... the potential energy surface provided by modern electronic structure ... screening approach, to determine the equilibrium geometry and composition ...
DTIC Science & Technology
... Although both compounds belong to the same chalcopyrite family, the nature of dominant acceptors is predicted to be different. ...
... nucl, electr) degrees of freedom are decoupled from the vibrational/rotational (vib, rot) ones (Born- Oppenheimer approximation), and further that ...
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...
National Technical Information Service (NTIS)
. In the present context it is particularly the oxygen environment which acts as such a reservoir, because it can oxygen chemical potential. 2.2 Calculating Gibbs free energies As apparent from eqs. (3) and (5 as the chemical potential of the oxygen environment. Since the RTO-EN-AVT-142 2 - 3 Ab Initio Atomistic
E-print Network
... higher temperatures above 650'C. Modeling at the ab initio, atomistic and ... with: self-aligning grips, a linear air bearing, piezo-actuator, miniature in ...
Rational design and advancement in materials science will ultimately rely on an atomic-scale understanding of the targeted functionality. Corresponding modeling must then address the behavior of electrons and the resulting interactions that govern the ele...
We study the behavior of SnO2 under rapid hydrostatic pressures using constant-pressure ab initio simulations. We find that the rutile-type SnO2 transforms into the CaCl2-type structure. At a high pressure of about 20 GPa, a phase transformation into a cubic fluorite-type structure is observed. The orthorhombic Pnma cotunnite-structured phase is formed ...
NASA Astrophysics Data System (ADS)
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 morphotropic phase ...
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 defects in hcp-Ti. The relative ...
Energy Citations Database
A new atomistic structural model is developed here for graphene sheets based on the stiffnesses from the REBO potential. Using this model, the flexural vibration natural frequencies and buckling loads of rectangular single-layer graphene sheets of different sizes, chiralities and boundary conditions are calculated. The newly developed atomistic structural ...
PubMed
In this work we show how the ab initio determination of van der Waals coefficients within time-dependent density functional theory can be used to build efficient and accurate atomistic models that describe the long-range interactions of proteins with other proteins and of proteins with semi-conducting surfaces. The model parameters are ...
We present a combined computational and experimental study on structural and electric properties of recently synthesized heteroaromatic dyes and their simple aggregates. Ab initio and density functional theory calculations are carried out to investigate ground state and excited state properties along with their modulation induced by the solvent described ...
The great power of the cluster-expansion method for atomistic simulations of the ground state properties and the thermodynamic properties of multi-component solids is highlighted. In the first part of the paper some recently developed combinations of this method with other atomistic simulation techniques (N-body potentials and cluster functionals) are ...
We report the first ab initio density-functional study of the strain field and Peierls stress of isolated <111> screw dislocations in bcc Mo and Ta. The local dislocation strain field is self-consistently coupled to the long-range elastic field using a flexible boundary condition method. This reduces the mesoscopic atomistic ...
An ab initio based approach to determine energies and structures for semicoherent interfaces is developed and applied to the Fe(001)/VN(001) system. To account for elastic displacements resulting from the lattice misfit, we compare an atomistic approach using a model potential (embedded-atom method) with a continuum approach using the ...
The ab initio/classical free energy perturbation (ABC-FEP) method proposed previously by Wood et al. [J. Chem. Phys. 110, 1329 (1999)] uses classical simulations to calculate solvation free energies within an empirical potential model, then applies free energy perturbation theory to determine the effect of changing the empirical solute-solvent interactions ...
as the chemical potential of the oxygen environment. Since the contributions to free energies in the gas phase structure of a surface free energy plot for a metal surface in contact with an oxygen environment can nicely ENVIRONMENTS 2.1 Surface free energy Here we will illustrate how this quite general concept works and what
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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, ...
Core Gen II back-up fuel cell design GCtool Software package developed at ANL for analysis of fuel cells adsorption PSAT Puget Sound Action Team PSAT Vehicle simulation software package developed at Argonne-Vis Ultraviolet-Visual V Vanadium V Volt VASP Vienna Ab-initio Simulation Package VC Vulcan carbon VHTS
deposition on Al(111) - STM FOV: 23 nm. Ti/Al(111) deposited at 400 K. #12;10 FT-IR Spectroscopy - atomic H, time-resolved, high-pressure. � X-ray microprobe � IR micro-spectroscopy � Surface microscopy & energetics. Ab-initio molecular dynamics - surface dynamics. FT-infrared reflection spectroscopy - hydrogen
... This study involves: Ab-initio crystal orbitals and polymer orbitals; Ab-initio coupled cluster program; Ab-initio quantum chemical calculations and ...
The structure of a Zr{sub 73}Pt{sub 27} metallic glass, which forms a Zr{sub 5}Pt{sub 3} (Mn{sub 5}Si{sub 3}-type) phase having local atomic clusters with distorted icosahedral coordination during the primary crystallization, has been investigated by means of x-ray diffraction and combining ab initio molecular-dynamics (MD) and reverse Monte Carlo (RMC) ...
... 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,. ...
Complex lattice Quasicontinuum theory is developed and applied to the description of ferroelectric phenomena. Quasicontinuum theory is a multiscale theory that provides a unified description of materials by combining atomistic and continuum approaches. It provides a seamless transition between atomistics and continuum, but the description of the material ...
Within the current effort to develop more efficient and less expensive solar cell devices, the polymer/fullerene photovoltaic (PV) structure is considered to be very promising. The crucial component of such a PV structure is the nano-scale heterojunction interface of the polymer and the fullerene. This interface must facilitate the dissociation of the exciton which is formed in the polymer, so ...
The advancement in new materials processing and fabrication techniques has made it possible to better control the atomistic level of structures in a way, which was not feasible only a decade ago. If one can couple this atomic control with a good understanding of the relationship between structure and properties, this will in the future lead to a significant contribution to the ...
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 potentials. We present a ...
Among the many considerable challenges faced in developing a rational basis for advanced alloy design, establishing accurate atomistic models is one of the most fundamental. Here we demonstrate how advanced imaging techniques in a double-aberration-corrected transmission electron microscope, combined with ab initio modeling, have been ...
We have performed an ab initio study of the thermodynamical properties of rare-earth�magnesium intermetallic compounds MgRE (RE=Y, Dy, Pr, Tb) with B2-type structures. The calculations were carried out in the framework of density functional theory and density functional perturbation theory in combination with the quasiharmonic approximation. The ...
The molecular probe N-methyl-6-quinolone (MQ) gives experimental access to its local chemical environment, e.g. inside a biomolecule. Using ab initio molecular dynamics (MD), it is possible to simulate the time evolution of the Stokes shift as a function of the actual atomistic coupling to the surrounding hydrogen bond network and thus ...
The pressure-induced phase transition in zinc sulfide is studied using a constant-pressure ab initio technique. The reversible phase transition from the zinc-blende structure to a rock-salt structure is successfully reproduced through the simulations. The transformation mechanism at the atomistic level is characterized and found to be ...
In this paper, we present our ab-initio study on energy configurations, minimum energy path (MEP), and migration energy for neutral indium diffusion in a uniaxial and biaxial tensile strained {100} silicon layer. Our ab-initio calculation of the electronic structure allowed us to figure out transient atomistic configurations during the ...
... 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)
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 larger ...
Misfolded metallo-proteins are potential causal agents in the onset of neuro-degenerative diseases, such as Alzheimer's and Parkinson's Diseases (PD). Experimental results involving metal chelation have shown significant promise in symptom reduction and misfolding reversal. We explore, through atomistic simulations, potential reaction pathways for the chelation of Cu^2+ from ...
Combined ab initio and grand canonical Monte Carlo simulations have been performed to investigate the dependence of hydrogen storage in single-walled carbon nanotubes (SWCNTs) on both tube curvature and chirality. The ab initio calculations at the density functional level of theory can provide useful information ...
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 originally proposed ...
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 originally proposed ...
The effect of chlorine (Cl) chemisorption on the energetics and atomic structure of the Cu(001) surface over a wide range of chlorine pressures and temperatures has been studied using equilibrium ab initio atomistic thermodynamics to elucidate the formation of cuprous chloride (CuCl) as part of the Deacon reaction on copper metal. The ...
Atomistic simulation of a vacancy-assisted dopant diffusion in silicon needs details of the dopant-vacancy interaction, i.e., the potential as a functional of dopant-vacancy separations. In this paper, the authors present a detailed study on the energetics of As-vacancy reaction in silicon and the lattice distortions surrounding the As-vacancy defect by using an ...
Peptoids are sequence-specific, oligo-N-substituted glycine polymers that can mimic the structural motifs and functionalities of proteins. Recently, novel sheet-like nanostructured materials have been self-assembled from peptoids under physiological conditions. These structures are biocompatible and may be selectively functionalized. We have constructed atomistic models of ...
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 ...
DOE Information Bridge
We demonstrate an atomistic nucleation and growth mechanism for single-wall carbon nanotubes (SWNTs) on catalytic nanoparticle surfaces based on a core-shell model. We show by ab initio calculations that strain relief between the metal core and carbon shell plays a crucial role in facilitating the hexagonal tubular growth. The ...
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 ...
A nucleation mechanism for the misfolding of ?-synuclein, the protein implicated in Parkinson's Disease (PD), is investigated using computer simulations. Through a combination of ab initio and classical simulation techniques, the conformational evolution of copper-ion-initiated misfolding of ?-synuclein is determined. Based on these investigations and ...
Ab initio molecular dynamics simulations are employed to study the atomistic mechanisms and pathways of high-pressure phase transformation in GaN and SiC. Our simulations bring a fundamental level of understanding of the wurtzite to rocksalt phase transformation that undergoes inhomogeneous displacements via a tetragonal atomic ...
We present a program called potfit which generates an effective atomic interaction potential by matching it to a set of reference data computed in first-principles calculations. It thus allows one to perform large-scale atomistic simulations of materials with physically justified potentials. We describe the fundamental principles behind the program, emphasizing its flexibility ...
Using ab initio molecular dynamics simulations, we find direct evidence that icosahedral clusters have a strong tendency to aggregate in Zr1?xCux liquids. Remarkably, the dynamic arrest effect is much more significant in aggregated icosahedral clusters than in nonaggregated ones by a factor of 2 or more. Simulations using a lattice model demonstrate that ...
The authors measure the persistence and contour lengths of DNA-psoralen complexes, as a function of psoralen concentration, for intercalated and crosslinked complexes. In both cases, the persistence length monotonically increases until a certain critical concentration is reached, above which it abruptly decreases and remains approximately constant. The contour length of the complexes exhibits no ...
Development of structural order in liquid aluminum upon rapid cooling is studied by ab initio molecular-dynamics simulations and the recently developed atomistic cluster alignment method. We show that there is a strong competition between icosahedral and fcc short-range orders (SROs) in the system. Although the liquid eventually ...
Atomistic simulations of alloys at the classic--or empirical--level face the challenge to correctly model basic thermodynamic properties. In this work we propose a methodology to generalize many-body classic potentials to incorporate complex formation energy curves. Application to Fe-Cr allows us to correctly predict the order vs segregation tendency in this alloy, as observed ...
Using classical and ab initio simulations, we study the interplay between the Au(111) surface reconstruction and monoatomic steps on a vicinal face. The experimentally observed discommensuration line patterns on a specific vicinal are reproduced and explained, and a complete description of the structure is given. An unusual atomic arrangement is shown to ...
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 element pairs that ...
As ULSI devices enter the nanoscale, ultra-shallow and highly electrically active junctions become necessary. New materials and 3D device structures as well as new process technologies are under exploration to meet the requirements of future devices. A detailed understanding of the atomistic mechanisms of point-defect/dopant interactions which govern diffusion and activation ...
... 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
... 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 ...
Solar energy applications require understanding of dynamical response of novel materials on nanometer scale. Our state-of-the-art non-adiabatic molecular dynamics techniques, implemented within time-dependent density functional theory, allow us to model such response at the atomistic level and in real time. The talk will focus on single and multiple exciton generation, ...
Recently it has become possible for the first time to directly observe dislocation kink motion by electron microscopy. The method is discussed in which ab initio quantum molecular dynamics calculations in combination with these images have deepened the understanding of the atomic processes involved in both ductility and fracture in single-crystal silicon, ...
We report on the determination of a high quality ab initiu potential energy surface (PES) and dipole
The issue of melting of pure iron and iron alloyed with lighter elements at high pressure is critical to the physics of the Earth. The iron melting curve in the relevant pressure range between 3 and 4 Mbar is reasonably well established from the theoretical point of view. However, so far no one attempted a direct atomistic simulation of iron alloyed with light elements. We ...
A detailed description, at the atomistic scale, of the dynamics of excess electrons and holes is fundamental in order to improve the performance of many optoelectronic devices. Among all recombination processes, nonradiative decay paths play a fundamental role in most semiconductor devices, such as optoelectronic devices and solar cells, limiting their efficiency. In this ...
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 lifetime. The addition of oversized solute ...
Ab initio density functional theory (DFT) calculations have been performed to examine various factors which may influence the ideal strength, namely multiaxial loading condition and structure with low symmetry. First, the effect of normal stress on the ideal shear strength (ISS) in covalent crystals, Si, C, Ge and SiC, was evaluated. It was found that the ...
