Plasma-Assisted Molecular-Beam Epitaxy, Y. Dong, R. M. Feenstra, D. W. Greve, J. C. Moore, M. D. Sievert, A. A. Baski
Physics Publications
We study the effect of introducing hydrogen gas through the rf-plasma source during plasma-assisted molecular-beam epitaxy of GaN(0001). The well-known smooth-to-rough transition that occurs for this surface as a function of decreasing Ga flux in the absence of H is found to persist even with H present, although the critical Ga flux for this transition increases. Under Ga-rich conditions, the presence of hydrogen is found to induce step bunching (facetting) on the surface. Conductive atomic force microscopy reveals that leakage current through dislocation cores is significantly reduced when hydrogen is present during the growth.
Magnetic Coupling Between Cr Atoms Doped At Bulk And Surface Sites Of Zno, Q. Wang, Q. Sun, Puru Jena, Y. Kawazoe
Magnetic Coupling Between Cr Atoms Doped At Bulk And Surface Sites Of Zno, Q. Wang, Q. Sun, Puru Jena, Y. Kawazoe
Physics Publications
Contrary to theoretical prediction that Cr-doped bulk ZnO is ferromagnetic, recent experiments on Cr-doped ZnOthin film reveal the coupling to be antiferromagnetic. Using first-principles calculations based on gradient corrected density functional theory, we show that a possible origin of this disagreement may be associated with the site preference of Cr. In bulk, when Cr substitutes Zn,bond contraction occurs and Cr atoms prefer to cluster around O atoms. The ferromagnetic coupling among Cr atoms is driven by Cr 3d and O 2p exchange interactions as in Cr2O cluster. However, when Cr atoms replace Zn on the surface, due to the different …
Role Of Titanium In Hydrogen Desorption In Crystalline Sodium Alanate, C. Moysés Araújo, Rajeev Ahuja, J. M. Osorio Guillén, Puru Jena
Role Of Titanium In Hydrogen Desorption In Crystalline Sodium Alanate, C. Moysés Araújo, Rajeev Ahuja, J. M. Osorio Guillén, Puru Jena
Physics Publications
The role of Ti in improving the thermodynamics of hydrogen desorption in crystalline sodium alanate (NaAlH4) has been investigated by using the density functional theory. The total energy calculations reveal that Ti prefers to occupy the Na site over that of the Al site when the atomic energies are used as the reference. However, the use of the cohesive energies of Al,Na, and Ti leads to the Al site being the least unfavorable one. Irrespective of whether Ti occupies the Na or the Al site, the energy necessary to remove a hydrogen atom from Ti substituted sodium alanate is significantly …
Spectroscopy And Carrier Dynamics In Cdse Self-Assembled Quantum Dots Embedded In Znxcdymg1−X−Yse, G. Comanescu, W. B. Wang, S. Gundry, B. Das, R. R. Alfano, M. N. Perez-Paz, M. C. Tamargo, M. Muñoz, I. Popov, L. L. Isaacs
Spectroscopy And Carrier Dynamics In Cdse Self-Assembled Quantum Dots Embedded In Znxcdymg1−X−Yse, G. Comanescu, W. B. Wang, S. Gundry, B. Das, R. R. Alfano, M. N. Perez-Paz, M. C. Tamargo, M. Muñoz, I. Popov, L. L. Isaacs
Physics Publications
Time-resolved and steady-state photoluminescence,reflectivity, and absorption experiments were performed on CdSequantum dots in ZnxCdyMg1−x−ySe barriers. Studies of the capture times of the photoexcited carriers into the quantum dots and of electron-hole recombination times inside the dots were performed. Photoluminescence rise time yielded capture times from 20 ps to 30 ps. All samples exhibit fast and slow photoluminescence decays, consistent with observing two independent but energetically overlapping decays. The faster relaxation times for the sample emitting in the blue range is 90 ps, whereas for the two samples emitting in the green it is 345 ps and 480 ps. The slower …
Structural Growth In Iron Oxide Clusters: Rings, Towers, And Hollow Drums, N. O. Jones, B. V. Reddy, F. Rasouli, Shiv N. Khanna
Structural Growth In Iron Oxide Clusters: Rings, Towers, And Hollow Drums, N. O. Jones, B. V. Reddy, F. Rasouli, Shiv N. Khanna
Physics Publications
It is shown that the transition from an elementary FeO molecule to the bulk rock-salt FeO proceeds via hollow rings, towers, and drums. Our first-principles electronic structure calculations carried out within a gradient-corrected density functional framework show that small FenOn (n=2,3,4,5) clusters form single, highly stable rings. Starting at Fe6O6, these elementary rings begin to assemble into nano columnar structures to form stable Fe6O6, Fe7O7, Fe8O8, Fe9O9, Fe10O10, and Fe12O12 towers. The rings and the empty towers can be further stabilized by capping O atoms at the ends, leading to FenOn+1 and FenOn+2 sequences. The theoretical results provide insight into …
Nearly-Free-Electron Gas In A Silicon Cage, J. Ulises Reveles, Shiv N. Khanna
Nearly-Free-Electron Gas In A Silicon Cage, J. Ulises Reveles, Shiv N. Khanna
Physics Publications
A systematic study of the ground state geometries, electronic structure, and stability of the metal (M) encapsulated MSi12 (M=Sc, Ti, V, Cr, Mn, Fe, Co, Ni) clusters has been carried out within a gradient-corrected density functional formalism. It is shown that the ground state of most MSi12 clusters has the lowest spin multiplicity as opposed to the high spin multiplicity in free transition metal atoms. Consequently, a proper inclusion of the spin conservation rules is needed to understand the variation of the binding energy of M to Si12 clusters. Using such rules, CrSi12 and FeSi12 are found to exhibit the …
First-Principles Study Of The Onset Of Noncollinearity In Mnn Clusters: Magnetic Arrangements In Mn5 And Mn6, T. Morisato, Shiv N. Khanna, Y. Kawazoe
First-Principles Study Of The Onset Of Noncollinearity In Mnn Clusters: Magnetic Arrangements In Mn5 And Mn6, T. Morisato, Shiv N. Khanna, Y. Kawazoe
Physics Publications
First-principles theoretical investigations of the noncollinearity of atomic spin moments in manganese clusters have been carried out within a gradient-corrected density-functional approach. Our studies on Mn5 and Mn6 include investigation of both collinear and noncollinear arrangements. It is shown that while the atomic structure of the ground state of Mn5 is a triangular bipyramid, the collinear and noncollinear arrangements have comparable energies and hence are degenerate. For Mn6, while the ground state has a square bipyramid arrangement, the noncollinear configuration is most stable making it the smallest cluster to feature a noncollinear ground state. The results are discussed in view …
Electroreflectance Spectroscopy In Self-Assembled Quantum Dots: Lens Symmetry, A. H. Rodríguez, C. Trallero-Giner, Martín Muñoz, María C. Tamargo
Electroreflectance Spectroscopy In Self-Assembled Quantum Dots: Lens Symmetry, A. H. Rodríguez, C. Trallero-Giner, Martín Muñoz, María C. Tamargo
Physics Publications
Modulated electroreflectance spectroscopy ΔR∕R of semiconductor self-assembled quantum dots is investigated. The structure is modeled as dots with lens shape geometry and circular cross section. A microscopic description of the electroreflectance spectrum and optical response in terms of an external electric field (F) and lens geometry have been considered. The field and lens symmetry dependence of all experimental parameters involved in the ΔR∕Rspectrum have been considered. Using the effective mass formalism the energies and the electronic states as a function of F and dot parameters are calculated. Also, in the framework of the strongly confined regime general expressions for the …
Electroreflectance Spectroscopy In Self-Assembled Quantum Dots: Lens Symmetry, A. H. Rodríguez, C. Trallero-Giner, Martín Muñoz, María C. Tamargo
Electroreflectance Spectroscopy In Self-Assembled Quantum Dots: Lens Symmetry, A. H. Rodríguez, C. Trallero-Giner, Martín Muñoz, María C. Tamargo
Physics Publications
Modulated electroreflectance spectroscopy Delta R/R of semiconductor self-assembled quantum dots is investigated. The structure is modeled as dots with lens shape geometry and circular cross section. A microscopic description of the electroreflectance spectrum and optical response in terms of an external electric field (F) and lens geometry have been considered. The field and lens symmetry dependence of all experimental parameters involved in the Delta R/R spectrum have been considered. Using the effective mass formalism the energies and the electronic states as a function of F and dot parameters are calculated. Also, in the framework of the strongly confined regime general …
First-Principles Study Of Ferromagnetic Coupling In Zn1-Xcrxte Thin Film, Q. Wang, Q. Sun, P. Jena, Y. Kawazoe
First-Principles Study Of Ferromagnetic Coupling In Zn1-Xcrxte Thin Film, Q. Wang, Q. Sun, P. Jena, Y. Kawazoe
Physics Publications
Using gradient-corrected density functional theory and supercell technique, we have calculated total energies, electronic structure, and magnetic properties of Cr-doped ZnTe in both bulk and thin-film configurations. Calculations with full geometry optimization for a Zn1−xCrxTesupercell were carried out for different Cr concentrations (x=0.095, 0.143, and 0.19) and by varying the sites Cr atoms occupy. We show that the ferromagnetic phase of Zn1−xCrxTe in both bulk and thin film is energetically the most preferable state irrespective of the concentration and∕or site occupation of the Cr atom. The strong hybridization between Cr3d and Te5p states is found to be responsible for the …
Magnetic Isomers And Local Moment Distribution In Mn5o And Mn6o Clusters, N. O. Jones, Shiv N. Khanna, T. Baruah, M. R. Pederson, W.-J. Zheng, J. M. Nilles, K. H. Bowen
Magnetic Isomers And Local Moment Distribution In Mn5o And Mn6o Clusters, N. O. Jones, Shiv N. Khanna, T. Baruah, M. R. Pederson, W.-J. Zheng, J. M. Nilles, K. H. Bowen
Physics Publications
A synergistic approach combining the experimental photoelectron spectroscopy and theoretical electronic structure studies is used to demonstrate the existence of magnetic isomers as well as configurations having comparable binding energies, identical spins, and yet differing in the distribution of local moments (called isomags). Our studies carried out on Mn5O and Mn6O clusters show that while the O atom occupies either bridge or hollow site with a binding energy of 6.88eV in Mn5, it prefers a hollow site with a binding energy of 7.18eV in Mn6 clusters. Mn5O is shown to possess two magnetic isomers with total spins of 13 and …
Spectroscopic Signature Of Magnetic Bistability In Mn2oà Anions And Its Implications For Piezomagnetism At The Nanoscale, Shiv N. Khanna, Puru Jena, W.-J. Zheng, J. M. Nilles, K. H. Bowen
Spectroscopic Signature Of Magnetic Bistability In Mn2oà Anions And Its Implications For Piezomagnetism At The Nanoscale, Shiv N. Khanna, Puru Jena, W.-J. Zheng, J. M. Nilles, K. H. Bowen
Physics Publications
A synergistic study, using gradient corrected density functional theory and photoelectron spectroscopy, shows that the presence of oxygen can fundamentally alter the interaction between two Mn atoms. The normally weak interaction between two Mn atoms exhibits strong bonding when an oxygen atom is added to form Mn2O. This allows the atomiclike magnetic moments of each Mn atom to couple either ferromagnetically or antiferromagnetically depending on whether Mn2O is anionic or neutral. Furthermore, the Mn2O− anion is found to possess an antiferromagnetic isomer that lies only 0.01 eV above its nearly degenerate ferromagnetic ground state. The possibility of exploiting this magnetic …
Energetics And Local Spin Magnetic Moment Of Single 3,4d Impurities Encapsulated In An Icosahedral Au12 Cage, Shan-Ying Wang, Jing-Zhi Yu, Hiroshi Mizuseki, Qiang Sun, Chong-Yu Wang, Yoshiyuki Kawazoe
Energetics And Local Spin Magnetic Moment Of Single 3,4d Impurities Encapsulated In An Icosahedral Au12 Cage, Shan-Ying Wang, Jing-Zhi Yu, Hiroshi Mizuseki, Qiang Sun, Chong-Yu Wang, Yoshiyuki Kawazoe
Physics Publications
The energetics and local spin magnetic moment of a single 3,4d impurity (Sc-Ni, Y-Pd) encapsulated in an icosahedral Au12 cage have been studied theoretically by using a real-space first-principles cluster method with generalized gradient approximation for exchange-correlation functional. The relativistic effect is considered by scalar relativistic pseudopotentials. All doped clusters show unexpected large relative binding energies compared with icosahedral Au13cluster. The smallest and the largest values appear at Pd and Zr, 2.186 and 7.791eV per cluster, respectively, indicating doping could stabilize the icosahedral Au12 cage and promote the formation of a new binary alloy cluster. Comparatively large magnetic moments are …
Classical Stern-Gerlach Profiles Of Mn5 And Mn6 Clusters, N. O. Jones, Shiv N. Khanna, Tunna Baruah, M. R. Pederson
Classical Stern-Gerlach Profiles Of Mn5 And Mn6 Clusters, N. O. Jones, Shiv N. Khanna, Tunna Baruah, M. R. Pederson
Physics Publications
Mn5 and Mn6 clusters have recently been found to exhibit Stern-Gerlach profiles marked by a central peak that broadens with the increasing field gradient. The profiles neither exhibit a reminiscence of space quantization as observed through a splitting of beams for the case of free atoms, nor a net deflection characteristic of superparamagnetic relaxations observed in other transition metal clusters. It is proposed that this new behavior results from a weak coupling of localized atomic moments. ab initio electronic structure studies are carried out to show that a Mn5cluster has isomers with spin magnetic moments of 3μB, 13μB, and 23μBwhile …
Magnetism And Energetics Of Mn-Doped Zno (101¯0) Thin Films, Q. Wang, Q. Sun, B. K. Rao, Puru Jena
Magnetism And Energetics Of Mn-Doped Zno (101¯0) Thin Films, Q. Wang, Q. Sun, B. K. Rao, Puru Jena
Physics Publications
First-principles calculations based on gradient corrected density functional theory are performed on Mn-doped ZnO thin film. Magnetism and energetics are studied for two Mn concentrations and varying Mn configurations. It is found that in the dilute limit when Mn atoms are far apart, the ferro-magnetic and antiferromagnetic states are energetically nearly degenerate. The resulting fluctuation would, therefore, make the system paramagnetic as found in the experiment. But, as the concentration of Mn atoms increases, there is a tendency for Mn atoms to form nearest neighbors and cluster around oxygen. For such a configuration, the antiferromagnetic coupling between Mn atoms is …