... agencies for Research Development Test and Evaluation ... a detailed comparison between ab initio and ... configurations is performed, testing in this ...
DTIC Science & Technology
Ab Initio calculations for defects and impurities in elemental and compound semiconductors Characterization of defects and impurities in compound semiconductors Modeling of...
Science.gov Websites
Ab-initio quantum chemical computations have been applied to a set of molecular clusters derived from Si5H12 to model defects in crystalline silicon involving boron, carbon, nitrogen, oxygen, and hydrogen. In computations of defect structure, hydrogen ato...
National Technical Information Service (NTIS)
Research completed during the period 1 Feb. 1990 - 28 Feb. 1994 is summarized in the following included papers: 'Ab Initio Statistical Mechanics of Structural Phase Transition'; 'Ab Initio Molecular Dynamics: Analytically Continued Energy Functionals and Insights into Iterative Solutions'; 'Ab ...
NASA Astrophysics Data System (ADS)
Ab initio supercell calculations of the binding energies predict complex formation between aluminum and carbon interstitials in SiC. In high-energy implanted SiC aluminum acceptor can form very stable complexes with two carbon interstitials. We also show that carbon vacancy can be attached to shallow aluminum acceptor. All of these ...
The stability of He in hcp-Ti was studied using ab initio method based on density functional theory. The results indicate that a single He atom prefers to occupy the tetrahedral site rather than the octahedral site. The interaction of He defects with Ti atoms has been used to explain the relative stabilities of He point ...
Energy Citations Database
Atomistic and ab initio methods are used to study structural and electronic properties of perfect and defective chalcopyrites, specifically, ZnGeP2 and CdGeAs2. These materials are important due to their suitability for nonlinear optical applications in t...
We report the results of a large-scale ab initio simulation of an intergranular glassy film (IGF) model in ?-Si3N4. It is shown that the stress-strain behavior under uniaxial load in the model with prismatic surfaces and few defective bonds is very different from an earlier IGF model with basal planes. The results are explained by the ...
Point defects in Fe and dilute FeCu alloys are investigated by ab initio calculations based on density functional theory. The relaxed vacancy and interstitial and substitutional Cu atom formation energies are determined as well as some migration energies. The binding energies of various Cu containing defects ...
... This study involves: Ab-initio crystal orbitals and polymer orbitals; Ab-initio coupled cluster program; Ab-initio quantum chemical calculations and ...
This bibliography lists the following reports: Optimized pseudopotentials, Ab-initio materials science and engineering using the molecular dynamics methods for total energy pseudopotential calculations, Oxygen complexes in Si, The enchanting properties of...
of BN Armchair and Zigzag Nanoarch Surfaces," S. Guerini, V. Lemos, P. Piquini. Nanotechnology 17, 556 (2006). "Formation Energy of Native Defects in BN Nanotubes: An ab initio...
National Renewable Energy Laboratory (NREL)
... positions signifi- F cantly affects the ab initio quantum chemical calculations or DDF = gk(R) O = (1/ FN,j)Nk(R)J I/d V, the PIXEL ...
Uranium (U), with the addition of small amount of niobium (Nb), is stainless. The Nb is fully miscible with the high temperature phase of U and tends to segregate upon cooling below 647 C. The starting point of segregation is the configuration of Nb subst...
... Title : Chalcopyrite Magnetic Semiconductors: An Ab-Initio Study of Their Structural, Electronic and Magnetic Properties. ...
... from federally funded research, testing and training ... for Research Development Test and Evaluation ... COMPENDIUM OF AB INITIO CALCULATIONS ...
... Accession Number : ADA219907. Title : An Ab Initio Study of the Geometry and Rotational Barrier of 4- Phenylimidazole. ...
... from federally funded research, testing and training ... and agencies for Research Development Test and Evaluation ... Title : Ab Initio Calculations of the ...
... Title : Ab Initio Calculation of Vibrational Absorption and Circular Dichroism Spectra Using Density Functional Force Fields. ...
... Title : AB Initio Quantum Chemical Investigations of Solubilities in Supercritical Solutions. Descriptive Note : Conference Paper,. ...
By use of ab initio density-functional total-energy calculations a point defect with a negative Hubbard U is identified, for the first time, in a chalcogenide system. It is found that in c-As2Se3 two non-interacting neutral Se antisite defects are unstabl...
We have investigated the influence of a variety of dimer vacancy defects on the reactivity of F2 molecules with the clean Si(100)-2 x 1 reconstructed surface via molecular dynamics using an ab-initio-derived Stillinger-Weber-type many-body potential. Our ...
Large-scale ab initio molecular dynamics simulations of ion-solid interactions in SiC reveal that significant charge transfer occurs between atoms, and defects can enhance charge transfer to surrounding atoms. The results demonstrate that charge transfer to and from recoiling atoms can alter the energy barriers and dynamics for stable ...
We have studied the energetics and charge tranfer of the (10,0) and (6,6) single walled carbon nanotubes with various defects such as monovacancy and Stone-Wales defect and their interaction with the Hydrogen Sulphide gas molecule using Ab Initio based computational method to design Single Walled Carbon Nanotube ...
Ab initio calculations based on density functional theory have been performed to determine the properties of self-interstitial atoms (SIAs), vacancies, and single H and He atoms in hcp-Er. The results show that the most stable configuration for a SIA is a basal octahedral configuration, while the octahedral (O), basal split, and crowdion (C) interstitial ...
The stability of the B2 CuxFe1?x Al phases and the energy of defect formation are studied using ab initio band calculations. For B2 CuxFe1?x Al alloys, vacancies in the 3d-metal sublattice and configurations with the minimum number of Fe-Cu bonds in the first coordination shell (including Fe antisite defects, which ...
... Title : AB Initio Study of the Electronic Magnetic Circular Dichroism ... functions are determined using as initio quantum chemical techniques including ...
Due to recent advances in methods and computers, the accuracy of ab calculations has reached a point
NASA Technical Reports Server (NTRS)
It is essential to know the arrangement of the atoms in a material in order to compute and understand its properties. Searching for stable structures of materials using first-principles electronic structure methods, such as density-functional-theory (DFT), is a rapidly growing field. Here we describe our simple, elegant and powerful approach to searching for structures with DFT, which we call ...
We identify the binding sites for adsorption of a single Ge atom on the Si(100) surface using ab initio total energy calculations. The calculated diffusion barriers are in excellent agreement with experimental estimates. Using a large supercell we resolve the controversy regarding the binding geometry and migration path for the adatom, and investigate the ...
DOE Information Bridge
PubMed
The atomic-scale processes that control the formation of carbon deposits on Ni catalysts in reforming applications are poorly understood. Ab initio Density Functional Theory calculations have been used to examine several key elementary steps in the complex network of chemical reactions that precedes carbon formation on practical catalysts. Attention has ...
Ab initio density functional theory calculations are carried out in order to predict the evolution of structural materials under aggressive working conditions such as cases with exposure to corrosion and irradiation, as well as to predict and investigate the properties of functional materials for photovoltaic energy applications. Structural metallic ...
The performance of high resolution semiconductor based radiation detectors at room temperature is hindered by intrinsic defects and accidental impurities. Experimental efforts to improve the properties of such materials are both time consuming and expensive, since they rely to a large extent on trial and error. In this talk, we show how a fully ab-initio ...
Based on ab initio density-functional calculations in supercells of 3C-SiC, the stable configurations of hydrogen and dihydrogen defects have been established. The calculated formation energies are used to give semiquantitative estimates for the concentration of hydrogen in SiC after chemical vapor deposition, low temperature H-plasma ...
An algorithm based on the quantum defect theory is proposed for computing the dynamic polarizability tensor for polar molecules. The algorithm makes use of ab initio methods developed for ground and lowlying electronic states. The computed refractive index and scattered-light depolarization coefficient for gaseous nitric oxide are in ...
The electronic and ionic structure of primary defects in silicon carbide (SiC) is studied using ab-initio plane-wave pseudopotential methods. The studied effects include the carbon and silicon vacancy, the silicon and carbon antisite, the antistructure-pa...
We find that quantum size effects not only play an important role in the electronic properties of defects in semiconductor nanocrystals, but also strongly affect the incorporation of defect atoms into the nanocrystals. In particular, using ab initio methods based on density functional theory, we predict that Mn ...
We have investigated by means of ab initio calculations the structural and electronic properties of hydrogenated graphene structures with distinct grain boundary defects. Our total energy results reveal that the adsorption of a single H is more stable at defect. Further total energy calculations indicate that the ...
We investigate chemical functionalization of graphene by carboxyl (COOH) groups using first principles computational methods. The binding energies and equilibrium geometries of COOH groups covalently attached to graphene clusters with no surface defects, Stone-Wales defects, and vacancies are examined in the framework of density functional theory combined ...
We investigate the mechanism of covalent sidewall functionalization of carbon nanotubes with carboxyl groups using first principles computational methods. The binding energies and equilibrium geometries of carboxylated nanotubes with no surface defects, Stone-Wales defects and vacancies are calculated in the framework of density functional theory combined ...
... AB-INITIO SIMULATION OF a/2110> ... 4. TITLE AND SUBTITLE AB-INITIO SIMULATION OF a/2110> SCREW DISLOCATIONS γ-TiAl 5c. ...
... ADP012740 TITLE: Ab Initio Study on Spin Polarization of III-V Compound Tips ... Ab initio study on spin polarization of III-V compound tips ...
Ab initio electronic structure methods can supplement CALPHAD in two major ways for subsequent applications to stability in complex alloys. The first one is rather immediate and concerns the direct input of ab initio energetics in CALPHAD databases. The o...
...with this part. The certificate shall be void ab initio for those vehicles causing the...issued, and the certificate may be deemed void ab initio. (C) The manufacturer...with this part. The certificate shall be void ab initio for those vehicles causing...
Code of Federal Regulations, 2010
We computed the Raman spectrum of amorphous GeTe by ab initio simulations and empirical bond polarizability models. The calculated spectrum is in very good agreement with experimental data and contains the signatures of all the peculiar local structures of the amorphous phase revealed by recent ab initio ...
The nature of deep defect states, in general, and those associated with group III elements (Ga, In, Tl) in narrow band-gap IV-VI semiconductors (PbTe and PbSe), in particular, have been of great interest over the past three decades. We present ab initio electronic structure calculations that give a new picture of these states compared ...
We report what is to our knowledge the first ab initio study of the singly charged divacancy in silicon to make direct comparison with mechanical response experiments. This novel approach, which does not rely upon energy differences which have proven to be too small to resolve reliably within the uncertainties of the local spin-density approximation ...
We present the results of ab initio calculations of several intrinsic and oxygen-containing defects in CaF2 including an F center, a substitutional O- ion, an O2--vacancy dipole, and FA(O2-) and F2A+(O2-) centers. The calculations have been performed using a hybrid density functional and an embedded cluster method. The calculated ...
By modeling ?-Zn4Sb3 material as a Zn36Sb30 crystal with defects, the crystal structure and thermal properties of ?-Zn4Sb3 are studied by ab initio method to explain its extremely low thermal conductivity at moderate temperature. The formation and migration energies of defects are calculated and used to explain the ...
The reduced-added Green's function technique in the quantum defect theory combines the advantages of analytical and ab initio methods in calculating frequency-dependent (dynamic) polarizabilities of atoms and molecules, providing an exact account for the high-excited and continuum electronic states. In the present paper this ...
Molybdenum's and tantalum's high strength and high-temperature stability makes these refractory metals very attractive for use in advanced process technologies; however, the pure metals are very brittle. To describe plastic deformation requires knowledge of how dislocations--the defects responsible for crystal plasticity--evolve under stress. A classical potential for ...
We report an ab initio study of Pb antisite defects in PbZrO{sub 3} (PZ) and Pb(Zr,Ti)O{sub 3} (PZT) perovskites. Also, we calculated the enthalpy of formation of PZ. Our results show that, under strong oxidizing conditions, Pb on the Zr-site antisite defects are unavoidable in PZ. Moreover, a positive enthalpy of ...
The phase stabilities of Y2Ti2O7 and Y2Zr2O7 under high pressure were investigated by ab initio methods. Pyrochlore-structured Y2Ti2O7 and defect-fluorite Y2Zr2O7 exhibit different responses to high pressure. Both the defect-fluorite and defect-cotunnite structures are energetically more stable ...
The reconstruction process of vacancy hole in carbon nanotube is investigated by tight-binding molecular dynamics simulations and by ab initio total energy calculations. In the molecular dynamics simulation, a vacancy hole is found to reconstruct into two separated pentagon-heptagon pair defects. As the result of reconstruction, the ...
... ADP023770. Title : ab-Initio Molecular Dynamics Simulations of Molten Ni-Based Superalloys. Descriptive Note : Conference paper. ...
... from federally funded research, testing and training ... for Research Development Test and Evaluation ... of Molecular Modelling and Ab initio Molecular ...
... from federally funded research, testing and training ... agencies for Research Development Test and Evaluation ... Title : New AB Initio Based Density ...
... from federally funded research, testing and training ... for Research Development Test and Evaluation ... Title : Development of Ab-initio Multibody ...
... Ab initio Energies Calculated Using 3 ... of the Transition States (TS ... Descriptors : *TRANSITIONS, *MOLECULES, COMPUTATIONS, COMPARISON ...
... Abstract : Results are presented from ab initio quantum chemical calculations on the ground state potential energy surface for the open shell ...
... from federally funded research, testing and training ... and agencies for Research Development Test and Evaluation ... Title : An Ab Initio Study of Solid ...
... from federally funded research, testing and training ... agencies for Research Development Test and Evaluation ... Title : An AB Initio Study of Dimethyl ...
... Accession Number : ADA523968. Title : Ab-initio Simulations of Molten Ni Alloys. Descriptive Note : Journal article (preprint). ...
... Title : Ab-Initio Molecular Dynamics Simulations of Molten Ni-Based Superalloys. Descriptive Note : Conference paper (preprint). ...
... from federally funded research, testing and training ... for Research Development Test and Evaluation ... Title : Ab-Initio Molecular Dynamics Simulations ...
... We carried out ab-initio quantum chemical calculations on these energetic cyclic ethers and generated the electrostatic molecular potential contour ...
Ab initio quantum chemical techniques have been used to investigate weakly bund complexes of H20 and SO2. An energy gradient program was used to ...
NASA Website
... Accession Number : ADA351780. Title : Ab Initio and DFT Potential Energy Surfaces for Cyanuric Chloride Reactions. Descriptive Note : Final rept. ...
... Ab initio study on atomic structures and physical properties of CdSe quantum nanodots ... Figure 2. Diagram of covered nanodots. ...
... Title : Ab Initio Study on Atomic Structures and Physical Properties of CdSe Quantum Nanodots. Descriptive Note : Final rept. ...
... from federally funded research, testing and training ... agencies for Research Development Test and Evaluation ... Title : Ab Initio Study of the Structure ...
... Rydberg I 'Flu state. Demoulin and Jungen (1974) used an ab initio quantum chemical approach, but only at the SCF level ...
... moment has been cancelled a priori for the electronic transition as a function of R(CC), using ab initio quantum chemical techniques including state ...
... from federally funded research, testing and training ... and agencies for Research Development Test and Evaluation ... Title : Ab Initio Study of Ultracold ...
1 AB INITIO STUDIES ON HEXAVALENT PHOSPHORUS COMPOUNDS Ashley L. Wilson* Aberdeen High School Aberdeen, Maryland 21001 ...
... Accession Number : ADA436055. Title : Ab Initio Studies on Hexavalent Phosphorus Compounds. Descriptive Note : Conference paper. ...
... from federally funded research, testing and training ... agencies for Research Development Test and Evaluation ... Title : Ab Initio Relativistic Study of ...
... Accession Number : ADA440631. Title : Ab Initio Quantum Chemical Study of Electron Transfer in Carboranes. Descriptive Note : Journal article. ...
... Accession Number : ADA270577. Title : Ab Initio Potential Energy Surface for the H + OCS Reaction. Descriptive Note : Final rept. ...
... [2"- ARMY RESEARCH LABORATORY [C Ab Initio Potential Energy Surface for H + OCS Reactions: Extended Basis Sets ...
... Results of this study substantiate findings from an earlier quantum chemical study using a lower ... for (I) and (II) based on the earlier ab initio study. ...
... Ab initio direct trajectory simulation on hydrogen atom transfer in 7-azaindole in the electronic excited state with assist of water molecules ...
... from federally funded research, testing and training ... for Research Development Test and Evaluation ... Title : Ab Initio Direct Trajectory Simulation on ...
... Title : Ab Initio Calculation of Vibrational Circular Dichroism Spectra Using Accurate Post-Self-Consistent-Field Force Fields: trans-2,3 ...
... from federally funded research, testing and training ... for Research Development Test and Evaluation ... Title : Ab Initio Calculation of Intermolecular ...
... from federally funded research, testing and training ... agencies for Research Development Test and Evaluation ... Title : AB Initio Propagator Theory of ...
The formation energies and the equilibrium concentration of vacancies, interstitial H, K, P, O and antisite structural defects with P and K in KH2PO4 (KDP) crystals are investigated by ab initio total-energy calculations. The formation energy of interstitial H is calculated to be about 2.06 eV and we suggest that it may be the dominant ...
In this work, we present ab initio studies of the electronic and transport properties of carbon nanoribbons with structural defects: divacancies and divacancies combined with the Stone-Wales-like (SW) defects. Simulations with defects in different positions with respect to the ribbons indicated ...
Vacancy formation and clustering significantly affect structural properties of transition-metal aluminides. Ab-initio quantum mechanical total-energy calculations using a full-potential linear combination of muffin-tin orbitals (LMTO) technique provide a convenient method of studying relevant characteristics such as changes in density of states, and charge redistribution ...
Ab initio molecular dynamics simulations are a powerful tool for examining liquids and amorphous materials; however, such simulations are often computationally intensive. We present a molecular dynamics method that dramatically reduces the computational load using a new algorithm based on Chebyshev-filtered subspace iteration. We apply this method to ...
Deleterious effects of radiation in nuclear reactor systems cause material degradation and the potential for component failure. Radiation damage is fundamentally due to freely migrating point defects produced in collision cascades. A reduction in the freely migrating point defect population should, then, reduce radiation damage and increase component ...
We report on the determination of a high quality ab initiu potential energy surface (PES) and dipole
The utility of diamond as an electronic material is compromised by the lack of a suitable shallow donor. Here, ab initio theory is used to investigate the donor levels of substitutional pnictogen (N, P, As, and Sb) and chalcogen (S, Se, and Te) impurities and chalcogen-hydrogen defects in diamond. Substitutional S is found to be a deep ...
with ab initio studies. The hafnium aluminate thin films with thickness of about 20 nm were deposited of a representative pseudobinary Hf-based material-hafnium aluminate as a function of aluminum concentration in the band gap of the nominally pure HfO2 films referred to as pure HfO2 therein , their individual changes
E-print Network
A general method based on ab initio quantum mechanical modelling and also utilizing semi-classical modelling of a type introduced by Mott-Littleton in 1938 is being implemented to describe the effects of a point defector impurity and/or their interaction ...
. Depiction of two badly strained regions in supercell sample S512HO. Note the badly strained bond angles. FIG to the contrary. In earlier ab initio work, we have shown3 that single or very localized highly strained bonds, but do contain a few spectral defects localized states in the gap due to badly strained bonds
Boron strongly modifies electronic and diffusion properties of graphite. We report the first ab initio study of boron interaction with the point defects in graphite, which includes structures, thermodynamics, and diffusion. A number of possible diffusion mechanisms of boron in graphite are suggested. We conclude that boron diffuses in ...
Energetics of a variety of point defects in MgO have been considered from an ab initio perspective using density functional theory. The considered defects are isolated Schottky and Frenkel defects and interstitial pairs, along with a number of Schottky defects and ...
Quantum transport properties of disordered graphene with structural defects (Stone-Wales and divacancies) are investigated using a realistic ?-?* tight-binding model elaborated from ab initio calculations. Mean free paths and semiclassical conductivities are then computed as a function of the nature and density of ...
We review results of our recent large-scale computer simulations of radiation-induced point defects, excitons and polarons in ABO3 perovskite crystals, focusing mostly on KNbO3 and KTaO3 as representative examples. We have calculated the atomic and electronic structure of defects, their optical absorption, defect-induced electron ...
First principles calculations have been performed to investigate defect equilibria of the silicon-boron pair complex (Si-B) in a GaAs matrix. For several charge states, the formation energies were evaluated within the Car-Parrinello scheme considering cation and anion substitutional site defects. The calculations, including the full relaxation of all ionic ...
The structures, stabilities, and electronic properties of the single-vacancy-defected fullerenes, C60 and C70, and the single- and double-vacancy-defected single-walled carbon nanotubes (SWCNTs) were studied within density functional theory. The isomerization barriers for the single-vacancy-defected C60 on the triplet potential energy ...
