A5062965277- Semiconductor materials and devices
- Advanced Chemical Physics Studies
- Silicon and Solar Cell Technologies
- Semiconductor materials and interfaces
- Surface and Thin Film Phenomena
- Semiconductor Quantum Structures and Devices
- Electron and X-Ray Spectroscopy Techniques
- Advancements in Semiconductor Devices and Circuit Design
- Machine Learning in Materials Science
- Electronic and Structural Properties of Oxides
- Integrated Circuits and Semiconductor Failure Analysis
- Advanced Semiconductor Detectors and Materials
- Molecular Junctions and Nanostructures
- Climate Change Policy and Economics
- Catalytic Processes in Materials Science
- Graphite, nuclear technology, radiation studies
- Atmospheric and Environmental Gas Dynamics
- Nuclear and radioactivity studies
- Diamond and Carbon-based Materials Research
- Nuclear reactor physics and engineering
- Quantum, superfluid, helium dynamics
- ZnO doping and properties
- Thin-Film Transistor Technologies
- History and advancements in chemistry
- Spectroscopy and Quantum Chemical Studies
Sandia National Laboratories
2013-2024
Advanced Device Technology (United States)
2011-2024
Sandia National Laboratories California
2005-2021
Dakota State University
2017
North Dakota State University
2017
ICF International (United States)
2012-2015
National Technical Information Service
2010-2012
Office of Scientific and Technical Information
2010-2012
Oak Ridge National Laboratory
2008-2011
Argonne National Laboratory
2011
Density functional theory (DFT) methods for calculating the quantum mechanical ground states of condensed matter systems are now a common and significant component materials research. The growing importance DFT reflects development sufficiently accurate functionals, efficient algorithms continuing improvements in computing capabilities. As problems to which is applied have become large complex, so sets calculations necessary investigating given problem. Highly versatile, powerful codes exist...
Abstract Modeling and simulation is transforming modern materials science, becoming an important tool for the discovery of new material phenomena, gaining insight into processes that govern behavior, and, increasingly, quantitative predictions can be used as part a design in full partnership with experimental synthesis characterization. essential bridge from good science to engineering, spanning fundamental understanding behavior deliberate technologies leveraging properties processes. This...
We present local density-functional results for structural and electronic properties of ${\mathrm{Al}}_{2}{\mathrm{O}}_{3}(0001)$, clean with Pt Ag adsorption. Significant surface relaxations penetrate to the third oxygen layer, 5.2 \AA{} below surface. The dominant mechanism metal adhesion is polarization relatively weak ( $\ensuremath{\simeq}0.4$ 0.6 eV/atom Pt, respectively); however, isolated atoms bind up $5\ifmmode\times\else\texttimes\fi{}$ as strongly an ionic bond induced by...
Germanium telluride undergoes rapid transition between polycrystalline and amorphous states under either optical or electrical excitation. While the crystalline phases are predicted to be semiconductors, germanium always exhibits -type metallic conductivity. We present a study of electronic structure formation energies vacancy antisite defects in both known phases. show that these intrinsic determine nature free-carrier transport telluride. vacancies require roughly one-third energy other...
Older adults make up 13% of the U.S. population, but are projected to account for 20% by 2040. Coinciding with this demographic shift, rate climate change is accelerating, bringing rising temperatures; increased risk floods, droughts, and wildfires; stronger tropical storms hurricanes; sea levels; other climate-related hazards. Americans expected be located in places that may relatively more affected change, including coastal zones large metropolitan areas.The objective review assess...
Two of the most popular generalized gradient approximations used in applications density functional theory, PW91 and PBE, are generally regarded as essentially equivalent. They produce similar numerical results for many simple properties, such lattice constants, bulk moduli, atomization energies. We examine more complex properties systems with electronic surface regions, specific application monovacancy formation energies Pt Al. A surprisingly large consistent discrepancy between PBE is...
Electronic structure calculations frequently invoke the supercell approximation and solve for electrostatic potentials within periodic boundary conditions. For systems that are electronically charged, or contain dipole (or higher) moments, this artifice introduces spurious due to interactions between system multipole moments of its images in aperiodic directions. I describe a method handle properly electron density electronic using supercells. The is divided into two pieces. A model local...
Quantitative predictions of defect properties in semiconductors using density functional theory have been crippled by two issues: the supercell approximation, which has incorrect boundary conditions for an isolated defect, and approximate functionals, that drastically underestimate band gap. I describe modifications to method incorporate appropriate point defects, identify a common electron reservoir net charge all deal with banding, bulk polarization. The computed level spectrum extended...
The conventional approach to treat charged defects in extended systems first principles calculations is via the supercell approximation using a neutralizing jellium charge. I explicitly show that errors resulting electrostatic potential surface are comparable band gap energy semiconductors, for cell sizes typically used simulations. present method eliminating divergence of Coulomb correctly treats local vicinity defect, mixed boundary condition approach.
The Heyd-Scuseria-Ernzerhof (HSE) density functionals are popular for their ability to improve upon the accuracy of standard semilocal such as Perdew-Burke-Ernzerhof (PBE), particularly semiconductor band gaps. They also have a reduced computational cost compared hybrid functionals, which results from restriction Fock exchange calculations small inter-electron separations. These defined by an overall fraction and length scale screening. We systematically examine this two-parameter space...
The electric power sector both affects and is affected by climate change. Numerous studies highlight the potential of to reduce greenhouse gas emissions. Yet fewer have explored physical impacts change on sector. present analysis examines how projected rising temperatures affect demand for supply electricity. We apply a common set temperature projections three well-known models in United States: US version Global Change Assessment Model (GCAM-USA), Regional Electricity Deployment System...
Abstract Abstract. This study is designed to examine the spatial variability of relationships among global NDVI (Normalized Difference Vegetation Index) data, remotely-sensed land surface temperature and gridded station precipitation data as well investigate potential for combined use bioclimate monitoring. The three variables are examined using single multiple temporal correlations analysis augmented by computation first annual harmonic each parameter. In addition, growing season liming...
We apply density functional theory (DFT) and the DFT+U technique to study adsorption of transition metal porphine molecules on atomistically flat Au(111) surfaces. DFT calculations using Perdew-Burke-Ernzerhof exchange correlation correctly predict palladium (PdP) low-spin ground state. PdP is found adsorb preferentially gold in a geometry, not an edgewise qualitative agreement with experiments substituted porphyrins. It exhibits no covalent bonding Au(111), binding energy small fraction...
This study analyzes the potential impacts of changes in temperature due to climate change on U.S. power sector, measuring energy, environmental, and economic system under two emissions trajectories—with without mitigation. It estimates impact heating cooling degree days, electricity demand, generating unit output efficiency. These effects are then integrated into a dispatch capacity planning model estimate investment decisions, emissions, costs, prices for 32 regions. Without mitigation...
On several metallic substrates, first-principles density-functional calculations of ${\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ 5--7 \AA{} films predict a structure, stabilized by interfacial electrostatics, which has no bulk counterpart. In two and three O-layer films, Al ions prefer distorted tetrahedral sites, over the normal octahedral sites. The film/substrate interface is found to consist strongly chemisorbed oxygen determining factor in geometry; these oxygens are only weakly perturbed...
Other| August 01, 1997 All-atom ab initio energy minimization of the kaolinite crystal structure J. David Hobbs; Hobbs Sandia National Laboratories, Computational Material Sciences Department, Albuquerque, NM, United States Search for other works by this author on: GSW Google Scholar Randall T. Cygan; Cygan Kathryn L. Nagy; Nagy Peter A. Schultz; Schultz Mark P. Sears American Mineralogist (1997) 82 (7-8): 657–662. https://doi.org/10.2138/am-1997-7-801 Article history first online: 02 Mar...
We show that oxygen vacancies are not necessary for the formation of E' centers in amorphous SiO₂ and a single O deficiency can lead to two charge traps. Employing molecular dynamics with reactive potential density functional theory, we generate an ensemble stoichiometric oxygen-deficient atomic structures identify low-energy network defects. Three-coordinated Si atoms appear several defects both O-deficient samples where, addition neutral vacancy, they as isolated
Transportation officials are increasingly faced with challenging decisions about how to design, plan, and manage infrastructure confront changes in climate extreme weather events. An understanding of which impacts affect at what point damage begins occur is a critical step toward assessing overall vulnerability risk. However, few resources exist help managers designers identify key thresholds indicators sensitivity impacts. This paper introduces matrix, tool developed for the U.S. Department...
A massively parallel ab initio computer code, which uses Gaussian bases, pseudopotentials, and the local density approximation, permits study of transition-metal systems with literally hundreds atoms. We present total energies relaxed geometries for Ru, Pd, Ag clusters N=55, 135, 140 The N=55 135 were chosen because simultaneous cubo-octahedral (fcc) icosahedral (icos) subshell closings, we find icos are preferred. Remarkably large compressions central atoms observed structures (up to 6%...
It has been known for over twenty years that rhombohedral c-germanium telluride is predicted to be a narrow gap semiconductor. However, it always displays p-type metallic conduction. This behaviour also observed in other chalcogenide materials, including Ge2Sb2Te5, commonly used optically and electrically switched, non-volatile memory, so of great interest. We present theoretical study the electronic structure perfect crystal formation energies germanium/tellurium vacancy antisite defects...
We report on the development of an accurate first-principles computational scheme for charge transport characteristics molecular monolayer junctions and its application to hexanedithiolate (C6DT) devices. Starting from Gaussian basis set density-functional calculations a junction model in slab geometry corresponding two bulk electrodes, we obtain transmission function using matrix Green's method analyze nature channels via atomic projected density states. Within developed formalism, by...
We report detailed molecular beam studies of the effects K adsorption on dissociative chemisorption probabilities S0 for D2 Pt(111). In contrast to conventional wisdom many other systems, we find that is a very strong poison rather than promoter H2 dissociation. decreases roughly exponentially with coverage ΘK. The effective cross section poisoning per adsorbed varies between 70 and 430 Å2, depending upon incident energy Ei. This suggests an extremely long-range electronic perturbation...
We investigate the structural properties and energy levels of simple intrinsic defects in gallium arsenide. The first-principles calculations (1) apply boundary conditions appropriate to charge supercells enable quantitatively accurate predictions defect transitions with a supercell approximation, (2) are demonstrated be converged respect cell size (3) assess sensitivity model construction Ga pseudopotential (3d core or 3d valence) density functionals (local generalized gradient...