The theory of trapping and diffusion of helium and hydrogen in metals is reviewed. The fundamental aspects of the behavior of these particles is emphasized and hence ab initio methods of calculation of interatomic potentials are described. In particular, ...
National Technical Information Service (NTIS)
... It is urged that theorists turn their attention to ab-initio energy band ... change in the electric susceptibility with interatomic distance (piezo-optic) tensor ...
DTIC Science & Technology
In this article, we investigate the dependence of interatomic Coulombic decay widths on the symmetry of the decaying state. In this type of decay, excited, ionized, and doubly ionized states of an atom or molecule can efficiently relax by ionizing their environment. We concentrate on an atom A and a neighboring atom B and consider such excited, ionized, or doubly ionized ...
Energy Citations Database
It has recently become possible for the first time to calculate ab initio two-ion and three-ion interatomic potentials in d-electron transition metals. The nature of these potentials for the 3d series metals is discussed. In the case of copper, where three-ion contributions may be neglected, application is made to the ion-thermal ...
Electronically excited states of atoms and molecules in an environment may decay in interatomic processes by transferring excess energy to neighboring species and ionizing them. The corresponding interatomic decay width is the most important characteristic of the decay allowing to calculate its efficiency and the final states' distribution. In this paper ...
PubMed
NASA Astrophysics Data System (ADS)
We present the results of an experimental and atomistic modeling investigation of the silicon/silver (Si/Ag) interfaces found in industrial solar cells. We use small ab initio calculations to parametrize a new interatomic potential for the Si/Ag interaction. This interatomic potential is then validated against ...
The ferroelectric [001], [011], and [111] instabilities in KNbO3 with up to 12.5 mol% Cu on K or Nb sites, respectively, are investigated using both ab initio density-functional theory and classical interatomic potentials. A doping level of only about 2�4 mol% Cu on K sites enhances the ferroelectric instabilities and induces a ...
We report orientation-specific, surface-sensitive structural characterization of colloidal CdSe nanorods with extended X-ray absorption fine structure spectroscopy and ab-initio density functional theory calculations. Our measurements of crystallographically-aligned CdSe nanorods show that they have reconstructed Cd-rich surfaces. They exhibit orientation-dependent changes in ...
Ultra high temperature ceramics including ZrB2 and HfB2 are characterized by high melting point, good strength, and reasonable oxidation resistance. These materials are of interest for use as sharp leading edges for hypersonic vehicles among other applications. Progress in computational modeling of UHTCs has been limited in part due to the absence of suitable interatomic ...
We present the result of ab initio modeling of the Ge(111)-(2 � 1) surface electronic structure in the presence of donor doping atom at certain position in the surface bilayer of (2 � 1) reconstruction. We briefly compare these results with the data of experimental low temperature STM investigations. Ab initio ...
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 believed to play an important role in the ...
The origin of long interatomic distances in suspended gold atomic chains formed from stretched nanowires remains the object of debate despite the large amount of theoretical and experimental work. Here, we report new atomic resolution electron microscopy observations acquired at room and liquid-nitrogen temperatures and theoretical results from ab ...
By using ab initio molecular dynamics calculations, we show that even where the graphene lattice constant contracts, as previously reported for freestanding graphene below room temperature, the average carbon-carbon distance increases with temperature, in both free and supported graphene. This results in a larger corrugation at higher temperature, which ...
In order to perform atomistic simulations of steel, it is necessary to have a detailed understanding of the complex interatomic interactions in transition metals and their alloys. The tight-binding approximation provides a computationally efficient, yet accurate, method to investigate such interactions. In the present work, an orthogonal tight-binding model for Fe, Mn and Cr, ...
Van der Waals broadening coefficients for numerous spectral transitions and radiator-perturber pairs are estimated by semi-empirical methods. The results are verified by ab initio electronic structure calculations and available experimental data. At the same time this allows to establish the range of applicability of Van der Waals approximation for ...
We extend our recently developed interatomic potentials for UO2 to the fuel system (U,Pu,Np)O2. We do so by fitting against an extensive database of ab initio results as well as to experimental measurements. The applicability of these interactions to a variety of mixed environments beyond the fitting domain is also assessed. The ...
Since their theoretical prediction in 1997, interatomic (intermolecular) Coulombic decay (ICD) and related processes have been in the focus of intensive theoretical and experimental research. The spectacular progress in this direction has been stimulated both by the fundamental importance of the discovered electronic decay phenomena and by the exciting possibility of their ...
A multiscale technique is developed that couples empirical molecular dynamics (MD) and ab�initio density functional theory (DFT). An overlap handshaking region between the empirical MD and ab�initio DFT regions is formulated and the interaction forces between the carbon atoms are calculated based on the second-generation reactive empirical bond order ...
... This study involves: Ab-initio crystal orbitals and polymer orbitals; Ab-initio coupled cluster program; Ab-initio quantum chemical calculations and ...
The energy gained by either of the two helium atoms in a helium dimer through simultaneous ionization and excitation can be efficiently transferred to the other helium atom, which then ionizes. The respective relaxation process called interatomic Coulombic decay (ICD) is the subject of the present paper. Specifically, we are interested in ICD of the lowest of the ionized ...
A fundamental understanding of radiation damage effects in solids is of great importance in assisting the development of structural materials with improved mechanical properties for nuclear energy applications. In this presentation, we discuss our recent theoretical investigation on the magnetic structure evolution in bulk Fe after an energetic particle has disturbed the lattice by a displacement ...
We study how the Mott metal-insulator transition (MIT) is affected when we have to deal with electrons with different angular momentum quantum numbers. For that purpose we apply ab initio quantum-chemical methods to lithium rings in order to investigate the analog of a MIT. By changing the interatomic distance we analyze the character ...
... 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,. ...
Calculation of the properties of dislocations by computer simulations requires, among other things, the availability of accurate interatomic potentials, ideally with ab-initioquality. For crystals with large unit cells and complex crystal structures, such as most minerals, the number and size of the calculations may severely limit the applicability of a ...
A scheme is proposed in the present study to predict the phase stability of binary alloys in the fcc--fcc metal systems. Based on the long-range empirical potential model, the interatomic potentials are first constructed for 15 binary metal systems of Cu, Ag, Au, Ni, Pd, and Pt, and then molecular statics calculations are carried out to predict the heats of formation of the ...
We demonstrate the feasibility of using classical atomistic simulations, i.e. molecular dynamics and molecular statics, to study the piezoelectric properties of ZnO using core-shell interatomic potentials. We accomplish this by reporting the piezoelectric constants for ZnO as calculated using two different classical interatomic core-shell potentials: that ...
We demonstrate the feasibility of using classical atomistic simulations, i.e.�molecular dynamics and molecular statics, to study the piezoelectric properties of ZnO using core-shell interatomic potentials. We accomplish this by reporting the piezoelectric constants for ZnO as calculated using two different classical interatomic core-shell potentials: ...
... Title : AB Initio Study of the Electronic Magnetic Circular Dichroism ... functions are determined using as initio quantum chemical techniques including ...
Advances in materials science and molecular biology followed rapidly from the ability to characterize atomic structure using single crystals. Structure determination is more difficult if single crystals are not available. Many complex inorganic materials that are of interest in nanotechnology have no periodic long-range order and so their structures cannot be solved using crystallographic methods. ...
Three-body nonadditive forces in systems of three spin-polarized alkali-metal atoms (Li, Na, K, Rb, and Cs) are investigated using high-level ab initio calculations. The nonadditive forces are found to be large, especially near the equilateral equilibrium geometries. For Li, they increase the three-atom potential well depth by a factor of 4 and reduce the ...
Ab initio molecular-orbital calculations have been performed for the systems Br exp +25 - Br exp +25 , I exp +25 - Te exp +24 , I exp +43 - Au exp +69 , and I exp +25 - Au exp +51 for different interatomic distances using the program 'BISON' based on Hart...
Due to recent advances in methods and computers, the accuracy of ab calculations has reached a point
NASA Technical Reports Server (NTRS)
The core structures of screw and edge dislocations on the basal and prism planes in Mg, and the associated gamma surfaces, were studied using an ab initio method and the embedded-atom-method interatomic potentials developed by Sun et al and Liu et al. The ab initio calculations predict that the ...
Prediction of properties of energetic materials using atomic-scale simulations techniques is one of the challenging areas of energetic materials (EM) research. Molecular dynamics (MD) simulation of EM using classical reactive interatomic potentials is a powerful modeling technique that is capable of addressing sub-nanometer and sub-picosecond length and time scales of shock ...
... 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
This dissertation describes the development and testing of modified embedded atom method (MEAM) interatomic potentials for Al, Si, Mg, Cu, Fe, and their alloys, with primary concentration on Mg-Al system. We performed the density functional theory (DFT) based ab initio calculations to determine the structural and elastic properties of ...
... 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 elastic moduli of magnesium (Mg) have been evaluated as functions of pressure and temperature through the use of fluctuation formulas and Monte Carlo simulation. The simulations employ {ital ab initio} interatomic potentials for Mg derived from generalized pseudopotential theory and used previously to predict the ...
A method is presented for expressing the occupied self-consistent-field (SCF) orbitals of a molecule exactly in terms of chemically deformed atomic minimal-basis-set orbitals that deviate as little as possible from free-atom SCF minimal-basis orbitals. The molecular orbitals referred to are the exact SCF orbitals, the free-atom orbitals referred to are the exact atomic SCF orbitals, and the ...
Nonbonding interactions of small alkane molecules were studied with ab initio methods. Previously reported energy data for ethane and propane dimers were supplemented with 1747 new configurations of dimers involving slightly larger hydrocarbons. The completed work provides interaction energy surfaces for all combinations of dimer pairs involving ethane, ...
The general aim of this study is to test the reliability of polarizable model potentials for the prediction of vibrational (infrared and Raman) spectra in highly anharmonic systems such as high temperature crystalline phases. By using an ab initio parametrized interatomic potential for SiO2 and molecular dynamics simulations, we ...
Extended X-ray absorption fine structure (EXAFS) backscattering amplitude and phase functions have been calculated from first principles for K and L edges for nearly every element in the periodic table by using a full curved wave formalism. These functions are tabulated for approximately half of the elements from boron through californium. The functions are calculated for the range 2 less than or ...
We have carried out ab initio molecular dynamics simulations of a liquid-vapor interfacial system consisting of a mixture of water and ammonia molecules. We have made a detailed analysis of the structural and dynamical properties of the bulk and interfacial regions of the mixture. Among structural properties, we have looked at the inhomogeneous density ...
We studied the effect of intense electronic excitations on the interatomic forces for electronic temperatures reached under intense laser irradiation and the possible melting of the underlying lattice. We use ab initio linear response to compute the phonon spectrum for a semi-conductor (Si) and two metals (Al and Au), using linear ...
We present a methodology used to generate interatomic potentials fitted on results of ab initio calculations. Our aim is to obtain models suitable for large-scale simulations in ionic solids. We fitted a potential based on the rigid-ion model in order to investigate the high-temperature properties of lithium oxide. Density-functional ...
Cu plays an important role in the embrittlement of pressure vessel steels under radiation and entities containing both Cu atoms and vacancies seem to appear as a consequence of displacement cascades. The characterisation of the stability as well as the migration of small Cu-vacancy complexes is thus necessary to understand and simulate the formation of these entities. For instance, cascade ageing ...
Completely self-consistent ab initio calculations of scattering of electrons between the lowest minima of the conduction band by short-wavelength phonons are performed for the first time for a group of А III В V semiconductor crystals. The structure constants, electron and vibrational spectra, and probabilities of scattering are ...
We report on the determination of a high quality ab initiu potential energy surface (PES) and dipole
Emphasis has been on the electronic materials: silica, titania, and ruthenia. Fundamental interest centered on nature of microstructure of these solids in the amorphous state, or mixed oxide state. New theoretical techniques have been implemented to examine such issues, based on ab initio pseudopotential methods and interatomic ...
We calculate the spatial distribution of the oscillating electron density for the low energy optical excitations in C(60), using ab initio time-dependent density functional theory. We contrast this with the unscreened free response of the Kohn-Sham eigenfunctions, in which the charge transfer is between hemispheres and the simple density oscillation ...
The ground-state properties of spin polarized hydrogen H{down_arrow} are obtained by means of diffusion Monte Carlo calculations. Using the most accurate to date ab initio H{down_arrow}-H{down_arrow} interatomic potential we have studied its gas phase, from the very dilute regime until densities above its freezing point. At very small ...
Orbital exponent optimization in the elementary ab-initio VB calculation of the ground states of H[subscript 2][superscript +], H[subscript 2], He[subscript 2][superscript +], He[subscript 2] gives a fair description of the exchange-overlap component of the interatomic interaction that is important in the bond region. Correct bond lengths and about 85% of ...
ERIC Educational Resources Information Center
A multi-scale approach is applied to study the static structure of Li70-Bi30 liquid alloy. In order to describe the interatomic interactions in this non-simple metal, we make a set of three empirical pair potentials fit ab-initio computations of the forces and energy in this system. Large scale classical simulations are performed using these fitted ...
We report on our studies of the structural properties of a hydrogen molecule dissolved in liquid water. The radial distribution function, coordination number and coordination number distribution are calculated using different representations of the interatomic forces within molecular dynamics (MD), Monte Carlo (MC) and ab initio ...
Short-range interatomic interactions in singlet He3 and He4 are discussed in terms of a single determinant of doubly occupied nonorthogonal localized orbitals through the formalism described in Paper I [V. Magnasco and G. F. Musso, J. Chem. Phys. 60, 3744 (1974)]. Ab-initio calculations using a minimal set of Slater 1s orbitals are reported for several ...
At what characteristic length scale does classical continuum elasticity cease to accurately describe small deformation mechanical behavior? The two dominant physical mechanisms that lead to size dependency of elastic behavior at the nanoscale are surface energy effects and nonlocal interactions. The latter arises due to the discrete structure of matter and the fluctuations in the ...
Analytical bond-order potentials for beryllium, beryllium carbide and beryllium hydride are presented. The reactive nature of the formalism makes the potentials suitable for simulations of non-equilibrium processes such as plasma-wall interactions in fusion reactors. The Be and Be-C potentials were fitted to ab initio calculations as well as to ...
We present an ab initio study of the influence of hydrogen impurities (atoms and molecules) on the atomic structure and electronic properties of Pd nanowires and atomic-size nanocontacts. Various atomic positions for hydrogen adsorption within palladium structures are considered. It is found that adsorbed hydrogen can penetrate into the atomic structure of ...
Theory links the reactivity of metal surfaces to the interatomic spacing and, hence, to the tangential strain. We point out that this proposition can be experimentally verified by exploiting a seemingly unrelated phenomenon, the mechanical deformation of solid bodies when charged in an electrolyte. Such experiments allow the strength of coupling between adsorption enthalpy and ...
The reliability of different variants of the electron gas density functional method for calculating the interaction energy of two closed-shell systems is examined. This is achieved by comparing the short range potentials predicted by electron gas theory with values which are exact within the assumption that the electron densities of the interacting atoms remain undistorted. It is concluded that, ...
The phonon densities of states of body-centered-cubic Fe-V alloys across the full composition range were studied by inelastic neutron scattering, nuclear resonant inelastic x-ray scattering, and ab initio calculations. The average phonon energy followed the inverse of the electronic heat capacity and the inverse of the electronic density of states at the ...
Using ab initio methods, the influence of chromium on the electron structure and magnetic properties of cementite Fe3C has been investigated depending on the chromium concentration and the possibility of the formation of a chromium carbide Cr3C has been considered. It has been established that it is the general positions of iron in the lattice of cementite ...
When computing the Peierls stress of screw dislocations in tantalum by means of classical molecular dynamics (CMD), we have observed that a suitable potential should be able to reproduce the complicated angular dependence of forces arising in the core structure of dislocations. This prevents the use of simple embedded atom potentials, but we notice that more generally, effective ...
Quantum-based atomistic simulations are being used to study fundamental deformation and defect properties relevant to the multiscale modeling of plasticity in bcc metals at both ambient and extreme conditions. Ab initio electronic-structure calculations on the elastic and ideal-strength properties of Ta and Mo help constrain and validate many-body ...
DOE Information Bridge
Phase field simulations suitable to describe interfacial phenomena at the mesoscale require as input parameters accurate interfacial energies as well as the interface mobilities. However, this information is not directly accessible by experiment. Furthermore, phenomena such as impurity segregation cannot be decoupled and their independent role in interfacial cohesion and mobility cannot be ...
As the density of a liquid alkali metal decreases along the liquid-vapor equilibrium curve, the average interatomic separation remains relatively constant while the average number of nearest neighbors decreases. At the critical point, there is a sharp drop in the electrical conductivity which, in cesium and rubidium, has been correlated with the formation of molecular ...
Ab initio, fully relativistic four component theory was used to determine atomic and interatomic many-body effects for the 4f X-ray photoelectron spectrum of an embedded UO8-12 cluster representing UO2. Many-body effects were included through the use of configuration interaction wavefunctions that allow the mixing of XPS allowed and ...
We analyze in detail the accessible relaxation pathways via electron emission of the Ne2+Ar states populated via the K-LL Auger decay of Ne+(1s-1)Ar. In particular, we concentrate on the ``direct'' interatomic Coulombic decay (ICD) of the Ne2+(2s-12p-1)Ar weakly bound doubly ionized states into the manifold of the Ne2+(2p-2)-Ar+(3p-1) repulsive triply ionized ones. To carry ...
An interatomic potential model for Si-Br systems has been developed for performing classical molecular dynamics (MD) simulations. This model enables us to simulate atomic-scale reaction dynamics during Si etching processes by Br{sup +}-containing plasmas such as HBr and Br{sub 2} plasmas, which are frequently utilized in state-of-the-art techniques for the fabrication of ...
An interatomic potential model for Si-Br systems has been developed for performing classical molecular dynamics (MD) simulations. This model enables us to simulate atomic-scale reaction dynamics during Si etching processes by Br+-containing plasmas such as HBr and Br2 plasmas, which are frequently utilized in state-of-the-art techniques for the fabrication of semiconductor ...
