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...
National Technical Information Service (NTIS)
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 other way, more involved, is the assessment of ...
DOE Information Bridge
Quantum mechanical-based (or ab initio) methods are used to predict the stability properties of materials although their application is limited to relatively simple systems in terms of structures and number of alloy components. However thermodynamics of c...
... the potential energy surface provided by modern electronic structure ... screening approach, to determine the equilibrium geometry and composition ...
DTIC Science & Technology
We present an algorithm for calculating the conformational thermodynamics of large, flexible molecules that combines ab initio electronic structure theory calculations with a torsional path integral Monte Carlo (TPIMC) simulation. The new algorithm overcomes the previous limitations of the TPIMC method by including the ...
NASA Astrophysics Data System (ADS)
... the PRMD code - in Step 1- will be validated and further studied using ab initio methods to determine kinetic and thermodynamic properties of the ...
... nucl, electr) degrees of freedom are decoupled from the vibrational/rotational (vib, rot) ones (Born- Oppenheimer approximation), and further that ...
Quantum mechanical-based (or ab initio) methods are used to predict the stability properties of materials although their application is limited to relatively simple systems in terms of structures and number of alloy components. However thermodynamics of complex multi-component alloys requires a more versatile approach afforded within ...
Energy Citations Database
Perturbative variational calculations of thermodynamic and structural properties of liquid metals, based on the use of ab initio and highly reliable nonlocal pseudopotentials for the electron-ion interactions and of the fluid of charged hard spheres as re...
Following our recent studies of the thermodynamic properties of azaspiropentane and borospiropentane, in consideration of their usefulness as new potential high energy materials, we follow up with ab initio calculations on the thermodynamic properties of azaborospiropentanes. Properties reported in this study ...
PubMed
An ab initio quantum-chemical study has been made of the possible existence in terms of structural and thermodynamic stabilities of the pentacoordinated nitrogen hydrides and fluorides, NF(n)H(5-n) for n=0 to 5. Three structurally stable species have been...
. 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
The study of phase stability, including order-disorder phenomena and structural transformations, in substitutional alloys is of great theoretical and technological interest. The goal is to perform ab-initio calculations of thermodynamical properties of al...
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...
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...
EPA Science Inventory
... This study involves: Ab-initio crystal orbitals and polymer orbitals; Ab-initio coupled cluster program; Ab-initio quantum chemical calculations and ...
The authors analyze the implications of the recently reported results of ab initio calculations of formation energies of the Fe-Cr alloy. The formation energies show a change in sign from negative to positive as Cr composition increases above {approx}10%. By developing a classic potential to evaluate the thermodynamic properties, they ...
We regularize the potential distribution framework to calculate the excess free energy of liquid water simulated with the BLYP-D density functional. Assuming classical statistical mechanical simulations at 350 K model the liquid at 298 K, the calculated free energy is found in fair agreement with experiments, but the excess internal energy and hence also the excess entropy are not. The utility of ...
This paper presents results obtained in ab initio calculations of the thermodynamic properties of B1 and B2 lithium fluoride under pressure. The data were used to calculate LiF isotherms and isochors at pressures from 0 to 500 GPa and temperatures up to the melting point. Calculated results are compared with available theoretical and ...
The constant-volume specific heat, the entropy, the phonon contributions to internal energy and Helmholtz free energy, and the atomic temperature factors of ?-quartz and stishovite, two allotropic forms of SiO2, are calculated as a function of temperature from ab initio phonon band structures. Available experimental data agree with our calculated values ...
We present a new technique which allows the fully {\\em ab initio} calculationof the chemical potential of a substitutional impurity in a high-temperaturecrystal, including harmonic and anharmonic lattice vibrations. The techniqueuses the combination of thermodynamic integration and reference modelsdeveloped recently for the {\\em ...
Development of fundamental thermodynamic relationships on organic materials from fossil substances proceeded along several fronts that ranged from proof studies for ab initio quantum mechanical calculations to application of basic thermodynamic relationsh...
Lattice dynamics and thermodynamic properties of antiferromagnetic Fe2SiO4-spinel have been studied using density functional theory. Phonon dispersions are obtained for several hydrostatic pressures up to 20 GPa. They are used to calculate thermodynamic properties within the quasiharmonic approximation. Comparison with ab ...
Lattice dynamics and thermodynamic properties of antiferromagnetic Fe(2)SiO(4)-spinel have been studied using density functional theory. Phonon dispersions are obtained for several hydrostatic pressures up to 20 GPa. They are used to calculate thermodynamic properties within the quasiharmonic approximation. Comparison with ab ...
... 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,. ...
... Title : AB Initio Study of the Electronic Magnetic Circular Dichroism ... functions are determined using as initio quantum chemical techniques including ...
A comprehensive study of static, dynamic and electronic properties of liquid Al in a thermodynamic state near its triple point was performed by means of 205-particle ab initio molecular dynamics simulations using Kohn-Sham density-functional theory and the Langevin equation of motion. The good agreement of the results with ...
Ab initio theoretical investigations of the dynamics and thermodynamics of a compressed Ne crystal performed using a model that explicitly takes account of the deformation of the electronic shells in the dipole approximation are presented. A dynamical matrix based on a non-empirical short-range repulsive potential and integration over ...
Zinc oxide is a key material for optoelectronic applications, whose transport properties are typically dominated by the lattice vibrations. We report here the phonon-dispersion relations of wurtzite ZnO at 10 K, as determined by using inelastic neutron scattering. The experimental data are analyzed with the aid of ab initio calculations based on ...
An acceleration mechanism of silane plasma chemical vapor deposition by diborane is proposed on the basis of an ab initio molecular orbital calculation. Hydrogen abstraction from the growing surface by BH2 is calculated to be much more favorable than that by SiH3 from both the kinetic and thermodynamic viewpoint. Thus, the abstraction ...
By combining thermodynamic database searching with first principles density functional theory and phonon lattice dynamics calculations, a theoretical screening methodology to identify most promising candidates for CO2 sorbents has been proposed (Duan & Sorescu, PRB(2009), JCP(2010)). For given solids, first we can search their thermodynamic properties ...
We describe a method for calculating thermodynamic properties of ionic liquids by using standard quantum statistical thermodynamics as characterized by ab initio techniques. We review briefly how thermochemical properties for different sized clusters of ionic liquids are calculated by standard ...
To better explain the unusual distribution and relative abundances of several 6- and 7-carbon amino acids found in meteorites, their thermodynamic properties were studied using accurate ab initio techniques. In addition to optimized structures and relative energies, vibrational frequency and thermochemical analysis of different ...
We assess the quantitative accuracy of the particle-in-cell (PIC) approximation used in recent ab initio predictions of the thermodynamic properties of hexagonal-close-packed iron at the conditions of the Earth's inner core. The assessment is made by comparing PIC predictions for a range of thermodynamic properties ...
Due to recent advances in methods and computers, the accuracy of ab calculations has reached a point
NASA Technical Reports Server (NTRS)
We present a calculational method to predict terminations of growing or as-deposited surfaces as a function of the deposition conditions. Such characterizations are valuable for understanding catalysis and growth phenomena. The method combines ab initio density-functional-theory calculations and experimental thermodynamical data with a ...
We present a fully [ital ab] [ital initio] calculation of the thermodynamic properties for silicon within the quasiharmonic approximation, making use of volume-dependent phonon frequencies obtained from pseudopotential local-density calculations. The temperature dependence of the thermal-expansion coefficient, specific heat (at ...
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 discussed. In the second ...
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 ...
... 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 ...
...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
The increased application of quantum mechanical-based methodologies to the study of alloy stability has required a re-assessment of the field. The focus is mainly on inorganic materials in the solid state. In a first part, after a brief overview of the so-called ab initio methods with their approximations, constraints, and limitations, recommendations are ...
A general set of methods is presented for calculating chemical potentials in solid and liquid mixtures using {\\em ab initio} techniques based on density functional theory (DFT). The methods are designed to give an {\\em ab initio} approach to treating chemical equilibrium between coexisting solid and liquid ...
... 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 ...
In this lecture we presented a methodology to obtain free energies from empirical potentials and applied it to the study of the phase diagram of FeCr. Subsequently, we used Metropolis Monte Carlo to analyze homogeneous and heterogeneous precipitation of the Cr rich solid solution {alpha}{prime}. These examples are part of our work in the area of steels for nuclear applications and can be found in ...
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
The aim of this thesis is to study metallic sodium clusters by numerical simulation. We have developed two ab initio molecular dynamics programs within the formalism of density functional theory. The first is based on the semi- classical extended Thomas-F...
Thermodynamic stabilities of ternary metal borides: An ab initio guide for synthesizing layered-plane boron phonon mode at in a large class of metal borides. Our results reveal interesting general trends step to overcome the limitations of the existing layered metal borides and to have a chance
Extensive first principles calculations are carried out to investigate gold-promoted TiO2(110) surfaces in terms of structure optimizations, electronic structure analyses, ab initio thermodynamics calculations of surface phase diagrams, and ab initio molecular dynamics simulations. All ...
Hydrogen is considered a promising candidate to achieve an alternative source to overcome future energy supply problems. Very recently, an ab initio molecular dynamics study of the hydrogen diffusion in sodium and lithium hydrides appeared by Ramzan and Ahuja [J. Appl. Phys. 106, 016104 (2009)]. Here, we alternatively report the calculation of the ...
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 ...
A prediction of four-membered cyclic boranes is presented. Structure and bonding of planar and puckered rings optimized at MBPT(2)/PVDZ level are discussed. Singlet-triplet gaps and thermodynamic stabilities of the rings based on Coupled Cluster calculations are given.
We study the potential energy landscape underlying the motion of monatomic liquids by quenching from random initial configurations (stochastic configurations) to the nearest local minimum of the potential energy. We show that this procedure reveals the underlying potential energy surface directly. This is in contrast to the common technique of quenching from a molecular dynamics trajectory which ...
. Kinslow Academic, New York, 1970 . 39 LASL Shock Hugoniot Data, edited by S. P. Marsh University of Cali a second-order polynomial to the E- c/a data and finding the c/a value at the minimum energy. By fitting, LDA, and experi- mental data of Ref. 12. FIG. 2. The Einstein temperatures obtained from the ionic
There has long been interest in the use of oxygenated hydrocarbon additives to conventional fuels. These oxygenates have been shown to reduce soot emissions in diesel engines and CO emissions in spark-ignition engines; and often allow diesel operation wit...
Zircon and Reidite are the polymorphs of ZrSiO4 minerals that are natural hosts of various radioactive elements in the crust of the earth. Its high permittivity also makes it a promising material for the gate dielectric material in metal-oxide semiconductors. Knowledge of the thermodynamic properties at high temperature and high is very important to consider its application as ...
We report on the determination of a high quality ab initiu potential energy surface (PES) and dipole
We propose a combined ab initio-spin quantum Monte Carlo (QMC) approach to compute thermodynamic properties of magnetic materials by first principles. The key to the proposed approach is a mapping of the magnetic long-range system onto an effective, nearest-neighbor quantum Heisenberg model, for which the QMC approach provides a ...
The thermodynamic, electronic, and structural properties of liquid Na-Li and Ca-Li alloys at high pressure have been studied using ab initio molecular dynamics simulations. Gibbs free energies of pure Na, Ca, Li, and their mixtures (Na-Li and Ca-Li) are computed from vibrational density of states to determine the mixing-demixing ...
The finite temperature density functional theory and quasiharmonic lattice dynamics have been used to compute numerous thermodynamic properties of hexagonal close packed magnesium using both the local density approximation (LDA) and the generalized gradient approximation (GGA) for the exchange-correlation potential. Generally, it is found that there exist only minor ...
Group contribution methods are powerful tools for estimating the thermophysical and thermodynamic properties of pure components and mixtures from experimental data on related substances. Among the problems with current group contribution methods is that there is no theoretical basis for defining functional groups and no a priori way of determining when a group contribution ...
This work has been undertaken in order to obtain data on thermodynamic properties of organic carbonates and to revise the group-additivity values necessary for predicting their standard enthalpies of formation and enthalpies of vaporization. The standard molar enthalpies of formation of dibenzyl carbonate, tert-butyl phenyl carbonate, and diphenyl carbonate were measured using ...
The energy dependence of surface reactions has been investigated through ab initio MD simulations for collisions between Al1+ and a gibbsite surface. No change in surface composition was observed for 0 eV initial kinetic energy of Al1+. An increase in energy to 3.5 eV resulted in extended surface migration of hydrogen, subsequent H2 formation and ...
Temperature and pressure dependent decomposition kinetics of HS2O7-(H2SO4)x (x=1-3) cluster ions were measured in a quadrupole ion trap mass spectrometer. The kinetic data were analyzed with a master equation model to obtain the decomposition energies and energy transfer parameters for channels leading to elimination of sulfur trioxide and in some cases sulfuric acid. The ion cluster structures, ...
Molecular dynamics (MD) is a powerful tool to probe the thermodynamic and kinetic properties of solid, glass and liquid phases. In classical molecular dynamics (CMD), empirical models are used to describe the force by considering bond, bend and dihedral angle contributions with parameters fitted to experimental data or first-principles calculations of small clusters. In the ...
The static and dynamic properties of liquid Sn at two di?erent thermodynamic states have been studied from the Orbital Free Ab-Initio Molecular Dynamics (OFAIMD) simulation method. This method is based on the density functional theory (DFT) of Hohenberg and Kohn. The exchange and correlation interaction is described here with the local density ...
One of the main research efforts of the recent years has been the development of an efficient way to select desired carbon nanotubes according to their size and their electronic properties. This selectivity would allow easier fabrication of field effect transistor and light-emitting diode devices with appropriate nanotubes. An appealing approach to assess this problem is to use the dependence of ...
Ab initio total energy calculations based on the exact muffin-tin orbitals method, combined with the coherent potential approximation, have been used to study the thermodynamical and elastic properties of substitutional refractory Ru1-xNixAl alloys. We have found that the elastic constants C' and C11 exhibit pronounced peculiarities ...
A method for calculating a priori thermodynamic functions (specific heat, entropy, free energy, and enthalpy) from a combination of single determinant ab initio calculations employing the 4-21NO basis and experimental data is developed and validated. An estimate of the r sub e geometry is determined by empirically correcting the ...
