... from federally funded research, testing and training ... and agencies for Research Development Test and Evaluation ... Title : Ab Initio Study of Ultracold ...
DTIC Science & Technology
An MCSCF approach is used to study low lying excited electronic states of CN- and CN in vacuo and in point charge lattices. The latter simulate the electrostatic potential that renders excited states of CN- stable against autoionization in ionic lattices....
National Technical Information Service (NTIS)
An MCSCF approach is used to study low lying excited electronic states of CN- and CN in vacuo and in point-charge lattices. The latter simulate the electrostatic potential that renders excited states of CN- stable against autoionization in ionic lattices....
We have studied structural and dynamical properties of Mg2Sn by employing an ab-initio pseudopotential method and a linear response scheme, within the generalised gradient approximation. The calculated lattice constant, bulk modulus and pressure derivative of bulk modulus are in agreement with previous ab-initio calculations and ...
Energy Citations Database
NASA Astrophysics Data System (ADS)
A systematic method for approximating the ab initio electronic energy of crystal lattices has been improved by the incorporation of long range electrostatic and dispersion interactions. The effect of these long range interactions on the optimization of the crystal structure is reported. The harmonic lattice ...
PubMed
Based on ab initio pseudopotential calculations, the results of investigations of the lattice dynamics of silver halides AgHal (Hal = Cl, Br, I) are presented. Equilibrium lattice parameters, phonon spectra, frequency densities and effective atomic-charge values are obtained for all types of crystals under study.
... collisions of Li and alkaline-earth or rare- earth atoms, such ... 2. "What we need to know about ultracold polar ... work for the Department of Defense ...
. The previous ab initio results on lattices of K atoms for coordination numbers z 8, 4, and 2 are analyzed these DFT results for K into contact with a simple and physically appealing quantum-chemical model proposed conclusions are given at the end of the paper. II. THEORETICAL METHOD We have performed the ab ...
E-print Network
We demonstrate a probe for nearest-neighbor correlations of fermionic quantum gases in optical lattices. It gives access to spin and density configurations of adjacent sites and relies on creating additional doubly occupied sites by perturbative lattice modulation. The measured correlations for different lattice temperatures are in ...
In an attempt to better understand the Ultraviolet absorption and emission spectra of hydroxide ion, we have carried out what we believe are the first ab initio quantum chemical calculations on excited electronic states of this ion. Because these excited ...
Early scattering experiments revealed that the proton was not a point particle but a bound state of many quarks and gluons. Deep inelastic scattering (DIS) experiments have accurately determined the probability of struck quarks carrying a fraction of the ...
We described our theoretical advances that influenced the experimental creation of vibrationally and translationally cold polar molecules. Our analysis includes multi-channel bound states of ground and excited electronic states. We excellent agreement wit...
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 ...
... This study involves: Ab-initio crystal orbitals and polymer orbitals; Ab-initio coupled cluster program; Ab-initio quantum chemical calculations and ...
Lattice distortions near impurity atoms in ?-Fe1?x Six alloys (x?0.05 0.06) are studied both experimentally using x-ray diffraction and theoretically by means of ab initio calculations. It is found that the distortions are more complex than experimental data suggest. The displacements of atoms near impurities are not determined by the ...
Lattice gauge theory provides our only means of performing ab initio calculations in the nonperturbative regime. It has thus become an increasingly important component of the Jefferson Lab physics program. In this paper, we describe the contributions of lattice QCD to our understanding of hadronic and nuclear ...
As dislocation motion is resisted by the Peierls barrier, cracks in brittle crystals can be lattice-trapped. The discrete lattice structure of a crystal under loading reflects this behavior of the defect's motion. By determining the energy barrier to crack motion at loads within the range of lattice trapping, the authors are ...
Applying time differential perturbed angular correlation (TDPAC) spectroscopy and ab initio calculations, we have investigated possible lattice instabilities in Sr(2)RuO(4) by studying the electric quadrupole interaction of a (111)Cd probe at the Ru site. We find evidence for a dynamic lattice distortion, revealed ...
For the equilibrium immiscible Fe-Cu system, ab initio calculations using the projector augmented wave method identify the relatively stable structures of the metastable Fe25Cu75 and Fe50Cu50 alloys to be both of fcc and determine their corresponding lattice constants and cohesive energies. Some of the 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,. ...
Combined ab initio and micromagnetic simulations are carried out to build up a direct relationship between critical switching current Jc and geometric structure (in-plane lattice constant a and film thickness) of FePt in magnetic tunnel junctions. Ab initio calculations predict that the strain ...
The lattice constants and cohesive energies of some possible metastable Cu-W compounds are obtained by ab initio calculation and the formation of a metastable phase at Cu75W25 is predicted for the equilibrium immiscible Cu-W system. The prediction is in agreement with the fact that a metastable hcp phase was indeed observed in the ...
The structural, electronic and dynamic properties of cesium chloride, ZrRu and ZrZn were studied by employing an ab initio pseudopotential method and a linear response scheme, within the generalized gradient approximation. The calculated lattice constant, bulk modulus and first-order pressure derivative of the bulk modulus were ...
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 ...
Cubic zirconia exhibits a soft phonon mode (X2-) which becomes dynamically unstable at low temperatures. Previous ab initio investigations into the temperature-induced stabilization of the soft mode treated it as an independent anharmonic oscillator. Calculations presented here, using the self-consistent ab initio ...
More than 99% of the mass of the visible universe is made up of protons and neutrons. Both particles are much heavier than their quark and gluon constituents, and the Standard Model of particle physics should explain this difference. We present a full ab initio calculation of the masses of protons, neutrons, and other light hadrons, using ...
An ab initio study of the doping of alkali halide crystals (AX: A=Li, Na, K,Rb; X=F, Cl, Br, I) by ns2 anions (Ag- and Cu-) is presented. Large activeclusters with 179 ions embedded in the surrounding crystalline lattice areconsidered in order to describe properly the lattice relaxation induced by theintroduction ...
We have studied the influence of additions of Al and Si on the lattice stability of face-centred-cubic (fcc) versus hexagonal-closed-packed (hcp) Fe�Mn random alloys, considering the influence of magnetism below and above the fcc N�el temperature. Employing two different ab initio approaches with respect to basis sets and treatment ...
We have studied the influence of additions of Al and Si on the lattice stability of face-centred-cubic (fcc) versus hexagonal-closed-packed (hcp) Fe-Mn random alloys, considering the influence of magnetism below and above the fcc N�el temperature. Employing two different ab initio approaches with respect to basis sets and treatment ...
The phonon-dispersion relations of the lightest wurtzite structure compound BeO have been determined from inelastic x-ray scattering (IXS) measurements and analyzed by ab initio calculations. Experimental data and calculations show good agreement and reconcile the existing controversies. The phonon linewidth of the longitudinal-optical phonon along ?-A ...
The ab-initio calculations based on density functional theory (DFT) are performed for Fe and C in their ground state crystal structures. Heats of formation are then calculated for different Fe-C alloy compounds. The lattice constant (volume), bulk modulus and shear moduli for cementite are determined from the total energy calculations. These material ...
Lithium oxide is an important material because of its high thermal conductivity and superionic behavior at high temperature. It behaves like a superionic conductor above 1200 K. Phonon frequencies have been calculated using ab-initio method. The calculations of phonon dispersion relation near unit cell volume corresponding to the superionic transition indicate softening of ...
Using ab initio density-functional theory, we study the role of interstitial hydrogen on the energetics of the phase transformation of iron from bcc to hcp along Bain�s pathway. The impurity creates an internal stress field that can be released through a tetragonal distortion of the lattice, promoting the bcc (ferromagnetic) ? fcc ...
General procedures for computing alloy phase equilibria from ab initio electronic structure calculations are reviewed and applied to the Al-Li phase diagram. Free energies were calculated by the cluster variation method (CVM) in the tetrahedron approximation for the fcc and bcc lattices and ordered superstructures. Input was provided ...
The relaxation of hot hydrogen atoms upon the dissociative adsorption of H2 on Pd(100) was studied by ab initio molecular dynamics simulations based on density functional theory, modeling the full dissociative adsorption process in a consistent manner. In spite of the nonlinear dependence of every single trajectory on the run conditions, on the average it ...
... Title : AB Initio Study of the Electronic Magnetic Circular Dichroism ... functions are determined using as initio quantum chemical techniques including ...
The complexity of current {ital ab} {ital initio} quantum-mechanical calculations of the total energy of given distributions of atoms on a periodic lattice often limits explorations to just a few configurations. We show how such a small number of calculations can be used instead to compute the interaction energies of a generalized ...
Ab initio molecular orbital calculations have been used to investigate the nature of lithium bonding in stage 1 lithium intercalated carbon anodes. This has been approximated by using layered carbon lattices such as coronene, (C(sub 24)H(sub 12)),anthrace...
Ab initio molecular orbital calculations have been used to investigate the influence of corannulene's curved carbon lattice (C(sub 20)H(sub 10)) on lithium intercalation. This has been approximated by investigating the reaction of lithium atoms with eithe...
Early scattering experiments revealed that the proton was not a point particle but a bound state of many quarks and gluons. Deep inelastic scattering (DIS) experiments have accurately determined the probability of struck quarks carrying a fraction of the proton's momentum. The current generation of experiments and Lattice QCD calculations will provide detailed ...
Due to recent advances in methods and computers, the accuracy of ab calculations has reached a point
NASA Technical Reports Server (NTRS)
Lattice Gauge Theory enables an ab initio study of the low-energy properties of Quantum Chromodynamics, the theory of the strong interaction. The author begins these lectures by presenting the lattice formulation of QCD, and then outline the benchmark calculation of lattice QCD, the ...
DOE Information Bridge
Lattice calculations provide an ab initio means for the study of QCD. Recent progress at understanding the spectrum and structure of nucleons from lattice QCD studies is reviewed. Measurements of the masses of the lightest particles for the lowest spin values are described and related to predictions of quark model. ...
In supernova cores, nuclear "pasta" phases such as a triangular lattice of rodlike nuclei and layered structure of slablike nuclei are considered to exist. However, it is still unclear whether or not they are actually formed in collapsing supernova cores. Using ab initio simulations called quantum molecular dynamics, here we solve this ...
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 initio ...
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 initio ...
Using ab-initio calculations, we study the properties of the multiferroic BiFeO3 compounds in the perfect cubic perovskite lattice structure. We show that the appearance of magnetism is energetically favorable. Except the ferromagnetic structure, there are three possible antiferromagnetic arrangements, which are close in energy, and for large values of the ...
Using ab initio calculations we have computed the lattice constants, bulk moduli, and local and total density of states of the MAX phases, Ti2TlC, Zr2TlC, and Hf2TlC in the hexagonal P63/mmc space group. The results for lattice constants are within 2% of experimental results. The bulk moduli are predicted to be ...
In the equilibrium immiscible Ru-Pd system, the total energies for five possible structures, i.e., A15, D09, D019, L12, and L60, with a stoichiometry of RuPd3 were calculated as a function of lattice constants, based on the Vienna Ab Initio Simulation Package (VASP). The calculation results predicted that the D019, L12, and L60 ...
This study investigates the electronic structure of Group IA cations intercalated into zeolites with the analcime (ANA) framework using ab initio periodic Hartree-Fock theory. The purpose of the study is to gain a better understanding of the role played by electron-donating species in zeolites in general, with specific applications to materials that have ...
A combination of ab initio and statistical thermodynamics, i.e., the cluster variation method (CVM), is applied to describe the FCC-based {gamma}-Fe[N]/{gamma}'-Fe{sub 4}N{sub 1-x} phase equilibrium. The ab initio calculated internal energies of ordered compounds, using the full-potential (linearized) ...
Protein structure prediction is regarded as a highly challenging problem both for the biology and for the computational communities. Many approaches have been developed in the recent years, moving to increasingly complex lattice models or even off-lattice models. This paper presents a Large Neighborhood Search (LNS) to find the native state for the ...
Epitaxial thin films prepared using an MgO target on silicon substrate often show constriction of lattice constant (a~4.1 A?). Detailed investigation of the crystal structure excluded the possibility that the epitaxial films are either cubic spinel MgO or magnesium silicate (a/2~4.1 A?). With such a constriction in rock salt MgO structure point defects must be induced into ...
Ultracold atoms in an optical lattice provide a unique toolbox for emulating the prototypical models of condensed matter physics. Before the optical lattice system can be trusted as a quantum simulator however, it needs to be validated and benchmarked against known results, for which quantum Monte Carlo simulations are ideally suited. In this talk, an ...
... 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
approximation (LDA) [34, 35], as implemented in the Vienna Ab-Initio Simulations Package (VASP) [36) operated at 15 kV and 300 W. Software for data acquisition and analysis have been described previously [26-surface OH groups, which destabilize Cu adatoms, are absent or are a minority species. Acknowledgements: VASP
Scientists have long pondered why the simple cubic structure is so rarely seen in nature. Only one element forms the simple cubic structure: polonium. There are `proofs' dating back to 1954 that the simple cubic lattice should be unstable. We will attempt to address the question of why polonium takes the simple cubic structure by means of ab ...
Using ab initio pseudopotentials the properties of electrons, phonons and electron-phonon interactions in highly compressed Si have been computed. In particular, the hexagonal phases have been predicted to be superconducting by this calculation. The superconducting transition temperature for hexagonal Si has been measured for pressures between 16-45 GPa ...
Here we demonstrate and characterize the H-diffusion behavior around a screw dislocation in body-centered cubic (bcc) ?-Fe by performing path-integral molecular dynamics modeling and adopting an ab initio�based potential. Counterintuitively, our results indicate that the H diffusivity along the dislocation line is significantly lower than ...
pseudopotentials,14,15 as implemented in the highly-efficient Vienna ab initio simulation package (VASP).16,17 We atoms, respectively. TABLE IV. First principles (VASP�GGA) calculated equilib- rium lattice parameter. ACKNOWLEDGMENTS The authors wish to thank Dr. Axel van de Walle for his kind help on the use of the ATAT software
In the paper the authors present the results of an ab initio calculation of the thermal expansion, the specific heat and the mean-square amplitude of vibration of a Lennard-Jones crystal, carried out in the quasi-harmonic approximation. The dynamical prob...
The ground-state properties of diamond are investigated using an ab initio density-functional pseudopotential scheme. The calculated equilibrium lattice constant, cohesive energy, and bulk modulus are in excellent agreement with experiment. Unlike Si and Ge, a double hump is found in the valence-electron charge density along the ...
First-principles density-functional calculations utilizing ab initio pseudopotentials and plane-wave expansions are used to determine lattice parameters, bulk moduli, and band structures for AlN, GaN and InN. It is found that large numbers of plane waves ...
A recently developed self-consistent ab initio lattice dynamical method has been applied to the high temperature body centered cubic (bcc) phase of La and Th, which are dynamically unstable at low temperatures. The bcc phase of these metals is found to be stabilized by phonon-phonon interactions. The calculated high temperature phonon ...
We have investigated the ground state structural, electronic and optical properties of CuAlSe2 compound by using density functional theory employing three different functionals for the exchange correlation (XC) potentials. Our calculation shows that given compound is direct band gap semiconductor. We noticed that (GGA-EV) shows good agreement with the experimental data.
Cesium iodide properties, both in the bulk and on (110) and (100) surfaces, are studied using density functional theory. The bulk lattice constant, bulk modulus, and elastic constants are in good agreement with the experimental values. The electronic band structure is also calculated, as well as the density of states. On the surfaces, relaxation of the atoms was performed, and ...
under contracts DOE B-341492, W-7405-ENG-48, and 1-B-333164. SvPablo [4], Medea [3], Paragraph [6 Review, to appear. [3] M. Calzarossa, L. Massari, A. Merlo, M. Pantano, and D. Tessera. Medea: A Tool
... 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 ...
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 unitarity limit describes interacting particles where the range of the interaction is zero and the scattering length is infinite. We present precision benchmark calculations for two-component fermions at unitarity using three different ab initio methods: Hamiltonian lattice formalism using iterated eigenvector methods, Euclidean ...
I convey an idea of the significant recent progress, which opens up good perspectives for high-precision ab-initio computations in heavy flavour physics based on lattice QCD. This report focuses on the strategy and the challenges of fully non-perturbative investigations in the B-meson sector, where the b-quark is treated within an effective theory, as ...
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 ...
A realistic Anderson lattice Hamiltonian for La/sub 2-//sub x/Sr/sub x/CuO/sub 4/ is derived from an extensive tight-binding parametrization of ab initio band structure. A solution of the Hamiltonian by the 1/N expansion technique gives remarkably good agreement with the data on thermodynamic, transport, and critical properties, e.g., ...
We demonstrate that magnetic vortices in which spins are coupled to polar lattice distortions via superexchange exhibit an unusually large linear magnetoelectric response. We show that the periodic arrays of vortices formed by frustrated spins on kagome lattices provide a realization of this concept; our ab initio ...
The authors use a combination of lattice simulation calculations and ab initio quantum mechanical techniques to study the adsorption behavior of methanol in ZSM-5. We locate the low-energy adsorption sites for the methanol molecule inside the pores of the ZSM-5 zeolite using lattice simulation techniques. ...
The formalism and the experimental conditions under which coherent inelastic x-ray scattering from phonons can be utilized to determine the vibrational density of states are presented. The validity of the approach is checked by comparison of results for diamond and MgO with ab initio lattice dynamics calculations and thermodynamic ...
In his recent paper, Shear modulus collapse of lattices at high pressure, J. Phys. Cond. Matt. 16 (2004) L125, V.V. Kechin claims that the zero temperature shear modulus of a metallic solid vanishes at a high critical pressure, and the critical pressures for this shear modulus collapse lie in the range 0 250 Mbar for elemental metals. Here we demonstrate that Kechin's ...
Measurements of the local susceptibility and 3d spin relaxation rate for single Fe impurities embedded in a nanocrystalline Nb host indicates the emergence of a local moment on Fe at and below a critical size of 11�nm. Our ab�initio electronic structure calculations show that the moment formation occurs due to Stoner enhancement arising from a size dependent ...
Achieving comprehensive information on thin film lattice dynamics so far has eluded well established spectroscopic techniques. We demonstrate here the novel application of grazing incidence inelastic x-ray scattering combined with ab initio calculations to determine the complete elastic stiffness tensor, the acoustic and low-energy ...
An accurate equation of state (EOS) is determined for the high-pressure orthorhombic phase of boron, B28, experimentally as well as from ab initio calculations. The unique feature of our experiment is that it is carried out on the single crystal of B28. In theory, we take into consideration the lattice vibrations, often neglected in ...
The supercell Pd16H has been investigated in order to describe the hydrogen migration in the palladium lattice, where the hydrogen atom moves between symmetric interstitial sites. Ab initio calculations of the barriers for hydrogen diffusion in relaxed and unrelaxed metal lattices have been performed in the local ...
The effect of the electron-phonon interaction on magnetization relaxation is studied within the framework of first-principles scattering theory for Fe, Co, and Ni by displacing atoms in the scattering region randomly with a thermal distribution. This �frozen thermal lattice disorder� approach reproduces the nonmonotonic damping behavior observed in ferromagnetic resonance ...
A recently proposed computational scheme based on local increments has been applied to the calculation of correlation contributions to the cohesive energy of the CaO crystal. Using {ital ab} {ital initio} quantum-chemical methods for evaluating individual increments, we obtain {approximately}80{percent} of the difference between the experimental and ...
Ordinary matter is described by six fundamental parameters: three couplings (gravitational, electromagnetic and strong) and three masses: the electron's (m) and those of the up (m) and down (m) quarks. An additional mass enters through quantum fluctuations: the strange quark mass (m). The three couplings and m are known with an accuracy of better than a few per mil. Despite their importance, m, m ...
The temperature-dependent mass diffusion coefficient is computed using transition state theory. Ab initio supercell phonon calculations of the entire system provide the attempt frequency, the activation enthalpy, and the activation entropy as a function of temperature. Effects due to thermal lattice expansion are included and found to ...
Ferroelectric (FE) materials display very peculiar structural, electrical, and electromechanical features. Their properties have been addressed, by means of ab initio simulations, from 1990. Since then, a great number of different contributions has greatly expanded our understanding of this important class of materials; quite often, these contributions ...
Substitution of more than 33% of the naturally abundant O16 in strontium titanate SrTiO3 by O18 causes the system to become ferroelectric at low temperatures. The ferroelectricity has been observed via susceptibility measurements, but to date the details of the ferroelectric phase and the phase transition are unclear. Using ab initio density functional ...
Using ab initio calculations, we have performed a study of the hydrostatic pressure effect on the equilibrium volume, lattice parameters, elastic modulus, and elastic anisotropy of selected M{2}AlC phases with M = Ti, V, Nb, and Ta. The deviations of our calculated volume change are lower than 3% comparing with experimental ...
A systematic study of ground state properties of cubic (3C) and hexagonal (6H, 4H, 2H) polytypes of normal (nonnitride) III-V compounds is reported using well-converged density-functional calculations within local density approximation, ab initio pseudopotentials, and projector-augmented wave method. Equilibrium results are obtained for ...
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 partial occupation of Zn at the ...
The initial stages of NaCl dissolution in liquid water have been examined with state-of-the-art ab initio molecular dynamics and free energy sampling techniques. Our simulations reveal a complex multi-step process triggered by the departure of Cl ions from the lattice, with a well-defined intermediate state wherein departing ions are ...
Cubic zirconia exhibits a soft phonon mode (X{sup -}{sub 2}), which becomes dynamically unstable at low temperatures. Previous ab initio invest.igations into the temperature-induced stabilization of the soft mode treated it as an independent anharmonic oscillator. Calculations presented here, using the self consistent ab ...
The structure state of carbon eutectoid steel has been studied by the in situ neutron diffraction method in the temperature range from room temperature to 800�C. It has been shown that an increase in the temperature is accompanied by a decrease in the concentration of carbon in cementite, whereas its weight fraction and the parameters of the orthorhombic lattice change ...
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 ...
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 molybdenum is developed which ...
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 of the many-body wave ...
Using ab initio methods, we theoretically investigate the adsorption of one and two Pt dimers on Cu(001). Treating the interaction of adsorbates on surfaces as a local phenomenon, a representation of the substrate by a large cluster of at least 62 Cu atoms allows one to treat the electronic structures of both systems, that is, the adsorbate and the ...
The Hoyle state plays a crucial role in the helium burning of stars heavier than our Sun and in the production of carbon and other elements necessary for life. This excited state of the carbon-12 nucleus was postulated by Hoyle as a necessary ingredient for the fusion of three alpha particles to produce carbon at stellar temperatures. Although the Hoyle state was seen experimentally more than a ...
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 with the results of more exact ...
A constant pressure ab initio MD technique and density functional theory with a generalized gradient approximation (GGA) was used to study the pressure-induced phase transition in wurtzite ZnTe. A first-order phase transition from the wurtzite structure to a Cmcm structure was successfully observed in a constant-pressure molecular dynamics simulation. This ...
We present the photoluminescence spectra of ?-glycine, L-alanine, and L-asparagine crystals. They are broad and structured, comprising green to ultraviolet emission in the 1.75-3.60 eV range. Absorption measurements show that the band gap energies of the crystals are of the order of 5.0 eV. Ab initio calculations of their electronic structures allow for ...
Using ab initio molecular dynamics we investigate the electronic and lattice structure of AFe2As2 (A=Ca,Sr,Ba) under pressure. We find that the structural phase transition (orthorhombic to tetragonal symmetry) is always accompanied by a magnetic phase transition in all the compounds while the nature of the transitions is different ...
Spectroscopic ellipsometry is used to determine the complex refractive index (n-ik), porosity, and thickness of porous silicon (PSi) films. These films are obtained by anodizing p-type crystalline silicon in a hydrofluoric acid bath. After etching, PSi samples are heated to 750 �C in a controlled oxygen environment. A detailed analysis of the ellipsometry data is performed in order to determine ...
Multiple-scattering XAFS-calculations at the oxygen K edge of Cu2O and the fluorine K edge of CaF2 by means of the FEFF code are compared to low- and room temperature experimental data. It is shown for CaF2 that the Debye model provides good estimates of room temperature Debye-Waller factors yielding 300 K XAFS-calculations well reproducing the experiment. For other cases like Cu2O, however, the ...
By using ab initio density functional theory, the structural characterizations and electronic properties of two large-diameter (13, 13) and (14, 14) armchair silicon carbide nanotube (SiCNT) bundles are investigated. Full structural optimizations show that the cross sections of these large-diameter SiCNTs in the bundles have a nearly hexagonal shape. The ...
Ab initio lattice dynamics based on linear response method are performed for high pressure phase of yttrium to describe electron-phonon coupling and subsequent superconducting behavior. The critical temperature Tc in fcc-Y increases monotonically with pressure up to 9.25 K at 31 GPa, which is quantitatively in excellent agreement with ...
We report on the determination of a high quality ab initiu potential energy surface (PES) and dipole
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 ...
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 ...
The equation of state (EOS) of alloys at high pressures is generalized with the cluster expansion method. It is shown that this provides a more accurate description. The low temperature EOSs of Ni-Al alloys on FCC and BCC lattices are obtained with density functional calculations, and the results are in good agreement with experiments. The merits of the generalized EOS model ...
Molecular dynamics simulations of NO-doped Ar solid upon Rydberg photoexcitation of the impurity have been carried out taking into account angular dependent potential energy surfaces (PESs) in the ground and excited states. To go beyond isotropic potentials simulations, the effects of anisotropy of potentials on the structure, dynamics, and energetics are investigated by taking into account two ...
Vibrational dynamics of the MnO lattice has been studied using density functional theory combined with the direct method. Considerations have been limited to the harmonic approximation. Ab initio calculated Hellmann-Feynman forces were used to obtain density of states and the dispersion relations of phonons in the MnO crystal. ...
Following a brief review of the past work published on the structural and mechanical properties of the ? -SiAlON crystal, an ab initio computational method is outlined, which was employed to investigate the material properties and electronic structure of the ?-Si6?zAlzOzN8?z , where z=0-5 , single crystal configuration. Using data of preferred ...
The elastic and thermodynamic properties of fcc-6LiF under high temperatures and pressures are investigated using the ab initio method and quasi-harmonic Debye model. The lattice constant of 6LiF at ground state is a little larger than that of LiF. When pressure is less than 10 GPa, crystal lattice is compressed ...
