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Articles 271 - 300 of 320

Full-Text Articles in Physics

Classical Stern-Gerlach Profiles Of Mn5 And Mn6 Clusters, N. O. Jones, Shiv N. Khanna, Tunna Baruah, M. R. Pederson Jan 2004

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 …

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Magnetism And Energetics Of Mn-Doped Zno (101¯0) Thin Films, Q. Wang, Q. Sun, B. K. Rao, Puru Jena Jan 2004

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 …

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Interactions Of Au Cluster Anions With Oxygen, Qiang Sun, Puru Jena, Young Dok Kim, Matthias Fischer, Gerd Ganteför Jan 2004

Interactions Of Au Cluster Anions With Oxygen, Qiang Sun, Puru Jena, Young Dok Kim, Matthias Fischer, Gerd Ganteför

Physics Publications

Experimental and theoretical evidence is presented for the nondissociative chemisorption of O2on free Au cluster anions (Au−n, n=number of atoms) with n=2, 4, 6 at room temperature, indicating that the stabilization of the activated di-oxygen species is the key for the unusual catalytic activities of Au-based catalysts. In contrast to Au−n with n=2, 4, 6, O2 adsorbs atomically on Aumonomer anions. For the Aumonomer neutral, calculations based on density functional theory reveal that oxygen should be molecularly bound. On Au dimer and tetramer neutrals, oxygen is molecularly bound with the O–O bond being less activated with respect to their …

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Competition Between Linear And Cyclic Structures In Monochromium Carbide Clusters Crcn- And Crcn (N=2-8): A Photoelectron Spectroscopy And Density Functional Study, Hua-Jin Zhai, Lai-Sheng Wang, P. Jena, G. L. Gutsev, C. W. Bauschlicher Jr. Jan 2004

Competition Between Linear And Cyclic Structures In Monochromium Carbide Clusters Crcn- And Crcn (N=2-8): A Photoelectron Spectroscopy And Density Functional Study, Hua-Jin Zhai, Lai-Sheng Wang, P. Jena, G. L. Gutsev, C. W. Bauschlicher Jr.

Physics Publications

Photoelectron spectroscopy (PES) is combined with density functional theory (DFT) to study the monochromium carbide clusters CrC−n and CrCn (n=2–8). Well-resolved PES spectra were obtained, yielding structural, electronic, and vibrational information about both the anionic and neutral clusters. Experimental evidence was observed for the coexistence of two isomers for CrC−2, CrC−3, CrC−4, and CrC−6. Sharp and well-resolved PES spectra were observed for CrC−n (n=4,6,8), whereas broad spectra were observed for CrC−5 and CrC−7. Extensive DFT calculations using the generalized gradient approximation were carried out for the ground and low-lying excited states of all the CrC−n and CrCn species, as well …

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Geometry And Electronic Structure Of V-N(Bz)(M) Complexes, Anil K. Kandalam, B. K. Rao, P. Jena, Ravindra Pandey Jan 2004

Geometry And Electronic Structure Of V-N(Bz)(M) Complexes, Anil K. Kandalam, B. K. Rao, P. Jena, Ravindra Pandey

Physics Publications

First-principles calculations based on the generalized gradient approximation to the density functional theory are performed to explore the global geometries, ground-state spin multiplicities, relative stabilities, and energetics of neutral and anionic Vn(Bz)m (n51 – 3, m51 – 4, with n ,m) complexes. The calculated results show that the Vn(benzene)m complexes clearly prefer sandwich structures to rice-ball structures. The ground-state spin multiplicities of the Vn(benzene)n11 complexes increased linearly with the size of the system (i.e., n). In the anionic complexes, the V(benzene)2 complex is found to be unstable against the autodetachment of the extra electron. The energy difference between adiabatic and …

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Periodic Table Of 3d-Metal Dimers And Their Ions, G. L. Gutsev, M. D. Mochena, P. Jena, C. W. Bauchlicher Jr., H. Partridge Iii Jan 2004

Periodic Table Of 3d-Metal Dimers And Their Ions, G. L. Gutsev, M. D. Mochena, P. Jena, C. W. Bauchlicher Jr., H. Partridge Iii

Physics Publications

The ground states of the mixed 3d-metal dimers TiV, TiCr, TiMn, TiFe, TiCo, TiNi, TiCu, TiZn, VCr, VMn, VFe, VCo, VNi, VCu, VZn, CrMn, CrFe, CrCo, CrNi, CrCu, CrZn, MnFe, MnCo, MnNi, MnCu, MnZn, FeCo, FeNi, FeCu, FeZn, CoNi, CoCu, CoZn, NiCu, NiZn, and CuZn along with their singly negatively and positively charged ions are assigned based on the results of computations using density functional theory with generalized gradient approximation for the exchange-correlation functional. Except for TiCo and CrMn, our assignment agrees with experiment. Computed spectroscopic constants (re,ωe,Do) are in fair agreement with experiment. The ground-state spin multiplicities of all …

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Appearance Of Bulk Properties In Small Tungsten Oxide Clusters, Q. Sun, B. K. Rao, P. Jena, D. Stolcic, Y. D. Kim, Gerd Gantefor, A. W. Castleman Jr. Jan 2004

Appearance Of Bulk Properties In Small Tungsten Oxide Clusters, Q. Sun, B. K. Rao, P. Jena, D. Stolcic, Y. D. Kim, Gerd Gantefor, A. W. Castleman Jr.

Physics Publications

Contrary to the conventional understanding that atomic clusters usually differ in properties and structure from the bulk constituents of which they are comprised, we show that even a dimer of tungsten oxide (WO3)2 possesses bulklike features and the geometry of a small cluster containing only 4 tungsten and 12 oxygen atoms bears the hallmarks of crystalline tungsten oxide, WO3. This observation, based on a synergistic approach involving mass distributions under quasisteady state conditions, photoelectron spectroscopy, and first principles molecular orbital theory, not only illustrates the existence of a class of strongly covalent or ionic materials whose embryonic forms are tiny …

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Formation And Properties Of Halogenated Aluminum Clusters, D. E. Bergeron, A. W. Castleman Jr., T. Morisato, S. N. Khanna Jan 2004

Formation And Properties Of Halogenated Aluminum Clusters, D. E. Bergeron, A. W. Castleman Jr., T. Morisato, S. N. Khanna

Physics Publications

The fast-flow tube reaction apparatus was employed to study the halogenation of aluminum clusters. For reactions with HX (X=Cl, Br, and I), acid-etching pathways are evident, and we present findings for several reactions, whereby AlnX− generation is energetically favorable. Tandem reaction experiments allowed us to establish that for AlnCl−, AlnI−, and AlnI−2, species with n=6, 7, and 15 are particularly resistant to attack by oxygen. Further, trends in reactivity suggest that, in general, iodine incorporation leaves the aluminum clusters’ electronic properties largely unperturbed. Ab initio calculations were performed to better interpret reaction mechanisms and elucidate the characteristics of the products. …

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First-Principles Study Of Magnetism In (112̄0) Zn1−Xmnxo Thin Film, Q. Wang, Puru Jena Jan 2004

First-Principles Study Of Magnetism In (112̄0) Zn1−Xmnxo Thin Film, Q. Wang, Puru Jena

Physics Publications

First-principles calculations of total energies and magnetism of Zn1−xMnxOthin film are performed by simulating it with a slab consisting of seven layers along (112̄0). It is shown that a single Mn atom shows very little preference for the site it occupies. This is consistent with the experimental finding that Mn atoms are homogeneously distributed in ZnO films. As the concentration of Mn atoms increases, antiferromagnetic coupling between Mn atoms becomes more favorable, and there is a tendency for Mn atoms to form clusters around oxygen, in agreement with recent experiments.

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Ferromagnetism In Cr-Doped Gan: A First-Principles Calculation, G. P. Das, B. K. Rao, Puru Jena Jan 2004

Ferromagnetism In Cr-Doped Gan: A First-Principles Calculation, G. P. Das, B. K. Rao, Puru Jena

Physics Publications

Electronic structure, energy bands, and magnetic properties of Cr-doped GaN have been calculated from first principles using a 32 atom supercell within the frame work of linearized muffin-tin orbital tight binding method and gradient-corrected density-functional theory. The coupling between Cr atoms is found to be ferromagnetic with a magnetic moment of 2.69μB at each Cr site. The magnetic moments of Ga and N sites are rather small, namely, 0.025μB and −0.025μB, respectively, yielding a total moment of 6μB per supercell. Parallel calculations done on small clusters of Cr-doped GaN also yield similar results indicating that magnetic coupling between Cr atoms …

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Magnetic Properties Of Al, V, Mn, And Ru Impurities In Fe–Co Alloys, B. V. Reddy, S. C. Deevi, S. N. Khanna Jan 2003

Magnetic Properties Of Al, V, Mn, And Ru Impurities In Fe–Co Alloys, B. V. Reddy, S. C. Deevi, S. N. Khanna

Physics Publications

Theoretical studies on the magnetic properties of impurities in Fe–Co alloys have been carried out using a molecular-orbital approach within a gradient corrected density functional formalism. The defected alloy is modeled by a large cluster and the calculations on the ordered alloy are used to show that a cluster containing 67 atoms can provide quantitative information on the local magnetic moment. It is found that although bulk Al, V, and Ru are nonmagnetic, all the impurities carry finite moments. While Al and V impurities couple antiferromagnetically, Ru impurities couple ferromagnetically to the host sites. It is shown that the observed …

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Nitrogen-Induced Magnetic Transition In Small Chromium Clusters, Q. Wang, Q. Sun, B. K. Rao, P. Jena, Y. Kawazoe Jan 2003

Nitrogen-Induced Magnetic Transition In Small Chromium Clusters, Q. Wang, Q. Sun, B. K. Rao, P. Jena, Y. Kawazoe

Physics Publications

Using density functional theory with generalized gradient approximation for exchange and correlation, we show that otherwise antiferromagnetically coupled chromium atoms in very small chromium clusters couple ferromagnetically when doped with a nitrogen atom, thus leading to giant magnetic moments. For example, the magnetic moment of Cr2N is found to be 9μBwhile that of Cr2 is 0μB. Strong bonding between Cr and N atoms brings about this magnetic transition. The Cr atoms nearest neighbor to N couple ferromagnetically with each other and antiferromagnetically with nitrogen. The significance of these results in understanding the ferromagnetic order in Cr-doped GaN is discussed.

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H-Substituted Anionic Carbon Clusters Cnh- (N <= 10): Density Functional Studies And Experimental Observations, L. Pan, B. K. Rao, A. K. Gupta, G. P. Das, P. Ayyub Jan 2003

H-Substituted Anionic Carbon Clusters Cnh- (N <= 10): Density Functional Studies And Experimental Observations, L. Pan, B. K. Rao, A. K. Gupta, G. P. Das, P. Ayyub

Physics Publications

We have studied the interaction of hydrogen with small neutral and anionic carbon clusters using density functional calculations. The geometry, stability, and electronic structure of these clusters show an odd–even alternation originating in the bonding nature of the carbon atoms. Our mass spectrometric measurements of the abundance of CnH− (n⩽10) cluster anions produced by gas-feed Cs sputtering from different crystallographic forms of carbon display similar odd–even alternation with the even-n clusters being relatively more abundant. The calculated trend in the adiabatic electron affinities shows a behavior similar to the experimental abundance pattern. We discuss a possible partial suppression of …

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Atomic Structure, Binding Energy, And Magnetic Properties Of Iron Atoms Supported On A Polyaromatic Hydrocarbon, L. Senapati, S. K. Nayak, B. K. Rao, P. Jena Jan 2003

Atomic Structure, Binding Energy, And Magnetic Properties Of Iron Atoms Supported On A Polyaromatic Hydrocarbon, L. Senapati, S. K. Nayak, B. K. Rao, P. Jena

Physics Publications

The atomic structure, energetics, and properties of gas-phase cluster complexes containing coronene (C24H12) molecule and up to two iron atoms are studied for the first time using density functional theory and generalized gradient approximation for exchange and correlation. The geometries of the neutral and cationic iron–coronene complexes are optimized without symmetry constraint and by examining the possibility that iron atoms could occupy various sites via individual π or bridging interactions. In both neutral and cationic complexes a single Fe atom is found to preferentially occupy the on-top site above the outer ring, while two Fe atoms dimerize and reside on …

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Afm, Cafm, And Efm Studies Of The Gan System, John C. Dickinson Jan 2003

Afm, Cafm, And Efm Studies Of The Gan System, John C. Dickinson

Theses and Dissertations

This thesis discusses a variety of techniques based on the atomic force microscope (AFM), and their application to the GaN materials system. In particular, the local conductivity and contact potential of surfaces have been measured using the techniques of Conductive AFM (CAFM) and Surface Potential Electric Force Microscopy (SPEFM), respectively. CAFM studies of GaN surfaces have revealed that prismatic planes around islands and pits on surfaces can lead to enhanced conductivity, which may be related to leakage problems in device applications. With regard to SP-EFM work, the change in surface potential associated with inversion domains on Ga-polar GaN has been …

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Electronic-Structure-Based Investigation Of Magnetism In The Fe8 Molecular Magnet, Mark R. Pederson, Jens Kortus, S. N. Khanna Jan 2002

Electronic-Structure-Based Investigation Of Magnetism In The Fe8 Molecular Magnet, Mark R. Pederson, Jens Kortus, S. N. Khanna

Physics Publications

We have performed density-functional-based electronic structure calculations on a single Fe8 molecular nanomagnet. Our calculated total moments and local moments are in excellent agreement with experiment. By including spin–orbit coupling we determine the easy, medium, and hard axes and find the ordering of the principle axes also agrees with experiment. From our calculated anisotropy Hamiltonian, we calculate the oscillations in the tunnel splittings and compare to the experimental results.

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Caging Of Ni Clusters By Benzene Molecules And Its Effect On The Magnetism Of Ni Clusters, B. K. Rao, P. Jena Jan 2002

Caging Of Ni Clusters By Benzene Molecules And Its Effect On The Magnetism Of Ni Clusters, B. K. Rao, P. Jena

Physics Publications

Global optimization of the geometry of small Ni clusters interacting with benzene molecules yields equilibrium structures where the Ni atoms find themselves caged between the benzene molecules. This leads to quenching of the Ni magnetic moment in most of the complexes even though the structure of the caged Ni clusters remain relatively unchanged from their otherwise free gas phase geometry. The accuracy of these predictions, based on density functional theory with generalized gradient approximation for exchange and correlation, is established by the good agreement achieved between the calculated and available experimental dissociation energies and ionization potentials.

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Spectroscopy Of Ni-N(Benzene)(M) Anion Complexes, B. K. Rao, P. Jena Jan 2002

Spectroscopy Of Ni-N(Benzene)(M) Anion Complexes, B. K. Rao, P. Jena

Physics Publications

Total energy calculations based on the generalized gradient approximation to the density functional theory reveal that the Ni(benzene) and Ni(benzene)2 anions are unstable against autodetachment of the additional electron while other anion complexes containing more than one Ni atom are stable. Although the adiabatic electron affinities increase with Ni content, they are significantly smaller than those in pure Ni clusters containing the same number of Ni atoms. The difference between adiabatic electron affinities and vertical detachment energies are around 0.2 eV in most cases, indicating that the equilibrium geometries of Nin(benzene)−m are not significantly altered from their corresponding neutral geometries. …

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Magnetic Moment And Anisotropy In Fencom Clusters, J. Kortus, T. Baruah, M. R. Pederson, C. Ashman, Shiv N. Khanna Jan 2002

Magnetic Moment And Anisotropy In Fencom Clusters, J. Kortus, T. Baruah, M. R. Pederson, C. Ashman, Shiv N. Khanna

Physics Publications

Electronic structure calculations of FenCom (n+m=5 and 13) are used to examine the effects of alloying on the magnetic moment and magnetic anisotropies. Our density-functional studies show that many mixed clusters have moments comparable to or higher than the pure clusters. The mixed clusters, however, have very low anisotropies and could be ideal as soft magnetic materials. It is shown that shape, composition, and compositional ordering must be considered for optimization of anisotropy energies.

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Reactivity And Electronic Structure Of Aluminum Clusters: The Aluminum-Nitrogen System, B. D. Leskiw, A. W. Castleman Jr., C. Ashman, S. N. Khanna Jan 2001

Reactivity And Electronic Structure Of Aluminum Clusters: The Aluminum-Nitrogen System, B. D. Leskiw, A. W. Castleman Jr., C. Ashman, S. N. Khanna

Physics Publications

The stability of anionic aluminum–nitrogen clusters has been examined and Al2N−, Al3N−2,Al5N−2, Al6N−3, Al8N−3, and Al9N−2 are found to be particularly stable. Theoreticaldensity functional calculations on neutral and anionic AlnN (n=1–8) clusters were performed and the stability and reaction energetics with oxygen examined. Clusters requiring less than 5.7 eV to remove an electron and an Al atom are shown to be resistant to the reaction with oxygen.

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Geometry, Electronic Structure, And Energetics Of Copper-Doped Aluminum Clusters, S. N. Khanna, C. Ashman, B. K. Rao, P. Jena Jan 2001

Geometry, Electronic Structure, And Energetics Of Copper-Doped Aluminum Clusters, S. N. Khanna, C. Ashman, B. K. Rao, P. Jena

Physics Publications

Using density functional theory and generalized gradient approximation for exchange-correlation potential, we have calculated the equilibrium geometries and energetics of neutral and negatively charged AlnCu (n=11,12,13,14) clusters. Unlike the alkali atom-doped aluminum clusters in the same size range, the copper atom resides inside the aluminum cluster cage. Furthermore, the 3d and 4s energy levels of Cu hybridize with the valence electrons of Al causing a redistribution of the molecular orbital energy levels of the Aln clusters. However, this redistribution does not affect the magic numbers of AlnCu clusters that could be derived by assuming that Cu donates one electron to …

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Electronic Structure And Chemical Bonding Of 3d-Metal Dimers Scx, X=Sc-Zn, G. L. Gutsev, P. Jena, B. K. Rao, S. N. Khanna Jan 2001

Electronic Structure And Chemical Bonding Of 3d-Metal Dimers Scx, X=Sc-Zn, G. L. Gutsev, P. Jena, B. K. Rao, S. N. Khanna

Physics Publications

The electronic and geometrical structures of the ground and excited states of the homonuclear Sc2, mixed ScTi, ScV, ScCr, ScMn, ScFe, ScCo, ScNi, ScCu, and ScZn 3d-metal dimers and their anions have been calculated using the density functional theory with generalized gradient approximation for the exchange-correlation potential. The ground states of the neutral dimers are found to be 5Σ−u (Sc2), 6Σ+ (ScTi), 7Σ+ (ScV), 4Σ+ (ScCr), 3Σ+ (ScMn), 2Δ(ScFe), 1Σ+ (ScCo), 2Σ+ (ScNi), 3Δ(ScCu), and 4Σ+ (ScZn). A natural bond analysis reveals an antiferrimagnetic spin coupling in the ground states of ScCr, ScMn, and ScFe. This is due to the …

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Energetics And Electronic Structure Of Carbon Doped Aluminum Clusters, B. K. Rao, P. Jena Jan 2001

Energetics And Electronic Structure Of Carbon Doped Aluminum Clusters, B. K. Rao, P. Jena

Physics Publications

The energetics and the electronic structure of AlnC clusters (n=3, 4, 5; 11, 12, 13) have been studied by a global optimization of their geometry without any symmetry constraint. The total energies of these clusters both in neutral and charged states are calculated using an all-electron basis and the generalized gradient approximation to the density functional theory. While Al4C and Al12C clusters share some characteristic features of closed shell structures, namely enhanced stability and low electron affinity compared to their neighboring sizes, their ionization potentials exhibit different behavior. These decrease steadily from Al3C to Al5C while that of Al12C is …

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Electronic Structure Of Chromium Oxides, Cron- And Cron (N=1-5) From Photoelectron Spectroscopy And Density Functional Theory Calculations, G. L. Gutsev, P. Jena, Hua-Jin Zhai, Lai-Sheng Wang Jan 2001

Electronic Structure Of Chromium Oxides, Cron- And Cron (N=1-5) From Photoelectron Spectroscopy And Density Functional Theory Calculations, G. L. Gutsev, P. Jena, Hua-Jin Zhai, Lai-Sheng Wang

Physics Publications

The electronic structure of CrO−n and CrOn (n=1–5) was investigated using anion photoelectron spectroscopy and density functional theory. Photoelectron spectra of CrO−n were obtained at several photon energies and yielded electron affinities, vibrational and electronic structure information about the neutral CrOn species. Density functional theory calculations were carried out for both the neutrals and anions and were used to interpret the experimental spectra. Several low-lying electronic states of CrO were observed and assigned from photodetachment of the CrO− ground state(6∑+) and an excited state (4∏), which is only 0.1 eV higher. The main spectral features of CrO−2 were interpreted based …

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Investigation Of Inversion Domains In Gan By Electric-Force Microscopy, K. M. Jones, P. Visconti, F. Yun, A. A. Baski, Hadis Morkoç Jan 2001

Investigation Of Inversion Domains In Gan By Electric-Force Microscopy, K. M. Jones, P. Visconti, F. Yun, A. A. Baski, Hadis Morkoç

Physics Publications

Inversion domains in III-nitride semiconductors degrade the performance of devicesfabricated in them. Consequently, it is imperative that we understand their electrostatic manifestation, the growth conditions under which such domains form, and an effective means of their identification. In what is nominally referred to as Ga-polarity samples, N-polarity domains have a polarization that is reversed with respect to the remainder of the surface, and therefore, have a different potential under strain. We have used surface-potential electric-force microscopy (SP-EFM) to image the electrostaticsurface potential of GaNgrown on sapphire, which is strained due to the thermal mismatch between the substrate and GaN. Employing …

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Magnetic Coupling In Neutral And Charged Cr-2, Mn-2, And Crmn Dimers, N. Desmarais, F. A. Reuse, S. N. Khanna Jan 2000

Magnetic Coupling In Neutral And Charged Cr-2, Mn-2, And Crmn Dimers, N. Desmarais, F. A. Reuse, S. N. Khanna

Physics Publications

Theoreticalab initio studies of neutral, cationic and anionic Cr2, Mn2, and CrMn dimers have been carried out to explore the progression of magnetic coupling with the number of electrons. It is shown that while Cr2 and Cr−2 have antiferromagnetically coupled atomic spins, Cr+2 has a ferromagneticground state closely followed by an antiferromagnetic state. On the other hand, all Mn2 dimers are ferromagnetic, irrespective of the charge. The neutral CrMn is ferrimagnetic while the charged CrMn are antiferromagnetic. In all cases, the charged dimers are found to be more stable than the neutral ones. The results are compared with available …

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Alkalization Of Aluminum Clusters, B. K. Rao, P. Jena Jan 2000

Alkalization Of Aluminum Clusters, B. K. Rao, P. Jena

Physics Publications

Equilibrium geometries, binding energies, ionization potentials, and electron affinities of neutral and charged Aln clusters (n⩽8) decorated with alkali atoms such as Li and K have been calculated using molecular orbital theory based on density functional formalism and generalized gradient approximation. While the electron affinities and the ionization potentials depend on size, no clear signatures of shell closings are found in this size range. Similar studies on Al5Xm  (X=Li, K, 1⩽m⩽4) also fail to provide any indication consistent with shell closings. On the other hand, the ionization potentials and electron affinities of aluminum clusters decrease with the addition of alkali …

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Experimental And Theoretical Study Of The Photoelectron Spectra Of Mnox-(X=1-3) Clusters, Gennady L. Gutsev, B. K. Rao, P. Jena, Xi Li, Lai-Sheng Wang Jan 2000

Experimental And Theoretical Study Of The Photoelectron Spectra Of Mnox-(X=1-3) Clusters, Gennady L. Gutsev, B. K. Rao, P. Jena, Xi Li, Lai-Sheng Wang

Physics Publications

We report a combined experimental and theoretical investigation of MnO−x and MnOx(x=1–3) clusters. Theoretically, geometrical configurations of various isomers of the clusters were optimized and vertical detachment energies for the anions were evaluated. The ground state of MnO− was predicted to be 5Σ+, followed by an excited state (7Σ+) 0.14 eV higher in energy. The ground state of MnO−2 is 5B2, with a 3B1 isomer 0.15 eV higher. MnO−3 is predicted to be a singlet D3h cluster. Vibrationally resolved photoelectron spectra of MnO−x were measured at several photon energies and under various experimental conditions, and were interpreted based on the …

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Theoretical Calculations Of Magnetic Order And Anisotropy Energies In Molecular Magnets, M. R. Pederson, D. V. Porezag, J. Kortus, S. N. Khanna Jan 2000

Theoretical Calculations Of Magnetic Order And Anisotropy Energies In Molecular Magnets, M. R. Pederson, D. V. Porezag, J. Kortus, S. N. Khanna

Physics Publications

We present theoretical electronic structure calculations on the nature of electronic states and the magnetic coupling in the Mn12O12 free cluster and the Mn12O12(RCOO)16(H2O)4 molecular magnetic crystal. The calculations have been performed with the all-electron full-potential NRLMOL code. We find that the free Mn12O12cluster relaxes to an antiferromagneticcluster with no net moment. However, when coordinated by sixteen HCOO ligands and four H2O groups, as it is in the molecular crystal, we find that the ferrimagnetic ordering and geometrical and magnetic structure observed in the experiments is restored. Local Mn moments for the free and ligandated molecular magnets are presented and …

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Structure And Stability Of The Alx And Alx- Species, Gennady L. Gutsev, Puru Jena, Rodney J. Bartlett Jan 1999

Structure And Stability Of The Alx And Alx- Species, Gennady L. Gutsev, Puru Jena, Rodney J. Bartlett

Physics Publications

The electronic and geometrical structures of the ground and low-lying excited states of the diatomic AlX and AlX− series (X=H, Li, Be, B, C, N, O, and F) are calculated by the coupled-cluster method with all singles and doubles and noniterative inclusion of triples using a large atomic natural orbital basis. All the ground-state AlX molecules except for AlF can attach an additional electron and form ground-state AlX− anions. The ground-state AlBe−, AlB−, AlC−, AlN−, and AlO− anions possess excited states that are stable toward autodetachment of an extra electron; AlBe− also has a second excited state. Low-lying excited states …

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