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2002

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Articles 2071 - 2100 of 3435

Full-Text Articles in Physical Sciences and Mathematics

Water Well And Spring Map Of The Harrodsburg 30 X 60 Minute Quadrangle, Kentucky, Bart Davidson Jan 2002

Water Well And Spring Map Of The Harrodsburg 30 X 60 Minute Quadrangle, Kentucky, Bart Davidson

Map and Chart--KGS

No abstract provided.


Water Well And Spring Map Of The Louisville 30 X 60 Minute Quadrangle, Kentucky, Bart Davidson Jan 2002

Water Well And Spring Map Of The Louisville 30 X 60 Minute Quadrangle, Kentucky, Bart Davidson

Map and Chart--KGS

No abstract provided.


Water Well And Spring Map Of The Falmouth, Cincinnati, And Madison 30 X 60 Minute Quadrangles, Kentucky, Bart Davidson Jan 2002

Water Well And Spring Map Of The Falmouth, Cincinnati, And Madison 30 X 60 Minute Quadrangles, Kentucky, Bart Davidson

Map and Chart--KGS

No abstract provided.


Effects Of Surface Morphology On The Anchoring And Electrooptical Dynamics Of Confined Nanoscale Liquid Crystalline Films, Alison Noble, Hye J. Kwon, Ralph G. Nuzzo Jan 2002

Effects Of Surface Morphology On The Anchoring And Electrooptical Dynamics Of Confined Nanoscale Liquid Crystalline Films, Alison Noble, Hye J. Kwon, Ralph G. Nuzzo

Educator Scholarship

The orientation and dynamics of two 40-nm thick films of 4-n-pentyl-4‘-cyanobiphenyl (5CB), a nematic liquid crystal, have been studied using step-scan Fourier transform infrared spectroscopy (FTIR). The films are confined in nanocavities bounded by an interdigitated electrode array (IDA) patterned on a zinc selenide (ZnSe) substrate. The effects of the ZnSe surface morphology (specifically, two variations of nanometer-scale corrugations obtained by mechanical polishing) on the initial ordering and reorientation dynamics of the electric-field-induced Freedericksz transition are presented here. The interaction of the 5CB with ZnSe surfaces bearing a spicular corrugation induces a homeotropic (surface normal) alignment of the …


The Continuum Problem, John Stillwell Jan 2002

The Continuum Problem, John Stillwell

Mathematics

No abstract provided.


Aftershocks And Pore Fluid Diffusion Following The 1992 Landers Earthquake, William Bosl, A Nur Jan 2002

Aftershocks And Pore Fluid Diffusion Following The 1992 Landers Earthquake, William Bosl, A Nur

Nursing and Health Professions Faculty Research and Publications

We model the evolution of regional stress following the 1992 Landers earthquake in order to test the importance of pore fluid flow in producing aftershocks. Rising fluid pressure due to pore fluid flow and the resulting Coulomb stress changes were found to be strongly correlated with the time and location of aftershock events. Regional aftershock frequencies computed by integrating pore pressure decay rates also agreed quite well with aftershock data. Calculations show that regions of rising postseismic poroelastic Coulomb stress overlap considerably with regions of positive coseismic Coulomb stress. Thus pore fluid flow, which affects pore pressure within faults and …


Organic Wheat : A Production Guide, Steven Mccoy Jan 2002

Organic Wheat : A Production Guide, Steven Mccoy

Bulletins 4000 -

Many people believe that organic agriculture systems can only work in high rainfall regions. However, some of Australia’s most successful organic farmers are the experienced organic wheatbelt growers who produce cereal, pulse and oilseed crops in different regions and soil types across the country.

Wheat is the major organic cereal crop grown in Australia - predominantly noodle and breadmaking wheats for export markets.

Farming systems developed by modern organic wheat growers can differ significantly in concept, strategies and techniques from those used by conventional growers. Successful conversion to organic requires careful planning and integration of the whole farming system over …


Spreadsheet Engineering: A Research Framework, Thomas A. Grossman Jr. Jan 2002

Spreadsheet Engineering: A Research Framework, Thomas A. Grossman Jr.

Business Analytics and Information Systems

Spreadsheet engineering adapts the lessons of software engineering to spreadsheets, providing eight principles as a framework for organizing spreadsheet programming recommendations. Spreadsheets raise issues inadequately addressed by software engineering. Spreadsheets are a powerful modeling language, allowing strategic rapid model change, and enabling exploratory modeling. Spreadsheets users learn slowly with experience because they focus on the problem domain not programming. The heterogeneity of spreadsheet users requires a taxonomy to guide recommendations. Deployment of best practices is difficult and merits research.


Atomization Energies And Enthalpies Of Formation Of The Snbin (N=1-3) Gaseous Molecules By Knudsen Cell Mass Spectrometry, Giovanni Meloni, Karl A. Gingerich Jan 2002

Atomization Energies And Enthalpies Of Formation Of The Snbin (N=1-3) Gaseous Molecules By Knudsen Cell Mass Spectrometry, Giovanni Meloni, Karl A. Gingerich

Chemistry Faculty Publications

The equilibria involving the gaseous species SnBi, SnBi2, and SnBi3 above the condensed system Bi–Sn contained in a graphite cell have been investigated by the Knudsen effusion technique combined with mass spectrometry. Third law enthalpies for the reactionsSnBin(g)=Sn(cond)+nBi(g), n=1–3, were evaluated. By combining the experimental reactionenthalpies with the appropriate thermodynamic data taken from literature, the following atomization energies, ΔaHo0, and enthalpies of formation,ΔfHo298.15, in kJ mol−1, have been derived: SnBi, 191.1±12.0 and 317.5±12.0; SnBi2, 415.2±15.0 and 303.0±15.0; SnBi3, 603.4±18.0 and 323.0±18.0.


Photoelectron Spectroscopy Of Clh2 - And Cld2 -: A Probe Of The Cl+H2 Van Der Waals Well And Spin-Orbit Excited States, Michael J. Ferguson, Giovanni Meloni, Harry Gomez, D M. Neumark Jan 2002

Photoelectron Spectroscopy Of Clh2 - And Cld2 -: A Probe Of The Cl+H2 Van Der Waals Well And Spin-Orbit Excited States, Michael J. Ferguson, Giovanni Meloni, Harry Gomez, D M. Neumark

Chemistry Faculty Publications

Photoelectron (PE) spectra of ClH−2 and ClD−2 were measured at 299 nm (4.154 eV). Photodetachment of these anions accesses the prereactive van der Waals well on the ground stateCl+H2potential energy surface, as well as the low-lying spin–orbit excited states resulting from the interaction of Cl and Cl* with H2. The PE spectra are dominated by two relatively narrow peaks corresponding to transitions to the neutral Cl⋅H2 and Cl*⋅H2 complexes. The energetics and widths of these features are interpreted in terms of the properties of the anion and neutral potential energy surfaces.


Experimental And Computational Study Of The New Gaseous Molecules Omnf And Omnf[Sub 2], G Balducci, M Campodonico, G Gigli, Giovanni Meloni, S N. Cesaro Jan 2002

Experimental And Computational Study Of The New Gaseous Molecules Omnf And Omnf[Sub 2], G Balducci, M Campodonico, G Gigli, Giovanni Meloni, S N. Cesaro

Chemistry Faculty Publications

The new gaseous species OMnF and OMnF2 were identified and studied by high-temperature Knudsen Cell Mass Spectrometry. Their thermochemical atomization energies were derived through the study of several all-gas equilibria in the temperature range 1735–1913 K. FTIR matrix isolation experiments together with ab initio and density functional calculations were performed to determine the molecular parameters, bond distances, and vibrational frequencies of OMnF(g) and OMnF2(g) . The results allowed us to evaluate a set of thermal functions for the new species that were used in the evaluation of the equilibrium data. The proposed atomization energies and enthalpies of formation are DaH0 …


Modis Snow-Cover Products, Dorothy K. Hall, George A. Riggs, Vincent V. Salomonson, Nicolo E. Digirolamo, Klaus J. Bayr Jan 2002

Modis Snow-Cover Products, Dorothy K. Hall, George A. Riggs, Vincent V. Salomonson, Nicolo E. Digirolamo, Klaus J. Bayr

United States National Aeronautics and Space Administration: Publications

On December 18, 1999, the Terra satellite was launched with a complement of five instruments including the Moderate Resolution Imaging Spectroradiometer (MODIS). Many geophysical products are derived from MODIS data including global snow-cover products. MODIS snow and ice products have been available through the National Snow and Ice Data Center (NSIDC) Distributed Active Archive Center (DAAC) since September 13, 2000. MODIS snow-cover products represent potential improvement to or enhancement of the currently available operational products mainly because the MODIS products are global and 500-m resolution, and have the capability to separate most snow and clouds. The MODIS snow-mapping algorithms are …


Early Spatial And Temporal Validation Of Modis Lai Product In The Southern Africa Kalahari, J. L. Privette, R. B. Myneni, Y. Knyazikhin, M. Mukelabai, G. Roberts, Y. Tian, Y. Wang, S. G. Leblanc Jan 2002

Early Spatial And Temporal Validation Of Modis Lai Product In The Southern Africa Kalahari, J. L. Privette, R. B. Myneni, Y. Knyazikhin, M. Mukelabai, G. Roberts, Y. Tian, Y. Wang, S. G. Leblanc

United States National Aeronautics and Space Administration: Publications

We evaluate the operational MODIS Leaf Area Index (LAI) product using field-sampled data collected at five sites in southern Africa in March 2000. One site (Mongu, Zambia) was sampled monthly throughout the year. All sites were along the International Geosphere Biosphere Programme’s (IGBP) Kalahari Transect, which features progressively lower annual precipitation, and hence, lower vegetation productivity, from north to south. The soils are consistently sandy. At each site, we sampled the vegetation overstory along three 750-m transects using the Tracing Radiation and Architecture in Canopies (TRAC) instrument. The resulting plant area index values were adjusted with ancillary stem area data …


Global Products Of Vegetation Leaf Area And Fraction Absorbed Par From Year One Of Modis Data, R. B. Myneni, S. Hoffman, Y. Knyazikhin, J. L. Privette, J. Glassy, Y. Tian, Y. Wang, X. Song, Y. Zhang, G. R. Smith, A. Lotsch, M. Friedl, J. T. Morisette, P. Votava, R. R. Nemani, S. W. Running Jan 2002

Global Products Of Vegetation Leaf Area And Fraction Absorbed Par From Year One Of Modis Data, R. B. Myneni, S. Hoffman, Y. Knyazikhin, J. L. Privette, J. Glassy, Y. Tian, Y. Wang, X. Song, Y. Zhang, G. R. Smith, A. Lotsch, M. Friedl, J. T. Morisette, P. Votava, R. R. Nemani, S. W. Running

United States National Aeronautics and Space Administration: Publications

An algorithm based on the physics of radiative transfer in vegetation canopies for the retrieval of vegetation green leaf area index (LAI) and fraction of absorbed photosynthetically active radiation (FPAR) from surface reflectances was developed and implemented for operational processing prior to the launch of the moderate resolution imaging spectroradiometer (MODIS) aboard the TERRA platform in December of 1999. The performance of the algorithm has been extensively tested in prototyping activities prior to operational production. Considerable attention was paid to characterizing the quality of the product and this information is available to the users as quality assessment (QA) accompanying the …


Multiscale Analysis And Validation Of The Modis Lai Product, Yuhong Tian, Curtis E. Woodcock, Yujie Wang, Jeff L. Privette, Nikolay V. Shabanov, Liming Zhou, Yu Zhang, Wolfgang Buermann, Jiarui Dong, Brita Veikkanen, Tuomas Häme, Kaj Andersson, Mutlu Ozdogan, Yuri Knyazikhin, Ranga B. Myneni Jan 2002

Multiscale Analysis And Validation Of The Modis Lai Product, Yuhong Tian, Curtis E. Woodcock, Yujie Wang, Jeff L. Privette, Nikolay V. Shabanov, Liming Zhou, Yu Zhang, Wolfgang Buermann, Jiarui Dong, Brita Veikkanen, Tuomas Häme, Kaj Andersson, Mutlu Ozdogan, Yuri Knyazikhin, Ranga B. Myneni

United States National Aeronautics and Space Administration: Publications

The development of appropriate ground-based validation techniques is critical to assessing uncertainties associated with satellite databased products. In this paper, the second of a two-part series, we present a method for validation of the Moderate Resolution Imaging Spectroradiometer Leaf Area Index (MODIS LAI) product with emphasis on the sampling strategy for field data collection. Using a hierarchical scene model, we divided 30-m resolution LAI and NDVI images from Maun (Botswana), Harvard Forest (USA) and Ruokulahti Forest (Finland) into individual scale images of classes, region and pixel. Isolating the effects associated with different landscape scales through decomposition of semivariograms not only …


Energy Balance Closure At Fluxnet Sites, Kell Wilson, Allen Goldstein, Eva Falge, Marc Aubinet, Dennis D. Baldocchi, Paul Berbigier, Christian Bernhofer, Reinhart Ceulemans, Han Dolman, Chris Field, Achim Grelle, Andreas Ibrom, B. E. Law, Andy Kowalski, Tilden Meyers, John Moncrieff, Russ Monson, Walter Oechel, John Tenhunen, Shashi Verma, Riccardo Valentini Jan 2002

Energy Balance Closure At Fluxnet Sites, Kell Wilson, Allen Goldstein, Eva Falge, Marc Aubinet, Dennis D. Baldocchi, Paul Berbigier, Christian Bernhofer, Reinhart Ceulemans, Han Dolman, Chris Field, Achim Grelle, Andreas Ibrom, B. E. Law, Andy Kowalski, Tilden Meyers, John Moncrieff, Russ Monson, Walter Oechel, John Tenhunen, Shashi Verma, Riccardo Valentini

School of Natural Resources: Faculty Publications

A comprehensive evaluation of energy balance closure is performed across 22 sites and 50 site-years in FLUXNET, a network of eddy covariance sites measuring long-term carbon and energy fluxes in contrasting ecosystems and climates. Energy balance closure was evaluated by statistical regression of turbulent energy fluxes (sensible and latent heat (LE)) against available energy (net radiation, less the energy stored) and by solving for the energy balance ratio, the ratio of turbulent energy fluxes to available energy. These methods indicate a general lack of closure at most sites, with amean imbalance in the order of 20%. The imbalance was prevalent …


Vadose Zone Processes And Chemical Transport, H. M. Gaber, Steven Comfort, Patrick J. Shea, Thomas A. Machacek Jan 2002

Vadose Zone Processes And Chemical Transport, H. M. Gaber, Steven Comfort, Patrick J. Shea, Thomas A. Machacek

School of Natural Resources: Faculty Publications

Permeable zerovalent iron (Fe0) barriers have become an estab- lished technology for remediating contaminated ground water. This same technology may be applicable for treating pesticides amenable to dehalogenation as they move downward in the vadose zone. By conducting miscible displacement experiments in the laboratory with metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide; a chloroacetanilide herbicide] under unsaturated flow, we provide proof-of-concept for such an approach. Transport experiments were conducted in repacked, unsaturated soil columns attached to vacuum chambers and run under constant matrix potential (-30 kPa) and Darcy flux (approximately 2 cm d-1 ). Treatments included soil …


Land Surface Dynamics In Kazakhstan: Dynamic Baselines And Change Detection, Geoffrey M. Henebry, Kirsten M. De Beurs, Anatoly A. Gitelson Jan 2002

Land Surface Dynamics In Kazakhstan: Dynamic Baselines And Change Detection, Geoffrey M. Henebry, Kirsten M. De Beurs, Anatoly A. Gitelson

School of Natural Resources: Faculty Publications

Analysis of the spatio-temporal structure of NDVI in the Pathfinder AVHRR Land data set for Kazakhstan from 1981-1999 reveals significant changes in the distributions of the scale of fluctuation (SOF) before and after 1992 in some ecoregions at certain phases of the growing season. These differences are likely due to actual influences on the land surface and not changes in sensor characteristics. Further analysis is required to identify and quantify these influences.


Wood Thrush Movements And Habitat Use: Effects Of Forest Management For Red-Cockaded Woodpeckers, Jason Lang, Larkin A. Powell, David Krementz, Michael J. Conroy Jan 2002

Wood Thrush Movements And Habitat Use: Effects Of Forest Management For Red-Cockaded Woodpeckers, Jason Lang, Larkin A. Powell, David Krementz, Michael J. Conroy

School of Natural Resources: Faculty Publications

We monitored adult and juvenile breeding-season movements and habitat use of radio-tagged Wood Thrushes (Hylocichla mustelina) at the Piedmont National Wildlife Refuge, central Georgia, USA. We investigated the effects that management for Red-cockaded Woodpeckers (Picoides borealis), thinning and burning >30 year old loblolly pine (Pinus taeda) habitat, had on Wood Thrushes, a ground-foraging and midstory-nesting species. Adult Wood Thrush pairs regularly moved long distances between nesting attempts (range 1 to 17,388 m). The only experimental effect we found on adult movements was a decrease in weekly emigration rates (AP) from thinned and burned compartments …


Realtime Data Filtering Models For Air Temperature Measurements, Kenneth G. Hubbard, X. Lin Jan 2002

Realtime Data Filtering Models For Air Temperature Measurements, Kenneth G. Hubbard, X. Lin

School of Natural Resources: Faculty Publications

Air temperature measurement biases caused by solar radiation and ambient wind speed are well-known. However, realtime air temperature filtering models are essential for generating homogeneous climate data by transforming one air temperature measurement system into another, and correcting in-situ air temperature biases especially for non-aspirated radiation shield systems. This study investigated the air temperature biases caused in the commonly used radiation shields in the United States, including the ASOS, MMTS, Gill, CRS, ASP-ES, and NON-ASPES shields along with corresponding temperature sensors. The realtime air temperature filtering models developed for each air temperature system are capable of removing the solar radiation …


Novel Algorithms For Remote Estimation Of Vegetation Fraction, Anatoly A. Gitelson, Yoram J. Kaufman, Robert Stark, Don Rundquist Jan 2002

Novel Algorithms For Remote Estimation Of Vegetation Fraction, Anatoly A. Gitelson, Yoram J. Kaufman, Robert Stark, Don Rundquist

School of Natural Resources: Faculty Publications

Spectral properties of a wheat canopy with vegetation fraction (VF) from 0% to 100% in visible and near-infrared (NIR) ranges of the spectrum were studied in order to devise a technique for remote estimation of VF. When VF was < 60%, from emergence till middle of the elongation stage, four distinct, and quite independent, spectral bands of reflectance existed in the visible range of the spectrum: 400 to 500 nm, 530 to 600 nm, near 670 nm, and around 700 nm. When VF was between 60% and 100%, reflectance in the NIR leveled off or even decreases with an increase of VF. The decreased reflectance in the NIR, occurring at or near the midseason, can be a limiting factor in the use of that spectral region for VF estimation. It was found that for VF > 60%, the information content of reflectance spectra in visible range can be expressed by only two independent pairs of spectral bands: (1) the blue from 400 to 500 nm and the red near 670 nm; (2) the green around 550 nm and the red edge region near 700 nm. We propose using only the visible range of the spectrum to quantitatively …


Geomorphology’S Role In The Study Of Weathering Of Cultural Stone, Gregpry A. Pope, Thomas R. Paradise, Thomas Meierding Jan 2002

Geomorphology’S Role In The Study Of Weathering Of Cultural Stone, Gregpry A. Pope, Thomas R. Paradise, Thomas Meierding

Department of Earth and Environmental Studies Faculty Scholarship and Creative Works

Great monumental places—Petra, Giza, Angkor, Stonehenge, Tikal, Macchu Picchu, Rapa Nui, to name a few—are links to our cultural past. They evoke a sense of wonderment for their aesthetic fascination if not for their seeming permanence over both cultural and physical landscapes. However, as with natural landforms, human constructs are subject to weathering and erosion. Indeed, many of our cultural resources suffer from serious deterioration, some natural, some enhanced by human impact. Groups from the United Nations to local civic and tourism assemblies are deeply interested in maintaining and preserving such cultural resources, from simple rock art to great temples. …


Effect Of Ga Content On Defect States In Cuin1-XGaXSe2 Photovoltaic Devices, Jennifer T. Heath, J. David Cohen, William N. Shafarman, Dongxiang Liao, Angus Rockett Jan 2002

Effect Of Ga Content On Defect States In Cuin1-XGaXSe2 Photovoltaic Devices, Jennifer T. Heath, J. David Cohen, William N. Shafarman, Dongxiang Liao, Angus Rockett

Faculty Publications

Defects in the band gap of CuIn1-xGaxSe2 have been characterized using transient photocapacitance spectroscopy. The measured spectra clearly show response from a band of defects centered around 0.8 eV from the valence band edge as well as an exponential distribution of band tail states. Despite Ga contents ranging from Ga/(In+Ga)=0.0 to 0.8, the defect bandwidth and its position relative to the valence band remain constant. This defect band may act as an important recombination center, contributing to the decrease in device efficiency with increasing Ga content.


Western Australia Soil Acidity Research And Development Update 2002 : Time To Lime, Department Of Agriculture And Food, Western Australia Jan 2002

Western Australia Soil Acidity Research And Development Update 2002 : Time To Lime, Department Of Agriculture And Food, Western Australia

Bulletins 4000 -

The Soil Acidity Research, Development and Extension Project has produced a summary of the activities, research results and recommendations each year and this book is the last in a series of seven.

The Department of Agriculture Western Australia, The University of Western Australia and CSIRO have supported the project with industry funds from The Grains Research and Development Corporation (GRDC) and The Natural Heritage Trust (NHT).

The high level of funding for soil acidity research, development and extension comes to an end in June 2002. It is now time for the management of soil acidity to be part of all …


An Adaptive, Kink-Based Approach To Path Integral Calculations, Randal W. Hall Jan 2002

An Adaptive, Kink-Based Approach To Path Integral Calculations, Randal W. Hall

Collected Faculty and Staff Scholarship

A kink-based expression for the canonical partition function is developed using Feynman’s path integral formulation of quantum mechanics and a discrete basis set. The approach is exact for a complete set of states. The method is tested on the 3×3 Hubbard model and overcomes the sign problem seen in traditional path integral studies of fermion systems. Kinks correspond to transitions between different N-electron states, much in the same manner as occurs in configuration interaction calculations in standard ab initio methods. The different N-electron states are updated, based on which states occur frequently during a Monte Carlo simulation, giving better estimates …


The Science Studio – A Workshop Approach To Introductory Physical Science, S. R. Chaudhury Jan 2002

The Science Studio – A Workshop Approach To Introductory Physical Science, S. R. Chaudhury

Journal of Mathematics and Science: Collaborative Explorations

This paper describes the Science Studio, an innovative workshop approach for instruction in a physical science course that combines aspects of traditional lecture and laboratory. The target audience for this introductory course is non-science majors, including prospective teachers. An inquiry-based, technology-rich learning environment has been created to allow students hands-on, in-depth exploration of topics in physics, and earth and space science. Course philosophy, course development, and sample activities are described in this paper, along with outcomes from a project-wide evaluation of the Virginia Collaborative for Excellence in the Preparation of Teachers (VCEPT), an investigation of change in student attitudes and …


A Future Teachers Conference – A Vehicle To Retain, Inform, And Inspire New And Prospective Teachers, J. Kasabian, L. Fathe, J. M. Dewar Jan 2002

A Future Teachers Conference – A Vehicle To Retain, Inform, And Inspire New And Prospective Teachers, J. Kasabian, L. Fathe, J. M. Dewar

Journal of Mathematics and Science: Collaborative Explorations

The Los Angeles Collaborative for Teacher Excellence (LACTE) Future Teachers Conference is a day-long learning event for beginning and pre-service K-12 math and science teachers. The Conference provides information, resources and connections tailored to the needs of prospective and new teachers. A unique aspect of the conference is that a group of new and future teachers serve as partners with college faculty on the planning committee. Thus the Conference not only serves to educate new and future teachers, but also provides leadership training for the planning team members; and, the presence of prospective and new teachers on the planning team …


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.


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.


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. …