initio phenomenological simulation: Topics by WorldWideScience.org

Sample records for initio phenomenological simulation

An ab initio chemical reaction model for the direct simulation Monte Carlo study of non-equilibrium nitrogen flows.

Science.gov (United States)

Mankodi, T K; Bhandarkar, U V; Puranik, B P

2017-08-28

A new ab initio based chemical model for a Direct Simulation Monte Carlo (DSMC) study suitable for simulating rarefied flows with a high degree of non-equilibrium is presented. To this end, Collision Induced Dissociation (CID) cross sections for N 2 +N 2 →N 2 +2N are calculated and published using a global complete active space self-consistent field-complete active space second order perturbation theory N 4 potential energy surface and quasi-classical trajectory algorithm for high energy collisions (up to 30 eV). CID cross sections are calculated for only a selected set of ro-vibrational combinations of the two nitrogen molecules, and a fitting scheme based on spectroscopic weights is presented to interpolate the CID cross section for all possible ro-vibrational combinations. The new chemical model is validated by calculating equilibrium reaction rate coefficients that can be compared well with existing shock tube and computational results. High-enthalpy hypersonic nitrogen flows around a cylinder in the transition flow regime are simulated using DSMC to compare the predictions of the current ab initio based chemical model with the prevailing phenomenological model (the total collision energy model). The differences in the predictions are discussed.
A Force Balanced Fragmentation Method for ab Initio Molecular Dynamic Simulation of Protein

Directory of Open Access Journals (Sweden)

Mingyuan Xu

2018-05-01

Full Text Available A force balanced generalized molecular fractionation with conjugate caps (FB-GMFCC method is proposed for ab initio molecular dynamic simulation of proteins. In this approach, the energy of the protein is computed by a linear combination of the QM energies of individual residues and molecular fragments that account for the two-body interaction of hydrogen bond between backbone peptides. The atomic forces on the caped H atoms were corrected to conserve the total force of the protein. Using this approach, ab initio molecular dynamic simulation of an Ace-(ALA9-NME linear peptide showed the conservation of the total energy of the system throughout the simulation. Further a more robust 110 ps ab initio molecular dynamic simulation was performed for a protein with 56 residues and 862 atoms in explicit water. Compared with the classical force field, the ab initio molecular dynamic simulations gave better description of the geometry of peptide bonds. Although further development is still needed, the current approach is highly efficient, trivially parallel, and can be applied to ab initio molecular dynamic simulation study of large proteins.
Charge carrier motion in disordered conjugated polymers: a multiscale ab-initio study

Energy Technology Data Exchange (ETDEWEB)

Vukmirovic, Nenad; Wang, Lin-Wang

2009-11-10

We developed an ab-initio multiscale method for simulation of carrier transport in large disordered systems, based on direct calculation of electronic states and electron-phonon coupling constants. It enabled us to obtain the never seen before rich microscopic details of carrier motion in conjugated polymers, which led us to question several assumptions of phenomenological models, widely used in such systems. The macroscopic mobility of disordered poly(3- hexylthiophene) (P3HT) polymer, extracted from our simulation, is in agreement with experimental results from the literature.
Ab Initio Molecular Dynamics Simulations of Furfural at the Liquid-Solid Interface

OpenAIRE

Sanwu Wang; Hongli Dang; Wenhua Xue; Darwin Shields; Xin Liu; Friederike C. Jentoft; Daniel E. Resasco

2013-01-01

The bonding configuration and the heat of adsorption of a furfural molecule on the Pd(111) surface were determined by ab initio density-functional-theory calculations. The dynamics of pure liquid water, the liquid-solid interface formed by liquid water and the Pd(111) surface, as well as furfural at the water-Pd interface, were investigated by ab initio molecular dynamics simulations at finite temperatures. Calculations and simulations suggest that the bonding configurati...
Ab initio simulation of dislocation cores in metals

International Nuclear Information System (INIS)

Ventelon, L.

2008-01-01

In the framework of the multi scale simulation of metals and alloys plasticity, the aim of this study is to develop a methodology of ab initio dislocations study and to apply it to the [111] screw dislocation in the bc iron. (A.L.B.)
Ab initio molecular dynamics simulation of liquid water by quantum Monte Carlo

International Nuclear Information System (INIS)

Zen, Andrea; Luo, Ye; Mazzola, Guglielmo; Sorella, Sandro; Guidoni, Leonardo

2015-01-01

Although liquid water is ubiquitous in chemical reactions at roots of life and climate on the earth, the prediction of its properties by high-level ab initio molecular dynamics simulations still represents a formidable task for quantum chemistry. In this article, we present a room temperature simulation of liquid water based on the potential energy surface obtained by a many-body wave function through quantum Monte Carlo (QMC) methods. The simulated properties are in good agreement with recent neutron scattering and X-ray experiments, particularly concerning the position of the oxygen-oxygen peak in the radial distribution function, at variance of previous density functional theory attempts. Given the excellent performances of QMC on large scale supercomputers, this work opens new perspectives for predictive and reliable ab initio simulations of complex chemical systems
Investigation of polarization effects in the gramicidin A channel from ab initio molecular dynamics simulations.

Science.gov (United States)

Timko, Jeff; Kuyucak, Serdar

2012-11-28

Polarization is an important component of molecular interactions and is expected to play a particularly significant role in inhomogeneous environments such as pores and interfaces. Here we investigate the effects of polarization in the gramicidin A ion channel by performing quantum mechanics/molecular mechanics molecular dynamics (MD) simulations and comparing the results with those obtained from classical MD simulations with non-polarizable force fields. We consider the dipole moments of backbone carbonyl groups and channel water molecules as well as a number of structural quantities of interest. The ab initio results show that the dipole moments of the carbonyl groups and water molecules are highly sensitive to the hydrogen bonds (H-bonds) they participate in. In the absence of a K(+) ion, water molecules in the channel are quite mobile, making the H-bond network highly dynamic. A central K(+) ion acts as an anchor for the channel waters, stabilizing the H-bond network and thereby increasing their average dipole moments. In contrast, the K(+) ion has little effect on the dipole moments of the neighboring carbonyl groups. The weakness of the ion-peptide interactions helps to explain the near diffusion-rate conductance of K(+) ions through the channel. We also address the sampling issue in relatively short ab initio MD simulations. Results obtained from a continuous 20 ps ab initio MD simulation are compared with those generated by sampling ten windows from a much longer classical MD simulation and running each window for 2 ps with ab initio MD. Both methods yield similar results for a number of quantities of interest, indicating that fluctuations are fast enough to justify the short ab initio MD simulations.
Ab initio determination of effective electron-phonon coupling factor in copper

Science.gov (United States)

Ji, Pengfei; Zhang, Yuwen

2016-04-01

The electron temperature Te dependent electron density of states g (ε), Fermi-Dirac distribution f (ε), and electron-phonon spectral function α2 F (Ω) are computed as prerequisites before achieving effective electron-phonon coupling factor Ge-ph. The obtained Ge-ph is implemented into a molecular dynamics (MD) and two-temperature model (TTM) coupled simulation of femtosecond laser heating. By monitoring temperature evolutions of electron and lattice subsystems, the result utilizing Ge-ph from ab initio calculation shows a faster decrease of Te and increase of Tl than those using Ge-ph from phenomenological treatment. The approach of calculating Ge-ph and its implementation into MD-TTM simulation is applicable to other metals.
Ab initio molecular dynamics simulation of laser melting of silicon

NARCIS (Netherlands)

Silvestrelli, P.-L.; Alavi, A.; Parrinello, M.; Frenkel, D.

1996-01-01

The method of ab initio molecular dynamics, based on finite temperature density functional theory, is used to simulate laser heating of crystal silicon. We have found that a high concentration of excited electrons dramatically weakens the covalent bond. As a result, the system undergoes a melting
Hexamethylcyclopentadiene: time-resolved photoelectron spectroscopy and ab initio multiple spawning simulations

DEFF Research Database (Denmark)

Wolf, T. J. A.; Kuhlman, Thomas Scheby; Schalk, O.

2014-01-01

comparing time-resolved photoelectron spectroscopy (TRPES) with ab initio multiple spawning (AIMS) simulations on the MS-MR-CASPT2 level of theory. We disentangle the relationship between two phenomena that dominate the immediate molecular response upon light absorption: a spectrally dependent delay...
Phonocatalysis. An ab initio simulation experiment

Directory of Open Access Journals (Sweden)

Kwangnam Kim

2016-06-01

Full Text Available Using simulations, we postulate and show that heterocatalysis on large-bandgap semiconductors can be controlled by substrate phonons, i.e., phonocatalysis. With ab initio calculations, including molecular dynamic simulations, the chemisorbed dissociation of XeF6 on h-BN surface leads to formation of XeF4 and two surface F/h-BN bonds. The reaction pathway and energies are evaluated, and the sorption and reaction emitted/absorbed phonons are identified through spectral analysis of the surface atomic motion. Due to large bandgap, the atomic vibration (phonon energy transfer channels dominate and among them is the match between the F/h-BN covalent bond stretching and the optical phonons. We show that the chemisorbed dissociation (the pathway activation ascent requires absorption of large-energy optical phonons. Then using progressively heavier isotopes of B and N atoms, we show that limiting these high-energy optical phonons inhibits the chemisorbed dissociation, i.e., controllable phonocatalysis.
Ab initio molecular dynamics simulation of hydrogen fluoride at several thermodynamic states

DEFF Research Database (Denmark)

Kreitmeir, M.; Bertagnolli, H.; Mortensen, Jens Jørgen

2003-01-01

Liquid hydrogen fluoride is a simple but interesting system for studies of the influence of hydrogen bonds on physical properties. We have performed ab initio molecular dynamics simulations of HF at several thermodynamic states, where we examine the microscopic structure of the liquid as well...
Phase diagrams from ab-initio calculations: Re-W and Fe-B

Energy Technology Data Exchange (ETDEWEB)

Hammerschmidt, Thomas; Bialon, Arthur; Palumbo, Mauro; Fries, Suzana G.; Drautz, Ralf [ICAMS, Ruhr-Universitaet Bochum (Germany)

2011-07-01

The CALPHAD (CaLculation of Phase Diagrams) method relies on Gibbs energy databases and is of limited predictive power in cases where only limited experimental data is available for constructing the Gibbs energy databases. This is problematic for, e.g., the calculation of the phase transformation kinetics within phase field simulations that not only require the thermodynamic equilibrium data but also information on metastable phases. Such information is difficult to obtain directly from experiment but ab-initio calculations may supplement experimental databases as they comprise metastable phases and arbitrary chemical compositions. We present simulations for two prototypical systems: Re-W and Fe-B. For both systems we calculate the heat of formation for an extensive set of structures using ab-initio calculations and employ the total energies in CALPHAD in order to determine the corresponding phase diagrams. We account for the configurational entropy within the Bragg-Williams approximation and neglect the phenomenological excess-term that is commonly used in CALPHAD as well as the contribution of phonons and electronic excitations to the free energy. According to our calculations the complex intermetallic phases in Re-W are stabilized by the configurational entropy. For Fe-B, we calculate metastable and stable phase diagrams including recently predicted new stable phases.
Studies of urea geometry by means of ab initio methods and computer simulations of liquids

OpenAIRE

Cirino, José Jair Vianna; Bertran, Celso Aparecido

2002-01-01

A study was carried out on the urea geometries using ab initio calculation and Monte Carlo computational simulation of liquids. The ab initio calculated results showed that urea has a non-planar conformation in the gas phase in which the hydrogen atoms are out of the plane formed by the heavy atoms. Free energies associated to the rotation of the amino groups of urea in water were obtained using the Monte Carlo method in which the thermodynamic perturbation theory is implemented. The magnitud...
Specific interactions between DNA and regulatory protein controlled by ligand-binding: Ab initio molecular simulation

Energy Technology Data Exchange (ETDEWEB)

Matsushita, Y., E-mail: kurita@cs.tut.ac.jp; Murakawa, T., E-mail: kurita@cs.tut.ac.jp; Shimamura, K., E-mail: kurita@cs.tut.ac.jp; Oishi, M., E-mail: kurita@cs.tut.ac.jp; Ohyama, T., E-mail: kurita@cs.tut.ac.jp; Kurita, N., E-mail: kurita@cs.tut.ac.jp [Department of Computer Science and Engineering, Toyohashi University of Technology, Tempaku-cho, Toyohashi, Aichi, 441-8580 (Japan)

2015-02-27

The catabolite activator protein (CAP) is one of the regulatory proteins controlling the transcription mechanism of gene. Biochemical experiments elucidated that the complex of CAP with cyclic AMP (cAMP) is indispensable for controlling the mechanism, while previous molecular simulations for the monomer of CAP+cAMP complex revealed the specific interactions between CAP and cAMP. However, the effect of cAMP-binding to CAP on the specific interactions between CAP and DNA is not elucidated at atomic and electronic levels. We here considered the ternary complex of CAP, cAMP and DNA in solvating water molecules and investigated the specific interactions between them at atomic and electronic levels using ab initio molecular simulations based on classical molecular dynamics and ab initio fragment molecular orbital methods. The results highlight the important amino acid residues of CAP for the interactions between CAP and cAMP and between CAP and DNA.
Specific interactions between DNA and regulatory protein controlled by ligand-binding: Ab initio molecular simulation

International Nuclear Information System (INIS)

Matsushita, Y.; Murakawa, T.; Shimamura, K.; Oishi, M.; Ohyama, T.; Kurita, N.

2015-01-01

The catabolite activator protein (CAP) is one of the regulatory proteins controlling the transcription mechanism of gene. Biochemical experiments elucidated that the complex of CAP with cyclic AMP (cAMP) is indispensable for controlling the mechanism, while previous molecular simulations for the monomer of CAP+cAMP complex revealed the specific interactions between CAP and cAMP. However, the effect of cAMP-binding to CAP on the specific interactions between CAP and DNA is not elucidated at atomic and electronic levels. We here considered the ternary complex of CAP, cAMP and DNA in solvating water molecules and investigated the specific interactions between them at atomic and electronic levels using ab initio molecular simulations based on classical molecular dynamics and ab initio fragment molecular orbital methods. The results highlight the important amino acid residues of CAP for the interactions between CAP and cAMP and between CAP and DNA
Bicanonical ab Initio Molecular Dynamics for Open Systems.

Science.gov (United States)

Frenzel, Johannes; Meyer, Bernd; Marx, Dominik

2017-08-08

Performing ab initio molecular dynamics simulations of open systems, where the chemical potential rather than the number of both nuclei and electrons is fixed, still is a challenge. Here, drawing on bicanonical sampling ideas introduced two decades ago by Swope and Andersen [ J. Chem. Phys. 1995 , 102 , 2851 - 2863 ] to calculate chemical potentials of liquids and solids, an ab initio simulation technique is devised, which introduces a fictitious dynamics of two superimposed but otherwise independent periodic systems including full electronic structure, such that either the chemical potential or the average fractional particle number of a specific chemical species can be kept constant. As proof of concept, we demonstrate that solvation free energies can be computed from these bicanonical ab initio simulations upon directly superimposing pure bulk water and the respective aqueous solution being the two limiting systems. The method is useful in many circumstances, for instance for studying heterogeneous catalytic processes taking place on surfaces where the chemical potential of reactants rather than their number is controlled and opens a pathway toward ab initio simulations at constant electrochemical potential.
Introducing ab initio based neural networks for transition-rate prediction in kinetic Monte Carlo simulations

Science.gov (United States)

Messina, Luca; Castin, Nicolas; Domain, Christophe; Olsson, Pär

2017-02-01

The quality of kinetic Monte Carlo (KMC) simulations of microstructure evolution in alloys relies on the parametrization of point-defect migration rates, which are complex functions of the local chemical composition and can be calculated accurately with ab initio methods. However, constructing reliable models that ensure the best possible transfer of physical information from ab initio to KMC is a challenging task. This work presents an innovative approach, where the transition rates are predicted by artificial neural networks trained on a database of 2000 migration barriers, obtained with density functional theory (DFT) in place of interatomic potentials. The method is tested on copper precipitation in thermally aged iron alloys, by means of a hybrid atomistic-object KMC model. For the object part of the model, the stability and mobility properties of copper-vacancy clusters are analyzed by means of independent atomistic KMC simulations, driven by the same neural networks. The cluster diffusion coefficients and mean free paths are found to increase with size, confirming the dominant role of coarsening of medium- and large-sized clusters in the precipitation kinetics. The evolution under thermal aging is in better agreement with experiments with respect to a previous interatomic-potential model, especially concerning the experiment time scales. However, the model underestimates the solubility of copper in iron due to the excessively high solution energy predicted by the chosen DFT method. Nevertheless, this work proves the capability of neural networks to transfer complex ab initio physical properties to higher-scale models, and facilitates the extension to systems with increasing chemical complexity, setting the ground for reliable microstructure evolution simulations in a wide range of alloys and applications.
From empirical to ab initio: transferable potentials in the atomistic simulation of amorphous carbons

International Nuclear Information System (INIS)

Marks, N.A.; Goringe, C.M.; McKenzie, D.R.; McCulloch, D.G.; Royal Melbourne Institute of Technology University, Melbourne, VIC

2000-01-01

Full text: Silicon is often described as the prototype covalent material, and when it comes to developing atomistic models this situation is well described by the sentiment that 'everything works for silicon'. The same cannot be said for carbon though, where the interaction potential has always proved problematical, be it with empirical, tight-binding or ab initio methods. Thus far the most decisive contributions to understanding amorphous carbon networks have come from ab initio simulations using the Car-Parrinello method, where the fully quantum treatment of the valence electrons has provided unexpected insight into the local structure. However such first principles calculations are restricted spatially and temporally to systems with approximately 100 atoms and times of order one picosecond. There is therefore demand for less expensive techniques capable of resolving important questions whose solution can only to found with larger simulations running for longer times. In the case of tetrahedral amorphous carbon, such issues include the release of compressive stress through annealing, the origin of graphitic surface layers and the nature of the film growth process and thermal spike. Against this background tight-binding molecular dynamics has emerged as a popular alternative to first principles methods, and our group has an ongoing program to understand film growth using one of the efficient variants of tight-binding. Another direction of research is a new empirical potential based on the Environment Dependent Interaction Potential (EDIP) recently developed for silicon. The EDIP approach represents a promising direction for empirical potentials through its use of ab initio data to motivate the functional form as well as the more conventional parametrisation. By inverting ab initio cohesive energy curves the authors of EDIP arrived at a pair potential expression which reduces to the well-known Stillinger-Weber form at integer coordination, while providing
Thermal transport in nanocrystalline Si and SiGe by ab initio based Monte Carlo simulation.

Science.gov (United States)

Yang, Lina; Minnich, Austin J

2017-03-14

Nanocrystalline thermoelectric materials based on Si have long been of interest because Si is earth-abundant, inexpensive, and non-toxic. However, a poor understanding of phonon grain boundary scattering and its effect on thermal conductivity has impeded efforts to improve the thermoelectric figure of merit. Here, we report an ab-initio based computational study of thermal transport in nanocrystalline Si-based materials using a variance-reduced Monte Carlo method with the full phonon dispersion and intrinsic lifetimes from first-principles as input. By fitting the transmission profile of grain boundaries, we obtain excellent agreement with experimental thermal conductivity of nanocrystalline Si [Wang et al. Nano Letters 11, 2206 (2011)]. Based on these calculations, we examine phonon transport in nanocrystalline SiGe alloys with ab-initio electron-phonon scattering rates. Our calculations show that low energy phonons still transport substantial amounts of heat in these materials, despite scattering by electron-phonon interactions, due to the high transmission of phonons at grain boundaries, and thus improvements in ZT are still possible by disrupting these modes. This work demonstrates the important insights into phonon transport that can be obtained using ab-initio based Monte Carlo simulations in complex nanostructured materials.

Solid-State Polymerization of Acetylene under Pressure: {ital Ab Initio} Simulation

Energy Technology Data Exchange (ETDEWEB)

Bernasconi, M.; Parrinello, M. [Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstr.1, D-70569 Stuttgart (Germany); Bernasconi, M. [Istituto Nazionale Fisica della Materia and Dipartimento di Fisica, Universita di Milano, Via Celoria 16, 20133 Milano (Italy); Chiarotti, G.; Focher, P.; Tosatti, E. [Istituto Nazionale Fisica della Materia and International School for Advanced Studies, Via Beirut 4, I-34014 Trieste (Italy); Tosatti, E. [International Centre for Theoretical Physics (ICTP), P.O.Box 586, I-34014 Trieste (Italy)

1997-03-01

We have simulated by {ital ab initio} constant pressure molecular dynamics the solid-state polymerization of acetylene recently observed experimentally in the pressure range 3.5{endash}14 GPa. We have found a massive polymerization only at much higher pressure (25 GPa). However, we have also found that a triplet exciton self-trapped on a single, {ital cis}-bent molecule in crystalline acetylene is a very effective polymerization seed at lower pressure ({lt}9GPa), much closer to the experimental threshold. Therefore, we propose that the polymerization observed experimentally is possibly catalyzed by a similar seed. We predict that injection of triplet excitons would greatly enhance the polymerization rate. {copyright} {ital 1997} {ital The American Physical Society}
Decarboxylation of furfural on Pd(111): Ab initio molecular dynamics simulations

Science.gov (United States)

Xue, Wenhua; Dang, Hongli; Shields, Darwin; Liu, Yingdi; Jentoft, Friederike; Resasco, Daniel; Wang, Sanwu

2013-03-01

Furfural conversion over metal catalysts plays an important role in the studies of biomass-derived feedstocks. We report ab initio molecular dynamics simulations for the decarboxylation process of furfural on the palladium surface at finite temperatures. We observed and analyzed the atomic-scale dynamics of furfural on the Pd(111) surface and the fluctuations of the bondlengths between the atoms in furfural. We found that the dominant bonding structure is the parallel structure in which the furfural plane, while slightly distorted, is parallel to the Pd surface. Analysis of the bondlength fluctuations indicates that the C-H bond is the aldehyde group of a furfural molecule is likely to be broken first, while the C =O bond has a tendency to be isolated as CO. Our results show that the reaction of decarbonylation dominates, consistent with the experimental measurements. Supported by DOE (DE-SC0004600). Simulations and calculations were performed on XSEDE's and NERSC's supercomputers.
Studies Of Urea Geometry By Means Of Ab Initio Methods And Computer Simulations Of Liquids [estudo Da Geometria Da Uréia Por Métodos Ab Initio E Simulaição Computacional De Líquidos

OpenAIRE

Cirino J.J.V.; Bertran C.A.

2002-01-01

A study was carried out on the urea geometries using ab initio calculation and Monte Carlo computational simulation of liquids. The ab initio calculated results showed that urea has a non-planar conformation in the gas phase in which the hydrogen atoms are out of the plane formed by the heavy atoms. Free energies associated to the rotation of the amino groups of urea in water were obtained using the Monte Carlo method in which the thermodynamic perturbation theory is implemented. The magnitud...
Electronic transport coefficients from ab initio simulations and application to dense liquid hydrogen

International Nuclear Information System (INIS)

Holst, Bastian; French, Martin; Redmer, Ronald

2011-01-01

Using Kubo's linear response theory, we derive expressions for the frequency-dependent electrical conductivity (Kubo-Greenwood formula), thermopower, and thermal conductivity in a strongly correlated electron system. These are evaluated within ab initio molecular dynamics simulations in order to study the thermoelectric transport coefficients in dense liquid hydrogen, especially near the nonmetal-to-metal transition region. We also observe significant deviations from the widely used Wiedemann-Franz law, which is strictly valid only for degenerate systems, and give an estimate for its valid scope of application toward lower densities.
Interaction of single-walled carbon nanotubes and saxitoxin: Ab initio simulations and biological responses in hippocampal cell line HT-22.

Science.gov (United States)

Ramos, Patrícia; Schmitz, Marcos; Filgueira, Daza; Votto, Ana Paula; Durruthy, Michael; Gelesky, Marcos; Ruas, Caroline; Yunes, João; Tonel, Mariana; Fagan, Solange; Monserrat, José

2017-07-01

Saxitoxins (STXs) are potent neurotoxins that also induce cytotoxicity through the generation of reactive oxygen species. Carbon nanotubes (CNTs) are nanomaterials that can promote a Trojan horse effect, facilitating the entry of toxic molecules to cells when adsorbed to nanomaterials. The interaction of pristine single-walled (SW)CNTs and carboxylated (SWCNT-COOH) nanotubes with STX was evaluated by ab initio simulation and bioassays using the cell line HT-22. Cells (5 × 10 4 cells/mL) were exposed to SWCNT and SWCNT-COOH (5 μg mL -1 ), STX (200 μg L -1 ), SWCNT+STX, and SWCNT-COOH+STX for 30 min or 24 h. Results of ab initio simulation showed that the interaction between SWCNT and SWCNT-COOH with STX occurs in a physisorption. The interaction of SWCNT+STX induced a decrease in cell viability. Cell proliferation was not affected in any treatment after 30 min or 24 h of exposure (p > 0.05). Treatment with SWCNT-COOH induced high reactive oxygen species levels, an effect attenuated in SWCNT-COOH+STX treatment. In terms of cellular oxygen consumption, both CNTs when coexposed with STX antagonize the toxin effect. Based on these results, it can be concluded that the results obtained in vitro corroborate the semiempirical evidence found using density functional theory ab initio simulation. Environ Toxicol Chem 2017;36:1728-1737. © 2016 SETAC. © 2016 SETAC.
Speed-up of ab initio hybrid Monte Carlo and ab initio path integral hybrid Monte Carlo simulations by using an auxiliary potential energy surface

International Nuclear Information System (INIS)

Nakayama, Akira; Taketsugu, Tetsuya; Shiga, Motoyuki

2009-01-01

Efficiency of the ab initio hybrid Monte Carlo and ab initio path integral hybrid Monte Carlo methods is enhanced by employing an auxiliary potential energy surface that is used to update the system configuration via molecular dynamics scheme. As a simple illustration of this method, a dual-level approach is introduced where potential energy gradients are evaluated by computationally less expensive ab initio electronic structure methods. (author)
Ab initio model of porous periclase

International Nuclear Information System (INIS)

Drummond, Neil D.; Swift, Damian C.; Ackland, Graeme J.

2004-01-01

A two-phase equilibrium equation of state (EOS) for periclase (MgO) was constructed using ab initio quantum mechanics, including a rigorous calculation of quasiharmonic phonon modes. Much of the shock wave data reported for periclase is on porous material. We compared the theoretical EOS with porous data using a simple 'snowplough' treatment and also a model using finite equilibration rates suitable for continuum mechanics simulations. (This model has been applied previously to various heterogeneous explosives as well as other porous materials.) The results were consistent and matched the data well at pressures above the regime affected by strength - and ramp-wave formation - during compaction. Ab initio predictions of the response of porous material have been cited recently as a novel and advanced capability; we feel that this is a fairly routine extension to established ab initio techniques
Potential Energy and Free Energy Surfaces of the Formic Acid Dimer: Correlared ab initio Calculations and Molecular Dynamics Simulations

Czech Academy of Sciences Publication Activity Database

Chocholoušová, Jana; Vacek, Jaroslav; Hobza, Pavel

2002-01-01

Roč. 4, - (2002), s. 2119-2122 ISSN 1463-9076 R&D Projects: GA MŠk LN00A032 Institutional research plan: CEZ:AV0Z4040901 Keywords : formic acid dimer * ab initio calculations * molecular dynamics simulations Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.838, year: 2002
Perspectives on phenomenology and simulation of severe accident in light water reactors

International Nuclear Information System (INIS)

Sugimoto, Jun

2014-01-01

Severe accident phenomena in light water reactors (LWRs) are generally characterized by their physically and chemically complex processes involved with high temperature core melt, multi-component and multi-phase flows, transport of radioactive materials and sometimes highly non-equilibrium state. Severe accident phenomenology is usually categorized into four phases; (1) fuel degradation, (2) in-vessel phenomena, (3) ex-vessel phenomena and (4) fission product release and transport. Among these, ex-vessel phenomena consist of five subcategories; 1) direct containment heating, 2) fuel coolant interaction (steam explosion), 3) molten core concrete interaction, 4) hydrogen behaviour and control and 5) containment failure/leakage. In the field of simulation of severe accident, severe accident analytical codes have been developed in the United States, EU and Japan, such as MAAP, MELCOR, ASTEC, THALES and SAMPSON. Many different kinds of analytical codes for the specific severe accident phenomena have also been developed worldwide. After the accident at Fukushima Daiichi Nuclear Power Station, review of severe accident research issues has been conducted and several issues are reconsidered, such as effects of BWR core degradation behaviors, sea water injection, pool scrubbing under rapid depressurization, containment failure/leakage and re-criticality. Some new experimental and analytical efforts have been started after the Fukushima accident. The present paper describes the perspectives on phenomenology and simulation of severe accident in LWRs, with the emphasis of insights obtained in the review of Fukushima accident. (author)
Investigation on electronic and magnetic properties of Mn2NiAl by ab initio calculations and Monte Carlo simulations

International Nuclear Information System (INIS)

Masrour, R.; Jabar, A.; Hlil, E.K.; Hamedoun, M.; Benyoussef, A.; Hourmatallah, A.; Rezzouk, A.; Bouslykhane, K.; Benzakour, N.

2017-01-01

Self-consistent ab initio calculations, based on Density Functional Theory (DFT) approach and using Full potential Linear Augmented Plane Wave (FLAPW) method, are performed to investigate both electronic and magnetic properties of the Mn 2 NiAl. Magnetic moment considered to lie along (001) axes are computed. Obtained data from ab initio calculations are used as input for Monte Carlo simulations to compute other magnetic parameters. Also, the magnetic properties of Mn 2 NiAl are studied using the Monte Carlo simulations. The variation of magnetization and magnetic susceptibility with the reduced temperature of Mn 2 NiAl are investigated. The transition temperature of this system is deduced for different values exchange interaction and crystal field. The thermal total magnetization has been obtained, and the magnetic hysteresis cycle is established. The total magnetic moment is superior to those obtained by the other method and is mainly determined by the antiparallel aligned Mn I , Mn II and Ni spin moments. The superparamagnetic phase is found at the neighborhood of transition temperature. - Highlights: • Ab initio calculations are used to study magnetic and electronic properties of Mn 2 NiX. • The transition temperature of Mn 2 NiX is established. • The magnetic hysteresis cycle of M n2 NiX (X = Al, Ga, In, Sn) is deduced. • The magnetic coercive field of Mn 2 NiX (X = Al, Ga, In, Sn) is given.
Investigation on electronic and magnetic properties of Mn{sub 2}NiAl by ab initio calculations and Monte Carlo simulations

Energy Technology Data Exchange (ETDEWEB)

Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, PB 63 46000 Safi (Morocco); Jabar, A. [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, PB 63 46000 Safi (Morocco); Hlil, E.K. [Institut Néel, CNRS, Université Grenoble Alpes, BP 166, F-38042 Grenoble cedex 9 (France); Hamedoun, M. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Benyoussef, A. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); Hourmatallah, A. [Equipe de Physique du Solide, Laboratoire LIPI, Ecole Normale Supérieure, BP 5206, Bensouda, Fes (Morocco); Rezzouk, A.; Bouslykhane, K.; Benzakour, N. [Laboratoire de Physique du Solide, Université Sidi Mohammed Ben Abdellah, Faculté des sciences DharMahraz, BP 1796, Fes (Morocco)

2017-04-15

Self-consistent ab initio calculations, based on Density Functional Theory (DFT) approach and using Full potential Linear Augmented Plane Wave (FLAPW) method, are performed to investigate both electronic and magnetic properties of the Mn{sub 2}NiAl. Magnetic moment considered to lie along (001) axes are computed. Obtained data from ab initio calculations are used as input for Monte Carlo simulations to compute other magnetic parameters. Also, the magnetic properties of Mn{sub 2}NiAl are studied using the Monte Carlo simulations. The variation of magnetization and magnetic susceptibility with the reduced temperature of Mn{sub 2}NiAl are investigated. The transition temperature of this system is deduced for different values exchange interaction and crystal field. The thermal total magnetization has been obtained, and the magnetic hysteresis cycle is established. The total magnetic moment is superior to those obtained by the other method and is mainly determined by the antiparallel aligned Mn{sub I}, Mn{sub II} and Ni spin moments. The superparamagnetic phase is found at the neighborhood of transition temperature. - Highlights: • Ab initio calculations are used to study magnetic and electronic properties of Mn{sub 2}NiX. • The transition temperature of Mn{sub 2}NiX is established. • The magnetic hysteresis cycle of M{sub n2}NiX (X = Al, Ga, In, Sn) is deduced. • The magnetic coercive field of Mn{sub 2}NiX (X = Al, Ga, In, Sn) is given.
Ab Initio Molecular-Dynamics Simulation of Neuromorphic Computing in Phase-Change Memory Materials.

Science.gov (United States)

Skelton, Jonathan M; Loke, Desmond; Lee, Taehoon; Elliott, Stephen R

2015-07-08

We present an in silico study of the neuromorphic-computing behavior of the prototypical phase-change material, Ge2Sb2Te5, using ab initio molecular-dynamics simulations. Stepwise changes in structural order in response to temperature pulses of varying length and duration are observed, and a good reproduction of the spike-timing-dependent plasticity observed in nanoelectronic synapses is demonstrated. Short above-melting pulses lead to instantaneous loss of structural and chemical order, followed by delayed partial recovery upon structural relaxation. We also investigate the link between structural order and electrical and optical properties. These results pave the way toward a first-principles understanding of phase-change physics beyond binary switching.
Ab initio STM and STS simulations on magnetic and nonmagnetic metallic surfaces

Energy Technology Data Exchange (ETDEWEB)

Dick, Alexey

2008-04-14

The aim of this work was to provide an in-depth understanding of a new generation of scan- ning tunneling microscopy experiments, performed employing different regimes of the STM: the spectroscopy-mode (the so-called Fourier Transformed STM, FT-STM), and the spin-sensitive mode (the so-called spin-polarized STM, SP-STM). In the present thesis ab initio tools are proposed that are based on DFT calculations to theoretically predict and analyze such types of the STM. The first part of this thesis focusses on the simulation of FT-STM, the mode that allows to probe local dispersion properties of the electrons at the surface. In order to provide the theoretical counterpart of the experimental FT-STM spectra we have introduced a new implicit approach that is derived from Tersoff-Hamann theory of the STM. The importance of an accurate description of surface wavefunctions at 5-15 A above the surface as well as the spurious quantum- size effects have been discussed in detail together with approaches to obtain converged FT-STM images. We applied our method to FT-STM experiments performed on Ag(110) surfaces. In the second part of the thesis we discuss the modeling of the spin-resolved STM, the mode that allows to characterize the magnetic structure of a surface. As a case system we studied here the magnetically-ordered transition-metal nitride surface Mn{sub 3}N{sub 2}(010). Because SP-STM experiments did not allow a conclusive understanding of the surface structure, we have first employed ab initio thermodynamics to figure out the most stable magnetic and atomic configuration of the surface that are consistent with experiments. To simulate SP-STM images on the most stable Mn{sub 3}N{sub 2}(010) surface we have employed the spin-generalized transfer-Hamiltonian formalism, assuming that the tip wavefunctions have dominant radial symmetry (s-like tip). (orig.)
Ab initio molecular dynamics simulations for the role of hydrogen in catalytic reactions of furfural on Pd(111)

Science.gov (United States)

Xue, Wenhua; Dang, Hongli; Liu, Yingdi; Jentoft, Friederike; Resasco, Daniel; Wang, Sanwu

2014-03-01

In the study of catalytic reactions of biomass, furfural conversion over metal catalysts with the presence of hydrogen has attracted wide attention. We report ab initio molecular dynamics simulations for furfural and hydrogen on the Pd(111) surface at finite temperatures. The simulations demonstrate that the presence of hydrogen is important in promoting furfural conversion. In particular, hydrogen molecules dissociate rapidly on the Pd(111) surface. As a result of such dissociation, atomic hydrogen participates in the reactions with furfural. The simulations also provide detailed information about the possible reactions of hydrogen with furfural. Supported by DOE (DE-SC0004600). This research used the supercomputer resources of the XSEDE, the NERSC Center, and the Tandy Supercomputing Center.
Lyapunov-based decentralized control of a rougher flotation phenomenological simulator

International Nuclear Information System (INIS)

Benaskeur, A.R.; Desbiens, A.

1999-01-01

In this paper a new approach to decentralized control of linear two-by-two plants is presented. The novelty lies in the use of a modified control function of Lyapunov and the introduction of an integral action in each manipulated variable, to ensure zero tracking errors. An appropriate choice of the regulated errors, allows the elimination of the cross terms in the obtained backstepping-based multivariable controller. It will be proven that if the H ∞ -norm of the plant interaction quotient is less than one, the centralized controller can be split up into two independent scalar output feedback regulators. Under these conditions, the global stability and zero tracking errors will still be guaranteed. The developed scheme is successfully applied to the control of a rougher flotation phenomenological simulator. (author)
The role of Metals in Amyloid Aggregation: A Test Case for ab initio Simulations

International Nuclear Information System (INIS)

Minicozzi, V.; Rossi, G. C.; Stellato, F.; Morante, S.

2007-01-01

First principle ab initio molecular dynamics simulations of the Car-Parrinello type have proved to be of invaluable help in understanding the microscopic mechanisms of chemical bonding both in solid state physics and in structural biophysics. In this work we present as test cases the study of the Cu coordination mode in two especially important examples: Prion protein and β-amyloids. Using medium size PC-clusters as well as larger parallel platforms, we are able to deal with systems comprising 300 to 500 atoms and 1000 to 1500 electrons for as long as 2-3 ps. We present structural results which confirm indications coming from NMR and XAS data
Research in Lattice Gauge Theory and in the Phenomenology of Neutrinos and Dark Matter

Energy Technology Data Exchange (ETDEWEB)

Meurice, Yannick L [Univ. of Iowa, Iowa City, IA (United States); Reno, Mary Hall [Univ. of Iowa, Iowa City, IA (United States)

2016-06-23

Research in theoretical elementary particle physics was performed by the PI Yannick Meurice and co-PI Mary Hall Reno. New techniques designed for precision calculations of strong interaction physics were developed using the tensor renormalization group method. Large-scale Monte Carlo simulations with dynamical quarks were performed for candidate models for Higgs compositeness. Ab-initio lattice gauge theory calculations of semileptonic decays of B-mesons observed in collider experiments and relevant to test the validity of the standard model were performed with the Fermilab/MILC collaboration. The phenomenology of strong interaction physics was applied to new predictions for physics processes in accelerator physics experiments and to cosmic ray production and interactions. A research focus has been on heavy quark production and their decays to neutrinos. The heavy quark contributions to atmospheric neutrino and muon fluxes have been evaluated, as have the neutrino fluxes from accelerator beams incident on heavy targets. Results are applicable to current and future particle physics experiments and to astrophysical neutrino detectors such as the IceCube Neutrino Observatory.
Research in Lattice Gauge Theory and in the Phenomenology of Neutrinos and Dark Matter

International Nuclear Information System (INIS)

Meurice, Yannick L; Reno, Mary Hall

2016-01-01

Research in theoretical elementary particle physics was performed by the PI Yannick Meurice and co-PI Mary Hall Reno. New techniques designed for precision calculations of strong interaction physics were developed using the tensor renormalization group method. Large-scale Monte Carlo simulations with dynamical quarks were performed for candidate models for Higgs compositeness. Ab-initio lattice gauge theory calculations of semileptonic decays of B-mesons observed in collider experiments and relevant to test the validity of the standard model were performed with the Fermilab/MILC collaboration. The phenomenology of strong interaction physics was applied to new predictions for physics processes in accelerator physics experiments and to cosmic ray production and interactions. A research focus has been on heavy quark production and their decays to neutrinos. The heavy quark contributions to atmospheric neutrino and muon fluxes have been evaluated, as have the neutrino fluxes from accelerator beams incident on heavy targets. Results are applicable to current and future particle physics experiments and to astrophysical neutrino detectors such as the IceCube Neutrino Observatory.
Ab initio simulations and neutron scattering studies of structure and dynamics in PdH

International Nuclear Information System (INIS)

Totolici, I.E.

2001-07-01

The work presented in this PhD thesis is concerned with the interpretation of the neutron scattering measurements from the palladium hydrogen system by means of ab initio electronic structure calculations. The motivation of performing such calculations was due to recent neutron scattering studies on this system that showed a strong directional dependence to the dynamical structure factor together with a complex dependence on energy. Here we attempt to describe the origin of these features by ab initio simulations of the dynamical structure factor. The method assumes an adiabatic separation of the motion of the proton and palladium atoms. The proton wave functions are calculated by a direct solution of the associated single-particle Schroedinger equation using a plane wave basis set method and a mapping of the adiabatic surface. The Fourier components of the adiabatic potential are obtained from LDA pseudopotential calculations. Using Fermi's golden rule within the Born approximation we were then able to calculate the dynamical structure factor, S(Q,ω), for exciting the proton from its ground state to various excited states as a function of the magnitude and direction of the scattering wave vector. The results are in agreement with the inelastic neutron scattering spectra and allow us to identify the origin of previous inexplicable features, in particular the strong directional dependence to the experimental data. The method was extended to investigate the expansion of the equilibrium lattice constant as a function of the H isotope when the zero-point energy of the proton/deuterium is explicitly taken into account in the relaxation process. The results we obtained predicted a bigger lattice constant for the hydride, as expected. Furthermore, other complex ab initio calculations were carried out in order to describe the origin of the large optic dispersion, seen previously in the coherent neutron scattering data. Our calculated dispersion proved to be in good
Core structure of screw dislocations in Fe from first-principles; Simulation ab initio des coeurs de dislocation vis dans le fer

Energy Technology Data Exchange (ETDEWEB)

Ventelon, L

2008-11-15

The various methods appropriate for the simulation of dislocations within first-principles calculations have been set up, improved and compared between them. They have been applied to study screw dislocations in body-centered cubic iron using the SIESTA code. A non-degenerate core structure is obtained; its detailed analysis reveals a dilatation effect. Taking it into account in an anisotropic elasticity model, allows explaining the cell-size dependence of the energetics, obtained within the dipole approach. The Peierls potential obtained in ab initio suggests that the metastable core configuration at halfway position in the Peierls barrier, predicted by empirical potential, does not exist. We show how to construct tri-periodic cells optimized to study kinked dislocations. Using empirical potential, we demonstrate the feasibility of ab initio calculations of Peierls stress and kink formation. (author)

Ab initio molecular dynamics simulation of aqueous solution of nitric oxide in different formal oxidation states

Science.gov (United States)

Venâncio, Mateus F.; Rocha, Willian R.

2015-10-01

Ab initio molecular dynamics simulations were used to investigate the early chemical events involved in the dynamics of nitric oxide (NOrad), nitrosonium cation (NO+) and nitroxide anion (NO-) in aqueous solution. The NO+ ion is very reactive in aqueous solution having a lifetime of ∼4 × 10-13 s, which is shorter than the value of 3 × 10-10 s predicted experimentally. The NO+ reacts generating the nitrous acid as an intermediate and the NO2- ion as the final product. The dynamics of NOrad revealed the reversibly formation of a transient anion radical species HONOrad -.
Ab Initio Calculations of Transport in Titanium and Aluminum Mixtures

Science.gov (United States)

Walker, Nicholas; Novak, Brian; Tam, Ka Ming; Moldovan, Dorel; Jarrell, Mark

In classical molecular dynamics simulations, the self-diffusion and shear viscosity of titanium about the melting point have fallen within the ranges provided by experimental data. However, the experimental data is difficult to collect and has been rather scattered, making it of limited value for the validation of these calculations. By using ab initio molecular dynamics simulations within the density functional theory framework, the classical molecular dynamics data can be validated. The dynamical data from the ab initio molecular dynamics can also be used to calculate new potentials for use in classical molecular dynamics, allowing for more accurate classical dynamics simulations for the liquid phase. For metallic materials such as titanium and aluminum alloys, these calculations are very valuable due to an increasing demand for the knowledge of their thermophysical properties that drive the development of new materials. For example, alongside knowledge of the surface tension, viscosity is an important input for modeling the additive manufacturing process at the continuum level. We are developing calculations of the viscosity along with the self-diffusion for aluminum, titanium, and titanium-aluminum alloys with ab initio molecular dynamics. Supported by the National Science Foundation through cooperative agreement OIA-1541079 and the Louisiana Board of Regents.
Light focusing through a multiple scattering medium: ab initio computer simulation

Science.gov (United States)

Danko, Oleksandr; Danko, Volodymyr; Kovalenko, Andrey

2018-01-01

The present study considers ab initio computer simulation of the light focusing through a complex scattering medium. The focusing is performed by shaping the incident light beam in order to obtain a small focused spot on the opposite side of the scattering layer. MSTM software (Auburn University) is used to simulate the propagation of an arbitrary monochromatic Gaussian beam and obtain 2D distribution of the optical field in the selected plane of the investigated volume. Based on the set of incident and scattered fields, the pair of right and left eigen bases and corresponding singular values were calculated. The pair of right and left eigen modes together with the corresponding singular value constitute the transmittance eigen channel of the disordered media. Thus, the scattering process is described in three steps: 1) initial field decomposition in the right eigen basis; 2) scaling of decomposition coefficients for the corresponding singular values; 3) assembling of the scattered field as the composition of the weighted left eigen modes. Basis fields are represented as a linear combination of the original Gaussian beams and scattered fields. It was demonstrated that 60 independent control channels provide focusing the light into a spot with the minimal radius of approximately 0.4 μm at half maximum. The intensity enhancement in the focal plane was equal to 68 that coincided with theoretical prediction.
Ab Initio Predictions of Structures and Densities of Energetic Solids

National Research Council Canada - National Science Library

Rice, Betsy M; Sorescu, Dan C

2004-01-01

We have applied a powerful simulation methodology known as ab initio crystal prediction to assess the ability of a generalized model of CHNO intermolecular interactions to predict accurately crystal...
Realization of prediction of materials properties by ab initio ...

Indian Academy of Sciences (India)

Unknown

alization of the results of ab initio molecular dynamics simulation on atom insertion process to C60 and to carbon nanotube ... micro-clusters to estimate absolute highest occupied mo- .... To analyse the observed properties theoretically,.
Ab initio transport across bismuth selenide surface barriers

KAUST Repository

Narayan, Awadhesh; Rungger, Ivan; Droghetti, Andrea; Sanvito, Stefano

2014-01-01

© 2014 American Physical Society. We investigate the effect of potential barriers in the form of step edges on the scattering properties of Bi2Se3(111) topological surface states by means of large-scale ab initio transport simulations. Our results
FANSY 1.0: a phenomenological model for simulation of coplanar particle generation in superhigh-energy hadron interactions

International Nuclear Information System (INIS)

Mukhamedshin, Rauf

2009-01-01

Simulations show that a phenomenon of coplanarity of most energetic subcores of γ-ray-hadron families found in mountain-based and stratospheric X-ray-emulsion chamber experiments requires to introduce a coplanar particle generation with large transverse momenta in hadron interactions at superhigh energies. Some physical mechanisms are considered. A phenomenological model, which makes it possible to simulate the coplanar particle generation, is presented. Different versions of this model are considered, their features are described and compared with those of models applied by the CORSIKA package. Cosmic-ray experimental data and simulated results are compared. Conclusion on features of hadron interactions at superhigh energies and some predictions with respect to LHC experiments are made. (orig.) 3
Highly scalable Ab initio genomic motif identification

KAUST Repository

Marchand, Benoit; Bajic, Vladimir B.; Kaushik, Dinesh

2011-01-01

We present results of scaling an ab initio motif family identification system, Dragon Motif Finder (DMF), to 65,536 processor cores of IBM Blue Gene/P. DMF seeks groups of mutually similar polynucleotide patterns within a set of genomic sequences and builds various motif families from them. Such information is of relevance to many problems in life sciences. Prior attempts to scale such ab initio motif-finding algorithms achieved limited success. We solve the scalability issues using a combination of mixed-mode MPI-OpenMP parallel programming, master-slave work assignment, multi-level workload distribution, multi-level MPI collectives, and serial optimizations. While the scalability of our algorithm was excellent (94% parallel efficiency on 65,536 cores relative to 256 cores on a modest-size problem), the final speedup with respect to the original serial code exceeded 250,000 when serial optimizations are included. This enabled us to carry out many large-scale ab initio motiffinding simulations in a few hours while the original serial code would have needed decades of execution time. Copyright 2011 ACM.
Virtual synthesis of crystals using ab initio MD: Case study on LiFePO4

Science.gov (United States)

Mishra, S. B.; Nanda, B. R. K.

2017-05-01

Molecular dynamics simulation technique is fairly successful in studying the structural aspects and dynamics of fluids. Here we study the ability of ab initio molecular dynamics (ab initio MD) to carry out virtual experiments to synthesize new crystalline materials and to predict their structures. For this purpose the olivine phosphate LiFePO4 (LFPO) is used as an example. As transition metal oxides in general are stabilized with layered geometry, we carried out ab initio MD simulations over a hypothetical layered configuration consisting of alternate LiPO2 and FeO2 layers. With intermittent steps of electron minimization, the resulted equilibrium lattice consist of PO4 tetrahedra and distorted Fe-O complexes similar to the one observed in the experimental lattice.
Problems of phenomenological simulation of the Dst variation

International Nuclear Information System (INIS)

Gul'el'mi, A.V.

1988-01-01

Stochastic generalization of RBM model, describing the D st -variation is suggested. The corresponding Fokker-Planck equation contains a new phenomenological parameter enabling to obtain the interval estimation of D st forecast. The structure of sources and sinks forming the D st -variation is considered from the viewpoint of critical phenomenon theory
Serious Gaming for Test & Evaluation of Clean-Slate (Ab Initio) National Airspace System (NAS) Designs

Science.gov (United States)

Allen, B. Danette; Alexandrov, Natalia

2016-01-01

Incremental approaches to air transportation system development inherit current architectural constraints, which, in turn, place hard bounds on system capacity, efficiency of performance, and complexity. To enable airspace operations of the future, a clean-slate (ab initio) airspace design(s) must be considered. This ab initio National Airspace System (NAS) must be capable of accommodating increased traffic density, a broader diversity of aircraft, and on-demand mobility. System and subsystem designs should scale to accommodate the inevitable demand for airspace services that include large numbers of autonomous Unmanned Aerial Vehicles and a paradigm shift in general aviation (e.g., personal air vehicles) in addition to more traditional aerial vehicles such as commercial jetliners and weather balloons. The complex and adaptive nature of ab initio designs for the future NAS requires new approaches to validation, adding a significant physical experimentation component to analytical and simulation tools. In addition to software modeling and simulation, the ability to exercise system solutions in a flight environment will be an essential aspect of validation. The NASA Langley Research Center (LaRC) Autonomy Incubator seeks to develop a flight simulation infrastructure for ab initio modeling and simulation that assumes no specific NAS architecture and models vehicle-to-vehicle behavior to examine interactions and emergent behaviors among hundreds of intelligent aerial agents exhibiting collaborative, cooperative, coordinative, selfish, and malicious behaviors. The air transportation system of the future will be a complex adaptive system (CAS) characterized by complex and sometimes unpredictable (or unpredicted) behaviors that result from temporal and spatial interactions among large numbers of participants. A CAS not only evolves with a changing environment and adapts to it, it is closely coupled to all systems that constitute the environment. Thus, the ecosystem that
Multiple time step integrators in ab initio molecular dynamics

International Nuclear Information System (INIS)

Luehr, Nathan; Martínez, Todd J.; Markland, Thomas E.

2014-01-01

Multiple time-scale algorithms exploit the natural separation of time-scales in chemical systems to greatly accelerate the efficiency of molecular dynamics simulations. Although the utility of these methods in systems where the interactions are described by empirical potentials is now well established, their application to ab initio molecular dynamics calculations has been limited by difficulties associated with splitting the ab initio potential into fast and slowly varying components. Here we present two schemes that enable efficient time-scale separation in ab initio calculations: one based on fragment decomposition and the other on range separation of the Coulomb operator in the electronic Hamiltonian. We demonstrate for both water clusters and a solvated hydroxide ion that multiple time-scale molecular dynamics allows for outer time steps of 2.5 fs, which are as large as those obtained when such schemes are applied to empirical potentials, while still allowing for bonds to be broken and reformed throughout the dynamics. This permits computational speedups of up to 4.4x, compared to standard Born-Oppenheimer ab initio molecular dynamics with a 0.5 fs time step, while maintaining the same energy conservation and accuracy
Perspective: Ab initio force field methods derived from quantum mechanics

Science.gov (United States)

Xu, Peng; Guidez, Emilie B.; Bertoni, Colleen; Gordon, Mark S.

2018-03-01

It is often desirable to accurately and efficiently model the behavior of large molecular systems in the condensed phase (thousands to tens of thousands of atoms) over long time scales (from nanoseconds to milliseconds). In these cases, ab initio methods are difficult due to the increasing computational cost with the number of electrons. A more computationally attractive alternative is to perform the simulations at the atomic level using a parameterized function to model the electronic energy. Many empirical force fields have been developed for this purpose. However, the functions that are used to model interatomic and intermolecular interactions contain many fitted parameters obtained from selected model systems, and such classical force fields cannot properly simulate important electronic effects. Furthermore, while such force fields are computationally affordable, they are not reliable when applied to systems that differ significantly from those used in their parameterization. They also cannot provide the information necessary to analyze the interactions that occur in the system, making the systematic improvement of the functional forms that are used difficult. Ab initio force field methods aim to combine the merits of both types of methods. The ideal ab initio force fields are built on first principles and require no fitted parameters. Ab initio force field methods surveyed in this perspective are based on fragmentation approaches and intermolecular perturbation theory. This perspective summarizes their theoretical foundation, key components in their formulation, and discusses key aspects of these methods such as accuracy and formal computational cost. The ab initio force fields considered here were developed for different targets, and this perspective also aims to provide a balanced presentation of their strengths and shortcomings. Finally, this perspective suggests some future directions for this actively developing area.
Quantum mechanical ab initio simulation of the electron screening effect in metal deuteride crystals

Energy Technology Data Exchange (ETDEWEB)

Huke, A.; Chun, S.M.; Biller, A.; Heide, P. [Technische Universitaet Berlin, Institut fuer Optik und Atomare Physik, Berlin (Germany); Czerski, K. [Technische Universitaet Berlin, Institut fuer Optik und Atomare Physik, Berlin (Germany); University of Szczecin, Institute of Physics, Szczecin (Poland)

2008-02-15

In antecedent experiments the electron screening energies of the d+d reactions in metallic environments have been determined to be enhanced by an order of magnitude in comparison to the case of gaseous deuterium targets. The analytical models describing averaged material properties have not been able to explain the experimental results so far. Therefore, a first effort has been undertaken to simulate the dynamics of reacting deuterons in a metallic lattice by means of an ab initio Hartree-Fock calculation of the total electrostatic force between the lattice and the successively approaching deuterons via path integration. The calculations have been performed for Li and Ta, clearly showing a migration of electrons from host metallic to the deuterium atoms. However, in order to avoid more of the necessary simplifications in the model the utilization of a massive parallel supercomputer would be required. (orig.) 3.
On a fast numerical tool for nuclear accidental dynamic phenomenology and application to the real time simulation of Lady Godiva

International Nuclear Information System (INIS)

Bindel, Laurent; Gamess, Andre; Jasserand, Frederic; Laporte, Sebastien

2003-01-01

This paper present a modern numerical method, implemented in a TUI-code named MacDSP, for solving any set of differential equations and in particular phenomenological accidental dynamic calculations. The speed efficiency of such an approach, thanks to the use of the hybrid-level power offered by C++ and an ad-hoc design, make it possible to construct the first kid of a family of real time simulator employing the video games technology DirectX TM : Lady Godiva Real Time Simulator. (author)
Simulations of the dissociation of small helium clusters with ab initio molecular dynamics in electronically excited states

International Nuclear Information System (INIS)

Closser, Kristina D.; Head-Gordon, Martin; Gessner, Oliver

2014-01-01

The dynamics resulting from electronic excitations of helium clusters were explored using ab initio molecular dynamics. The simulations were performed with configuration interaction singles and adiabatic classical dynamics coupled to a state-following algorithm. 100 different configurations of He 7 were excited into the 2s and 2p manifold for a total of 2800 trajectories. While the most common outcome (90%) was complete fragmentation to 6 ground state atoms and 1 excited state atom, 3% of trajectories yielded bound, He 2 * , and <0.5% yielded an excited helium trimer. The nature of the dynamics, kinetic energy release, and connections to experiments are discussed
Orbital free ab initio molecular dynamics simulation study of some static and dynamic properties of liquid noble metals

Directory of Open Access Journals (Sweden)

G.M. Bhuiyan

2012-10-01

Full Text Available Several static and dynamic properties of liquid Cu, Ag and Au at thermodynamic states near their respective melting points, have been evaluated by means of the orbital free ab-initio molecular dynamics simulation method. The calculated static structure shows good agreement with the available X-ray and neutron diffraction data. As for the dynamic properties, the calculated dynamic structure factors point to the existence of collective density excitations along with a positive dispersion for l-Cu and l-Ag. Several transport coefficients have been obtained which show a reasonable agreement with the available experimental data.
Absolute acidity of clay edge sites from ab-initio simulations

Science.gov (United States)

Tazi, Sami; Rotenberg, Benjamin; Salanne, Mathieu; Sprik, Michiel; Sulpizi, Marialore

2012-10-01

We provide a microscopic understanding of the solvation structure and reactivity of the edges of neutral clays. In particular we address the tendency to deprotonation of the different reactive groups on the (0 1 0) face of pyrophyllite. Such information cannot be inferred directly from titration experiments, which do not discriminate between different sites and whose interpretation resorts to macroscopic models. The determination of the corresponding pKa then usually relies on bond valence models, sometimes improved by incorporating some structural information from ab-initio simulations. Here we use density functional theory based molecular dynamics simulations, combined with thermodynamic integration, to compute the free energy of the reactions of water with the different surface groups, leading to a deprotonated site and an aqueous hydronium ion. Our approach consistently describes the clay and water sides of the interface and includes naturally electronic polarization effects. It also allows to investigate the structure and solvation of all sites separately. We find that the most acidic group is SiOH, due to its ability to establish strong hydrogen bonds with adsorbed water, as it also happens on the quartz and amorphous silica surfaces. The acidity constant of AlOH2 is only 1 pKa unit larger. Finally, the pKa of AlOH is outside the possible range in water and this site should not deprotonate in aqueous solution. We show that the solvation of surface sites and hence their acidity is strongly affected by the proximity of other sites, in particular for AlOH and AlOH2 which share the same Al. We discuss the implications of our findings on the applicability of bond valence models to predict the acidity of edge sites of clays.
Ethical reasoning through simulation: a phenomenological analysis of student experience.

Science.gov (United States)

Lewis, Gareth; McCullough, Melissa; Maxwell, Alexander P; Gormley, Gerard J

2016-01-01

Medical students transitioning into professional practice feel underprepared to deal with the emotional complexities of real-life ethical situations. Simulation-based learning (SBL) may provide a safe environment for students to probe the boundaries of ethical encounters. Published studies of ethics simulation have not generated sufficiently deep accounts of student experience to inform pedagogy. The aim of this study was to understand students' lived experiences as they engaged with the emotional challenges of managing clinical ethical dilemmas within a SBL environment. This qualitative study was underpinned by an interpretivist epistemology. Eight senior medical students participated in an interprofessional ward-based SBL activity incorporating a series of ethically challenging encounters. Each student wore digital video glasses to capture point-of-view (PoV) film footage. Students were interviewed immediately after the simulation and the PoV footage played back to them. Interviews were transcribed verbatim. An interpretative phenomenological approach, using an established template analysis approach, was used to iteratively analyse the data. Four main themes emerged from the analysis: (1) 'Authentic on all levels?', (2)'Letting the emotions flow', (3) 'Ethical alarm bells' and (4) 'Voices of children and ghosts'. Students recognised many explicit ethical dilemmas during the SBL activity but had difficulty navigating more subtle ethical and professional boundaries. In emotionally complex situations, instances of moral compromise were observed (such as telling an untruth). Some participants felt unable to raise concerns or challenge unethical behaviour within the scenarios due to prior negative undergraduate experiences. This study provided deep insights into medical students' immersive and embodied experiences of ethical reasoning during an authentic SBL activity. By layering on the human dimensions of ethical decision-making, students can understand their
Understanding phenomenology.

LENUS (Irish Health Repository)

Flood, Anne

2012-01-31

Phenomenology is a philosophic attitude and research approach. Its primary position is that the most basic human truths are accessible only through inner subjectivity, and that the person is integral to the environment. This paper discusses the theoretical perspectives related to phenomenology, and includes a discussion of the methods adopted in phenomenological research.

Ab initio pseudopotential theory

International Nuclear Information System (INIS)

Yin, M.T.; Cohen, M.L.

1982-01-01

The ab initio norm-conserving pseudopotential is generated from a reference atomic configuration in which the pseudoatomic eigenvalues and wave functions outside the core region agree with the corresponding ab initio all-electron results within the density-functional formalism. This paper explains why such pseudopotentials accurately reproduce the all-electron results in both atoms and in multiatomic systems. In particular, a theorem is derived to demonstrate the energy- and perturbation-independent properties of ab initio pseudopotentials
Ab initio study of phase equilibria in TiCx

DEFF Research Database (Denmark)

Korzhavyi, P.A.; Pourovskii, L.V.; Hugosson, H.W.

2002-01-01

The phase diagram for the vacancy-ordered structures in the substoichiometric TiCx (x = 0.5-1.0) has been established from Monte Carlo simulations with the long-range pair and multisite effective interactions obtained from ab initio calculations. Three ordered superstructures of vacancies (Ti2C, Ti...
Ab initio atomic simulation of hydrogen and iodine effects in zirconium

International Nuclear Information System (INIS)

Domain, Ch.

2002-03-01

In this work we present ab initio atomic simulations concerning the effects of hydrogen and iodine in hexagonal zirconium. We first studied the point defects in the dilute Zr-H (and to a less extend Zr-H-O) systems and concluded that it is better described within the generalised gradient approximation for the exchange and correlation functional. We calculated the hydrogen thermal diffusion coefficient in solid solution that agree very well with the experimental values. The calculated formation energy of different self-interstitial configuration are rather small (around 3 eV) and close to each other indicating the high complexity of these defects. We studied the core structure of the screw dislocation that has a preferential prismatic spreading. We also calculated the gamma surface for different gliding planes. The influence of hydrogen, that induces a significant reduction of the gamma surfaces excess energies, allows to qualitatively explain experimental results regarding some hydrogen effects on hexagonal zirconium plastic deformation. We also discussed the effect of zirconium hydride stoichiometry on gamma surfaces. The results concerning the iodine and oxygen adsorption on zirconium surfaces, inducing the evaluation of the effective surface energy reduction as a function of the iodine partial pressure allow for a better description of iodine induced stress corrosion cracking of zirconium. (author)
Ab initio study of electron-ion structure factors in binary liquids with different types of chemical bonding

International Nuclear Information System (INIS)

Klevets, Ivan; Bryk, Taras

2014-01-01

Electron-ion structure factors, calculated in ab initio molecular dynamics simulations, are reported for several binary liquids with different kinds of chemical bonding: metallic liquid alloy Bi–Pb, molten salt RbF, and liquid water. We derive analytical expressions for the long-wavelength asymptotes of the partial electron-ion structure factors of binary systems and show that the analytical results are in good agreement with the ab initio simulation data. The long-wavelength behaviour of the total charge structure factors for the three binary liquids is discussed
Dynamic influent pollutant disturbance scenario generation using a phenomenological modelling approach

DEFF Research Database (Denmark)

Gernaey, Krist; Flores Alsina, Xavier; Rosen, Christian

2011-01-01

: the larger the simulated sewer network, the smoother the simulated diurnal flow rate and concentration variations. In the discussion, it is pointed out how the proposed phenomenological models can be expanded to other applications, for example to represent heavy metal or organic micro-pollutant loads......Activated Sludge Models are widely used for simulation-based evaluation of wastewater treatment plant (WWTP) performance. However, due to the high workload and cost of a measuring campaign on a full-scale WWTP, many simulation studies suffer from lack of sufficiently long influent flow rate...... and concentration time series representing realistic wastewater influent dynamics. In this paper, a simple phenomenological modelling approach is proposed as an alternative to generate dynamic influent pollutant disturbance scenarios. The presented set of models is constructed following the principles of parsimony...
A Simplified Ab Initio Cosmic-ray Modulation Model with Simulated Time Dependence and Predictive Capability

Science.gov (United States)

Moloto, K. D.; Engelbrecht, N. E.; Burger, R. A.

2018-06-01

A simplified ab initio approach is followed to model cosmic-ray proton modulation, using a steady-state three-dimensional stochastic solver of the Parker transport equation that simulates some effects of time dependence. Standard diffusion coefficients based on Quasilinear Theory and Nonlinear Guiding Center Theory are employed. The spatial and temporal dependences of the various turbulence quantities required as inputs for the diffusion, as well as the turbulence-reduced drift coefficients, follow from parametric fits to results from a turbulence transport model as well as from spacecraft observations of these turbulence quantities. Effective values are used for the solar wind speed, magnetic field magnitude, and tilt angle in the modulation model to simulate temporal effects due to changes in the large-scale heliospheric plasma. The unusually high cosmic-ray intensities observed during the 2009 solar minimum follow naturally from the current model for most of the energies considered. This demonstrates that changes in turbulence contribute significantly to the high intensities during that solar minimum. We also discuss and illustrate how this model can be used to predict future cosmic-ray intensities, and comment on the reliability of such predictions.
Mechanical properties of carbynes investigated by ab initio total-energy calculations

DEFF Research Database (Denmark)

Castelli, Ivano E.; Salvestrini, Paolo; Manini, Nicola

2012-01-01

As sp carbon chains (carbynes) are relatively rigid molecular objects, can we exploit them as construction elements in nanomechanics? To answer this question, we investigate their remarkable mechanical properties by ab initio total-energy simulations. In particular, we evaluate their linear...
Identity of the SU(3) model phenomenological hamiltonian and the hamiltonian of nonaxial rotator

International Nuclear Information System (INIS)

Filippov, G.F.; Avramenko, V.I.; Sokolov, A.M.

1984-01-01

Interpretation of nonspheric atomic nuclei spectra on the basis of phenomenological hamiltonians of SU(3) model showed satisfactory agreement of simulation calculations with experimental data. Meanwhile physical sense of phenomenological hamiltonians was not yet discussed. It is shown that phenomenological hamiltonians of SU(3) model are reduced to hamiltonian of nonaxial rotator but with additional items of the third and fourth powers angular momentum operator of rotator
Nonequilibrium Chemical Effects in Single-Molecule SERS Revealed by Ab Initio Molecular Dynamics Simulations

Energy Technology Data Exchange (ETDEWEB)

Fischer, Sean A.; Apra, Edoardo; Govind, Niranjan; Hess, Wayne P.; El-Khoury, Patrick Z.

2017-02-03

Recent developments in nanophotonics have paved the way for achieving significant advances in the realm of single molecule chemical detection, imaging, and dynamics. In particular, surface-enhanced Raman scattering (SERS) is a powerful analytical technique that is now routinely used to identify the chemical identity of single molecules. Understanding how nanoscale physical and chemical processes affect single molecule SERS spectra and selection rules is a challenging task, and is still actively debated. Herein, we explore underappreciated chemical phenomena in ultrasensitive SERS. We observe a fluctuating excited electronic state manifold, governed by the conformational dynamics of a molecule (4,4’-dimercaptostilbene, DMS) interacting with a metallic cluster (Ag20). This affects our simulated single molecule SERS spectra; the time trajectories of a molecule interacting with its unique local environment dictates the relative intensities of the observable Raman-active vibrational states. Ab initio molecular dynamics of a model Ag20-DMS system are used to illustrate both concepts in light of recent experimental results.
Valve-specific, analytic-phenomenological modelling of spray dispersion in zero-dimensional simulation; Ventilspezifische, analytisch-phaenomenologische Modellierung der Sprayausbreitung fuer die nulldimensionale Simulation

Energy Technology Data Exchange (ETDEWEB)

Schuerg, F.; Arndt, S. [Robert Bosch GmbH, Stuttgart (Germany); Weigand, B. [Stuttgart Univ. (Germany). Inst. fuer Thermodynamik der Luft- und Raumfahrt

2007-07-01

Spray-guided combustion processes for gasoline direct injection offer a great fuel saving potential. The quality of mixture formation has direct impact on combustion and emissions and ultimately on the technical feasibility of the consumption advantage. Therefore, it is very important to select the optimal mixture formation strategy. A systematic optimization of the mixture formation process based on experiments or three-dimensional computational fluid dynamics requires tremendous effort. An efficient alternative is the application-oriented, zero-dimensional numerical simulation of mixture formation. With a systemic model formulation in terms of global thermodynamic and fluid mechanical balance equations, the presented simulation model considers all relevant aspects of the mixture formation process. A comparison with measurements in a pressure/temperature chamber using laser-induced exciplex fluorescence tomography revealed a very satisfactory agreement between simulation and experiment. The newly developed, analytic-phenomenological spray propagation model precisely captures the injector-specific mixture formation characteristics of an annular-orifice injector in terms of penetration and volume. Vaporization rate and mean air/fuel ratio as the key quantities of mixture formation are correctly reproduced. Thus, the simulation model is suited to numerically assess the quality and to optimize the strategy of mixture formation. (orig.)
Ab initio molecular dynamics simulation of interstitial diffusion in Ni–Cr alloys and implications for radiation induced segregation

Energy Technology Data Exchange (ETDEWEB)

Barnard, L., E-mail: lmbarnard@wisc.edu; Morgan, D., E-mail: ddmorgan@wisc.edu

2014-06-01

In this study, ab initio molecular dynamics, implemented via density functional theory, is used to simulate self-interstitial diffusion in pure Ni and in the Ni-18 at.% Cr model alloy. Interstitial tracer diffusivities are measured from simulation results for pure Ni and for both Ni and Cr in the Ni–18Cr alloy. An Arrhenius function fit to these tracer diffusivities is then used in a rate theory model for radiation induced segregation, along with the experimentally measured vacancy diffusivities. It is predicted that interstitial diffusion has a tendency to cause Cr enrichment near grain boundaries, partially counterbalancing the tendency for vacancy diffusion to cause Cr depletion. This results in more mild Cr depletion than would result if only the vacancy diffusion were accounted for, in better agreement with experiment. This physical description of RIS in Ni–Cr alloys, which invokes the effects of both vacancy and interstitial diffusion, is distinct from the conventional description which accounts only for the effect of vacancy diffusion.
Ab initio molecular dynamics simulation of interstitial diffusion in Ni–Cr alloys and implications for radiation induced segregation

International Nuclear Information System (INIS)

Barnard, L.; Morgan, D.

2014-01-01

In this study, ab initio molecular dynamics, implemented via density functional theory, is used to simulate self-interstitial diffusion in pure Ni and in the Ni-18 at.% Cr model alloy. Interstitial tracer diffusivities are measured from simulation results for pure Ni and for both Ni and Cr in the Ni–18Cr alloy. An Arrhenius function fit to these tracer diffusivities is then used in a rate theory model for radiation induced segregation, along with the experimentally measured vacancy diffusivities. It is predicted that interstitial diffusion has a tendency to cause Cr enrichment near grain boundaries, partially counterbalancing the tendency for vacancy diffusion to cause Cr depletion. This results in more mild Cr depletion than would result if only the vacancy diffusion were accounted for, in better agreement with experiment. This physical description of RIS in Ni–Cr alloys, which invokes the effects of both vacancy and interstitial diffusion, is distinct from the conventional description which accounts only for the effect of vacancy diffusion
Multiscale Quantum Mechanics/Molecular Mechanics Simulations with Neural Networks.

Science.gov (United States)

Shen, Lin; Wu, Jingheng; Yang, Weitao

2016-10-11

Molecular dynamics simulation with multiscale quantum mechanics/molecular mechanics (QM/MM) methods is a very powerful tool for understanding the mechanism of chemical and biological processes in solution or enzymes. However, its computational cost can be too high for many biochemical systems because of the large number of ab initio QM calculations. Semiempirical QM/MM simulations have much higher efficiency. Its accuracy can be improved with a correction to reach the ab initio QM/MM level. The computational cost on the ab initio calculation for the correction determines the efficiency. In this paper we developed a neural network method for QM/MM calculation as an extension of the neural-network representation reported by Behler and Parrinello. With this approach, the potential energy of any configuration along the reaction path for a given QM/MM system can be predicted at the ab initio QM/MM level based on the semiempirical QM/MM simulations. We further applied this method to three reactions in water to calculate the free energy changes. The free-energy profile obtained from the semiempirical QM/MM simulation is corrected to the ab initio QM/MM level with the potential energies predicted with the constructed neural network. The results are in excellent accordance with the reference data that are obtained from the ab initio QM/MM molecular dynamics simulation or corrected with direct ab initio QM/MM potential energies. Compared with the correction using direct ab initio QM/MM potential energies, our method shows a speed-up of 1 or 2 orders of magnitude. It demonstrates that the neural network method combined with the semiempirical QM/MM calculation can be an efficient and reliable strategy for chemical reaction simulations.
Ab initio vel ex eventu

Science.gov (United States)

Thiessen, P. A.; Treder, H.-J.

Der gegenwärtige Stand der physikalischen Erkenntnis, in Sonderheit die Atomistik und die Quantentheorie, ermöglicht (in wohldefinierten Energie-Bereichen) eine ab initio-Berechnung aller physikalischen und chemischen Prozesse und Strukturen. Die Schrödinger-Gleichung erlaubt zusammen mit den Prinzipien der Quantenstatistik (Pauli-Prinzip) aus dem Planckschen Wirkungsquantum h und den atomischen Konstanten die Berechnung aller Energieumsätze, Zeitabläufe etc., die insbesondere die chemische Physik bestimmen. Die Rechenresultate gelten auch quantitativ bis auf die unvermeidliche Stochastik.Die ab initio-Berechnungen korrespondieren einerseits und sind andererseits komplementär zu den auf den Methoden der theoretischen Chemie und der klassischen Thermodynamik beruhenden Ergebnissen ex eventu. Die theoretische Behandlung ab initio führt zu mathematischen Experimenten, die die Laboratoriums-Experimente ergänzen oder auch substituieren.Translated AbstractAb initio vel ex eventuThe present state of physical knowledge, in peculiar atomistic and quantum theory, makes an ab initio calculation of all physical and chemical processes and structures possible (in well defined reaches of energy). The Schrödinger equation together with the principles of quantum statistics (Pauli principle) permits from the Planck and atomistic constants to calculate all exchanges of energy, courses of time, etc. which govern chemical physics. The calculated results are valid even quantitatively apart from the unavoidable stochastics.These ab initio calculations on the one hand correspond and are on the other complimentary to results ex eventu based on the methods of theoretical chemistry and classical thermodynamics. Theoretical treatment ab initio leads to mathematical experiments which add to or even substitute experiments in the laboratory.
Phenomenology is not Phenomenalism. Is there such a thing as phenomenology of sport?

Directory of Open Access Journals (Sweden)

Jan Halák

2014-06-01

Full Text Available Background: The application of the philosophical mode of investigation called "phenomenology" in the context of sport. Objective: The goal is to show how and why the phenomenological method is very often misused in sport-related research. Methods: Interpretation of the key texts, explanation of their meaning. Results: The confrontation of concrete sport-related texts with the original meaning of the key phenomenological notions shows mainly three types of misuse - the confusion of phenomenology with immediacy, with an epistemologically subjectivist stance (phenomenalism, and with empirical research oriented towards objects in the world. Conclusions: Many of the discussed authors try to take over the epistemological validity of phenomenology for their research, which itself is not phenomenological, and it seems that this is because they are lacking such a methodological foundation. We believe that an authentically phenomenological analysis of sport is possible, but it must respect the basic distinctions that differentiate phenomenology from other styles of thinking.
Ab initio van der waals interactions in simulations of water alter structure from mainly tetrahedral to high-density-like

DEFF Research Database (Denmark)

Møgelhøj, Andreas; Kelkkanen, Kari André; Wikfeldt, K Thor

2011-01-01

The structure of liquid water at ambient conditions is studied in ab initio molecular dynamics simulations in the NVE ensemble using van der Waals (vdW) density-functional theory, i.e., using the new exchange-correlation functionals optPBE-vdW and vdW-DF2, where the latter has softer nonlocal...... protocol could cause the deviation. An O-O PCF consisting of a linear combination of 70% from vdW-DF2 and 30% from low-density liquid water, as extrapolated from experiments, reproduces near-quantitatively the experimental O-O PCF for ambient water. This suggests the possibility that the new functionals...... shows some resemblance with experiment for high-density water ( Soper , A. K. and Ricci , M. A. Phys. Rev. Lett. 2000 , 84 , 2881 ), but not directly with experiment for ambient water. Considering the accuracy of the new functionals for interaction energies, we investigate whether the simulation...
Phenomenological Lagrangians

International Nuclear Information System (INIS)

Weinberg, S.

1979-01-01

The author presents an argument that phenomenological Lagrangians can be used not only to reproduce the soft pion results of current algebra, but also to justify these results, without any use of operator algebra, and shows how phenomenological Lagrangians can be used to calculate corrections to the leading soft pion results to any desired order in external momenta. The renormalization group is used to elucidate the structure of these corrections. Corrections due to the finite mass of the pion are treated and speculations are made about another possible application of phenomenological Lagrangians. (Auth.)
Iron -chromium alloys and free surfaces: from ab initio calculations to thermodynamic modeling

International Nuclear Information System (INIS)

Levesque, M.

2010-11-01

Ferritic steels possibly strengthened by oxide dispersion are candidates as structural materials for generation IV and fusion nuclear reactors. Their use is limited by incomplete knowledge of the iron-chromium phase diagram at low temperatures and of the phenomena inducing preferential segregation of one element at grain boundaries or at surfaces. In this context, this work contributes to the multi-scale study of the model iron-chromium alloy and their free surfaces by numerical simulations. This study begins with ab initio calculations of properties related to the mixture of atoms of iron and chromium. We highlight complex dependency of the magnetic moments of the chromium atoms on their local chemical environment. Surface properties are also proving sensitive to magnetism. This is the case of impurity segregation of chromium in iron and of their interactions near the surface. In a second step, we construct a simple energy model for high numerical efficiency. It is based on pair interactions on a rigid lattice to which are given local chemical environment and temperature dependencies. With this model, we reproduce the ab initio results at zero temperature and experimental results at high temperature. We also deduce the solubility limits at all intermediate temperatures with mean field approximations that we compare to Monte Carlo simulations. The last step of our work is to introduce free surfaces in our model. We then study the effect of ab initio calculated bulk and surface properties on surface segregation.Finally, we calculate segregation isotherms. We therefore propose an evolution model of surface composition of iron-chromium alloys as a function of bulk composition. which are given local chemical environment and temperature dependencies. With this model, we reproduce the ab initio results at zero temperature and experimental results at high temperature. We also deduce the solubility limits at all intermediate temperatures with mean field approximations that
Conducting phenomenological research: Rationalizing the methods and rigour of the phenomenology of practice.

Science.gov (United States)

Errasti-Ibarrondo, Begoña; Jordán, José Antonio; Díez-Del-Corral, Mercedes P; Arantzamendi, María

2018-03-15

To offer a complete outlook in a readable easy way of van Manen's hermeneutic-phenomenological method to nurses interested in undertaking phenomenological research. Phenomenology, as research methodology, involves a certain degree of complexity. It is difficult to identify a single article or author which sets out the didactic guidelines that specifically guide research of this kind. In this context, the theoretical-practical view of Max van Manen's Phenomenology of Practice may be seen as a rigorous guide and directive on which researchers may find support to undertake phenomenological research. Discussion paper. This discussion paper is based on our own experiences and supported by literature and theory. Our central sources of data have been the books and writings of Max van Manen and his website "Phenomenologyonline". The principal methods of the hermeneutic-phenomenological method are addressed and explained providing an enriching overview of phenomenology of practice. A proposal is made for the way the suggestions made by van Manen might be organized for use with the methods involved in Phenomenology of Practice: Social sciences, philosophical and philological methods. Thereby, nurse researchers interested in conducting phenomenological research may find a global outlook and support to understand and conduct this type of inquiry which draws on the art. The approach in this article may help nurse scholars and researchers reach an overall, encompassing perspective of the main methods and activities involved in doing phenomenological research. Nurses interested in doing phenomenology of practice are expected to commit with reflection and writing. © 2018 John Wiley & Sons Ltd.
A variable hard sphere-based phenomenological inelastic collision model for rarefied gas flow simulations by the direct simulation Monte Carlo method

Energy Technology Data Exchange (ETDEWEB)

Prasanth, P S; Kakkassery, Jose K; Vijayakumar, R, E-mail: y3df07@nitc.ac.in, E-mail: josekkakkassery@nitc.ac.in, E-mail: vijay@nitc.ac.in [Department of Mechanical Engineering, National Institute of Technology Calicut, Kozhikode - 673 601, Kerala (India)

2012-04-01

A modified phenomenological model is constructed for the simulation of rarefied flows of polyatomic non-polar gas molecules by the direct simulation Monte Carlo (DSMC) method. This variable hard sphere-based model employs a constant rotational collision number, but all its collisions are inelastic in nature and at the same time the correct macroscopic relaxation rate is maintained. In equilibrium conditions, there is equi-partition of energy between the rotational and translational modes and it satisfies the principle of reciprocity or detailed balancing. The present model is applicable for moderate temperatures at which the molecules are in their vibrational ground state. For verification, the model is applied to the DSMC simulations of the translational and rotational energy distributions in nitrogen gas at equilibrium and the results are compared with their corresponding Maxwellian distributions. Next, the Couette flow, the temperature jump and the Rayleigh flow are simulated; the viscosity and thermal conductivity coefficients of nitrogen are numerically estimated and compared with experimentally measured values. The model is further applied to the simulation of the rotational relaxation of nitrogen through low- and high-Mach-number normal shock waves in a novel way. In all cases, the results are found to be in good agreement with theoretically expected and experimentally observed values. It is concluded that the inelastic collision of polyatomic molecules can be predicted well by employing the constructed variable hard sphere (VHS)-based collision model.

Ab-initio simulations of pressure effects on structural and electronic properties of iron based superconductors

International Nuclear Information System (INIS)

Tomic, Milan

2013-01-01

The ab-initio molecular dynamics framework has been the cornerstone of computational solid state physics in the last few decades. Although it is already a mature field it is still rapidly developing to accommodate the growth in solid state research as well as to efficiently utilize the increase in computing power. Starting from the first principles, the ab-initio molecular dynamics provides essential information about structural and electronic properties of matter under various external conditions. In this thesis we use the ab-initio molecular dynamics to study the behavior of BaFe 2 As 2 and CaFe 2 As 2 under the application of external pressure. BaFe 2 As 2 and CaFe 2 As 2 belong to the family of iron based superconductors which are a novel and promising superconducting materials. The application of pressure is one of two key methods by which electronic and structural properties of iron based superconductors can be modified, the other one being doping (or chemical pressure). In particular, it has been noted that pressure conditions have an important effect, but their exact role is not fully understood. To better understand the effect of different pressure conditions we have performed a series of ab-initio simulations of pressure application. In order to apply the pressure with arbitrary stress tensor we have developed a method based on the Fast Inertial Relaxation Engine, whereby the unit cell and the atomic positions are evolved according to the metadynamical equations of motion. We have found that the application of hydrostatic and c axis uniaxial pressure induces a phase transition from the magnetically ordered orthorhombic phase to the non-magnetic collapsed tetragonal phase in both BaFe 2 As 2 and CaFe 2 As 2 . In the case of BaFe 2 As 2 , an intermediate tetragonal non-magnetic tetragonal phase is observed in addition. Application of the uniaxial pressure parallel to the c axis reduces the critical pressure of the phase transition by an order of magnitude
Hydration structures of U(III) and U(IV) ions from ab initio molecular dynamics simulations

International Nuclear Information System (INIS)

Leung, Kevin; Nenoff, Tina M.

2012-01-01

We apply DFT+U-based ab initio molecular dynamics simulations to study the hydration structures of U(III) and U(IV) ions, pertinent to redox reactions associated with uranium salts in aqueous media. U(III) is predicted to be coordinated to 8 water molecules, while U(IV) has a hydration number between 7 and 8. At least one of the innershell water molecules of the hydrated U(IV) complex becomes spontaneously deprotonated. As a result, the U(IV)–O pair correlation function exhibits a satellite peak at 2.15 Å associated with the shorter U(IV)–(OH − ) bond. This feature is not accounted for in analysis of extended x-ray absorption fine structure and x-ray adsorption near edge structure measurements, which yield higher estimates of U(IV) hydration numbers. This suggests that it may be useful to include the effect of possible hydrolysis in future interpretation of experiments, especially when the experimental pH is close to the reported hydrolysis equilibrium constant value.
Ab initio molecular dynamics simulations of low energy recoil events in MgO

International Nuclear Information System (INIS)

Petersen, B. A.; Liu, B.; Weber, W. J.; Oak Ridge National Laboratory; Zhang, Y.; Oak Ridge National Laboratory

2017-01-01

In this paper, low-energy recoil events in MgO are studied using ab initio molecular dynamics simulations to reveal the dynamic displacement processes and final defect configurations. Threshold displacement energies, E_d, are obtained for Mg and O along three low-index crystallographic directions, [100], [110], and [111]. The minimum values for E_d are found along the [110] direction consisting of the same element, either Mg or O atoms. Minimum threshold values of 29.5 eV for Mg and 25.5 eV for O, respectively, are suggested from the calculations. For other directions, the threshold energies are considerably higher, 65.5 and 150.0 eV for O along [111] and [100], and 122.5 eV for Mg along both [111] and [100] directions, respectively. These results show that the recoil events in MgO are partial-charge transfer assisted processes where the charge transfer plays an important role. Finally, there is a similar trend found in other oxide materials, where the threshold displacement energy correlates linearly with the peak partial-charge transfer, suggesting this behavior might be universal in ceramic oxides.
Conformational Sampling by Ab Initio Molecular Dynamics Simulations Improves NMR Chemical Shift Predictions

Czech Academy of Sciences Publication Activity Database

Dračínský, Martin; Möller, H. M.; Exner, T. E.

2013-01-01

Roč. 9, č. 8 (2013), s. 3806-3815 ISSN 1549-9618 R&D Projects: GA ČR GA13-24880S Institutional support: RVO:61388963 Keywords : ab initio molecular dynamics * NMR spectroscopy * DFT calculations * hydration Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.310, year: 2013
Calcium ions in aqueous solutions: Accurate force field description aided by ab initio molecular dynamics and neutron scattering

Science.gov (United States)

Martinek, Tomas; Duboué-Dijon, Elise; Timr, Štěpán; Mason, Philip E.; Baxová, Katarina; Fischer, Henry E.; Schmidt, Burkhard; Pluhařová, Eva; Jungwirth, Pavel

2018-06-01

We present a combination of force field and ab initio molecular dynamics simulations together with neutron scattering experiments with isotopic substitution that aim at characterizing ion hydration and pairing in aqueous calcium chloride and formate/acetate solutions. Benchmarking against neutron scattering data on concentrated solutions together with ion pairing free energy profiles from ab initio molecular dynamics allows us to develop an accurate calcium force field which accounts in a mean-field way for electronic polarization effects via charge rescaling. This refined calcium parameterization is directly usable for standard molecular dynamics simulations of processes involving this key biological signaling ion.
Exceptional phenomenology

DEFF Research Database (Denmark)

Aggerholm, Kenneth; Moltke Martiny, Kristian

Phenomenological research is in traditional terms a matter of going 'back to the things themselves', as Husserl famously stated. But if phenomenology is to renew itself in creative ways and reveal new aspects of human experience it is of value to look for a certain kind of phenomena: exceptions. ...
Mechanistic Insights into Radical-Mediated Oxidation of Tryptophan from ab Initio Quantum Chemistry Calculations and QM/MM Molecular Dynamics Simulations.

Science.gov (United States)

Wood, Geoffrey P F; Sreedhara, Alavattam; Moore, Jamie M; Wang, John; Trout, Bernhardt L

2016-05-12

An assessment of the mechanisms of (•)OH and (•)OOH radical-mediated oxidation of tryptophan was performed using density functional theory calculations and ab initio plane-wave Quantum Mechanics/Molecular Mechanics (QM/MM) molecular dynamics simulations. For the (•)OH reactions, addition to the pyrrole ring at position 2 is the most favored site with a barrierless reaction in the gas phase. The subsequent degradation of this adduct through a H atom transfer to water was intermittently observed in aqueous-phase molecular dynamics simulations. For the (•)OOH reactions, addition to the pyrrole ring at position 2 is the most favored pathway, in contrast to the situation in the model system ethylene, where concerted addition to the double bond is preferred. From the (•)OOH position 2 adduct QM/MM simulations show that formation of oxy-3-indolanaline occurs readily in an aqueous environment. The observed transformation starts from an initial rupture of the O-O bond followed by a H atom transfer with the accompanying loss of an (•)OH radical to solution. Finally, classical molecular dynamics simulations were performed to equate observed differential oxidation rates of various tryptophan residues in monoclonal antibody fragments. It was found that simple parameters derived from simulation correlate well with the experimental data.
Phenomenology as research method or substantive metaphysics? An overview of phenomenology's uses in nursing.

Science.gov (United States)

Earle, Vicki

2010-10-01

In exploring phenomenological literature, it is evident that the term 'phenomenology' holds rather different meanings depending upon the context. Phenomenology has been described as both a philosophical movement and an approach to human science research. The phenomenology of Husserl, Heidegger, Gadamer, and Merleau-Ponty was philosophical in nature and not intended to provide rules or procedures for conducting research. The Canadian social scientist, van Manen, however, introduced specific guidelines for conducting human science research, which is rooted in hermeneutic phenomenology and this particular method has been employed in professional disciplines such as education, nursing, clinical psychology, and law. The purpose of this paper is to explore the difference between the phenomenological method as described by van Manen and that of other philosophers such as Husserl, Heidegger, Gadamer, and Merleau-Ponty. In so doing, the author aims to address the blurred boundaries of phenomenology as a research method and as a philosophical movement and highlight the influence of these blurred boundaries on nursing knowledge development.
Phenomenology and homeopathy.

Science.gov (United States)

Whitmarsh, Tom

2013-07-01

There is a great overlap between the way of seeing the world in clinical homeopathy and in the technical philosophical system known as phenomenology. A knowledge of phenomenologic principles reveals Hahnemann to have been an unwitting phenomenologist. The ideas of phenomenology as applied to medicine show that homeopathy is the ideal medical system to fulfill the goals of coming ever closer to true patient concerns and experience of illness. Copyright © 2013 The Faculty of Homeopathy. Published by Elsevier Ltd. All rights reserved.
Phenomenology in Its Original Sense.

Science.gov (United States)

van Manen, Max

2017-05-01

In this article, I try to think through the question, "What distinguishes phenomenology in its original sense?" My intent is to focus on the project and methodology of phenomenology in a manner that is not overly technical and that may help others to further elaborate on or question the singular features that make phenomenology into a unique qualitative form of inquiry. I pay special attention to the notion of "lived" in the phenomenological term "lived experience" to demonstrate its critical role and significance for understanding phenomenological reflection, meaning, analysis, and insights. I also attend to the kind of experiential material that is needed to focus on a genuine phenomenological question that should guide any specific research project. Heidegger, van den Berg, and Marion provide some poignant exemplars of the use of narrative "examples" in phenomenological explorations of the phenomena of "boredom," "conversation," and "the meaningful look in eye-contact." Only what is given or what gives itself in lived experience (or conscious awareness) are proper phenomenological "data" or "givens," but these givens are not to be confused with data material that can be coded, sorted, abstracted, and accordingly analyzed in some "systematic" manner. The latter approach to experiential research may be appropriate and worthwhile for various types of qualitative inquiry but not for phenomenology in its original sense. Finally, I use the mythical figure of Kairos to show that the famous phenomenological couplet of the epoché-reduction aims for phenomenological insights that require experiential analysis and attentive (but serendipitous) methodical inquiry practices.
Ab initio assisted process modeling for Si-based nanoelectronic devices

International Nuclear Information System (INIS)

Windl, Wolfgang

2005-01-01

In this paper, we discuss concepts and examples of ab initio calculations assisting physics-based process simulation. We focus on how to determine diffusion and reaction constants, where modern methods such as the nudged elastic band method allow a systematic and reliable search for the minimum energy migration path and barrier. We show that once the saddle point is determined, the underlying harmonic transition state theory also allows to calculate the prefactors. The discussed examples include nitrogen diffusion, boron deactivation and boron interface segregation. Finally, some concepts are discussed for future device technologies such as molecular devices, where the currently prevalent multiscale approach (kinetic parameters used in higher level models like diffusion-reaction or kinetic Monte Carlo modeling) would not be sensible anymore. As an example, we described the ab initio temperature-accelerated dynamics modeling of contact formation in carbon nanotube devices
Phenomenological approach to spin fluctuations in itinerant magnets and superconductors from ab initio calculations

Energy Technology Data Exchange (ETDEWEB)

Ortenzi, Luciano

2013-10-17

In this thesis I study the interplay between magnetism and superconductivity in itinerant magnets and superconductors. I do this by applying a semiphenomenological method to four representative compounds. In particular I use the discrepancies (whenever present) between density functional theory (DFT) calculations and the experiments in order to construct phenomenological models which explain the magnetic, superconducting and optical properties of four representative systems. I focus my attention on the superconducting and normal state properties of the recently discovered APt3P superconductors, on superconducting hole-doped CuBiSO, on the optical properties of LaFePO and finally on the ferromagnetic-paramagnetic transition of Ni3Al under pressure. At the end I present a new method which aims to describe the effect of spin fluctuations in itinerant magnets and superconductors that can be used to monitor the evolution of the electronic structure from non magnetic to magnetic in systems close to a quantum critical point.
On the room-temperature phase diagram of high pressure hydrogen: An ab initio molecular dynamics perspective and a diffusion Monte Carlo study

International Nuclear Information System (INIS)

Chen, Ji; Ren, Xinguo; Li, Xin-Zheng; Alfè, Dario; Wang, Enge

2014-01-01

The finite-temperature phase diagram of hydrogen in the region of phase IV and its neighborhood was studied using the ab initio molecular dynamics (MD) and the ab initio path-integral molecular dynamics (PIMD). The electronic structures were analyzed using the density-functional theory (DFT), the random-phase approximation, and the diffusion Monte Carlo (DMC) methods. Taking the state-of-the-art DMC results as benchmark, comparisons of the energy differences between structures generated from the MD and PIMD simulations, with molecular and dissociated hydrogens, respectively, in the weak molecular layers of phase IV, indicate that standard functionals in DFT tend to underestimate the dissociation barrier of the weak molecular layers in this mixed phase. Because of this underestimation, inclusion of the quantum nuclear effects (QNEs) in PIMD using electronic structures generated with these functionals leads to artificially dissociated hydrogen layers in phase IV and an error compensation between the neglect of QNEs and the deficiencies of these functionals in standard ab initio MD simulations exists. This analysis partly rationalizes why earlier ab initio MD simulations complement so well the experimental observations. The temperature and pressure dependencies for the stability of phase IV were also studied in the end and compared with earlier results
Meteorite Impact-Induced Rapid NH3 Production on Early Earth: Ab Initio Molecular Dynamics Simulation

Science.gov (United States)

Shimamura, Kohei; Shimojo, Fuyuki; Nakano, Aiichiro; Tanaka, Shigenori

2016-12-01

NH3 is an essential molecule as a nitrogen source for prebiotic amino acid syntheses such as the Strecker reaction. Previous shock experiments demonstrated that meteorite impacts on ancient oceans would have provided a considerable amount of NH3 from atmospheric N2 and oceanic H2O through reduction by meteoritic iron. However, specific production mechanisms remain unclear, and impact velocities employed in the experiments were substantially lower than typical impact velocities of meteorites on the early Earth. Here, to investigate the issues from the atomistic viewpoint, we performed multi-scale shock technique-based ab initio molecular dynamics simulations. The results revealed a rapid production of NH3 within several picoseconds after the shock, indicating that shocks with greater impact velocities would provide further increase in the yield of NH3. Meanwhile, the picosecond-order production makes one expect that the important nitrogen source precursors of amino acids were obtained immediately after the impact. It was also observed that the reduction of N2 proceeded according to an associative mechanism, rather than a dissociative mechanism as in the Haber-Bosch process.
Ab-initio simulations of pressure effects on structural and electronic properties of iron based superconductors

Energy Technology Data Exchange (ETDEWEB)

Tomic, Milan

2013-07-01

The ab-initio molecular dynamics framework has been the cornerstone of computational solid state physics in the last few decades. Although it is already a mature field it is still rapidly developing to accommodate the growth in solid state research as well as to efficiently utilize the increase in computing power. Starting from the first principles, the ab-initio molecular dynamics provides essential information about structural and electronic properties of matter under various external conditions. In this thesis we use the ab-initio molecular dynamics to study the behavior of BaFe{sub 2}As{sub 2} and CaFe{sub 2}As{sub 2} under the application of external pressure. BaFe{sub 2}As{sub 2} and CaFe{sub 2}As{sub 2} belong to the family of iron based superconductors which are a novel and promising superconducting materials. The application of pressure is one of two key methods by which electronic and structural properties of iron based superconductors can be modified, the other one being doping (or chemical pressure). In particular, it has been noted that pressure conditions have an important effect, but their exact role is not fully understood. To better understand the effect of different pressure conditions we have performed a series of ab-initio simulations of pressure application. In order to apply the pressure with arbitrary stress tensor we have developed a method based on the Fast Inertial Relaxation Engine, whereby the unit cell and the atomic positions are evolved according to the metadynamical equations of motion. We have found that the application of hydrostatic and c axis uniaxial pressure induces a phase transition from the magnetically ordered orthorhombic phase to the non-magnetic collapsed tetragonal phase in both BaFe{sub 2}As{sub 2} and CaFe{sub 2}As{sub 2}. In the case of BaFe{sub 2}As{sub 2}, an intermediate tetragonal non-magnetic tetragonal phase is observed in addition. Application of the uniaxial pressure parallel to the c axis reduces the
Limitations of Ab Initio Predictions of Peptide Binding to MHC Class II Molecules

DEFF Research Database (Denmark)

Zhang, Hao; Lund, Ole; Nielsen, Morten

2010-01-01

potentials derived from the analysis of known protein structures; energetic evaluation of different peptide snapshots in a molecular dynamics simulation; and direct analysis of contacts made in known 3D structures of peptide:MHC complexes. These methods are ab initio in that they require structural data...
Hydrated Electron Transfer to Nucleobases in Aqueous Solutions Revealed by Ab Initio Molecular Dynamics Simulations.

Science.gov (United States)

Zhao, Jing; Wang, Mei; Fu, Aiyun; Yang, Hongfang; Bu, Yuxiang

2015-08-03

We present an ab initio molecular dynamics (AIMD) simulation study into the transfer dynamics of an excess electron from its cavity-shaped hydrated electron state to a hydrated nucleobase (NB)-bound state. In contrast to the traditional view that electron localization at NBs (G/A/C/T), which is the first step for electron-induced DNA damage, is related only to dry or prehydrated electrons, and a fully hydrated electron no longer transfers to NBs, our AIMD simulations indicate that a fully hydrated electron can still transfer to NBs. We monitored the transfer dynamics of fully hydrated electrons towards hydrated NBs in aqueous solutions by using AIMD simulations and found that due to solution-structure fluctuation and attraction of NBs, a fully hydrated electron can transfer to a NB gradually over time. Concurrently, the hydrated electron cavity gradually reorganizes, distorts, and even breaks. The transfer could be completed in about 120-200 fs in four aqueous NB solutions, depending on the electron-binding ability of hydrated NBs and the structural fluctuation of the solution. The transferring electron resides in the π*-type lowest unoccupied molecular orbital of the NB, which leads to a hydrated NB anion. Clearly, the observed transfer of hydrated electrons can be attributed to the strong electron-binding ability of hydrated NBs over the hydrated electron cavity, which is the driving force, and the transfer dynamics is structure-fluctuation controlled. This work provides new insights into the evolution dynamics of hydrated electrons and provides some helpful information for understanding the DNA-damage mechanism in solution. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Ab initio studies on [bmim][PF6]–CO2 mixture and CO2 clusters

Indian Academy of Sciences (India)

Wintec

Ionic liquids; supercritical carbon dioxide; ab initio; molecular dynamics. 1. Introduction .... Several experi- mental and simulation studies have been carried out to .... from an analysis of its electronic polarizability (α), which is a measure of the ...
Investigation of the Hydroxylation Mechanism of Noncoupled Copper Oxygenases by Ab Initio Molecular Dynamics Simulations

Czech Academy of Sciences Publication Activity Database

Meliá, C.; Ferrer, S.; Řezáč, Jan; Parisel, O.; Reinaud, O.; Moliner, V.; de la Lande, A.

2013-01-01

Roč. 19, č. 51 (2013), s. 17328-17337 ISSN 0947-6539 Institutional support: RVO:61388963 Keywords : ab initio calculations * copper * electron transfer * enzymes * molecular dynamics * reaction mechanisms Subject RIV: CC - Organic Chemistry Impact factor: 5.696, year: 2013
Understanding hydration of Zn(2+) in hydrothermal fluids with ab initio molecular dynamics

NARCIS (Netherlands)

Liu, X.; Lu, X.; Wang, R.; Meijer, E.J.

2011-01-01

With ab initio molecular dynamics simulations, the free-energy profiles of hydrated Zn2+ are calculated for both gaseous and aqueous systems from ambient to supercritical conditions, and from the derived free-energy information, the speciation of hydrated Zn2+ has been revealed. It is shown that the

Computationally efficient and quantitatively accurate multiscale simulation of solid-solution strengthening by ab initio calculation

Czech Academy of Sciences Publication Activity Database

Ma, D.; Friák, Martin; von Pezold, J.; Raabe, D.; Neugebauer, J.

2015-01-01

Roč. 85, FEB (2015), s. 53-66 ISSN 1359-6454 Institutional support: RVO:68081723 Keywords : Solid-solution strengthening * DFT * Peierls–Nabarro model * Ab initio * Al alloys Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 5.058, year: 2015
Collective rotation from ab initio theory

International Nuclear Information System (INIS)

Caprio, M.A.; Maris, P.; Vary, J.P.; Smith, R.

2015-01-01

Through ab initio approaches in nuclear theory, we may now seek to quantitatively understand the wealth of nuclear collective phenomena starting from the underlying internucleon interactions. No-core configuration interaction (NCCI) calculations for p-shell nuclei give rise to rotational bands, as evidenced by rotational patterns for excitation energies, electromagnetic moments and electromagnetic transitions. In this review, NCCI calculations of 7–9 Be are used to illustrate and explore ab initio rotational structure, and the resulting predictions for rotational band properties are compared with experiment. We highlight the robustness of ab initio rotational predictions across different choices for the internucleon interaction. (author)
Ab initio theory for current-induced molecular switching: Melamine on Cu(001)

KAUST Repository

Ohto, Tatsuhiko

2013-05-28

Melamine on Cu(001) is mechanically unstable under the current of a scanning tunneling microscope tip and can switch among configurations. However, these are not equally accessible, and the switching critical current depends on the bias polarity. In order to explain such rich phenomenology, we have developed a scheme to evaluate the evolution of the reaction paths and activation barriers as a function of bias, which is rooted in the nonequilibrium Green\\'s function method implemented within density functional theory. This, combined with the calculation of the inelastic electron tunneling spectroscopy signal, allows us to identify the vibrational modes promoting the observed molecular conformational changes. Finally, once our ab initio results are used within a resonance model, we are able to explain the details of the switching behavior, such as its dependence on the bias polarity, and the noninteger power relation between the reaction rate constants and both the bias voltage and the electric current. © 2013 American Physical Society.
Ab initio theory for current-induced molecular switching: Melamine on Cu(001)

KAUST Repository

Ohto, Tatsuhiko; Rungger, Ivan; Yamashita, Koichi; Nakamura, Hisao; Sanvito, Stefano

2013-01-01

Melamine on Cu(001) is mechanically unstable under the current of a scanning tunneling microscope tip and can switch among configurations. However, these are not equally accessible, and the switching critical current depends on the bias polarity. In order to explain such rich phenomenology, we have developed a scheme to evaluate the evolution of the reaction paths and activation barriers as a function of bias, which is rooted in the nonequilibrium Green's function method implemented within density functional theory. This, combined with the calculation of the inelastic electron tunneling spectroscopy signal, allows us to identify the vibrational modes promoting the observed molecular conformational changes. Finally, once our ab initio results are used within a resonance model, we are able to explain the details of the switching behavior, such as its dependence on the bias polarity, and the noninteger power relation between the reaction rate constants and both the bias voltage and the electric current. © 2013 American Physical Society.
Putting phenomenology in its place: some limits of a phenomenology of medicine.

Science.gov (United States)

Sholl, Jonathan

2015-12-01

Several philosophers have recently argued that phenomenology is well-suited to help understand the concepts of health, disease, and illness. The general claim is that by better analysing how illness appears to or is experienced by ill individuals--incorporating the first-person perspective--some limitations of what is seen as the currently dominant third-person or 'naturalistic' approaches to understand health and disease can be overcome. In this article, after discussing some of the main insights and benefits of the phenomenological approach, I develop three general critiques of it. First, I show that what is often referred to as naturalism tends to be misunderstood and/or misrepresented, resulting in straw-man arguments. Second, the concept of normality is often problematically employed such that some aspects of naturalism are actually presupposed by many phenomenologists of medicine. Third, several of the key phenomenological insights and concepts, e.g. having vs. being a body, the alienation of illness, the epistemic role of the first-person perspective, and the idea of health within illness, each bring with them new problems that limit their utility. While acknowledging the possible contributions of phenomenology, these criticisms point to some severe limitations of bringing phenomenological insights to bear on the problems facing philosophy of medicine that should be addressed if phenomenology is to add anything substantially new to its debates.
Hydrogen atom injection into carbon surfaces by comparison between Monte-Carlo, molecular dynamics and ab-initio calculations

International Nuclear Information System (INIS)

Ito, A.; Kenmotsu, T.; Kikuhara, Y.; Inai, K.; Ohya, K.; Wang, Y.; Irle, S.; Morokuma, K.; Nakamura, H.

2009-01-01

Full text: To understand the plasma-wall interaction on divertor plates, we investigate the interaction of hydrogen atoms and carbon materials used in the high heat flux components by the use of the following simulations. Monte-Carlo (MC) method based on binary collision approximation can calculate the sputtering process of hydrogen atoms on the carbon material quickly. Classical molecular dynamics (MD) method employs multi-body potential models and can treat realistic structures of crystal and molecule. The ab-initio method can calculate electron energy in quantum mechanics, which is regarded as realistic potential for atoms. In the present paper, the interaction of the hydrogen and the carbon material is investigated using the multi-scale (MC, MD and ab-initio) methods. The bombardment of hydrogen atoms onto the carbon material is simulated by the ACAT-code of the MC method, which cannot represent the structure of crystal, and the MD method using modified reactive empirical bond order (REBO) potential, which treats single crystal graphite and amorphous carbon. Consequently, we clarify that the sputtering yield and the reflection rate calculated by the ACAT-code agree with those on the amorphous carbon calculated by the MD. Moreover, there are many kinds of REBO potential for the MD. Adsorption, reflection and penetration rates between a hydrogen atom and a graphene surface are calculated by the MD simulations using the two kinds of potential model. For the incident energy of less than 1 eV, the MD simulation using the modified REBO potential, which is based on Brenner's REBO potential in 2002, shows that reflection is dominant, while the most popular Brenner's REBO potential in 1990 shows that adsorption is dominant. This reflection of the low energy injection is caused by a small potential barrier for the hydrogen atom in the modified REBO potential. The small potential barrier is confirmed by the ab-initio calculations, which are hybrid DFT (B3LYP/cc-pVDZ), ab-initio
Resolving the HONO formation mechanism in the ionosphere via ab initio molecular dynamic simulations.

Science.gov (United States)

He, Rongxing; Li, Lei; Zhong, Jie; Zhu, Chongqin; Francisco, Joseph S; Zeng, Xiao Cheng

2016-04-26

Solar emission produces copious nitrosonium ions (NO(+)) in the D layer of the ionosphere, 60 to 90 km above the Earth's surface. NO(+) is believed to transfer its charge to water clusters in that region, leading to the formation of gaseous nitrous acid (HONO) and protonated water cluster. The dynamics of this reaction at the ionospheric temperature (200-220 K) and the associated mechanistic details are largely unknown. Using ab initio molecular dynamics (AIMD) simulations and transition-state search, key structures of the water hydrates-tetrahydrate NO(+)(H2O)4 and pentahydrate NO(+)(H2O)5-are identified and shown to be responsible for HONO formation in the ionosphere. The critical tetrahydrate NO(+)(H2O)4 exhibits a chain-like structure through which all of the lowest-energy isomers must go. However, most lowest-energy isomers of pentahydrate NO(+)(H2O)5 can be converted to the HONO-containing product, encountering very low barriers, via a chain-like or a three-armed, star-like structure. Although these structures are not the global minima, at 220 K, most lowest-energy NO(+)(H2O)4 and NO(+)(H2O)5 isomers tend to channel through these highly populated isomers toward HONO formation.
Structural investigation of water-acetonitrile mixtures: An ab initio, molecular dynamics and X-ray diffraction study

International Nuclear Information System (INIS)

Bako, Imre; Megyes, Tuende; Palinkas, Gabor

2005-01-01

In this work, we present a study on water-acetonitrile (AN) mixtures by molecular dynamics ab initio and X-ray diffraction techniques. Comparison of the experimental total G(r) functions of the mixtures with the results of molecular dynamics simulation shows an overall good agreement. The properties of hydrogen bonded clusters (water clusters, and water-AN clusters) in these mixtures have been determined. Two different types of AN-water dimers were identified by ab initio quantum chemical calculation. One of these structures proved to be a true H-bonded dimer and the other a dipole bound dimer
Hybrid classical/quantum simulation for infrared spectroscopy of water

Science.gov (United States)

Maekawa, Yuki; Sasaoka, Kenji; Ube, Takuji; Ishiguro, Takashi; Yamamoto, Takahiro

2018-05-01

We have developed a hybrid classical/quantum simulation method to calculate the infrared (IR) spectrum of water. The proposed method achieves much higher accuracy than conventional classical molecular dynamics (MD) simulations at a much lower computational cost than ab initio MD simulations. The IR spectrum of water is obtained as an ensemble average of the eigenvalues of the dynamical matrix constructed by ab initio calculations, using the positions of oxygen atoms that constitute water molecules obtained from the classical MD simulation. The calculated IR spectrum is in excellent agreement with the experimental IR spectrum.
Ab Initio Analysis of Auger-Assisted Electron Transfer.

Science.gov (United States)

Hyeon-Deuk, Kim; Kim, Joonghan; Prezhdo, Oleg V

2015-01-15

Quantum confinement in nanoscale materials allows Auger-type electron-hole energy exchange. We show by direct time-domain atomistic simulation and analytic theory that Auger processes give rise to a new mechanism of charge transfer (CT) on the nanoscale. Auger-assisted CT eliminates the renown Marcus inverted regime, rationalizing recent experiments on CT from quantum dots to molecular adsorbates. The ab initio simulation reveals a complex interplay of the electron-hole and charge-phonon channels of energy exchange, demonstrating a variety of CT scenarios. The developed Marcus rate theory for Auger-assisted CT describes, without adjustable parameters, the experimental plateau of the CT rate in the region of large donor-acceptor energy gap. The analytic theory and atomistic insights apply broadly to charge and energy transfer in nanoscale systems.
Structural, electronic and magnetic properties of LaCr2Si2C: Ab initio calculation, mean field approximation and Monte-Carlo simulation

Science.gov (United States)

Endichi, A.; Zaari, H.; Benyoussef, A.; El Kenz, A.

2018-06-01

The magnetic behavior of LaCr2Si2C compound is investigated in this work, using first principle methods, Monte Carlo simulation (MCS) and mean field approximation (MFA). The structural, electronic and magnetic properties are described using ab initio method in the framework of the Generalized Gradient Approximation (GGA), and the Full Potential-Linearized Augmented Plane Wave (FP-LAPW) method implemented in the WIEN2K packages. We have also computed the coupling terms between magnetic atoms which are used in Hamiltonian model. A theoretical study realized by mean field approximation and Monte Carlo Simulation within the Ising model is used to more understand the magnetic properties of this compound. Thereby, our results showed a ferromagnetic ordering of the Cr magnetic moments below the Curie temperature of 30 K (Tc magnetization, the energy, the specific heat and the susceptibility. This material shows the small sign of supra-conductivity; and future researches could be focused to enhance the transport and magnetic properties of this system.
Philosophy of phenomenology: how understanding aids research.

Science.gov (United States)

Converse, Mary

2012-01-01

To assist the researcher in understanding the similarities and differences between the Husserlian and Heideggerian philosophies of phenomenology, and how that philosophy can inform nursing research as a useful methodology. Nurse researchers using phenomenology as a methodology need to understand the philosophy of phenomenology to produce a research design that is philosophically congruent. However, phenomenology has a long and complex history of development, and may be difficult to understand and apply. The author draws from Heidegger (1962), Gadamer (2004), and nurse scholars and methodologists. To give the reader a sense of the development of the philosophy of phenomenology, the author briefly recounts its historical origins and interpretations, specifically related to Husserl, Heidegger and Gadamer. The author outlines the ontological and epistemological assumptions of Husserlian and Heideggerian phenomenology and guidance for methodology inspired by these philosophers. Difficulties with engaging in phenomenological research are addressed, especially the processes of phenomenological reduction and bracketing, and the lack of clarity about the methods of interpretation. Despite its complexity, phenomenology can provide the nurse researcher with indepth insight into nursing practice. An understanding of phenomenology can guide nurse researchers to produce results that have meaning in nursing patient care.
Electronic properties of liquid Hg-In alloys : Ab-initio molecular dynamics study

International Nuclear Information System (INIS)

Sharma, Nalini; Ahluwalia, P. K.; Thakur, Anil

2016-01-01

Ab-initio molecular dynamics simulations are performed to study the structural properties of liquid Hg-In alloys. The interatomic interactions are described by ab-initio pseudopotentials given by Troullier and Martins. Three liquid Hg-In alloys (Hg_1_0In_9_0, Hg_3_0In_7_0_,_. Hg_5_0In_5_0, Hg_7_0In_3_0, and Hg_9_0Pb_1_0) at 299 K are considered. The calculated results for liquid Hg (l-Hg) and lead (l-In) are also drawn. Along with the calculated results of considered five liquid alloys of Hg-In alloy. The results obtained from electronic properties namely total density of state and partial density of states help to find the local arrangement of Hg and In atoms and the presence of liquid state in the considered five alloys.
An ab-initio study of mechanical, dynamical and electronic properties of MgEu intermetallic

Science.gov (United States)

Kumar, S. Ramesh; Jaiganesh, G.; Jayalakshmi, V.

2018-04-01

The theoretical investigation on the mechanical, dynamical and electronic properties of MgEu in CsCl-type structure has been carried out through the ab-initio calculations within the framework of the density functional theory and the density functional perturbation theory. For the purpose, Vienna Ab initio Simulation Package and Phonopy packages were used. Our calculated ground-state properties of MgEu are in good agreement with other available results. Our computed elastic constants and phonon spectrum results suggest that MgEu is mechanically and dynamically stable up to 5 GPa. The thermodynamic quantities as a function of temperatures are also reported and discussed. The band structure, density of states and charge density also calculated to understand the electronic properties of MgEu.
Structural, dynamical, electronic, and bonding properties of laser-heated silicon: An ab initio molecular-dynamics study

NARCIS (Netherlands)

Silvestrelli, P.-L.; Alavi, A.; Parrinello, M.; Frenkel, D.

1997-01-01

The method of ab initio molecular dynamics, based on finite-temperature density-functional theory, is used to simulate laser heating of crystalline silicon. We found that a high concentration of excited electrons dramatically weakens the covalent bonding. As a result the system undergoes a melting
Phenomenology and Meaning Attribution

African Journals Online (AJOL)

John Paley. (2017). Phenomenology as Qualitative Research: A Critical Analysis of Meaning Attribution. ... basic philosophical nature of phenomenological meaning and inquiry, and that he not ... In keeping with the title of my book, Researching. Lived Experience ...... a quantitative social science that can make generalizing.
Ab-initio atomic level stress and role of d-orbitals in CuZr, CuZn and CuY

Science.gov (United States)

Ojha, Madhusudan; Nicholson, Don M.; Egami, Takeshi

2015-03-01

Atomic level stress offers a new tool to characterize materials within the local approximation to density functional theory (DFT). Ab-initio atomic level stresses in B2 structures of CuZr, CuZn and CuY are calculated and results are explained on the basis of d-orbital contributions to Density of States (DOS). The overlap of d-orbital DOS plays an important role in the relative magnitude of atomic level stresses in these structures. The trends in atomic level stresses that we observed in these simple B2 structures are also seen in complex structures such as liquids, glasses and solid solutions. The stresses are however modified by the different coordination and relaxed separation distances in these complex structures. We used the Locally Self-Consistent Multiple Scattering (LSMS) code and Vienna Ab-initio Simulation Package (VASP) for ab-initio calculations.
Ab initio molecular dynamics, iterative methods and multiscale approaches in electronic structure calculations

International Nuclear Information System (INIS)

Bernholc, J.

1998-01-01

The field of computational materials physics has grown very quickly in the past decade, and it is now possible to simulate properties of complex materials completely from first principles. The presentation has mostly focused on first-principles dynamic simulations. Such simulations have been pioneered by Car and Parrinello, who introduced a method for performing realistic simulations within the context of density functional theory. The Car-Parrinello method and related plane wave approaches are reviewed in depth. The Car-Parrinello method was reviewed and illustrated with several applications: the dynamics of the C 60 solid, diffusion across Si steps, and computing free energy differences. Alternative ab initio simulation schemes, which use preconditioned conjugate gradient techniques for energy minimization and dynamics were also discussed
High pressure elastic properties of minerals from ab initio simulations: The case of pyrope, grossular and andradite silicate garnets

International Nuclear Information System (INIS)

Erba, A.; Mahmoud, A.; Dovesi, R.; Belmonte, D.

2014-01-01

A computational strategy is devised for the accurate ab initio simulation of elastic properties of crystalline materials under pressure. The proposed scheme, based on the evaluation of the analytical stress tensor and on the automated computation of pressure-dependent elastic stiffness constants, is implemented in the CRYSTAL solid state quantum-chemical program. Elastic constants and related properties (bulk, shear and Young moduli, directional seismic wave velocities, elastic anisotropy index, Poisson's ratio, etc.) can be computed for crystals of any space group of symmetry. We apply such a technique to the study of high-pressure elastic properties of three silicate garnet end-members (namely, pyrope, grossular, and andradite) which are of great geophysical interest, being among the most important rock-forming minerals. The reliability of this theoretical approach is proved by comparing with available experimental measurements. The description of high-pressure properties provided by several equations of state is also critically discussed
Phenomenological reports diagnose accuracy of eyewitness identification decisions.

Science.gov (United States)

Palmer, Matthew A; Brewer, Neil; McKinnon, Anna C; Weber, Nathan

2010-02-01

This study investigated whether measuring the phenomenology of eyewitness identification decisions aids evaluation of their accuracy. Witnesses (N=502) viewed a simulated crime and attempted to identify two targets from lineups. A divided attention manipulation during encoding reduced the rate of remember (R) correct identifications, but not the rates of R foil identifications or know (K) judgments in the absence of recollection (i.e., K/[1-R]). Both RK judgments and recollection ratings (a novel measure of graded recollection) distinguished correct from incorrect positive identifications. However, only recollection ratings improved accuracy evaluation after identification confidence was taken into account. These results provide evidence that RK judgments for identification decisions function in a similar way as for recognition decisions; are consistent with the notion of graded recollection; and indicate that measures of phenomenology can enhance the evaluation of identification accuracy. Copyright 2009 Elsevier B.V. All rights reserved.

Proposal for novel curcumin derivatives as potent inhibitors against Alzheimer's disease: Ab initio molecular simulations on the specific interactions between amyloid-beta peptide and curcumin

Science.gov (United States)

Ota, Shintaro; Fujimori, Mitsuki; Ishimura, Hiromi; Shulga, Sergiy; Kurita, Noriyuki

2017-10-01

Accumulation of amyloid-β (Aβ) peptides in a brain is closely related with the pathogenesis of Alzheimer's disease. To suppress the production of Aβ peptides, we propose novel curcumin derivatives and investigate their binding properties with the amyloid precursor protein (APP), using protein-ligand docking as well as ab initio molecular simulations. Our proposed derivative (curcumin XIV) is found to have a large binding energy with APP and interacts strongly with the cleavage site Ala19 by secretase. It is thus expected that curcumin XIV can protect APP from the secretase attack and be a potent inhibitor against the production of Aβ peptides.
A PHENOMENOLOGICAL RESEARCH ON MORAL PHILOSOPHY

Directory of Open Access Journals (Sweden)

CIPRIAN IULIAN ŞOPTICĂ

2011-05-01

Full Text Available The subject of this article concerns the what, the how and the whyof moral phenomenology. The first question we take into consideration is „What is moral phenomenology”? The second question which arises is „How to pursue moral phenomenology”? The third question is „Why pursue moral phenomenology”? We will analyze the study Moral phenomenology:foundation issues1, by which the American phenomenologist Uriah Kriegel aims three lines of research: the definition of moral phenomenology and the description of field research within the phenomenological tradition; the establishment of a method of moral phenomenology research; the emphasis of the purpose of such research and its importance for moral philosophy in general.
Theoretical study of silicon carbide under irradiation at the nano scale: classical and ab initio modelling; Etude theorique a l'echelle nanometrique du carbure de silicium sous irradiation: modelisation classique et ab initio

Energy Technology Data Exchange (ETDEWEB)

Lucas, G

2006-10-15

The behaviour of silicon carbide under irradiation has been studied using classical and ab initio simulations, focusing on the nano scale elementary processes. First, we have been interested in the calculation of threshold displacement energies, which are difficult to determine both experimentally and theoretically, and also the associated Frenkel pairs. In the framework of this thesis, we have carried out simulations in classical and ab initio molecular dynamics. For the classical approach, two types of potentials have been used: the Tersoff potential, which led to non satisfactory results, and a new one which has been developed during this thesis. This potential allows a better modelling of SiC under irradiation than most of the empirical potentials available for SiC. It is based on the EDIP potential, initially developed to describe defects in silicon, that we have generalized to SiC. For the ab initio approach, the feasibility of the calculations has been validated and average energies of 19 eV for the C and 38 eV for the Si sublattices have been determined, close to the values empirically used in the fusion community. The results obtained with the new potential EDIP are globally in agreement with those values. Finally, the elementary processes involved in the crystal recovery have been studied by calculating the stability of the created Frenkel pairs and determining possible recombination mechanisms with the nudged elastic band method. (author)
What Is Film Phenomenology?

NARCIS (Netherlands)

Hanich, Julian; Ferencz-Flatz, Christian

2016-01-01

In this article Christian Ferencz-Flatz and I try to give an answer to the question what film phenomenology actually is. We proceed in three steps. First, we provide a survey of five different research practices within current film phenomenological writing: We call them excavation, explanation,
Resolving the Origins of Crystalline Anharmonicity Using Terahertz Time-Domain Spectroscopy and ab Initio Simulations.

Science.gov (United States)

Ruggiero, Michael T; Zeitler, J Axel

2016-11-17

Anharmonicity has been shown to be an important piece of the fundamental framework that dictates numerous observable phenomena. In particular, anharmonicity is the driving force of vibrational relaxation processes, mechanisms that are integral to the proper function of numerous chemical processes. However, elucidating its origins has proven difficult due to experimental and theoretical challenges, specifically related to separating the anharmonic contributions from other unrelated effects. While no one technique is particularly suited for providing a complete picture of anharmonicity, by combining multiple complementary methods such a characterization can be made. In this study the role of individual atomic interactions on the anharmonic properties of crystalline purine, the building block of many DNA and RNA nucleobases, is studied by experimental terahertz time-domain spectroscopy and first-principles density functional theory (DFT) and ab initio molecular dynamics simulations (AIMD). In particular, the detailed vibrational information provided by the DFT calculations is used to interpret the atomic origins of anharmonic-related effects as determined by the AIMD calculations, which are in good agreement with the experimental data. The results highlight that anharmonicity is especially pronounced in the intermolecular interactions, particularly along the amine hydrogen bond coordinate, and yields valuable insight into what is similarly observed complex biosystems and crystalline solids.
Embodiment and psychopathology: a phenomenological perspective.

Science.gov (United States)

Fuchs, Thomas; Schlimme, Jann E

2009-11-01

To survey recent developments in phenomenological psychopathology. We present the concept of embodiment as a key paradigm of recent interdisciplinary approaches from the areas of philosophy, psychology, psychiatry and neuroscience. This requires a short overview on the phenomenological concept of embodiment; in particular, on the distinction of subject and object body. A psychopathology of embodiment may be based on these and other distinctions, in particular on a polarity of disembodiment and hyperembodiment, which is illustrated by the examples of schizophrenia and depression. Recent contributions to phenomenological accounts of these disorders are presented. Finally, the study discusses the relationship of phenomenological and neuropsychiatric perspectives on embodiment. A phenomenology of embodiment may be combined with enactive approaches to cognitive neuroscience in order to overcome dualist concepts of the mind as an inner realm of representations that mirror the outside world. Phenomenological and ecological concepts of embodiment should also be conjoined to enable a new, advanced understanding of mental illness.
Estudo da geometria da uréia por métodos ab initio e simulação computacional de líquidos

Directory of Open Access Journals (Sweden)

Cirino José Jair Vianna

2002-01-01

Full Text Available A study was carried out on the urea geometries using ab initio calculation and Monte Carlo computational simulation of liquids. The ab initio calculated results showed that urea has a non-planar conformation in the gas phase in which the hydrogen atoms are out of the plane formed by the heavy atoms. Free energies associated to the rotation of the amino groups of urea in water were obtained using the Monte Carlo method in which the thermodynamic perturbation theory is implemented. The magnitude of the free energy obtained from this simulation did not permit us to conclude that urea is non-planar in water.
Ab initio derivation of model energy density functionals

International Nuclear Information System (INIS)

Dobaczewski, Jacek

2016-01-01

I propose a simple and manageable method that allows for deriving coupling constants of model energy density functionals (EDFs) directly from ab initio calculations performed for finite fermion systems. A proof-of-principle application allows for linking properties of finite nuclei, determined by using the nuclear nonlocal Gogny functional, to the coupling constants of the quasilocal Skyrme functional. The method does not rely on properties of infinite fermion systems but on the ab initio calculations in finite systems. It also allows for quantifying merits of different model EDFs in describing the ab initio results. (letter)
Exploring the ab initio/classical free energy perturbation method: The hydration free energy of water

International Nuclear Information System (INIS)

Sakane, Shinichi; Yezdimer, Eric M.; Liu, Wenbin; Barriocanal, Jose A.; Doren, Douglas J.; Wood, Robert H.

2000-01-01

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 to corresponding interactions calculated from ab initio methods. This approach allows accurate calculation of solvation free energies using an atomistic description of the solvent and solute, with interactions calculated from first principles. Results can be obtained at a feasible computational cost without making use of approximations such as a continuum solvent or an empirical cavity formation energy. As such, the method can be used far from ambient conditions, where the empirical parameters needed for approximate theories of solvation may not be available. The sources of error in the ABC-FEP method are the approximations in the ab initio method, the finite sample of configurations, and the classical solvent model. This article explores the accuracy of various approximations used in the ABC-FEP method by comparing to the experimentally well-known free energy of hydration of water at two state points (ambient conditions, and 973.15 K and 600 kg/m3). The TIP4P-FQ model [J. Chem. Phys. 101, 6141 (1994)] is found to be a reliable solvent model for use with this method, even at supercritical conditions. Results depend strongly on the ab initio method used: a gradient-corrected density functional theory is not adequate, but a localized MP2 method yields excellent agreement with experiment. Computational costs are reduced by using a cluster approximation, in which ab initio pair interaction energies are calculated between the solute and up to 60 solvent molecules, while multi-body interactions are calculated with only a small cluster (5 to 12 solvent molecules). Sampling errors for the ab initio contribution to
Clustering/anticlustering effects on the GeSi Raman spectra at moderate (Ge,Si) contents: Percolation scheme vs. ab initio calculations

Science.gov (United States)

Torres, V. J. B.; Hajj Hussein, R.; Pagès, O.; Rayson, M. J.

2017-02-01

We test a presumed ability behind the phenomenological percolation scheme used for the basic description of the multi-mode Raman spectra of mixed crystals at one dimension along the linear chain approximation, to determine, via the Raman intensities, the nature of the atom substitution, as to whether this is random or due to local clustering/anticlustering. For doing so, we focus on the model percolation-type GeySi1-y system characterized by six oscillators { 1 × ( G e - G e ) , 3 × ( G e - S i ) , 2 × ( S i - S i ) } and place the study around the critical compositions y ˜ (0.16, 0.71, and 0.84) corresponding to nearly matching of intensities between the like Raman modes from a given multiplet ( G e - S i triplet or S i - S i doublet). The interplay between the GeySi1-y Raman intensities predicted by the percolation scheme depending on a suitable order parameter κ of local clustering/anticlustering is found to be consistent with ab initio calculations of the GeySi1-y Raman spectra done with the Ab Initio Modeling PROgram code using large (64-, 216-, and 512-atoms) disordered cubic supercells matching the required ( y , κ ) values. The actual "percolation vs. ab initio" comparative insight at moderate/dilute-(Ge,Si) limits, with an emphasis on the κ -induced intra-bond transfer of oscillator strength, extends a pioneering one earlier achieved at an intermediate composition ( y ˜ 0.50) by using small (32-atom) supercells [O. Pagès et al., J. Appl. Phys. 114, 033513 (2013)], mainly concerned with the inter-bond transfer of oscillator strength, providing altogether a complete picture.
Explicit polarization (X-Pol) potential using ab initio molecular orbital theory and density functional theory.

Science.gov (United States)

Song, Lingchun; Han, Jaebeom; Lin, Yen-lin; Xie, Wangshen; Gao, Jiali

2009-10-29

The explicit polarization (X-Pol) method has been examined using ab initio molecular orbital theory and density functional theory. The X-Pol potential was designed to provide a novel theoretical framework for developing next-generation force fields for biomolecular simulations. Importantly, the X-Pol potential is a general method, which can be employed with any level of electronic structure theory. The present study illustrates the implementation of the X-Pol method using ab initio Hartree-Fock theory and hybrid density functional theory. The computational results are illustrated by considering a set of bimolecular complexes of small organic molecules and ions with water. The computed interaction energies and hydrogen bond geometries are in good accord with CCSD(T) calculations and B3LYP/aug-cc-pVDZ optimizations.
Short- and medium-range order in a Zr73Pt27 glass: Experimental and simulation studies

International Nuclear Information System (INIS)

Wang, S.Y.; Wang, C.Z.; Li, M.Z.; Huang, L.; Ott, R.T.; Kramer, M.J.; Sordelet, D.J.; Ho, K.M.

2008-01-01

The structure of a Zr 73 Pt 27 metallic glass, which forms a Zr 5 Pt 3 (Mn 5 Si 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) simulations. The ab initio MD simulation provides an accurate description of short-range structural and chemical ordering in the glass. A three-dimensional atomistic model of 18?000 atoms for the glass structure has been generated by the RMC method utilizing both the structure factor S(k) from x-ray diffraction experiment and the partial pair-correlation functions from ab initio MD simulation. Honeycutt and Andersen index and Voronoi cell analyses, respectively, were used to characterize the short- and medium-range order in the atomistic structure models generated by ab initio MD and RMC simulations. The ab initio results show that an icosahedral type of short-range order is predominant in the glass state. Furthermore, analysis of the atomic model from the constrained RMC simulations reveals that the icosahedral-like clusters are packed in arrangements having higher-order correlations, thus establishing medium-range topological order up to two or three cluster shells.
High-throughput ab-initio dilute solute diffusion database.

Science.gov (United States)

Wu, Henry; Mayeshiba, Tam; Morgan, Dane

2016-07-19

We demonstrate automated generation of diffusion databases from high-throughput density functional theory (DFT) calculations. A total of more than 230 dilute solute diffusion systems in Mg, Al, Cu, Ni, Pd, and Pt host lattices have been determined using multi-frequency diffusion models. We apply a correction method for solute diffusion in alloys using experimental and simulated values of host self-diffusivity. We find good agreement with experimental solute diffusion data, obtaining a weighted activation barrier RMS error of 0.176 eV when excluding magnetic solutes in non-magnetic alloys. The compiled database is the largest collection of consistently calculated ab-initio solute diffusion data in the world.
High pressure elastic properties of minerals from ab initio simulations: The case of pyrope, grossular and andradite silicate garnets

Energy Technology Data Exchange (ETDEWEB)

Erba, A., E-mail: alessandro.erba@unito.it; Mahmoud, A.; Dovesi, R. [Dipartimento di Chimica and Centre of Excellence NIS (Nanostructured Interfaces and Surfaces), Università di Torino, via Giuria 5, IT-10125 Torino (Italy); Belmonte, D. [DISTAV, Università di Genova, Corso Europa 26, 16132 Genoa (Italy)

2014-03-28

A computational strategy is devised for the accurate ab initio simulation of elastic properties of crystalline materials under pressure. The proposed scheme, based on the evaluation of the analytical stress tensor and on the automated computation of pressure-dependent elastic stiffness constants, is implemented in the CRYSTAL solid state quantum-chemical program. Elastic constants and related properties (bulk, shear and Young moduli, directional seismic wave velocities, elastic anisotropy index, Poisson's ratio, etc.) can be computed for crystals of any space group of symmetry. We apply such a technique to the study of high-pressure elastic properties of three silicate garnet end-members (namely, pyrope, grossular, and andradite) which are of great geophysical interest, being among the most important rock-forming minerals. The reliability of this theoretical approach is proved by comparing with available experimental measurements. The description of high-pressure properties provided by several equations of state is also critically discussed.
A study on the 0D phenomenological model for diesel engine simulation: Application to combustion of Neem methyl esther biodiesel

International Nuclear Information System (INIS)

Ngayihi Abbe, Claude Valery; Nzengwa, Robert; Danwe, Raidandi; Ayissi, Zacharie Merlin; Obonou, Marcel

2015-01-01

Highlights: • We elaborate a 0D model for prediction of diesel engine operating parameters. • We implement the model for Neem methyl ester biodiesel combustion. • We show methyl butanoate and butyrate can be used as surrogates for biodiesel. • The model predicts fuel spray, in cylinder gaseous state and NOx emissions. • We show the model can be effective both in accuracy and computational speed. - Abstract: The design and monitoring of modern diesel engines running on alternative fuels require reliable models that can validly substitute experimental tests and predict their operating characteristics under different load conditions. Although there exists a multitude of models for diesel engines, 0D phenomenological models present the advantages of giving fast and accurate computed results. These models are useful for predicting fuel spray characteristics and instantaneous gas state. However, there are few reported studies on the application of 0D phenomenological models on biodiesel fuel combustion in diesel engines. This work reports the elaboration, validation and application on Neem methyl ester biodiesel (NMEB) combustion of a 0D phenomenological model for diesel engine simulation. The model addresses some specific aspects of diesel engine modeling found in previous studies such as the compromise between computers cost, accurateness and model simplicity, the reduction of the number of empirical fitting constant, the prediction of combustion kinetics with reduction of the need of experimental curve fitting, the ability to simultaneously predict under various loads engine thermodynamic and spray parameters as well as emission characteristics and finally the ability to simulate diesel engine parameters when fueled by alternative fuels. The proposed model predicts fuel spray behavior, in cylinder combustion and nitric oxides (NOx) emissions. The model is implemented through a Matlab code. The model is mainly based on Razlejtsev’s spray evaporation model
Influence of the ab initio n–d cross sections in the critical heavy-water benchmarks

International Nuclear Information System (INIS)

Morillon, B.; Lazauskas, R.; Carbonell, J.

2013-01-01

Highlights: ► We solve the three nucleon problem using different NN potential (MT, AV18 and INOY) to calculate the Neutron–deuteron cross sections. ► These cross sections are compared to the existing experimental data and to international libraries. ► We describe the different sets of heavy water benchmarks for which the Monte Carlo simulations have been performed including our new Neutron–deuteron cross sections. ► The results obtained by the ab initio INOY potential have been compared with the calculations based on the international library cross sections and are found to be of the same quality. - Abstract: The n–d elastic and breakup cross sections are computed by solving the three-body Faddeev equations for realistic and semi-realistic nucleon–nucleon potentials. These cross sections are inserted in the Monte Carlo simulation of the nuclear processes considered in the International Handbook of Evaluated Criticality Safety Benchmark Experiments (ICSBEP Handbook). The results obtained using thes ab initio n–d cross sections are compared with those provided by the most renown international libraries
Free energy landscape of electrocatalytic CO2 reduction to CO on aqueous FeN4 center embedded graphene studied by ab initio molecular dynamics simulations

Science.gov (United States)

Sheng, Tian; Sun, Shi-Gang

2017-11-01

Experiments have found that the porphyrin-like FeN4 site in Fe-N-C materials is highly efficient for the electrochemical reduction of CO2 into CO. In this work, we investigated the reduction mechanisms on FeN4 embedded graphene layer catalyst with some explicit water molecules by combining the constrained ab initio molecular dynamics simulations and thermodynamic integrations. The reaction free energy and electron transfer in each elementary step were identified. The initial CO2 activation was identified to go through the first electron transfer to form adsorbed CO2- anion and the CO desorption was the rate limiting step in the overall catalytic cycle.
A theoretical-spectroscopy, ab initio-based study of the electronic ground state of 121SbH3

International Nuclear Information System (INIS)

Yurchenko, Sergei N.; Carvajal, Miguel; Yachmenev, Andrey; Thiel, Walter; Jensen, Per

2010-01-01

For the stibine isotopologue 121 SbH 3 , we report improved theoretical calculations of the vibrational energies below 8000 cm -1 and simulations of the rovibrational spectrum in the 0-8000 cm -1 region. The calculations are based on a refined ab initio potential energy surface and on a new dipole moment surface obtained at the coupled cluster CCSD(T) level. The theoretical results are compared with the available experimental data in order to validate the ab initio surfaces and the TROVE computational method [Yurchenko SN, Thiel W, Jensen P. J Mol Spectrosc 2007;245:126-40] for calculating rovibrational energies and simulating rovibrational spectra of arbitrary molecules in isolated electronic states. A number of predicted vibrational energies of 121 SbH 3 are provided in order to stimulate new experimental investigations of stibine. The local-mode character of the vibrations in stibine is demonstrated through an analysis of the results in terms of local-mode theory.
A phenomenological model for the chemo-responsive shape memory effect in amorphous polymers undergoing viscoelastic transition

International Nuclear Information System (INIS)

Lu, Haibao; Huang, Wei Min

2013-01-01

We present a phenomenological approach to study the viscoelastic transition and working mechanism of the chemo-responsive shape memory effect (SME) in amorphous shape memory polymers (SMPs). Both the copolymerization viscosity model and Doolittle equation are initially applied to quantitatively identify the influential factors behind the chemo-responsive SME in the SMPs exposure to a right solvent. After this, the Williams–Landel–Ferry (WLF) equation is employed to couple the viscosity (η), time–temperature shift factor (α τ ) and glass transition temperature (T g ) in amorphous polymers. By means of combining the WLF and Arrhenius equations together, the inductively decreased transition temperature is confirmed as the driving force for the chemo-responsive SME. Finally, a phenomenological viscoelastic model is proposed and then verified by the available experimental data reported in the literature and then compared with the simulation results of a semi-empirical model. This phenomenological model is expected to provide a powerful simulation tool for theoretical prediction and experimental substantiation of the chemo-responsive SME in amorphous SMPs by viscoelastic transition. (paper)
An ab initio molecular

Indian Academy of Sciences (India)

mechanisms of two molecular crystals: An ab initio molecular dynamics ... for Computation in Molecular and Materials Science and Department of Chemistry, School of ..... NSAF Foundation of National Natural Science Foun- ... Matter 14 2717.

Theoretical study of silicon carbide under irradiation at the nano scale: classical and ab initio modelling

International Nuclear Information System (INIS)

Lucas, G.

2006-10-01

The behaviour of silicon carbide under irradiation has been studied using classical and ab initio simulations, focusing on the nano scale elementary processes. First, we have been interested in the calculation of threshold displacement energies, which are difficult to determine both experimentally and theoretically, and also the associated Frenkel pairs. In the framework of this thesis, we have carried out simulations in classical and ab initio molecular dynamics. For the classical approach, two types of potentials have been used: the Tersoff potential, which led to non satisfactory results, and a new one which has been developed during this thesis. This potential allows a better modelling of SiC under irradiation than most of the empirical potentials available for SiC. It is based on the EDIP potential, initially developed to describe defects in silicon, that we have generalized to SiC. For the ab initio approach, the feasibility of the calculations has been validated and average energies of 19 eV for the C and 38 eV for the Si sublattices have been determined, close to the values empirically used in the fusion community. The results obtained with the new potential EDIP are globally in agreement with those values. Finally, the elementary processes involved in the crystal recovery have been studied by calculating the stability of the created Frenkel pairs and determining possible recombination mechanisms with the nudged elastic band method. (author)
Structures and Electronic Properties of Cu{sub 3}O{sub n} (n =1-6) Clusters using ab initio Monte Carlo Simulations

Energy Technology Data Exchange (ETDEWEB)

Bae, Gyun-Tack [Chungbuk National University, Cheongju (Korea, Republic of)

2016-05-15

We studied the structures and electronic properties of copper oxide clusters, Cu{sub 3}O{sub n} (n =1-6), using ab initio Monte Carlo simulations and density functional theory calculations. All lowest energy structures of neutral and charged Cu{sub 3}O{sub n} clusters with n =1-6 are optimized with the B3LYP functional and LANL2DZ basis set. We found that the lowest energy structures of neutral and charged Cu{sub 3}O{sub n} (n =1-6) clusters are planar or near-planar. Selected electronic properties including atomization energies, ionization energies, electron affinities, second difference in energies, HOMO - LUMO gaps, and Bader charges are calculated and examined for each n. We concluded that the Cu{sub 3}O{sub 3} cluster is the first ring structure and the most stable structure.
Being Mindful as a Phenomenological Attitude.

Science.gov (United States)

Gustin, Lena Wiklund

2017-08-01

The purpose of this article is to reflect on being mindful as a phenomenological attitude rather than on describing mindfulness as a therapeutic intervention. I will also explore the possibilities that being mindful might open up in relation to nursing research and holistic nursing. I will describe and interpret mindfulness as a state of being by means of van Manen's phenomenological method, using the language of phenomenology rather than the language of reductionist science. Thus, this article can be considered a reflective narrative, describing both the process of orienting to the phenomenon, making preunderstandings-including own experiences of mindfulness-visible, and a thematic analysis of nine scientific articles describing the phenomenon. Being mindful as a phenomenological attitude can be described as a deliberate intentionality, where the person is present in the moment and open to what is going on, bridling personal values and accepting the unfamiliar, thus achieving a sense of being peacefully situated in the world, and able to apprehend one's being-in-the-world. Being mindful as a phenomenological attitude can contribute not only to phenomenological nursing research but also support nurses' presence and awareness.
Ab initio molecular dynamics simulations on the structural change of liquid eutectic alloy Si15Te85 from 673 to 1373 k

International Nuclear Information System (INIS)

Wang Yubing; Zhao Gang; Liu Changsong; Zhu Zhengang

2010-01-01

Using ab initio molecular dynamics simulations and inherent structure formalism, the local atomic structure and electronic properties of liquid Si 15 Te 85 alloy were studied at eight different temperatures from 673 to 1373 K. In comparison with available experimental data, our calculated structure factors are acceptable. With increasing temperature from 773 to 1173 K, the calculated total coordination number N Total increases gradually in contrast to the behavior of a classical isotropic fluid. Our results of pair-correlation functions, bond-angle distribution functions and angular limited triplet correlation functions suggest that the temperature-dependence of the preserved sp 3 hybridization of Si atoms and Peierls-type distorted local structure around Te atoms both play important roles in the structural change of Si 15 Te 85 characterized by thermodynamic anomalies.
Ab initio and Gordon--Kim intermolecular potentials for two nitrogen molecules

International Nuclear Information System (INIS)

Ree, F.H.; Winter, N.W.

1980-01-01

Both ab initio MO--LCAO--SCF and the electron-gas (or Gordon--Kim) methods have been used to compute the intermolecular potential (Phi) of N 2 molecules for seven different N 2 --N 2 orientations. The ab initio calculations were carried out using a [4s3p] contracted Gaussian basis set with and without 3d polarization functions. The larger basis set provides adequate results for Phi>0.002 hartree or intermolecular separations less than 6.5--7 bohr. We use a convenient analytic expression to represent the ab initio data in terms of the intermolecular distance and three angles defining the orientations of the two N 2 molecules. The Gordon--Kim method with Rae's self-exchange correction yields Phi, which agrees reasonably well over a large repulsive range. However, a detailed comparison of the electron kinetic energy contributions shows a large difference between the ab initio and the Gordon--Kim calculations. Using the ab initio data we derive an atom--atom potential of the two N 2 molecules. Although this expression does not accurately fit the data at some orientations, its spherical average agrees with the corresponding average of the ab initio Phi remarkably well. The spherically averaged ab initio Phi is also compared with the corresponding quantities derived from experimental considerations. The approach of the ab initio Phi to the classical quadrupole--quadrupole interaction at large intermolecular separation is also discussed
360°-View of Quantum Theory and Ab Initio Simulation at Extreme Conditions: 2014 Sanibel Symposium

International Nuclear Information System (INIS)

Cheng, Hai-Ping

2016-01-01

The Sanibel Symposium 2014 was held February 16-21, 2014, at the King and Prince, St. Simons Island, GA. It was successful in bringing condensed-matter physicists and quantum chemists together productively to drive the emergence of those specialties. The Symposium had a significant role in preparing a whole generation of quantum theorists. The 54th Sanibel meeting looked to the future in two ways. We had 360°-View sessions to honor the exceptional contributions of Rodney Bartlett (70), Bill Butler (70), Yngve Öhrn (80), Fritz Schaefer (70), and Malcolm Stocks (70). The work of these five has greatly impacted several generations of quantum chemists and condensed matter physicists. The ''360°'' is the sum of their ages. More significantly, it symbolizes a panoramic view of critical developments and accomplishments in theoretical and computational chemistry and physics oriented toward the future. Thus, two of the eight 360°-View sessions focused specifically on younger scientists. The 360°-View program was the major component of the 2014 Sanibel meeting. Another four sessions included a sub-symposium on ab initio Simulations at Extreme Conditions, with focus on getting past the barriers of present-day Born-Oppenheimer molecular dynamics by advances in finite-temperature density functional theory, orbital-free DFT, and new all-numerical approaches.
Excited state non-adiabatic dynamics of the smallest polyene, trans 1,3-butadiene. II. Ab initio multiple spawning simulations

Science.gov (United States)

Glover, William J.; Mori, Toshifumi; Schuurman, Michael S.; Boguslavskiy, Andrey E.; Schalk, Oliver; Stolow, Albert; Martínez, Todd J.

2018-04-01

The excited state non-adiabatic dynamics of the smallest polyene, trans 1,3-butadiene (BD), has long been the subject of controversy due to its strong coupling, ultrafast time scales and the difficulties that theory faces in describing the relevant electronic states in a balanced fashion. Here we apply Ab Initio Multiple Spawning (AIMS) using state-averaged complete active space multistate second order perturbation theory [SA-3-CAS(4/4)-MSPT2] which describes both static and dynamic electron correlation effects, providing a balanced description of both the initially prepared bright 11Bu (ππ*) state and non-adiabatically coupled dark 21Ag state of BD. Importantly, AIMS allows for on-the-fly calculations of experimental observables. We validate our approach by directly simulating the time resolved photoelectron-photoion coincidence spectroscopy results presented in Paper I [A. E. Boguslavskiy et al., J. Chem. Phys. 148, 164302 (2018)], demonstrating excellent agreement with experiment. Our simulations reveal that the initial excitation to the 11Bu state rapidly evolves via wavepacket dynamics that follow both bright- and dark-state pathways as well as mixtures of these. In order to test the sensitivity of the AIMS results to the relative ordering of states, we considered two hypothetical scenarios biased toward either the bright 1Bu or the dark 21Ag state. In contrast with AIMS/SA-3-CAS(4/4)-MSPT2 simulations, neither of these scenarios yields favorable agreement with experiment. Thus, we conclude that the excited state non-adiabatic dynamics in BD involves both of these ultrafast pathways.
Postmodernism, phenomenology and afriphenomenology | Francis ...

African Journals Online (AJOL)

In this paper, I aimed to study the relationship between postmodernism and phenomenology. In the study, I established that postmodernism and phenomenology bear similar ontological marking, which base their concepts and methodologies on an individualistic framework. On the basis of such ontological framework, ...
Learning from Twentieth Century Hermeneutic Phenomenology for ...

African Journals Online (AJOL)

The implications of commonalities in the contributions of five key thinkers in twentieth century phenomenology are discussed in relation to both original aims and contemporary projects. It is argued that, contrary to the claims of Husserl, phenomenology can only operate as hermeneutic phenomenology. Hermeneutics arose ...
Estudo da geometria da uréia por métodos ab initio e simulação computacional de líquidos

OpenAIRE

Cirino,José Jair Vianna; Bertran,Celso Aparecido

2002-01-01

A study was carried out on the urea geometries using ab initio calculation and Monte Carlo computational simulation of liquids. The ab initio calculated results showed that urea has a non-planar conformation in the gas phase in which the hydrogen atoms are out of the plane formed by the heavy atoms. Free energies associated to the rotation of the amino groups of urea in water were obtained using the Monte Carlo method in which the thermodynamic perturbation theory is implemented. The magnitud...
Simulated non-contact atomic force microscopy for GaAs surfaces based on real-space pseudopotentials

International Nuclear Information System (INIS)

Kim, Minjung; Chelikowsky, James R.

2014-01-01

We simulate non-contact atomic force microscopy (AFM) with a GaAs(1 1 0) surface using a real-space ab initio pseudopotential method. While most ab initio simulations include an explicit model for the AFM tip, our method does not introduce the tip modeling step. This approach results in a considerable reduction of computational work, and also provides complete AFM images, which can be directly compared to experiment. By analyzing tip-surface interaction forces in both our results and previous ab initio simulations, we find that our method provides very similar force profile to the pure Si tip results. We conclude that our method works well for systems in which the tip is not chemically active.
Interplay of I-TASSER and QUARK for template-based and ab initio protein structure prediction in CASP10.

Science.gov (United States)

Zhang, Yang

2014-02-01

We develop and test a new pipeline in CASP10 to predict protein structures based on an interplay of I-TASSER and QUARK for both free-modeling (FM) and template-based modeling (TBM) targets. The most noteworthy observation is that sorting through the threading template pool using the QUARK-based ab initio models as probes allows the detection of distant-homology templates which might be ignored by the traditional sequence profile-based threading alignment algorithms. Further template assembly refinement by I-TASSER resulted in successful folding of two medium-sized FM targets with >150 residues. For TBM, the multiple threading alignments from LOMETS are, for the first time, incorporated into the ab initio QUARK simulations, which were further refined by I-TASSER assembly refinement. Compared with the traditional threading assembly refinement procedures, the inclusion of the threading-constrained ab initio folding models can consistently improve the quality of the full-length models as assessed by the GDT-HA and hydrogen-bonding scores. Despite the success, significant challenges still exist in domain boundary prediction and consistent folding of medium-size proteins (especially beta-proteins) for nonhomologous targets. Further developments of sensitive fold-recognition and ab initio folding methods are critical for solving these problems. Copyright © 2013 Wiley Periodicals, Inc.
Ab initio simulation of amorphous silicon

International Nuclear Information System (INIS)

Cooper, N.C.; McKenzie, D.R.; Goringe, C.M.

1999-01-01

Full text: A first-principles Car-Parrinello molecular dynamics simulation of amorphous silicon is presented. Density Functional Theory is used to describe the forces between the atoms in a 64 atom supercell which is periodically repeated throughout space in order to generate an infinite network of atoms (a good approximation to a real solid). A quench from the liquid phase is used to achieve a quenched amorphous structure, which is subjected to an annealing cycle to improve its stability. The final, annealed network is in better agreement with experiment than any previous simulation of amorphous silicon. Significantly, the predicted average first-coordination numbers of 3.56 and 3.84 for the quenched and annealed structures from this simulation agree very closely with the experimental values of 3.55 and 3.90 respectively, whereas all previous simulations yielded first coordination numbers greater than 4. This improved agreement in coordination numbers is important because it supports the experimental finding that dangling bonds (which are associated with under-coordinated atoms) are more prevalent than floating bonds (the strained, longer bond of a five coordinate atom) in pure amorphous silicon. Finally, the effect of adding hydrogen to amorphous silicon was investigated by specifically placing hydrogen atoms at the likely defect sites. After a structural relaxation to optimise the positions of these hydrogen atoms, the localised electronic states associated with these defects are absent. Thus hydrogen is responsible for removing these defect states (which are able to trap carriers) from the edge of the band gap of the amorphous silicon. These results confirm the widely held ideas about the effect of hydrogen in producing remarkable improvements in the electronic properties of amorphous silicon
Ab initio valence calculations in chemistry

CERN Document Server

Cook, D B

1974-01-01

Ab Initio Valence Calculations in Chemistry describes the theory and practice of ab initio valence calculations in chemistry and applies the ideas to a specific example, linear BeH2. Topics covered include the Schrödinger equation and the orbital approximation to atomic orbitals; molecular orbital and valence bond methods; practical molecular wave functions; and molecular integrals. Open shell systems, molecular symmetry, and localized descriptions of electronic structure are also discussed. This book is comprised of 13 chapters and begins by introducing the reader to the use of the Schrödinge
A phenomenological approach to simulating the evolution of radioactive-waste container damage due to pitting corrosion

International Nuclear Information System (INIS)

Henshall, G.A.

1995-01-01

The damage to high-level radioactive-waste containers by pitting corrosion is an important design and performance assessment consideration. It is desirable to calculate the evolution of the pit depth distribution, not just the time required for initial penetration of the containers, so that the area available for advective of diffusive release of radionuclides through the container can be estimated. A phenomenological approach for computing the time evolution of these distributions is presented which combines elements of the deterministic and stochastic aspects of pit growth. The consistency of this approach with the mechanisms believed to control the evolution of the pit depth distribution is discussed. Qualitative comparisons of preliminary model predictions with a variety of experimental data from the literature are shown to be generally favorable. The sensitivity of the simulated distributions to changes in the input parameters is discussed. Finally, the results of the current model are compared to those of existing approaches based on extreme-value statistics, particularly regarding the extrapolation of laboratory data to large exposed surface areas
A PHENOMENOLOGICAL RESEARCH ON MORAL PHILOSOPHY

OpenAIRE

CIPRIAN IULIAN ŞOPTICĂ

2011-01-01

The subject of this article concerns the what, the how and the whyof moral phenomenology. The first question we take into consideration is „What is moral phenomenology”? The second question which arises is „How to pursue moral phenomenology”? The third question is „Why pursue moral phenomenology”? We will analyze the study Moral phenomenology:foundation issues1, by which the American phenomenologist Uriah Kriegel aims three lines of research: the definition of moral phenomenology and the desc...
Phenomenology & Sociality

DEFF Research Database (Denmark)

Gahrn-Andersen, Rasmus; Cowley, Stephen

2017-01-01

Although cognitive science has recently asked how human sociality is constituted, there is no clear and consistent account of the emergence of human style social agency. Previously, we have critiqued views based on 'participatory sense-making' by arguing that agency requires a distinctive kind...... of phenomenology that enables a diachronic social experience. In advancing the positive argument, we link developmental psychology to phenomenological insights by focusing on child-caregiver dynamics around the middle of the second year. Having developed very basic social skills, an infant comes to feel normative....... Developmental events thus transform the child's experience and drive the emergence of social agency. Once the child has successfully dealt with the environment’s normative perturbations she is able to develop the skills of a fully-fledged human social agent....
Low-energy phenomenological chiral Lagrangians

International Nuclear Information System (INIS)

Cavopol, A.V.

1987-01-01

We develop a phenomenological Lagrangian that satisfies the requirements of the so called alternative schemes designed to model low energy meson phenomenology. Linear and nonlinear σ type Lagrangians and symmetry breaking schemes are used to describe pions that exhibit masses proportional to the square of the symmetry breaking term's coefficient, ε. (m π 2 ∼ 0(ε 2 )). The invariance of the theory under coordinate dependent transformations is achieved by introducing gauge fields for both linear and nonlinear Lagrangians. Finally, analogies between the minimal symmetry breaking terms in Quantum Electrodynamics and in our phenomenological lagrangians are used to generate a discussion of the quark-pion mass dependence indicated by the model
Husserlian phenomenology and nursing in a unitary-transformative paradigm

DEFF Research Database (Denmark)

Hall, Elisabeth

1996-01-01

. The phenomenological methodology according to Spiegelberg is described, and exemplified through the author's ongoing study. Different critiques of phenomenology and phenomenological reports are mentioned, and the phenomenological description is illustrated as the metaphor «using a handful of colors». The metaphor...... is used to give phenomenological researchers and readers an expanding reality picturing, including memories and hopes and not only a reality of the five senses. It is concluded that phenomenology as a world view and methodology can contribute to nursing research and strengthen the identity of nursing...
Fuel solution criticality accident studies with the SILENE reactor: phenomenology, consequences and simulated intervention

International Nuclear Information System (INIS)

Barbry, F.

1984-01-01

After defining the content and the objectives of criticality accident studies, the SILENE reactor, a means of studying fuel solution criticality accidents, is presented. Information obtained from the CRAC and SILENE experimental programs are then presented; they concern power excursion phenomenology, radiological consequences, and finally guide-lines for current and future programs

Atomic defects in monolayer WSe2 tunneling FETs studied by systematic ab initio calculations

Science.gov (United States)

Wu, Jixuan; Fan, Zhiqiang; Chen, Jiezhi; Jiang, Xiangwei

2018-05-01

Atomic defects in monolayer WSe2 tunneling FETs (TFETs) are studied through systematic ab initio calculations aiming at performance predictions and enhancements. The effects of various defect positions and different passivation atoms are characterized in WSe2 TFETs by rigorous ab initio quantum transport simulations. It is suggested that the Se vacancy (VSe) defect located in the gate-controlled channel region tends to increase the OFF current (I off), whereas it can be well suppressed by oxygen passivation. It is demonstrated that chlorine (Cl) passivation at the source-side tunneling region can largely suppress I off, leading to an impressively improved on–off ratio (I on/I off) compared with that without any defect. However, it is also observed that randomly positioned atomic defects tend to induce significant fluctuation of the TFET output. Further discussions are made with focus on the performance-variability trade-off for robust circuit design.
AXISYMMETRIC AB INITIO CORE-COLLAPSE SUPERNOVA SIMULATIONS OF 12-25 M{sub Sun} STARS

Energy Technology Data Exchange (ETDEWEB)

Bruenn, Stephen W.; Yakunin, Konstantin N. [Department of Physics, Florida Atlantic University, 777 Glades Road, Boca Raton, FL 33431-0991 (United States); Mezzacappa, Anthony; Hix, W. Raphael; Lingerfelt, Eric J. [Physics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6354 (United States); Lentz, Eric J. [Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996-1200 (United States); Messer, O. E. Bronson [National Center for Computational Sciences, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6164 (United States); Blondin, John M. [Department of Physics, North Carolina State University, Raleigh, NC 27695-8202 (United States); Endeve, Eirik [Computer Science and Mathematics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6164 (United States); Marronetti, Pedro, E-mail: bruenn@fau.edu [Physics Division, National Science Foundation, Arlington, VA 22207 (United States)

2013-04-10

We present an overview of four ab initio axisymmetric core-collapse supernova simulations employing detailed spectral neutrino transport computed with our CHIMERA code and initiated from Woosley and Heger progenitors of mass 12, 15, 20, and 25 M{sub Sun }. All four models exhibit shock revival over {approx}200 ms (leading to the possibility of explosion), driven by neutrino energy deposition. Hydrodynamic instabilities that impart substantial asymmetries to the shock aid these revivals, with convection appearing first in the 12 M{sub Sun} model and the standing accretion shock instability appearing first in the 25 M{sub Sun} model. Three of the models have developed pronounced prolate morphologies (the 20 M{sub Sun} model has remained approximately spherical). By 500 ms after bounce the mean shock radii in all four models exceed 3000 km and the diagnostic explosion energies are 0.33, 0.66, 0.65, and 0.70 Bethe (B = 10{sup 51} erg) for the 12, 15, 20, and 25 M{sub Sun} models, respectively, and are increasing. The three least massive of our models are already sufficiently energetic to completely unbind the envelopes of their progenitors (i.e., to explode), as evidenced by our best estimate of their explosion energies, which first become positive at 320, 380, and 440 ms after bounce. By 850 ms the 12 M{sub Sun} diagnostic explosion energy has saturated at 0.38 B, and our estimate for the final kinetic energy of the ejecta is {approx}0.3 B, which is comparable to observations for lower mass progenitors.
First principles simulations

International Nuclear Information System (INIS)

Palummo, M.; Reining, L.; Ballone, P.

1993-01-01

In this paper we outline the major features of the ''ab-initio'' simulation scheme of Car and Parrinello, focusing on the physical ideas and computational details at the basis of its efficiency and success. We briefly review the main applications of the method. We discuss the limitations of the standard scheme, as well as recent developments proposed in order to extend the reach of the method. Moreover, we consider more in detail two specific subjects. First, we describe a simple improvement (Gradient Corrections) on the basic approximation of the ''ab-initio'' simulation, i.e. the Local Density Approximation. These corrections can be easily and efficiently included in the Car-Parrinello code, bringing computed structural and cohesive properties significantly closer to their experimental values. Finally, we discuss the choice of the pseudopotential, with special attention to the possibilities and limitations of the last generation of soft pseudopotentials. (orig.)
Cost-Effective Method for Free-Energy Minimization in Complex Systems with Elaborated Ab Initio Potentials.

Science.gov (United States)

Bistafa, Carlos; Kitamura, Yukichi; Martins-Costa, Marilia T C; Nagaoka, Masataka; Ruiz-López, Manuel F

2018-05-22

We describe a method to locate stationary points in the free-energy hypersurface of complex molecular systems using high-level correlated ab initio potentials. In this work, we assume a combined QM/MM description of the system although generalization to full ab initio potentials or other theoretical schemes is straightforward. The free-energy gradient (FEG) is obtained as the mean force acting on relevant nuclei using a dual level strategy. First, a statistical simulation is carried out using an appropriate, low-level quantum mechanical force-field. Free-energy perturbation (FEP) theory is then used to obtain the free-energy derivatives for the target, high-level quantum mechanical force-field. We show that this composite FEG-FEP approach is able to reproduce the results of a standard free-energy minimization procedure with high accuracy, while simultaneously allowing for a drastic reduction of both computational and wall-clock time. The method has been applied to study the structure of the water molecule in liquid water at the QCISD/aug-cc-pVTZ level of theory, using the sampling from QM/MM molecular dynamics simulations at the B3LYP/6-311+G(d,p) level. The obtained values for the geometrical parameters and for the dipole moment of the water molecule are within the experimental error, and they also display an excellent agreement when compared to other theoretical estimations. The developed methodology represents therefore an important step toward the accurate determination of the mechanism, kinetics, and thermodynamic properties of processes in solution, in enzymes, and in other disordered chemical systems using state-of-the-art ab initio potentials.
Phenomenology of Baryon Resonances

Energy Technology Data Exchange (ETDEWEB)

Doring, Michael [George Washington Univ., Washington, DC (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Landay, Justin [George Washington Univ., Washington, DC (United States); Mai, Maxim [George Washington Univ., Washington, DC (United States); Molina, Raquel [Univ. of Sao Paulo (Brazil); Ronchen, Deborah [Univ. of Bonn (Germany)

2018-04-01

Results for light baryon spectroscopy by different collaborations and the state of the art in the subfield is reviewed. Highlights contain common efforts of different phenomenology groups and the impact of recent high-precision data from ELSA, JLab, MAMI, and other facilities. Questions will be addressed, on one side, of how to proceed to reach conclusive answers in baryon spectroscopy, and, on the other side, how phenomenology can be connected to theory in a meaningful way.
Molecular Dynamics Simulations with Quantum Mechanics/Molecular Mechanics and Adaptive Neural Networks.

Science.gov (United States)

Shen, Lin; Yang, Weitao

2018-03-13

Direct molecular dynamics (MD) simulation with ab initio quantum mechanical and molecular mechanical (QM/MM) methods is very powerful for studying the mechanism of chemical reactions in a complex environment but also very time-consuming. The computational cost of QM/MM calculations during MD simulations can be reduced significantly using semiempirical QM/MM methods with lower accuracy. To achieve higher accuracy at the ab initio QM/MM level, a correction on the existing semiempirical QM/MM model is an attractive idea. Recently, we reported a neural network (NN) method as QM/MM-NN to predict the potential energy difference between semiempirical and ab initio QM/MM approaches. The high-level results can be obtained using neural network based on semiempirical QM/MM MD simulations, but the lack of direct MD samplings at the ab initio QM/MM level is still a deficiency that limits the applications of QM/MM-NN. In the present paper, we developed a dynamic scheme of QM/MM-NN for direct MD simulations on the NN-predicted potential energy surface to approximate ab initio QM/MM MD. Since some configurations excluded from the database for NN training were encountered during simulations, which may cause some difficulties on MD samplings, an adaptive procedure inspired by the selection scheme reported by Behler [ Behler Int. J. Quantum Chem. 2015 , 115 , 1032 ; Behler Angew. Chem., Int. Ed. 2017 , 56 , 12828 ] was employed with some adaptions to update NN and carry out MD iteratively. We further applied the adaptive QM/MM-NN MD method to the free energy calculation and transition path optimization on chemical reactions in water. The results at the ab initio QM/MM level can be well reproduced using this method after 2-4 iteration cycles. The saving in computational cost is about 2 orders of magnitude. It demonstrates that the QM/MM-NN with direct MD simulations has great potentials not only for the calculation of thermodynamic properties but also for the characterization of
Excited state non-adiabatic dynamics of the smallest polyene, trans 1,3-butadiene. II. Ab initio multiple spawning simulations.

Science.gov (United States)

Glover, William J; Mori, Toshifumi; Schuurman, Michael S; Boguslavskiy, Andrey E; Schalk, Oliver; Stolow, Albert; Martínez, Todd J

2018-04-28

The excited state non-adiabatic dynamics of the smallest polyene, trans 1,3-butadiene (BD), has long been the subject of controversy due to its strong coupling, ultrafast time scales and the difficulties that theory faces in describing the relevant electronic states in a balanced fashion. Here we apply Ab Initio Multiple Spawning (AIMS) using state-averaged complete active space multistate second order perturbation theory [SA-3-CAS(4/4)-MSPT2] which describes both static and dynamic electron correlation effects, providing a balanced description of both the initially prepared bright 1 1 B u (ππ*) state and non-adiabatically coupled dark 2 1 A g state of BD. Importantly, AIMS allows for on-the-fly calculations of experimental observables. We validate our approach by directly simulating the time resolved photoelectron-photoion coincidence spectroscopy results presented in Paper I [A. E. Boguslavskiy et al., J. Chem. Phys. 148, 164302 (2018)], demonstrating excellent agreement with experiment. Our simulations reveal that the initial excitation to the 1 1 B u state rapidly evolves via wavepacket dynamics that follow both bright- and dark-state pathways as well as mixtures of these. In order to test the sensitivity of the AIMS results to the relative ordering of states, we considered two hypothetical scenarios biased toward either the bright 1 B u or the dark 2 1 A g state. In contrast with AIMS/SA-3-CAS(4/4)-MSPT2 simulations, neither of these scenarios yields favorable agreement with experiment. Thus, we conclude that the excited state non-adiabatic dynamics in BD involves both of these ultrafast pathways.
Numerical simulation in material science: principles and applications

International Nuclear Information System (INIS)

Ruste, Jacky

2006-06-01

The objective is here to describe the main simulation techniques currently used in material science. After a presentation of the concepts of modelling and simulation, of their objectives and uses, of the issue of simulation scale, and of means of numeric simulation, the author addresses simulations performed at a nano-scopic scale: 'ab-initio' methods, molecular dynamics, examples of applications of ab-initio methods to energy issues or to the study of surface properties of nano-materials. The next chapter addresses various Monte Carlo methods (Metropolis, atomic kinetics, objects kinetics, transport with the simulation of particle trajectories, generation of random numbers). The next parts address simulations performed at a mesoscopic scale (simulation and microstructure, phase field methods, dynamics of discrete dislocations, homogeneous chemical kinetics) and at a macroscopic scale (medium discretization with the notion of mesh, simulation of structure mechanics and of fluid behaviour). The issues of code coupling and scale coupling are then discussed. The last part proposes an overview of virtual metallurgy and modelling of industrial processes (welding, vacuum arc re-fusion, rolling, forming)
Phenomenology and its application in medicine.

Science.gov (United States)

Carel, Havi

2011-02-01

Phenomenology is a useful methodology for describing and ordering experience. As such, phenomenology can be specifically applied to the first person experience of illness in order to illuminate this experience and enable health care providers to enhance their understanding of it. However, this approach has been underutilized in the philosophy of medicine as well as in medical training and practice. This paper demonstrates the usefulness of phenomenology to clinical medicine. In order to describe the experience of illness, we need a phenomenological approach that gives the body a central role and acknowledges the primacy of perception. I present such a phenomenological method and show how it could usefully illuminate the experience of illness through a set of concepts taken from Merleau-Ponty. His distinction between the biological body and the body as lived, analysis of the habitual body, and the notions of motor intentionality and intentional arc are used to capture the experience of illness. I then discuss the applications this approach could have in medicine. These include narrowing the gap between objective assessments of well-being in illness and subjective experiences which are varied and diverse; developing a more attuned dialogue between physicians and patients based on a thick understanding of illness; developing research methods that are informed by phenomenology and thus go beyond existing qualitative methods; and providing medical staff with a concrete understanding of the impact of illness on the life-world of patients.
Ab Initio Liquid Water Dynamics in Aqueous TMAO Solution.

Science.gov (United States)

Usui, Kota; Hunger, Johannes; Sulpizi, Marialore; Ohto, Tatsuhiko; Bonn, Mischa; Nagata, Yuki

2015-08-20

Ab initio molecular dynamics (AIMD) simulations in trimethylamine N-oxide (TMAO)-D2O solution are employed to elucidate the effects of TMAO on the reorientational dynamics of D2O molecules. By decomposing the O-D groups of the D2O molecules into specific subensembles, we reveal that water reorientational dynamics are retarded considerably in the vicinity of the hydrophilic TMAO oxygen (O(TMAO)) atom, due to the O-D···O(TMAO) hydrogen-bond. We find that this reorientational motion is governed by two distinct mechanisms: The O-D group rotates (1) after breaking the O-D···O(TMAO) hydrogen-bond, or (2) together with the TMAO molecule while keeping this hydrogen-bond intact. While the orientational slow-down is prominent in the AIMD simulation, simulations based on force field models exhibit much faster dynamics. The simulated angle-resolved radial distribution functions illustrate that the O-D···O(TMAO) hydrogen-bond has a strong directionality through the sp(3) orbital configuration in the AIMD simulation, and this directionality is not properly accounted for in the force field simulation. These results imply that care must be taken when modeling negatively charged oxygen atoms as single point charges; force field models may not adequately describe the hydration configuration and dynamics.
Simulation of charge transfer and orbital rehybridization in molecular and condensed matter systems

Science.gov (United States)

Nistor, Razvan A.

The mixing and shifting of electronic orbitals in molecules, or between atoms in bulk systems, is crucially important to the overall structure and physical properties of materials. Understanding and accurately modeling these orbital interactions is of both scientific and industrial relevance. Electronic orbitals can be perturbed in several ways. Doping, adding or removing electrons from systems, can change the bond-order and the physical properties of certain materials. Orbital rehybridization, driven by either thermal or pressure excitation, alters the short-range structure of materials and changes their long-range transport properties. Macroscopically, during bond formation, the shifting of electronic orbitals can be interpreted as a charge transfer phenomenon, as electron density may pile up around, and hence, alter the effective charge of, a given atom in the changing chemical environment. Several levels of theory exist to elucidate the mechanisms behind these orbital interactions. Electronic structure calculations solve the time-independent Schrodinger equation to high chemical accuracy, but are computationally expensive and limited to small system sizes and simulation times. Less fundamental atomistic calculations use simpler parameterized functional expressions called force-fields to model atomic interactions. Atomistic simulations can describe systems and time-scales larger and longer than electronic-structure methods, but at the cost of chemical accuracy. In this thesis, both first-principles and phenomenological methods are addressed in the study of several encompassing problems dealing with charge transfer and orbital rehybridization. Firstly, a new charge-equilibration method is developed that improves upon existing models to allow next-generation force-fields to describe the electrostatics of changing chemical environments. Secondly, electronic structure calculations are used to investigate the doping dependent energy landscapes of several high
360⁰ -View of Quantum Theory and Ab Initio Simulation at Extreme Conditions: 2014 Sanibel Symposium

Energy Technology Data Exchange (ETDEWEB)

Cheng, Hai-Ping [Univ. of Florida, Gainesville, FL (United States)

2016-09-02

The Sanibel Symposium 2014 was held February 16-21, 2014, at the King and Prince, St. Simons Island, GA. It was successful in bringing condensed-matter physicists and quantum chemists together productively to drive the emergence of those specialties. The Symposium had a significant role in preparing a whole generation of quantum theorists. The 54th Sanibel meeting looked to the future in two ways. We had 360⁰-View sessions to honor the exceptional contributions of Rodney Bartlett (70), Bill Butler (70), Yngve Öhrn (80), Fritz Schaefer (70), and Malcolm Stocks (70). The work of these five has greatly impacted several generations of quantum chemists and condensed matter physicists. The “360⁰” is the sum of their ages. More significantly, it symbolizes a panoramic view of critical developments and accomplishments in theoretical and computational chemistry and physics oriented toward the future. Thus, two of the eight 360⁰-View sessions focused specifically on younger scientists. The 360⁰-View program was the major component of the 2014 Sanibel meeting. Another four sessions included a sub-symposium on ab initio Simulations at Extreme Conditions, with focus on getting past the barriers of present-day Born-Oppenheimer molecular dynamics by advances in finite-temperature density functional theory, orbital-free DFT, and new all-numerical approaches.
Ab-initio ZORA calculations

NARCIS (Netherlands)

Faas, S.; Snijders, Jaap; van Lenthe, J.H.; HernandezLaguna, A; Maruani, J; McWeeny, R; Wilson, S

2000-01-01

In this paper we present the first application of the ZORA (Zeroth Order Regular Approximation of the Dirac Fock equation) formalism in Ab Initio electronic structure calculations. The ZORA method, which has been tested previously in the context of Density Functional Theory, has been implemented in
Phenomenological aspects of D-branes

International Nuclear Information System (INIS)

Quevedo, F.

2003-01-01

A general overview is presented on string phenomenology, emphasizing the role played by D-branes. A general discussion of the main challenges for string phenomenology is followed by recent progress made in constructing realistic models from D-branes and anti-branes at singularities and also from intersecting D-branes. Some possible cosmological implications of these classes of string models are also mentioned. (author)
Phenomenological aspects of D-branes

Energy Technology Data Exchange (ETDEWEB)

Quevedo, F [Centre for Mathematical Sciences, DAMTP, University of Cambridge, Cambridge (United Kingdom)

2003-08-15

A general overview is presented on string phenomenology, emphasizing the role played by D-branes. A general discussion of the main challenges for string phenomenology is followed by recent progress made in constructing realistic models from D-branes and anti-branes at singularities and also from intersecting D-branes. Some possible cosmological implications of these classes of string models are also mentioned. (author)
A phenomenological calculus of Wiener description space.

Science.gov (United States)

Richardson, I W; Louie, A H

2007-10-01

The phenomenological calculus is a categorical example of Robert Rosen's modeling relation. This paper is an alligation of the phenomenological calculus and generalized harmonic analysis, another categorical example. Our epistemological exploration continues into the realm of Wiener description space, in which constitutive parameters are extended from vectors to vector-valued functions of a real variable. Inherent in the phenomenology are fundamental representations of time and nearness to equilibrium.
Ab initio calculation of the shear viscosity of neon in the liquid and hypercritical state over a wide pressure and temperature range

Science.gov (United States)

Eggenberger, Rolf; Gerber, Stefan; Huber, Hanspeter; Searles, Debra; Welker, Marc

1992-08-01

The shear viscosity is calculated ab initio for the liquid and hypercritical state, i.e. a previously published potential for Ne 2, obtained from ab initio calculations including electron correlation, is used in classical equilibrium molecular dynamics simulations to obtain the shear viscosity from a Green-Kubo integral. The quality of the results is quite uniform over a large pressure range up to 1000 MPa and a wide temperature range from 26 to 600 K. In most cases the calculated shear viscosity deviates by less than 10% from the experimental value, in general the error being only a few percent.
Phenomenological Characteristics of Future Thinking in Alzheimer's Disease.

Science.gov (United States)

Moustafa, Ahmed A; El Haj, Mohamad

2018-05-11

This study investigates phenomenological reliving of future thinking in Alzheimer's disease (AD) patients and matched controls. All participants were asked to imagine in detail a future event, and afterward, were asked to rate phenomenological characteristics of their future thinking. As compared to controls, AD participants showed poor rating for reliving, travel in time, visual imagery, auditory imagery, language, and spatiotemporal specificity. However, no significant differences were observed between both groups in emotion and importance of future thinking. Results also showed lower rating for visual imagery relative to remaining phenomenological features in AD participants compared to controls; conversely, these participants showed higher ratings for emotion and importance of future thinking. AD seems to compromise some phenomenological characteristics of future thinking, especially, visual imagery; however, other phenomenological characteristics, such as emotion, seem to be relatively preserved in these populations. By highlighting the phenomenological experience of future thinking in AD, our paper opens a unique window into the conscious experience of the future in AD patients.
Quantitative verification of ab initio self-consistent laser theory.

Science.gov (United States)

Ge, Li; Tandy, Robert J; Stone, A D; Türeci, Hakan E

2008-10-13

We generalize and test the recent "ab initio" self-consistent (AISC) time-independent semiclassical laser theory. This self-consistent formalism generates all the stationary lasing properties in the multimode regime (frequencies, thresholds, internal and external fields, output power and emission pattern) from simple inputs: the dielectric function of the passive cavity, the atomic transition frequency, and the transverse relaxation time of the lasing transition.We find that the theory gives excellent quantitative agreement with full time-dependent simulations of the Maxwell-Bloch equations after it has been generalized to drop the slowly-varying envelope approximation. The theory is infinite order in the non-linear hole-burning interaction; the widely used third order approximation is shown to fail badly.
Ab initio study of intrinsic profiles of liquid metals and their reflectivity

Science.gov (United States)

del Rio, B. G.; Souto, J.; Alemany, M. M. G.; González, L. E.

2017-08-01

The free surfaces of liquid metals are known to exhibit a stratified profile that, in favourable cases, shows up in experiments as a peak in the ratio between the reflectivity function and that of an ideal step-like profile. This peak is located at a wave-vector related to the distance between the layers of the profile. In fact the surface roughness produced by thermally induced capillary waves causes a depletion of the previous so called intrinsic reflectivity by a damping factor that may hinder the observation of the peak. The behaviour of the intrinsic reflectivity below the layering peak is however far from being universal, with systems as Ga or In where the reflectiviy falls uniformly towards the q → 0 value, others like Sn or Bi where a shoulder appears at intermediate wavevectors, and others like Hg which show a minimum. We have performed extensive ab initio simulations of the free liquid surfaces of Bi, Pb and Hg, that yield direct information on the structure of the profiles and found that the macroscopic capillary wave theory usually employed in order to remove the capillary wave components fails badly in some cases for the typical sample sizes affordable in ab initio simulations. However, a microscopic method for the determination of the intrinsic profile is shown to be succesful in obtaining meaningful intrinsic profiles and corresponding reflectivities which reproduce correctly the qualitative behaviour observed experimentally.

Phenomenology and adapted physical activity: philosophy and professional practice.

Science.gov (United States)

Standal, Øyvind F

2014-01-01

Through the increased use of qualitative research methods, the term phenomenology has become a quite familiar notion for researchers in adapted physical activity (APA). In contrast to this increasing interest in phenomenology as methodology, relatively little work has focused on phenomenology as philosophy or as an approach to professional practice. Therefore, the purpose of this article is to examine the relevance of phenomenology as philosophy and as pedagogy to the field of APA. First, phenomenology as philosophy is introduced through three key notions, namely the first-person perspective, embodiment, and life-world. The relevance of these terms to APA is then outlined. Second, the concept of phenomenological pedagogy is introduced, and its application and potential for APA are discussed. In conclusion, it is argued that phenomenology can help theorize ways of understanding human difference in movement contexts and form a basis of action-oriented research aiming at developing professional practice.
Choosing phenomenology as a guiding philosophy for nursing research.

Science.gov (United States)

Matua, Gerald Amandu

2015-03-01

To provide an overview of important methodological considerations that nurse researchers need to adhere to when choosing phenomenology as a guiding philosophy and research method. Phenomenology is a major philosophy and research method in the humanities, human sciences and arts disciplines with a central goal of describing people's experiences. However, many nurse researchers continue to grapple with methodological issues related to their choice of phenomenological method. The author conducted online and manual searches of relevant research books and electronic databases. Using an integrative method, peer-reviewed research and discussion papers published between January 1990 and December 2011 and listed in the CINAHL, Science Direct, PubMed and Google Scholar databases were reviewed. In addition, textbooks that addressed research methodologies such as phenomenology were used. Although phenomenology is widely used today to broaden understanding of human phenomena relevant to nursing practice, nurse researchers often fail to adhere to acceptable scientific and phenomenological standards. Cognisant of these challenges, researchers are expected to indicate in their work the focus of their investigations, designs, and approaches to collecting and analysing data. They are also expected to present their findings in an evocative and expressive manner. Choosing phenomenology requires researchers to understand it as a philosophy, including basic assumptions and tenets of phenomenology as a research method. This awareness enables researchers, especially novices, to make important methodological decisions, particularly those necessary to indicate the study's scientific rigour and phenomenological validity. This paper adds to the discussion of phenomenology as a guiding philosophy for nursing research. It aims to guide new researchers on important methodological decisions they need to make to safeguard their study's scientific rigour and phenomenological validity.
String phenomenology

CERN Document Server

Ibáñez, Luis E

2015-01-01

This chapter reviews a number of topics in the field of string phenomenology, focusing on orientifold/F-theory models yielding semirealistic low-energy physics. The emphasis is on the extraction of the low-energy effective action and possible tests of specific models at the LHC.
Ab initio molecular dynamics study of pressure-induced phase transition in ZnS

International Nuclear Information System (INIS)

Martinez, Israel; Durandurdu, Murat

2006-01-01

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 due to a monoclinic modification of the simulation cell, similar to that obtained in SiC. This observation supports the universal transition state of high-pressure zinc-blende to rock-salt transition in semiconductor compounds. We also study the role of stress deviations on the transformation mechanism and find that the system follows the same transition pathway under nonhydrostatic compressions as well
A Phenomenology of Expert Musicianship

DEFF Research Database (Denmark)

Høffding, Simon

This dissertation develops a phenomenology of expert musicianship through an interdisciplinary approach that integrates qualitative interviews with the Danish String Quartet with philosophical analyses drawing on ideas and theses found in phenomenology, philosophy of mind, cognitive science...... and psychology of music. The dissertation is structured through the asking, analyzing and answering of three primary questions, namely: 1) What is it like to be an expert? 2) What is the general phenomenology of expert musicianship? 3) What happens to the self in deep musical absorption? The first question...... targets a central debate in philosophy and psychology on whether reflection is conducive for, or detrimental to, skillful performance. My analyses show that the concepts assumed in the literature on this question are poorly defined and gloss over more important features of expertise. The second question...
Phenomenological Research Method, Design and Procedure: A ...

African Journals Online (AJOL)

Phenomenological Research Method, Design and Procedure: A Phenomenological Investigation of the Phenomenon of Being-in-Community as Experienced by Two Individuals Who Have Participated in a Community Building Workshop.
Empirical Phenomenology: A Qualitative Research Approach (The ...

African Journals Online (AJOL)

Empirical Phenomenology: A Qualitative Research Approach (The Cologne Seminars) ... and practical application of empirical phenomenology in social research. ... and considers its implications for qualitative methods such as interviewing ...
Dreaming Consciousness: A Contribution from Phenomenology

Directory of Open Access Journals (Sweden)

Nicola Zippel

2016-08-01

Full Text Available The central aim of this paper is to offer a historical reconstruction of phenomenological studies on dreaming and to put forward a draft for a phenomenological theory of the dream state. Prominent phenomenologists have offered an extremely valuable interpretation of the dream as an intentional process, stressing its relevance in understanding the complexity of the mental life of subject, the continuous interplay between reality and unreality, and the possibility of building parallel spheres of experience influencing the development of personal identity. Taking into consideration the main characteristics of dream experience emphasized by these scholars, in the final part of the paper I propose to elaborate a new phenomenology of dreaming, which should be able to offer a theoretical description of dream states. My sketched proposal is based on Eugen Fink’s notion of the dream as “presentification”. By combining the past and the present of phenomenological investigation, I aim at suggesting a philosophical framework to explain the intentional features of dreaming as Erlebnis.
Oxide nanostructures on a Nb surface and related systems: experiments and ab initio calculations

International Nuclear Information System (INIS)

Kuznetsov, Mikhail V; Razinkin, A S; Ivanovskii, Alexander L

2011-01-01

This review discusses the state of the art in two related research areas: the surfaces of niobium and of its related group IV-VI transition metals, and surface (primarily oxide) nanostructures that form on niobium (and group IV-VI d-metals) due to gas adsorption or impurity diffusion from the bulk. Experimental (X-ray photoelectron spectroscopy, photoelectron diffraction, scanning tunneling microscopy) and theoretical (ab initio simulation) results on d-metal surfaces are summarized and reviewed. (reviews of topical problems)
Ab Initio Calculation of Hyperfine Interaction Parameters: Recent Evolutions, Recent Examples

International Nuclear Information System (INIS)

Cottenier, Stefaan; Vanhoof, Veerle; Torumba, Doru; Bellini, Valerio; Cakmak, Mehmet; Rots, Michel

2004-01-01

For some years already, ab initio calculations based on Density Functional Theory (DFT) belong to the toolbox of the field of hyperfine interaction studies. In this paper, the standard ab initio approach is schematically sketched. New features, methods and possibilities that broke through during the past few years are listed, and their relation to the standard approach is explained. All this is illustrated by some highlights of recent ab initio work done by the Nuclear Condensed Matter Group at the K.U.Leuven.
Phenomenology dependent timescales

International Nuclear Information System (INIS)

Ouzounian, G.

2002-01-01

As required by the French act, Dec. 1991, construction projects for disposing of radioactive wastes have to be submitted to the Parliament by 2006. One of the most important points to allow for a decision at this time will be to gain confidence. The major difficulty in such a technical and societal project is to be able to carry out a demonstration of the safety ver timescales which are out of the scope of any experiment. Among the arguments involved for the safety case are a series of simulations which objective is to assess the level of safety which can be reached, and its robustness to various internal defects (construction of the drifts, welding of canisters...) or external events (intrusion with deep boreholes, climate change, faulting...). Confidence in the simulations can be achieved if they are transparent, based on well understood processes. However, the complexity of the disposal system is such that temptation was great by the past to simplify the models, with a poor level of reporting on justifications, thus leading to what has been described as black-box models. In the frame of the demonstration to be brought out for 2006, ANDRA has developed an approach consisting first to describe and analyse all the processes occurring over time and space in the repository. Once this type of information has been gathered in a structured way, then further analyses leading to abstractions, simplifications can be performed in order to facilitate simulations as required for the safety demonstration. The first stage of the approach has been called the phenomenological analysis of the repository situations PARS). This work gives rise to a reference book in which our knowledge has been reported before being used for the safety demonstration. If also represent a reference for all technical and scientific knowledge based applications, such as digital modeling which is the basis for simulations, the repository design, the reversibility study, including the definition of a
Phenomenological realism, superconductivity and quantum mechanics

International Nuclear Information System (INIS)

Shomar, T.L.E.

1998-01-01

The central aim of this thesis is to present a new kind of realism that is driven not from the traditional realism/anti-realism debate but from the practice of physicists. The usual debate focuses on discussions about the truth of theories and their fit with nature, while the real practices of the scientists are forgotten. The position I shall defend is called 'phenomenological realism': theories are merely tools to construct other theories and models, including phenomenological models; phenomenological models are the vehicles of representation. The realist doctrine was recently undermined by the argument from the pessimistic meta-induction, also known as the argument from scientific revolutions. I argue that phenomenological realism is a new kind of scientific realism which can overcome the problem generated by the argument from scientific revolutions, and which depend on the scientific practice. The realist tried to overcome this problem by suggesting various types of theory dichotomy. I claim that different types of dichotomy presented by realists did not overcome the problem, these dichotomies cut through theory vertically. I argue for a different kind of dichotomy between high level theoretical abstractions and low-level theoretical representations. I claim that theoretical work in physics have two distinct types depending on the way they are built these are: theoretical models which built depending on a top-down approach and phenomenological models which are built depending on a bottom-up approach, this dichotomy cuts the division along a horizontal line between low and high level theory. I present two case studies. One from superconductivity where I contrast the BCS theory of superconductivity with the phenomenological model of Landau and Ginzburg. I show how in that field of physics the historical developments favoured phenomenological models over high-level theoretical abstraction. I show how the BCS theory of superconductivity was constructed, and why it
Ab initio path-integral molecular dynamics and the quantum nature of hydrogen bonds

International Nuclear Information System (INIS)

Feng Yexin; Chen Ji; Wang Enge; Li Xin-Zheng

2016-01-01

The hydrogen bond (HB) is an important type of intermolecular interaction, which is generally weak, ubiquitous, and essential to life on earth. The small mass of hydrogen means that many properties of HBs are quantum mechanical in nature. In recent years, because of the development of computer simulation methods and computational power, the influence of nuclear quantum effects (NQEs) on the structural and energetic properties of some hydrogen bonded systems has been intensively studied. Here, we present a review of these studies by focussing on the explanation of the principles underlying the simulation methods, i.e., the ab initio path-integral molecular dynamics. Its extension in combination with the thermodynamic integration method for the calculation of free energies will also be introduced. We use two examples to show how this influence of NQEs in realistic systems is simulated in practice. (topical review)
From Husserl to van Manen. A review of different phenomenological approaches.

Science.gov (United States)

Dowling, Maura

2007-01-01

This paper traces the development of phenomenology as a philosophy originating from the writings of Husserl to its use in phenomenological research and theory development in nursing. The key issues of phenomenological reduction and bracketing are also discussed as they play a pivotal role in the how phenomenological research studies are approached. What has become to be known as "new" phenomenology is also explored and the key differences between it and "traditional" phenomenology are discussed. van Manen's phenomenology is also considered in light of its contemporary popularity among nurse researchers.
Phenomenologies of Higgs messenger models

Energy Technology Data Exchange (ETDEWEB)

Zheng Sibo; Yu Yao; Wu Xinggang [Department of Physics, Chongqing University, Chongqing 401331 (China)

2011-08-11

In this Letter, we investigate the phenomenologies of models where the Higgs sector plays the role of messengers in gauge mediation. The minimal Higgs sector and its extension are considered respectively. We find that there exist viable models when an appropriate parity is imposed. Phenomenological features in these kind of models include three sum rules for scalar masses, light gluino as well as one-loop {mu} and two-loop B{mu} terms.
Dual topological unitarization -- phenomenological aspect

International Nuclear Information System (INIS)

Tan, C.I.

1978-01-01

An assessment is provided on the viability of dual topological unitarization as a practical scheme for organizing and interpreting hadronic phenomena at current machine energies. Previous detailed reviews are complemented, with emphasis on phenomenological aspects and more recent developments. Diffraction scattering, a test of P--f identity hypothesis, the flavor model, the P--f identity versus the Veneziano two-jet picture, and an illustration of the new phenomenology are included. 24 references
Creativity in phenomenological methodology

DEFF Research Database (Denmark)

Dreyer, Pia; Martinsen, Bente; Norlyk, Annelise

2014-01-01

on the methodologies of van Manen, Dahlberg, Lindseth & Norberg, the aim of this paper is to argue that the increased focus on creativity and arts in research methodology is valuable to gain a deeper insight into lived experiences. We illustrate this point through examples from empirical nursing studies, and discuss......Nursing research is often concerned with lived experiences in human life using phenomenological and hermeneutic approaches. These empirical studies may use different creative expressions and art-forms to describe and enhance an embodied and personalised understanding of lived experiences. Drawing...... may support a respectful renewal of phenomenological research traditions in nursing research....
Ab initio thermodynamics for the growth of ultra-thin Cu film on a perfect Mg O(001) surface

Energy Technology Data Exchange (ETDEWEB)

Zhukovskii, Yuri F. [Institute for Solid State Physics, University of Latvia, Kengaraga str. 8, Riga LV-1063 (Latvia)]. E-mail: quantzh@latnet.lv; Fuks, David [Materials Engineering Department, Ben-Gurion University of the Negev, POB 653, Beer-Sheva IL-84105 (Israel); Kotomin, Eugene A. [Institute for Solid State Physics, University of Latvia, Kengaraga str. 8, Riga LV-1063 (Latvia); Dorfman, Simon [Department of Physics, Israel Institute of Technology-Technion, Haifa IL-32000 (Israel)

2005-12-15

Controlled growth of thin metallic films on oxide substrates is important for numerous micro-and nano electronic applications. Our ab initio study is devoted to the periodic slab simulations for a series of ordered 2a Cu superlattices on the regular Mg O(001) substrate. Submonolayer and monolayer substrate Cu coverages were calculated using the Daft-Gaga method, as implemented into the Crystal-98 code. The results of ab initio calculations have been combined with thermodynamic theory which allows US to predict the growth mode of ultra-thin metal films (spinodal decomposition vs. nucleation-and-growth regime) as a function of the metal coverage and the temperature, and to estimate the metal density in clusters. We show that 3a cluster formation becomes predominant already at low Cu coverages, in agreement with the experiment.
Ab initio thermodynamics for the growth of ultra-thin Cu film on a perfect Mg O(001) surface

International Nuclear Information System (INIS)

Zhukovskii, Yuri F.; Fuks, David; Kotomin, Eugene A.; Dorfman, Simon

2005-01-01

Controlled growth of thin metallic films on oxide substrates is important for numerous micro-and nano electronic applications. Our ab initio study is devoted to the periodic slab simulations for a series of ordered 2a Cu superlattices on the regular Mg O(001) substrate. Submonolayer and monolayer substrate Cu coverages were calculated using the Daft-Gaga method, as implemented into the Crystal-98 code. The results of ab initio calculations have been combined with thermodynamic theory which allows US to predict the growth mode of ultra-thin metal films (spinodal decomposition vs. nucleation-and-growth regime) as a function of the metal coverage and the temperature, and to estimate the metal density in clusters. We show that 3a cluster formation becomes predominant already at low Cu coverages, in agreement with the experiment
Ab initio molecular dynamics simulation of structural transformation in zinc blende GaN under high pressure

International Nuclear Information System (INIS)

Xiao, H.Y.; Gao, Fei; Zu, X.T.; Weber, W.J.

2010-01-01

High-pressure induced zinc blende to rocksalt phase transition in GaN has been investigated by ab initio molecular dynamics method to characterize the transformation mechanism at the atomic level. It was shown that at 100 GPa GaN passes through tetragonal and monoclinic states before rocksalt structure is formed. The transformation mechanism is consistent with that for other zinc blende semiconductors obtained from the same method. Detailed structural analysis showed that there is no bond breaking involved in the phase transition.

Modeling Disordered Materials with a High Throughput ab-initio Approach

Science.gov (United States)

2015-11-13

Modeling Disordered Materials with a High Throughput ab - initio Approach Kesong Yang,1 Corey Oses,2 and Stefano Curtarolo3, 4 1Department of...J. Furthmüller, Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set, Phys. Rev. B 54, 11169–11186 (1996
Embedded atom approach for gold–silicon system from ab initio

Indian Academy of Sciences (India)

In the present paper, an empirical embedded atom method (EAM) potential for gold–silicon (Au–Si) is developed by fitting to ab initio force (the 'force matching' method) and experimental data. The force database is generated within ab initio molecular dynamics (AIMD). The database includes liquid phase at various ...
Ab Initio Predictions of Hexagonal Zr(B,C,N) Polymorphs for Coherent Interface Design

Energy Technology Data Exchange (ETDEWEB)

Hu, Chongze [Univ. of Minnesota-Twin Cities, Minneapolis, MN (United States); Huang, Jingsong [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Sumpter, Bobby G. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Meletis, Efstathios [Univ. of Texas at Arlington, Arlington, TX (United States); Dumitrica, Traian [Univ. of Minnesota-Twin Cities, Minneapolis, MN (United States)

2017-10-27

Density functional theory calculations are used to explore hexagonal (HX) NiAs-like polymorphs of Zr(B,C,N) and compare with corresponding Zr(B,C,N) Hagg-like face-centered cubic rocksalt (B1) phases. While all predicted compounds are mechanically stable according to the Born-Huang criteria, only HX Zr(C,N) are found dynamically stable from ab initio molecular dynamics simulations and lattice dynamics calculations. HX ZrN emerges as a candidate structure with ground state energy, elastic constants, and extrinsic mechanical parameters comparable with those of B1 ZrN. Ab initio band structure and semi-classical Boltzmann transport calculations predict a metallic character and a monotonic increase in electrical conductivity with the number of valence electrons. Electronic structure calculations indicate that the HX phases gain their stability and mechanical attributes by Zr d- non-metal p hybridization and by broadening of Zr d bands. Furthermore, it is shown that the HX ZrN phase provides a low-energy coherent interface model for connecting B1 ZrN domains, with significant energetic advantage over an atomistic interface model derived from high resolution transmission electron microscopy images. The ab initio characterizations provided herein should aid the experimental identification of non-Hagg-like hard phases. Furthermore, the results can also enrich the variety of crystalline phases potentially available for designing coherent interfaces in superhard nanostructured materials and in materials with multilayer characteristics.
Ab initio molecular dynamics simulations on the structural change of liquid eutectic alloy Si{sub 15}Te{sub 85} from 673 to 1373 k

Energy Technology Data Exchange (ETDEWEB)

Wang Yubing, E-mail: ybwang1985@gmail.co [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Post Office 1129, Hefei 230031 (China); Zhao Gang [Department of Physics and Electronic Engineering, Ludong University, Hongqi Road, No. 186, Yantai 264025 (China); Liu Changsong; Zhu Zhengang [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Post Office 1129, Hefei 230031 (China)

2010-01-15

Using ab initio molecular dynamics simulations and inherent structure formalism, the local atomic structure and electronic properties of liquid Si{sub 15}Te{sub 85} alloy were studied at eight different temperatures from 673 to 1373 K. In comparison with available experimental data, our calculated structure factors are acceptable. With increasing temperature from 773 to 1173 K, the calculated total coordination number N{sub Total} increases gradually in contrast to the behavior of a classical isotropic fluid. Our results of pair-correlation functions, bond-angle distribution functions and angular limited triplet correlation functions suggest that the temperature-dependence of the preserved sp{sup 3} hybridization of Si atoms and Peierls-type distorted local structure around Te atoms both play important roles in the structural change of Si{sub 15}Te{sub 85} characterized by thermodynamic anomalies.
Modelling the local atomic structure of molybdenum in nuclear waste glasses with ab initio molecular dynamics simulations.

Science.gov (United States)

Konstantinou, Konstantinos; Sushko, Peter V; Duffy, Dorothy M

2016-09-21

The nature of chemical bonding of molybdenum in high level nuclear waste glasses has been elucidated by ab initio molecular dynamics simulations. Two compositions, (SiO 2 ) 57.5 -(B 2 O 3 ) 10 -(Na 2 O) 15 -(CaO) 15 -(MoO 3 ) 2.5 and (SiO 2 ) 57.3 -(B 2 O 3 ) 20 -(Na 2 O) 6.8 -(Li 2 O) 13.4 -(MoO 3 ) 2.5 , were considered in order to investigate the effect of ionic and covalent components on the glass structure and the formation of the crystallisation precursors (Na 2 MoO 4 and CaMoO 4 ). The coordination environments of Mo cations and the corresponding bond lengths calculated from our model are in excellent agreement with experimental observations. The analysis of the first coordination shell reveals two different types of molybdenum host matrix bonds in the lithium sodium borosilicate glass. Based on the structural data and the bond valence model, we demonstrate that the Mo cation can be found in a redox state and the molybdate tetrahedron can be connected with the borosilicate network in a way that inhibits the formation of crystalline molybdates. These results significantly extend our understanding of bonding in Mo-containing nuclear waste glasses and demonstrate that tailoring the glass composition to specific heavy metal constituents can facilitate incorporation of heavy metals at high concentrations.
Phenomenology of the innovative question when based on wonderment

DEFF Research Database (Denmark)

Herholdt-Lomholdt, Sine Maria; Hansen, Finn Thorbjørn

This paper questions, how we, from a phenomenological point of view, can describe and understand the phenomenology of innovative questions and processes of questioning when based in a wonderdriven approach to innovation and entrepreneurship. Approach: In our research we take on a phenomenological...
Critical appraisal of rigour in interpretive phenomenological nursing research.

Science.gov (United States)

de Witt, Lorna; Ploeg, Jenny

2006-07-01

This paper reports a critical review of published nursing research for expressions of rigour in interpretive phenomenology, and a new framework of rigour specific to this methodology is proposed. The rigour of interpretive phenomenology is an important nursing research methods issue that has direct implications for the legitimacy of nursing science. The use of a generic set of qualitative criteria of rigour for interpretive phenomenological studies is problematic because it is philosophically inconsistent with the methodology and creates obstacles to full expression of rigour in such studies. A critical review was conducted of the published theoretical interpretive phenomenological nursing literature from 1994 to 2004 and the expressions of rigour in this literature identified. We used three sources to inform the derivation of a proposed framework of expressions of rigour for interpretive phenomenology: the phenomenological scholar van Manen, the theoretical interpretive phenomenological nursing literature, and Madison's criteria of rigour for hermeneutic phenomenology. The nursing literature reveals a broad range of criteria for judging the rigour of interpretive phenomenological research. The proposed framework for evaluating rigour in this kind of research contains the following five expressions: balanced integration, openness, concreteness, resonance, and actualization. Balanced integration refers to the intertwining of philosophical concepts in the study methods and findings and a balance between the voices of study participants and the philosophical explanation. Openness is related to a systematic, explicit process of accounting for the multiple decisions made throughout the study process. Concreteness relates to usefulness for practice of study findings. Resonance encompasses the experiential or felt effect of reading study findings upon the reader. Finally, actualization refers to the future realization of the resonance of study findings. Adoption of this
Phenomenological modeling of argon Z-pinch implosions

International Nuclear Information System (INIS)

Whitney, K.G.; Thornhill, J.W.; Deeney, C.; LePell, P.D.; Coulter, M.C.

1992-01-01

The authors investigate some of the effects of plasma turbulence on the K-shell emission dynamics of argon gas puff Z-pinch implosions. The increases that turbulence produces in the plasma viscosity, heat conductivity, and electrical resistivity are modeled phenomenologically using multipliers for these quantities in the MHD calculations. The choice of multipliers was made by benchmarking a 1-D MHD simulation of a Physics International Inc. argon gas puff experiment against the inferred densities and temperatures achieved in the experiment. These multipliers were then used to study the parametric dependence of the K-shell emission on the energy input to the argon plasma for a fixed mass loading. Comparisons between turbulent and non-turbulent argon implosions are made
Ethics in Husserl’s Phenomenology

OpenAIRE

Hasan FathZadeh

2013-01-01

Starting with the ego's consciousness and emphasizing on staying at this realm, Husserl is accused of ignoring the absolute alterity of the other and reducing it to the presence of consciousness. By reducing the other he misses ethics and so embeds the violence at the heart of phenomenological discourse. Here we discuss on this criticism and then we try to defend Husserl against it. By putting phenomenology in its eidetic realm, we will try to answer these criticisms.
A review on ab initio studies of static, transport, and optical properties of polystyrene under extreme conditions for inertial confinement fusion applications

Science.gov (United States)

Hu, S. X.; Collins, L. A.; Boehly, T. R.; Ding, Y. H.; Radha, P. B.; Goncharov, V. N.; Karasiev, V. V.; Collins, G. W.; Regan, S. P.; Campbell, E. M.

2018-05-01

Polystyrene (CH), commonly known as "plastic," has been one of the widely used ablator materials for capsule designs in inertial confinement fusion (ICF). Knowing its precise properties under high-energy-density conditions is crucial to understanding and designing ICF implosions through radiation-hydrodynamic simulations. For this purpose, systematic ab initio studies on the static, transport, and optical properties of CH, in a wide range of density and temperature conditions (ρ = 0.1 to 100 g/cm3 and T = 103 to 4 × 106 K), have been conducted using quantum molecular dynamics (QMD) simulations based on the density functional theory. We have built several wide-ranging, self-consistent material-properties tables for CH, such as the first-principles equation of state, the QMD-based thermal conductivity (κQMD) and ionization, and the first-principles opacity table. This paper is devoted to providing a review on (1) what results were obtained from these systematic ab initio studies; (2) how these self-consistent results were compared with both traditional plasma-physics models and available experiments; and (3) how these first-principles-based properties of polystyrene affect the predictions of ICF target performance, through both 1-D and 2-D radiation-hydrodynamic simulations. In the warm dense regime, our ab initio results, which can significantly differ from predictions of traditional plasma-physics models, compared favorably with experiments. When incorporated into hydrocodes for ICF simulations, these first-principles material properties of CH have produced significant differences over traditional models in predicting 1-D/2-D target performance of ICF implosions on OMEGA and direct-drive-ignition designs for the National Ignition Facility. Finally, we will discuss the implications of these studies on the current small-margin ICF target designs using a CH ablator.
Phenomenology of Freedom and Responsibility in Sartre’s Existentialist Ethics

Directory of Open Access Journals (Sweden)

Mindaugas Briedis

2011-03-01

Full Text Available Freedom and responsibility in one way or another were discussed by all exorcists of non-perspective thinking, i.e., existentialists. However, the phenomenological roots of existentialist ethics still did not receive proper academic attention. In this article I explore J. P. Sartre’s conception of freedom and responsibility uncovering how phenomenological insights can be subordinated and sometimes guide intentions of existentialism. On the other hand, Sartre’s view delivers perfect opportunity to analyse conflation of phenomenological ontology and existentialist ethics. Although Sartre interprets key notions of Husserl and Heidegger primarily in phenomenological manner, the analysis leads away from classical phenomenology and opens up a new outlook at classical ethical dilemmas. Thirdly, the lack of clear ethical claims in phenomenology could be reduced by showing that the ethical potential of phenomenology was partly actualized in existentialism. Besides these primary goals the article opens up a possibility to critically compare the conception of Sartre’s phenomenological-existentialist ethics with other ethical and ontological perspectives, i.e., stoicism, Christianity, psychoanalysis, Marxism, Kant and etc.
Phenomenology as a resource for patients.

Science.gov (United States)

Carel, Havi

2012-04-01

Patient support tools have drawn on a variety of disciplines, including psychotherapy, social psychology, and social care. One discipline that has not so far been used to support patients is philosophy. This paper proposes that a particular philosophical approach, phenomenology, could prove useful for patients, giving them tools to reflect on and expand their understanding of their illness. I present a framework for a resource that could help patients to philosophically examine their illness, its impact on their life, and its meaning. I explain the need for such a resource, provide philosophical grounding for it, and outline the epistemic and existential gains philosophy offers. Illness often begins as an intrusion on one's life but with time becomes a way of being. I argue that this transition impacts on core human features such as the experience of space and time, human abilities, and adaptability. It therefore requires philosophical analysis and response. The paper uses ideas from Husserl and Merleau-Ponty to present such a response in the form of a phenomenological toolkit for patients. The toolkit includes viewing illness as a form of phenomenological reduction, thematizing illness, and examining illness as altering the ill person's being in the world. I suggest that this toolkit could be offered to patients as a workshop, using phenomenological concepts, texts, and film clips to reflect on illness. I conclude by arguing that examining illness as a limit case of embodied existence deepens our understanding of phenomenology.
The Domain-Specificity of Creativity: Insights from New Phenomenology

Science.gov (United States)

Julmi, Christian; Scherm, Ewald

2015-01-01

The question of the domain-specificity of creativity represents one of the key questions in creativity research. This article contributes to the discussion by applying insights from "new phenomenology," which is a phenomenological movement from Germany initiated by philosopher Hermann Schmitz. The findings of new phenomenology suggest…
QCD phenomenology

International Nuclear Information System (INIS)

Gaillard, M.K.

1979-01-01

Selected topics in QCD phenomenology are reviewed: the development of an effective jet perturbation series with applications to factorization, energy flow analysis and photon physics; implications of non-perturbative phenomena for hard scattering processes and the pseudoscalar mass spectrum; resonance properties as extracted from the combined technologies of perturbative and non-perturbative QCD. (orig.)
Ab-Initio Modelling Of Surface Site Reactivity And Fluid Transport In Clay Minerals Case Study: Pyrophyllite

International Nuclear Information System (INIS)

Churakov, S.V.

2005-01-01

Pyrophyllite, Al 2 [Si 4 O 10 ](OH) 2 , is the simplest structural prototype for 2:1 dioctahedral phyllosilicate. Because the net electric charge in pyrophyllite is zero, it is the best candidate for investigating the non electrostatic contribution to sorption and transport phenomena in clays. Using ab-initio simulations, we have investigated the reactivity and structure of the water-solid interface on the basal plane and edge sites of pyrophyllite. The calculations predict slightly hydrophobic behaviour of the basal plane. For the high water coverage (100), (110) and (-110), lateral facets have a lower energy than for the (010), (130) and (-130) surfaces. Analysis of the surface reactivity reveals that the =Al-OH groups are most easily protonated on the (010), (130) and (-130) facets. The =Al-O-Si= sites will be protonated on the (100), (130), (110), (-110) and (-130) surfaces. The =Al-OH 2 complexes are more easily de-protonated than the =Si-OH and =Al-OH sites. A spontaneous, reversible exchange of the protons between the solution and the edge sites has been observed in ab-initio molecular dynamics simulations at 300 K. Such near-surface proton diffusion may result in a significant contribution to the diffusion coefficients measured in neutron scattering experiments. (author)
Phenomenological scattering-rate model for the simulation of the current density and emission power in mid-infrared quantum cascade lasers

Energy Technology Data Exchange (ETDEWEB)

Kurlov, S. S. [Department of Physics, Humboldt-Universität zu Berlin, Newtonstraße 15, 12489 Berlin (Germany); Institute of Semiconductor Physics, National Academy of Sciences, pr. Nauki 45, Kiev-03028 (Ukraine); Flores, Y. V.; Elagin, M.; Semtsiv, M. P.; Masselink, W. T. [Department of Physics, Humboldt-Universität zu Berlin, Newtonstraße 15, 12489 Berlin (Germany); Schrottke, L.; Grahn, H. T. [Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5–7, 10117 Berlin (Germany); Tarasov, G. G. [Institute of Semiconductor Physics, National Academy of Sciences, pr. Nauki 45, Kiev-03028 (Ukraine)

2016-04-07

A phenomenological scattering-rate model introduced for terahertz quantum cascade lasers (QCLs) [Schrottke et al., Semicond. Sci. Technol. 25, 045025 (2010)] is extended to mid-infrared (MIR) QCLs by including the energy dependence of the intersubband scattering rates for energies higher than the longitudinal optical phonon energy. This energy dependence is obtained from a phenomenological fit of the intersubband scattering rates based on published lifetimes of a number of MIR QCLs. In our approach, the total intersubband scattering rate is written as the product of the exchange integral for the squared moduli of the envelope functions and a phenomenological factor that depends only on the transition energy. Using the model to calculate scattering rates and imposing periodical boundary conditions on the current density, we find a good agreement with low-temperature data for current-voltage, power-current, and energy-photon flux characteristics for a QCL emitting at 5.2 μm.
Toward a Conceptualization of Mixed Methods Phenomenological Research

OpenAIRE

Mayoh, Joanne; Onwuegbuzie, A.J.

2015-01-01

Increasingly, researchers are recognizing the benefits of expanding research designs that are rooted in one tradition (i.e., monomethod design) into a design that incorporates or interfaces with the other tradition. The flexibility of phenomenologically driven methods provides one such example. Indeed, phenomenological research methods work extremely well as a component of mixed methods research approaches. However, to date, a mixed methods version of phenomenological research has not been fo...
Hydration and Ion Pairing in Aqueous Mg2+ and Zn2+ Solutions: Force-Field Description Aided by Neutron Scattering Experiments and Ab Initio Molecular Dynamics Simulations.

Science.gov (United States)

Duboué-Dijon, Elise; Mason, Philip E; Fischer, Henry E; Jungwirth, Pavel

2018-04-05

Magnesium and zinc dications possess the same charge and have an almost identical size, yet they behave very differently in aqueous solutions and play distinct biological roles. It is thus crucial to identify the origins of such different behaviors and to assess to what extent they can be captured by force-field molecular dynamics simulations. In this work, we combine neutron scattering experiments in a specific mixture of H 2 O and D 2 O (the so-called null water) with ab initio molecular dynamics simulations to probe the difference in the hydration structure and ion-pairing properties of chloride solutions of the two cations. The obtained data are used as a benchmark to develop a scaled-charge force field for Mg 2+ that includes electronic polarization in a mean field way. We show that using this electronic continuum correction we can describe aqueous magnesium chloride solutions well. However, in aqueous zinc chloride specific interaction terms between the ions need to be introduced to capture ion pairing quantitatively.
Summation of Parquet diagrams as an ab initio method in nuclear structure calculations

International Nuclear Information System (INIS)

Bergli, Elise; Hjorth-Jensen, Morten

2011-01-01

Research highlights: → We present a Green's function based approach for doing ab initio nuclear structure calculations. → In particular the sum the subset of so-called Parquet diagrams. → Applying the theory to a simple but realistic model, results in good agreement with other ab initio methods. → This opens up for ab initio calculations for medium-heavy nuclei. - Abstract: In this work we discuss the summation of the Parquet class of diagrams within Green's function theory as a possible framework for ab initio nuclear structure calculations. The theory is presented and some numerical details are discussed, in particular the approximations employed. We apply the Parquet method to a simple model, and compare our results with those from an exact solution. The main conclusion is that even at the level of approximation presented here, the results shows good agreement with other comparable ab initio approaches.
Consistent microscopic and phenomenological analysis of composite particle opticle potential

International Nuclear Information System (INIS)

Mukhopadhyay, Sheela; Srivastava, D.K.; Ganguly, N.K.

1976-01-01

A microscopic calculation of composits particle optical potential has been done using a realistic nucleon-helion interaction and folding it with the density distribution of the targets. The second order effects were simulated by introducing a scaling factor which was searched on to reproduce the experimental scattering results. Composite particle optical potential was also derived from the nucleon-nucleus optical potential. The second order term was explicitly treated as a parameter. Elastic scattering of 20 MeV 3 H on targets ranging from 40 Ca to 208 Pb to 208 Pb have also been analysed using phenomenological optical model. Agreement of these results with the above calculations verified the consistency of the microscopic theory. But the equivalent sharp radius calculated with n-helion interaction was observed to be smaller than phenomenological value. This was attributed to the absence of saturation effects in the density-independent interaction used. Saturation has been introduced by a density dependent term of the form (1-c zetasup(2/3)), where zeta is the compound density of the target helion system. (author)

On "being inspired" by Husserl's Phenomenology: reflections on Omery's exposition of phenomenology as a method of nursing research.

Science.gov (United States)

Porter, E J

1998-09-01

The impact of Omery's article, "Phenomenology: A Method for Nursing Research," on nursing science is appraised. In particular, the influence of her emphasis on "being inspired" was compared with that of her detailed reviews of psychological phenomenologic methods. The author's experience of "being inspired" by Husserl's book, Ideas, is described. The author also discusses the tapping of this resource during three phases of her development as a researcher: (1) appraising methods derived from Husserl's phenomenology; (2) spelling out an approach, with help; and (3) "making clearer while glancing-toward." Omery's proposed linkage between philosophic inspiration and methodologic development is highlighted as a challenge to nurse researchers.
Erbium(III) in aqueous solution: an ab initio molecular dynamics study.

Science.gov (United States)

Canaval, Lorenz R; Sakwarathorn, Theerathad; Rode, Bernd M; Messner, Christoph B; Lutz, Oliver M D; Bonn, Günther K

2013-12-05

Structural and dynamical properties of the erbium(III) ion in water have been obtained by means of ab initio quantum mechanical charge field molecular dynamics (QMCF-MD) simulations for the ground state and an excited state. The quality of the simulations has been monitored by recording UV/vis and Raman spectra of dilute solutions of ErCl3 and Er(NO3)3 in water and by comparison with EXAFS data from literature. Slight deviations between these data can be mainly attributed to relativistic effects, which are not sufficiently considered by the methodological framework. In both simulations, a mixture of coordination numbers eight and nine and a ligand exchange on the picosecond range are observed. The strength of the Er-ligand bond is considerably lower than that of trivalent transition metal ions but higher than that for La(III) and Ce(III) in aqueous solution. The main difference between ground state and excited state is the ligand exchange rate of the first shell. The second hydration shell is stable in both cases but with significantly different properties.
Towards hydrogen metallization: an Ab initio approach; Vers la metallisation de l`hydrogene: approche AB initio

Energy Technology Data Exchange (ETDEWEB)

Bernard, St

1998-12-31

The quest for metallic hydrogen is a major goal for both theoretical and experimental condensed matter physics. Hydrogen and deuterium have been compressed up to 200 GPa in diamond anvil cells, without any clear evidence for a metallic behaviour. Loubeyere has recently suggested that hydrogen could metallize, at pressures within experimental range, in a new Van der Waals compound: Ar(H{sub 2}){sub 2} which is characterized at ambient pressure by an open and anisotropic sublattice of hydrogen molecules, stabilized by an argon skeleton. This thesis deals with a detailed ab initio investigation, by Car-Parrinello molecular dynamics methods, of the evolution under pressure of this compound. In a last chapter, we go to much higher pressures and temperatures, in order to compare orbital and orbital free ab initio methods for the dense hydrogen plasma. (author) 109 refs.
Towards hydrogen metallization: an Ab initio approach; Vers la metallisation de l`hydrogene: approche AB initio

Energy Technology Data Exchange (ETDEWEB)

Bernard, St

1999-12-31

The quest for metallic hydrogen is a major goal for both theoretical and experimental condensed matter physics. Hydrogen and deuterium have been compressed up to 200 GPa in diamond anvil cells, without any clear evidence for a metallic behaviour. Loubeyere has recently suggested that hydrogen could metallize, at pressures within experimental range, in a new Van der Waals compound: Ar(H{sub 2}){sub 2} which is characterized at ambient pressure by an open and anisotropic sublattice of hydrogen molecules, stabilized by an argon skeleton. This thesis deals with a detailed ab initio investigation, by Car-Parrinello molecular dynamics methods, of the evolution under pressure of this compound. In a last chapter, we go to much higher pressures and temperatures, in order to compare orbital and orbital free ab initio methods for the dense hydrogen plasma. (author) 109 refs.
Phenomenological aspects of the cognitive rumination construct.

Science.gov (United States)

Meyer, Leonardo Fernandez; Taborda, José Geraldo Vernet; da Costa, Fábio Antônio; Soares, Ana Luiza Alfaya Galego; Mecler, Kátia; Valença, Alexandre Martins

2015-01-01

To evaluate the importance of phenomenological aspects of the cognitive rumination (CR) construct in current empirical psychiatric research. We searched SciELO, Scopus, ScienceDirect, MEDLINE, OneFile (GALE), SpringerLink, Cambridge Journals and Web of Science between February and March of 2014 for studies whose title and topic included the following keywords: cognitive rumination; rumination response scale; and self-reflection. The inclusion criteria were: empirical clinical study; CR as the main object of investigation; and study that included a conceptual definition of CR. The studies selected were published in English in biomedical journals in the last 10 years. Our phenomenological analysis was based on Karl Jaspers' General Psychopathology. Most current empirical studies adopt phenomenological cognitive elements in conceptual definitions. However, these elements do not seem to be carefully examined and are indistinctly understood as objective empirical factors that may be measured, which may contribute to misunderstandings about CR, erroneous interpretations of results and problematic theoretical models. Empirical studies fail when evaluating phenomenological aspects of the cognitive elements of the CR construct. Psychopathology and phenomenology may help define the characteristics of CR elements and may contribute to their understanding and hierarchical organization as a construct. A review of the psychopathology principles established by Jasper may clarify some of these issues.
Multiscale modeling of current-induced switching in magnetic tunnel junctions using ab initio spin-transfer torques

Science.gov (United States)

Ellis, Matthew O. A.; Stamenova, Maria; Sanvito, Stefano

2017-12-01

There exists a significant challenge in developing efficient magnetic tunnel junctions with low write currents for nonvolatile memory devices. With the aim of analyzing potential materials for efficient current-operated magnetic junctions, we have developed a multi-scale methodology combining ab initio calculations of spin-transfer torque with large-scale time-dependent simulations using atomistic spin dynamics. In this work we introduce our multiscale approach, including a discussion on a number of possible schemes for mapping the ab initio spin torques into the spin dynamics. We demonstrate this methodology on a prototype Co/MgO/Co/Cu tunnel junction showing that the spin torques are primarily acting at the interface between the Co free layer and MgO. Using spin dynamics we then calculate the reversal switching times for the free layer and the critical voltages and currents required for such switching. Our work provides an efficient, accurate, and versatile framework for designing novel current-operated magnetic devices, where all the materials details are taken into account.
The phase diagrams of KCaF3 and NaMgF3 by ab initio simulations

Science.gov (United States)

Jakymiw, Clément; Vočadlo, Lidunka; Dobson, David P.; Bailey, Edward; Thomson, Andrew R.; Brodholt, John P.; Wood, Ian G.; Lindsay-Scott, Alex

2018-04-01

ABF3 compounds have been found to make valuable low-pressure analogues for high-pressure silicate phases that are present in the Earth's deep interior and that may also occur in the interiors of exoplanets. The phase diagrams of two of these materials, KCaF3 and NaMgF3, have been investigated in detail by static ab initio computer simulations based on density functional theory. Six ABF3 polymorphs were considered, as follows: the orthorhombic perovskite structure (GdFeO3-type; space group Pbnm); the orthorhombic CaIrO3 structure ( Cmcm; commonly referred to as the "post-perovskite" structure); the orthorhombic Sb2S3 and La2S3 structures (both Pmcn); the hexagonal structure previously suggested in computer simulations of NaMgF3 ( P63/ mmc); the monoclinic structure found to be intermediate between the perovskite and CaIrO3 structures in CaRhO3 ( P21/ m). Volumetric and axial equations of state of all phases considered are presented. For KCaF3, as expected, the perovskite phase is shown to be the most thermodynamically stable at atmospheric pressure. With increasing pressure, the relative stability of the KCaF3 phases then follows the sequence: perovskite → La2S3 structure → Sb2S3 structure → P63/ mmc structure; the CaIrO3 structure is never the most stable form. Above about 2.6 GPa, however, none of the KCaF3 polymorphs are stable with respect to dissociation into KF and CaF2. The possibility that high-pressure KCaF3 polymorphs might exist metastably at 300 K, or might be stabilised by chemical substitution so as to occur within the standard operating range of a multi-anvil press, is briefly discussed. For NaMgF3, the transitions to the high-pressure phases occur at pressures outside the normal range of a multi-anvil press. Two different sequences of transitions had previously been suggested from computer simulations. With increasing pressure, we find that the relative stability of the NaMgF3 phases follows the sequence: perovskite → CaIrO3 structure → Sb2
Ab initio potential for solids

DEFF Research Database (Denmark)

Chetty, N.; Stokbro, Kurt; Jacobsen, Karsten Wedel

1992-01-01

. At the most approximate level, the theory is equivalent to the usual effective-medium theory. At all levels of approximation, every term in the total-energy expression is calculated ab initio, that is, without any fitting to experiment or to other calculations. Every step in the approximation procedure can...
Simulating the universe(s) II: phenomenology of cosmic bubble collisions in full general relativity

Energy Technology Data Exchange (ETDEWEB)

Wainwright, Carroll L.; Aguirre, Anthony [SCIPP and Department of Physics, University of California, 1156 High St., Santa Cruz, CA, 95064 (United States); Johnson, Matthew C. [Department of Physics and Astronomy, York University, 4700 Keele St., Toronto, On, M3J 1P3 Canada (Canada); Peiris, Hiranya V., E-mail: cwainwri@ucsc.edu, E-mail: mjohnson@perimeterinstitute.ca, E-mail: aguirre@scipp.ucsc.edu, E-mail: h.peiris@ucl.ac.uk [Department of Physics and Astronomy, University College London, Gower St., London, WC1E 6BT U.K. (United Kingdom)

2014-10-01

Observing the relics of collisions between bubble universes would provide direct evidence for the existence of an eternally inflating Multiverse; the non-observation of such events can also provide important constraints on inflationary physics. Realizing these prospects requires quantitative predictions for observables from the properties of the possible scalar field Lagrangians underlying eternal inflation. Building on previous work, we establish this connection in detail. We perform a fully relativistic numerical study of the phenomenology of bubble collisions in models with a single scalar field, computing the comoving curvature perturbation produced in a wide variety of models. We also construct a set of analytic predictions, allowing us to identify the phenomenologically relevant properties of the scalar field Lagrangian. The agreement between the analytic predictions and numerics in the relevant regions is excellent, and allows us to generalize our results beyond the models we adopt for the numerical studies. Specifically, the signature is completely determined by the spatial profile of the colliding bubble just before the collision, and the de Sitter invariant distance between the bubble centers. The analytic and numerical results support a power-law fit with an index 1< κ ∼< 2. For collisions between identical bubbles, we establish a lower-bound on the observed amplitude of collisions that is set by the present energy density in curvature.
Feasible and realiable ab initio atomistic modeling for nuclear waste management

Energy Technology Data Exchange (ETDEWEB)

Beridze, George

2016-07-01

, successful modeling of the important, from the long-term stability point of view, thermochemical and thermodynamical properties of the prospective nuclear waste forms, such as monazite- and pyrochlore-type ceramics. These include the heat capacities, the excess enthalpies of mixing or thermochemical parameters of phase transitions, to name but a few. The performed here benchmarking and application studies give a solid basis and paths for the quest to find and design computationally feasible ab initio computational methods, which would allow for reliable and meaningful simulations of materials relevant for nuclear waste management.
Feasible and realiable ab initio atomistic modeling for nuclear waste management

International Nuclear Information System (INIS)

Beridze, George

2016-01-01

, successful modeling of the important, from the long-term stability point of view, thermochemical and thermodynamical properties of the prospective nuclear waste forms, such as monazite- and pyrochlore-type ceramics. These include the heat capacities, the excess enthalpies of mixing or thermochemical parameters of phase transitions, to name but a few. The performed here benchmarking and application studies give a solid basis and paths for the quest to find and design computationally feasible ab initio computational methods, which would allow for reliable and meaningful simulations of materials relevant for nuclear waste management.
Book Review Psychotherapy and Phenomenology By Ian Rory ...

African Journals Online (AJOL)

Book Review Psychotherapy and Phenomenology By Ian Rory Owen (2006) ... Psychotherapy and Phenomenology: On Freud, Husserl and Heidegger. New York: iUniverse. Soft Cover (352 ... AJOL African Journals Online. HOW TO USE ...
Study on Exploration of Azeotropic Point of Pb-Sb Alloys by Vacuum Distillation and Ab Initio Molecular Dynamic Simulation

Science.gov (United States)

Song, Bingyi; Jiang, Wenlong; Yang, Bin; Chen, Xiumin; Xu, Baoqiang; Kong, Lingxin; Liu, Dachun; Dai, Yongnian

2016-10-01

The possibility of the separation of Pb-Sb alloys by vacuum distillation was investigated theoretically. The results show that Pb and Sb can be separated by vacuum distillation. However, the experimental results show that vacuum distillation technique does not provide clear separation. According to the literature, Pb-Sb alloys belong to azeotropic compounds under some certain temperature; the experiment and computer simulation were carried out based on the exceptional condition so as to analyze the reason from the experiment and microstructure of Pb-Sb alloys perspective. The separation of Pb-Sb alloys by vacuum distillation was experimentally carried out to probe the azeotropic point. Also, the functions, such as partial radial distributions functions, the structure factor, mean square displacement, and the density of state, were calculated by ab-initio molecular dynamics for the representation of the structure and properties of Pb-Sb alloys with different composition of Sb. The experimental results indicate that there exists common volatilization for Pb-Sb alloys when Sb content is 16.5 wt pct. On the other hand, the calculation results show that there is an intense interaction between Pb and Sb when Sb content is 22 wt pct, which supports the experimental results although Sb content is slightly deviation.
Spectroscopic study of uracil, 1-methyluracil and 1-methyl-4-thiouracil: Hydrogen bond interactions in crystals and ab-initio molecular dynamics

Science.gov (United States)

Brela, Mateusz Z.; Boczar, Marek; Malec, Leszek M.; Wójcik, Marek J.; Nakajima, Takahito

2018-05-01

Hydrogen bond networks in uracil, 1-methyluracil and 1-methyl-4-thiouracil were studied by ab initio molecular dynamics as well as analysis of the orbital interactions. The power spectra calculated by ab initio molecular dynamics for atoms involved in hydrogen bonds were analyzed. We calculated spectra by using anharmonic approximation based on the autocorrelation function of the atom positions obtained from the Born-Oppenheimer simulations. Our results show the differences between hydrogen bond networks in uracil and its methylated derivatives. The studied methylated derivatives, 1-methyluracil as well as 1-methyl-4-thiouracil, form dimeric structures in the crystal phase, while uracil does not form that kind of structures. The presence of sulfur atom instead oxygen atom reflects weakness of the hydrogen bonds that build dimers.
Phenomenological structure functions and Gribov-Lipatov relation

International Nuclear Information System (INIS)

Choudhary, D.K.; Misra, A.K.

1987-01-01

An analysis of the Giribov-Lipatov relation using the phenomenological forms of the structure function F 2 ep is made. The analysis indicate breakdown of the relation at PETRA energies. Plausible reasons of the breakdown of Gribov-Lipatov relation are discussed together with its phenomenological form. 33 refs., 6 figures. (author)
Monte Carlo simulation of asymmetrical growth of cube-shaped nanoparticles

International Nuclear Information System (INIS)

Wang Yuanyuan; Xie Huaqing; Wu Zihua; Xing Jiaojiao

2016-01-01

We simulated the asymmetrical growth of cube-shaped nanoparticles by applying the Monte Carlo method. The influence of the specific mechanisms on the crystal growth of nanoparticles has been phenomenologically described by efficient growth possibilities along different directions (or crystal faces). The roles of the thermodynamic and kinetic factors have been evaluated in three phenomenological models. The simulation results would benefit the understanding about the cause and manner of the asymmetrical growth of nanoparticles. (paper)
The promise of 'sporting bodies' in phenomenological thinking

DEFF Research Database (Denmark)

Ravn, Susanne; Høffding, Simon

2017-01-01

phenomenology to empirically investigate the domain of sport and exercise, phenomenologists employ empirical data to substantiate their claims concerning foundational conditions of our being-in-the-world. In this article, we suggest a way to enhance the collaboration between the two fields by pointing out......For decades, qualitative researchers have used phenomenological thinking to advance reflections on particular kinds of lifeworlds. As emphasised by Allen-Collinson phenomenology offers a continuing promise of ‘bringing the body back in’ to theories on sport and physical activity. Turning...... and giving examples of the resource of ‘the factual variation.’ Coined by Shaun Gallagher and developed from the Husserlian eidetic variation, the factual variation uses exceptional cases, normally from pathology, to shed new light on foundational phenomenological concepts. Drawing on our research of sports...
How to develop a phenomenological model of disability

DEFF Research Database (Denmark)

Martiny, Kristian Møller Moltke

2015-01-01

During recent decades various researchers from health and social sciences have been debating what it means for a person to be disabled. A rather overlooked approach has developed alongside this debate, primarily inspired by the philosophical tradition called phenomenology. This paper develops...... a phenomenological model of disability by arguing for a different methodological and conceptual framework from that used by the existing phenomenological approach. The existing approach is developed from the phenomenology of illness, but the paper illustrates how the case of congenital disabilities, looking...... at the congenital disorder called cerebral palsy (CP), presents a fundamental problem for the approach. In order to understand such congenital cases as CP, the experience of disability is described as being gradually different from, rather than a disruption of, the experience of being abled, and it is argued...
The Phenomenology of Small-Scale Turbulence

Science.gov (United States)

Sreenivasan, K. R.; Antonia, R. A.

I have sometimes thought that what makes a man's work classic is often just this multiplicity [of interpretations], which invites and at the same time resists our craving for a clear understanding. Wright (1982, p. 34), on Wittgenstein's philosophy Small-scale turbulence has been an area of especially active research in the recent past, and several useful research directions have been pursued. Here, we selectively review this work. The emphasis is on scaling phenomenology and kinematics of small-scale structure. After providing a brief introduction to the classical notions of universality due to Kolmogorov and others, we survey the existing work on intermittency, refined similarity hypotheses, anomalous scaling exponents, derivative statistics, intermittency models, and the structure and kinematics of small-scale structure - the latter aspect coming largely from the direct numerical simulation of homogeneous turbulence in a periodic box.
Phenomenological aspects of the cognitive rumination construct

Directory of Open Access Journals (Sweden)

Leonardo Fernandez Meyer

2015-03-01

Full Text Available Objective: To evaluate the importance of phenomenological aspects of the cognitive rumination (CR construct in current empirical psychiatric research.Method: We searched SciELO, Scopus, ScienceDirect, MEDLINE, OneFile (GALE, SpringerLink, Cambridge Journals and Web of Science between February and March of 2014 for studies whose title and topic included the following keywords: cognitive rumination; rumination response scale; and self-reflection. The inclusion criteria were: empirical clinical study; CR as the main object of investigation; and study that included a conceptual definition of CR. The studies selected were published in English in biomedical journals in the last 10 years. Our phenomenological analysis was based on Karl Jaspers' General Psychopathology.Results: Most current empirical studies adopt phenomenological cognitive elements in conceptual definitions. However, these elements do not seem to be carefully examined and are indistinctly understood as objective empirical factors that may be measured, which may contribute to misunderstandings about CR, erroneous interpretations of results and problematic theoretical models.Conclusion: Empirical studies fail when evaluating phenomenological aspects of the cognitive elements of the CR construct. Psychopathology and phenomenology may help define the characteristics of CR elements and may contribute to their understanding and hierarchical organization as a construct. A review of the psychopathology principles established by Jasper may clarify some of these issues.

Phenomenology and theory of confinement

International Nuclear Information System (INIS)

Pervushin, V.N.

1987-01-01

Phenomenological and theoretical arguments of the separation of the hadronization dynamics from confinement and the idea of the ''kinematic'' confinement are discussed. The recent theory contains results which point out that the Wilson criterion and the confinement potentials are not sufficient for explaining the phenomenological confinement in the sense of zero color amplitudes or Green functions. However, these potentials well explain the hadron spectrum and spontaneous breaking of chiral symmetry, i.e., the hadronization dynamics. The ''kinematic'' confinement can be explained by the topological degeneration of all color-particle physical states in QCD. This degeneration arises if the theory is quantized by explicitly solving the gauge and dynamic constraints: all color states are defined up to gauge(phase) factors describing the map of the three-dimensional space onto SU(3) c -group (π 3 (SU(3) c =Z). The total probability of the color particle generation is equal to zero due to the destructive interference of these phase factors. As a result, in QCD there remains only a hadron sector used in the phenomenology
Phenomenology of R-parity violating minimal supergravity

International Nuclear Information System (INIS)

Bernhardt, M.A.

2008-02-01

We investigate in detail the low-energy spectrum of the P 6 violating minimal supergravity model using the SOFTSUSY spectrum code. We impose the experimental constraints from the measurement of the anomalous magnetic moment of the muon (g-2) μ , the b→sγ decay, the branching ration of B s →μ + μ - , as well as the mass bound from direct searches at colliders, in particular the Higgs boson and the lightest Chargino. We focus on regions, where the lightest neutralino is not the lightest supersymmetric particle (LSP). In these regions of parameter space either the lightest scalar tau or one of the sneutrinos is the LSP. We suggest four benchmark points with typical spectra and novel collider signatures which we investigate with a parton level Monte-Carlo simulation. We give an outlook for their detailed phenomenological analysis and simulation by the LHC collaborations, then including detector effects. In addition, we discuss a full Monte-Carlo simulation for single slepton production in association with a single top quark via an LQD type operator at the hadron colliders LHC and Tevatron. We present these results and show a predicted range of detectability for this process- for small couplings in various minimal supergravity models at the LHC. (orig.)
Phenomenology of R-parity violating minimal supergravity

Energy Technology Data Exchange (ETDEWEB)

Bernhardt, M.A.

2008-02-15

We investigate in detail the low-energy spectrum of the P{sub 6} violating minimal supergravity model using the SOFTSUSY spectrum code. We impose the experimental constraints from the measurement of the anomalous magnetic moment of the muon (g-2){sub {mu}}, the b{yields}s{gamma} decay, the branching ration of B{sub s}{yields}{mu}{sup +}{mu}{sup -}, as well as the mass bound from direct searches at colliders, in particular the Higgs boson and the lightest Chargino. We focus on regions, where the lightest neutralino is not the lightest supersymmetric particle (LSP). In these regions of parameter space either the lightest scalar tau or one of the sneutrinos is the LSP. We suggest four benchmark points with typical spectra and novel collider signatures which we investigate with a parton level Monte-Carlo simulation. We give an outlook for their detailed phenomenological analysis and simulation by the LHC collaborations, then including detector effects. In addition, we discuss a full Monte-Carlo simulation for single slepton production in association with a single top quark via an LQD type operator at the hadron colliders LHC and Tevatron. We present these results and show a predicted range of detectability for this process- for small couplings in various minimal supergravity models at the LHC. (orig.)
Phenomenology as first philosophy | Allsobrook | South African ...

African Journals Online (AJOL)

The paper interprets phenomenology as a mode of inquiry that addresses fundamental questions of first philosophy, beyond the limitation of the practice by its leading theorists to the study of mere appearances. I draw on Adorno's critique of phenomenology to show that it has typically functioned as a mode of first ...
Heidegger’s phenomenology of the invisible

Directory of Open Access Journals (Sweden)

Andrzej SERAFIN

2016-12-01

Full Text Available Martin Heidegger has retrospectively characterized his philosophy as “phenomenology of the invisible”. This paradoxical formula suggests that the aim of his thinking was to examine the origin of the phenomena. Furthermore, Heidegger has also stated that his philosophy is ultimately motivated by a theological interest, namely the question of God’s absence. Following the guiding thread of those remarks, this essay analyzes the essential traits of Heidegger’s thought by interpreting them as an attempt to develop a phenomenology of the invisible. Heidegger’s attitude towards physics and metaphysics, his theory of truth, his reading of Aristotle, his concept of Dasein, his understanding of nothingness are all situated within the problematic context of the relation between the invisible and the revealed. Heidegger’s thought is thereby posited at the point of intersection of phenomenology, ontology, and theology.
The use of phenomenology in mental health nursing research.

Science.gov (United States)

Picton, Caroline Jane; Moxham, Lorna; Patterson, Christopher

2017-12-18

Historically, mental health research has been strongly influenced by the underlying positivism of the quantitative paradigm. Quantitative research dominates scientific enquiry and contributes significantly to understanding our natural world. It has also greatly benefitted the medical model of healthcare. However, the more literary, silent, qualitative approach is gaining prominence in human sciences research, particularly mental healthcare research. To examine the qualitative methodological assumptions of phenomenology to illustrate the benefits to mental health research of studying the experiences of people with mental illness. Phenomenology is well positioned to ask how people with mental illness reflect on their experiences. Phenomenological research is congruent with the principles of contemporary mental healthcare, as person-centred care is favoured at all levels of mental healthcare, treatment, service and research. Phenomenology is a highly appropriate and suitable methodology for mental health research, given it includes people's experiences and enables silent voices to be heard. This overview of the development of phenomenology informs researchers new to phenomenological enquiry. ©2017 RCN Publishing Company Ltd. All rights reserved. Not to be copied, transmitted or recorded in any way, in whole or part, without prior permission of the publishers.
Phenomenology tools on cloud infrastructures using OpenStack

International Nuclear Information System (INIS)

Campos, I.; Fernandez-del-Castillo, E.; Heinemeyer, S.; Lopez-Garcia, A.; Pahlen, F.; Borges, G.

2013-01-01

We present a new environment for computations in particle physics phenomenology employing recent developments in cloud computing. On this environment users can create and manage ''virtual'' machines on which the phenomenology codes/tools can be deployed easily in an automated way. We analyze the performance of this environment based on ''virtual'' machines versus the utilization of physical hardware. In this way we provide a qualitative result for the influence of the host operating system on the performance of a representative set of applications for phenomenology calculations. (orig.)
Phenomenology tools on cloud infrastructures using OpenStack

Science.gov (United States)

Campos, I.; Fernández-del-Castillo, E.; Heinemeyer, S.; Lopez-Garcia, A.; Pahlen, F.; Borges, G.

2013-04-01

We present a new environment for computations in particle physics phenomenology employing recent developments in cloud computing. On this environment users can create and manage "virtual" machines on which the phenomenology codes/tools can be deployed easily in an automated way. We analyze the performance of this environment based on "virtual" machines versus the utilization of physical hardware. In this way we provide a qualitative result for the influence of the host operating system on the performance of a representative set of applications for phenomenology calculations.
Quantum Gravity Phenomenology

OpenAIRE

Amelino-Camelia, Giovanni

2003-01-01

Comment: 9 pages, LaTex. These notes were prepared while working on an invited contribution to the November 2003 issue of Physics World, which focused on quantum gravity. They intend to give a non-technical introduction (accessible to readers from outside quantum gravity) to "Quantum Gravity Phenomenology"
Phenomenology tools on cloud infrastructures using OpenStack

Energy Technology Data Exchange (ETDEWEB)

Campos, I.; Fernandez-del-Castillo, E.; Heinemeyer, S.; Lopez-Garcia, A. [Instituto de Fisica de Cantabria (CSIC-UC), Santander (Spain); Pahlen, F. [Instituto de Fisica de Cantabria (CSIC-UC), Santander (Spain); University of Zaragoza, Instituto de Biocomputacion y Fisica de Sistemas Complejos - BIFI, Zaragoza (Spain); Borges, G. [Laboratorio de Instrumentacao e Fisica Experimental de Particulas - LIP, Lisbon (Portugal)

2013-04-15

We present a new environment for computations in particle physics phenomenology employing recent developments in cloud computing. On this environment users can create and manage ''virtual'' machines on which the phenomenology codes/tools can be deployed easily in an automated way. We analyze the performance of this environment based on ''virtual'' machines versus the utilization of physical hardware. In this way we provide a qualitative result for the influence of the host operating system on the performance of a representative set of applications for phenomenology calculations. (orig.)
The role of supersymmetry phenomenology in particle physics

International Nuclear Information System (INIS)

Wells, James D.

2000-01-01

Supersymmetry phenomenology is an important component of particle physics today. I provide a definition of supersymmetry phenomenology, outline the scope of its activity, and argue its legitimacy. This essay derives from a presentation given at the 2000 SLAC Summer Institute
The role of supersymmetry phenomenology in particle physics

OpenAIRE

Wells, James D.

2000-01-01

Supersymmetry phenomenology is an important component of particle physics today. I provide a definition of supersymmetry phenomenology, outline the scope of its activity, and argue its legitimacy. This essay derives from a presentation given at the 2000 SLAC Summer Institute.
Ab initio calculation of a global potential, vibrational energies, and wave functions for HCN/HNC, and a simulation of the (A-tilde)-(X-tilde) emission spectrum

Science.gov (United States)

Bowman, Joel M.; Gazdy, Bela; Bentley, Joseph A.; Lee, Timothy J.; Dateo, Christopher E.

1993-01-01

A potential energy surface for the HCN/HNC system which is a fit to extensive, high-quality ab initio, coupled-cluster calculations is presented. All HCN and HNC states with energies below the energy of the first delocalized state are reported and characterized. Vibrational transition energies are compared with all available experimental data on HCN and HNC, including high CH-overtone states up to 23,063/cm. A simulation of the (A-tilde)-(X-tilde) stimulated emission pumping (SEP) spectrum is also reported, and the results are compared to experiment. Franck-Condon factors are reported for odd bending states of HCN, with one quantum of vibrational angular momentum, in order to compare with the recent assignment by Jonas et al. (1992), on the basis of axis-switching arguments of a number of previously unassigned states in the SEP spectrum.
Deuteron stripping reactions using dirac phenomenology

Science.gov (United States)

Hawk, E. A.; McNeil, J. A.

2001-04-01

In this work deuteron stripping reactions are studied using the distorted wave born approximation employing dirac phenomenological potentials. In 1982 Shepard and Rost performed zero-range dirac phenomenological stripping calculations and found a dramatic reduction in the predicted cross sections when compared with similar nonrelativistic calculations. We extend the earlier work by including full finite range effects as well as the deuteron's internal D-state. Results will be compared with traditional nonrelativistic approaches and experimental data at low energy.
The Phenomenological Pomeron. What is it?

International Nuclear Information System (INIS)

Donnachie, A.

1994-01-01

The standard phenomenology of the soft pomeron is recalled. The evidence for the soft pomeron having a well-defined Parton content is outlined. The role of the pomeron in deep inelastic scattering at small x is discussed, and it is suggested that the standard phenomenology is incompatible with the HERA data. It is shown how minijets can be included naturally as part of the soft pomeron, and that they do not contribute separately to total cross sections
Research Method and Phenomenological Pedagogy. Reflections from Piero Bertolini

Directory of Open Access Journals (Sweden)

Luca Ghirotto

2016-10-01

Full Text Available Inspired by Husserlian phenomenology, Piero Bertolini defined the phenomenological pedagogy and education as a scientific discipline (Bertolini, 2005. This project remains an undetermined one as there is still room for defining its research methods. This article intends to propose a contribution to the discussion of research methodology, in line with the assumptions of Piero Bertolini (1988 phenomenological pedagogy. In particular, starting from the definition of phenomenological pedagogy and education, it aims to answer the question: what are the research strategies through which to build a viable and rigorous educational knowledge, able to grasp the personal transformation and development in a context of inter-subjectivity? Accordingly, I shall discuss data collection and analysis strategies.
Many-body optimization using an ab initio monte carlo method.

Science.gov (United States)

Haubein, Ned C; McMillan, Scott A; Broadbelt, Linda J

2003-01-01

Advances in computing power have made it possible to study solvated molecules using ab initio quantum chemistry. Inclusion of discrete solvent molecules is required to determine geometric information about solute/solvent clusters. Monte Carlo methods are well suited to finding minima in many-body systems, and ab initio methods are applicable to the widest range of systems. A first principles Monte Carlo (FPMC) method was developed to find minima in many-body systems, and emphasis was placed on implementing moves that increase the likelihood of finding minimum energy structures. Partial optimization and molecular interchange moves aid in finding minima and overcome the incomplete sampling that is unavoidable when using ab initio methods. FPMC was validated by studying the boron trifluoride-water system, and then the method was used to examine the methyl carbenium ion in water to demonstrate its application to solvation problems.
Understanding the Key Tenets of Heidegger’s Philosophy for Interpretive Phenomenological Research

Directory of Open Access Journals (Sweden)

Marcella Horrigan-Kelly

2016-11-01

Full Text Available Martin Heidegger’s phenomenology provides methodological guidance for qualitative researchers seeking to explicate the lived experience of study participants. However, most phenomenological researchers apply his philosophy loosely. This is not surprising because Heidegger’s phenomenological philosophy is challenging and the influence of his philosophy in shaping the conduct of interpretive phenomenological research is broadly debated. This article presents an exploration of Dasein, a key tenet of Martin Heidegger’s interpretive phenomenology and explicates its usefulness for phenomenological research. From this perspective, we present guidance for researchers planning to utilize Heidegger’s philosophy underpinning their research.
Relativistic phenomenological equations and transformation laws of relative coefficients

Directory of Open Access Journals (Sweden)

Patrizia Rogolino

2017-06-01

Full Text Available The aim of this paper is to derive the phenomenological equations in the context of special relativistic non-equilibrium thermodynamics with internal variables. In particular, after introducing some results developed in our previous paper, by means of classical non-equilibrium thermodynamic procedure and under suitable assumptions on the entropy density production, the phenomenological equations and transformation laws of phenomenological coefficients are derived. Finally, some symmetries of aforementioned coefficients are obtained.
Visual Arts as a Tool for Phenomenology

Directory of Open Access Journals (Sweden)

Anna S. CohenMiller

2017-12-01

Full Text Available In this article I explain the process and benefits of using visual arts as a tool within a transcendental phenomenological study. I present and discuss drawings created and described by four participants over the course of twelve interviews. Findings suggest the utility of visual arts methods within the phenomenological toolset to encourage participant voice through easing communication and facilitating understanding.

Structural properties of iron nitride on Cu(100): An ab-initio molecular dynamics study

KAUST Repository

Heryadi, Dodi

2011-01-01

Due to their potential applications in magnetic storage devices, iron nitrides have been a subject of numerous experimental and theoretical investigations. Thin films of iron nitride have been successfully grown on different substrates. To study the structural properties of a single monolayer film of FeN we have performed an ab-initio molecular dynamics simulation of its formation on a Cu(100) substrate. The iron nitride layer formed in our simulation shows a p4gm(2x2) reconstructed surface, in agreement with experimental results. In addition to its structural properties, we are also able to determine the magnetization of this thin film. Our results show that one monolayer of iron nitride on Cu(100) is ferromagnetic with a magnetic moment of 1.67 μ B. © 2011 Materials Research Society.
Neutron relativistic phenomenological and microscopic optical potential

International Nuclear Information System (INIS)

Shen Qing-biao; Feng Da-chun; Zhuo Yi-zhong

1991-01-01

In this paper, both the phenomenological and microscopic neutron relativistic optical potentials are presented. The global neutron relativistic phenomenological optical potential (RPOP) based on the available experimental data for various nuclei ranging from C to U with incident energies E n =20--1000 MeV has been obtained through an automatic search of the best parameters by computer. Then the nucleon relativistic microscopic optical potential (RMOP) is studied by utilizing the effective Lagrangian based on the popular Walecka model. Through comparison between the theoretical results and experimental data we shed some insight into both the RMOP and RPOP. Further improvement concerning how to combine the phenomenological potential with the microscopic one in order to reduce the number of free parameters appearing in the RPOP is suggested
Approximate deconvolution models of turbulence analysis, phenomenology and numerical analysis

CERN Document Server

Layton, William J

2012-01-01

This volume presents a mathematical development of a recent approach to the modeling and simulation of turbulent flows based on methods for the approximate solution of inverse problems. The resulting Approximate Deconvolution Models or ADMs have some advantages over more commonly used turbulence models – as well as some disadvantages. Our goal in this book is to provide a clear and complete mathematical development of ADMs, while pointing out the difficulties that remain. In order to do so, we present the analytical theory of ADMs, along with its connections, motivations and complements in the phenomenology of and algorithms for ADMs.
Phenomenology of stochastic exponential growth

Science.gov (United States)

Pirjol, Dan; Jafarpour, Farshid; Iyer-Biswas, Srividya

2017-06-01

Stochastic exponential growth is observed in a variety of contexts, including molecular autocatalysis, nuclear fission, population growth, inflation of the universe, viral social media posts, and financial markets. Yet literature on modeling the phenomenology of these stochastic dynamics has predominantly focused on one model, geometric Brownian motion (GBM), which can be described as the solution of a Langevin equation with linear drift and linear multiplicative noise. Using recent experimental results on stochastic exponential growth of individual bacterial cell sizes, we motivate the need for a more general class of phenomenological models of stochastic exponential growth, which are consistent with the observation that the mean-rescaled distributions are approximately stationary at long times. We show that this behavior is not consistent with GBM, instead it is consistent with power-law multiplicative noise with positive fractional powers. Therefore, we consider this general class of phenomenological models for stochastic exponential growth, provide analytical solutions, and identify the important dimensionless combination of model parameters, which determines the shape of the mean-rescaled distribution. We also provide a prescription for robustly inferring model parameters from experimentally observed stochastic growth trajectories.
The cruel and unusual phenomenology of solitary confinement.

Science.gov (United States)

Gallagher, Shaun

2014-01-01

What happens when subjects are deprived of intersubjective contact? This paper looks closely at the phenomenology and psychology of one example of that deprivation: solitary confinement. It also puts the phenomenology and psychology of solitary confinement to use in the legal context. Not only is there no consensus on whether solitary confinement is a "cruel and unusual punishment," there is no consensus on the definition of the term "cruel" in the use of that legal phrase. I argue that we can find a moral consensus on the meaning of "cruelty" by looking specifically at the phenomenology and psychology of solitary confinement.
The Role of Phenomenology of Merleau- ponty in Medicine

OpenAIRE

Somayeh Rafighi; Mohammad Asghari

2017-01-01

Today, phenomenology, with an emphasis on direct explanations with regard to the lived experience of people is interest of different areas. With emphasis on body, Merleau- Ponty's phenomenology is considered in medical science. In his phenomenology, Merleau- Ponty gives new definition of body and names it lived body. Lived body is against of mechanical body and is the central of subjectivity and being- in- the – world and included all of existential aspects of man. Such definition enable doct...
Phenomenological Intentionality meets an Ego-less State | Barnes ...

African Journals Online (AJOL)

When using the phenomenological method, one aims to capture the essential structures of lived experiences. It has been my experience that phenomenology does this well, when researching experiences that are lived through our bodily senses and understood with our minds. When trying to capture and describe ...
Comparative classical and 'ab initio' molecular dynamics study of molten and glassy germanium dioxide

International Nuclear Information System (INIS)

Hawlitzky, M; Horbach, J; Binder, K; Ispas, S; Krack, M

2008-01-01

A molecular dynamics (MD) study of the static and dynamic properties of molten and glassy germanium dioxide is presented. The interactions between the atoms are modeled by the classical pair potential proposed by Oeffner and Elliott (OE) (1998 Phys. Rev. B 58 14791). We compare our results to experiments and previous simulations. In addition, an 'ab initio' method, the so-called Car-Parrinello molecular dynamics (CPMD), is applied to check the accuracy of the structural properties, as obtained by the classical MD simulations with the OE potential. As in a similar study for SiO 2 , the structure predicted by CPMD is only slightly softer than that resulting from the classical MD. In contrast to earlier simulations, both the static structure and dynamic properties are in very good agreement with pertinent experimental data. MD simulations with the OE potential are also used to study the relaxation dynamics. As previously found for SiO 2 , for high temperatures the dynamics of molten GeO 2 is compatible with a description in terms of mode coupling theory
Towards hydrogen metallization: an Ab initio approach

International Nuclear Information System (INIS)

Bernard, St.

1998-01-01

The quest for metallic hydrogen is a major goal for both theoretical and experimental condensed matter physics. Hydrogen and deuterium have been compressed up to 200 GPa in diamond anvil cells, without any clear evidence for a metallic behaviour. Loubeyere has recently suggested that hydrogen could metallize, at pressures within experimental range, in a new Van der Waals compound: Ar(H 2 ) 2 which is characterized at ambient pressure by an open and anisotropic sublattice of hydrogen molecules, stabilized by an argon skeleton. This thesis deals with a detailed ab initio investigation, by Car-Parrinello molecular dynamics methods, of the evolution under pressure of this compound. In a last chapter, we go to much higher pressures and temperatures, in order to compare orbital and orbital free ab initio methods for the dense hydrogen plasma. (author)
Ab initio transport across bismuth selenide surface barriers

KAUST Repository

Narayan, Awadhesh

2014-11-24

© 2014 American Physical Society. We investigate the effect of potential barriers in the form of step edges on the scattering properties of Bi2Se3(111) topological surface states by means of large-scale ab initio transport simulations. Our results demonstrate the suppression of perfect backscattering, while all other scattering processes, which do not entail a complete spin and momentum reversal, are allowed. Furthermore, we find that the spin of the surface state develops an out-of-plane component as it traverses the barrier. Our calculations reveal the existence of quasibound states in the vicinity of the surface barriers, which appear in the form of an enhanced density of states in the energy window corresponding to the topological state. For double barriers we demonstrate the formation of quantum well states. To complement our first-principles results we construct a two-dimensional low-energy effective model and illustrate its shortcomings. Our findings are discussed in the context of a number of recent experimental works.
Single-ion 4f element magnetism: an ab-initio look at Ln(COT)2(-).

Science.gov (United States)

Gendron, Frédéric; Pritchard, Benjamin; Bolvin, Hélène; Autschbach, Jochen

2015-12-14

The electron densities associated with the Ln 4f shell, and spin and orbital magnetizations ('magnetic moment densities'), are investigated for the Ln(COT)2(-) series. The densities are obtained from ab-initio calculations including spin-orbit coupling. For Ln = Ce, Pr the magnetizations are also derived from crystal field models and shown to agree with the ab-initio results. Analysis of magnetizations from ab-initio calculations may be useful in assisting research on single molecule magnets.
Simulation and modelling of advanced Argentinian nuclear fuels

International Nuclear Information System (INIS)

Marino, A.; Losada, E.; Demarco, G.; Garces, J.; Marino, A.; Jaroszewicz, S.; Mosca, H.; Demarco, G.

2011-01-01

The BaCo code (Barra Combustible, Spanish expression for 'fuel rod') was developed to simulate the nuclear fuel rods behaviour under irradiation. The generation of nucleo electricity in Argentina is based on PHWR NPP and, as a consequence, BaCo is focused on PHWR fuels keeping full compatibility with PWR, WWER, among others type of fuels (commercial, experimental or prototypes). BaCo includes additional extensions for 3D calculations, statistical improvements, fuel design and batch analysis. Research on new fuels and cladding materials properties based on ab initio and multiscale modelling are currently under development to be included in BaCo simulations in order to be applied to Generation IV reactors. The ab initio and multiscale modelling can enhance the field of application of the code by including a strong physical basement covering the unavailable data needed for those improvements. (authors)
Women, Anger, and Aggression: An Interpretative Phenomenological Analysis

Science.gov (United States)

Eatough, Virginia; Smith, Jonathan A.; Shaw, Rachel

2008-01-01

This study reports a qualitative phenomenological investigation of anger and anger-related aggression in the context of the lives of individual women. Semistructured interviews with five women are analyzed using interpretative phenomenological analysis. This inductive approach aims to capture the richness and complexity of the lived experience of…
Elucidating the breathing of the metal-organic framework MIL-53(Sc) with ab initio molecular dynamics simulations and in situ X-ray powder diffraction experiments.

Science.gov (United States)

Chen, Linjiang; Mowat, John P S; Fairen-Jimenez, David; Morrison, Carole A; Thompson, Stephen P; Wright, Paul A; Düren, Tina

2013-10-23

Ab initio molecular dynamics (AIMD) simulations have been used to predict structural transitions of the breathing metal-organic framework (MOF) MIL-53(Sc) in response to changes in temperature over the range 100-623 K and adsorption of CO2 at 0-0.9 bar at 196 K. The method has for the first time been shown to predict successfully both temperature-dependent structural changes and the structural response to variable sorbate uptake of a flexible MOF. AIMD employing dispersion-corrected density functional theory accurately simulated the experimentally observed closure of MIL-53(Sc) upon solvent removal and the transition of the empty MOF from the closed-pore phase to the very-narrow-pore phase (symmetry change from P2(1)/c to C2/c) with increasing temperature, indicating that it can directly take into account entropic as well as enthalpic effects. We also used AIMD simulations to mimic the CO2 adsorption of MIL-53(Sc) in silico by allowing the MIL-53(Sc) framework to evolve freely in response to CO2 loadings corresponding to the two steps in the experimental adsorption isotherm. The resulting structures enabled the structure determination of the two CO2-containing intermediate and large-pore phases observed by experimental synchrotron X-ray diffraction studies with increasing CO2 pressure; this would not have been possible for the intermediate structure via conventional methods because of diffraction peak broadening. Furthermore, the strong and anisotropic peak broadening observed for the intermediate structure could be explained in terms of fluctuations of the framework predicted by the AIMD simulations. Fundamental insights from the molecular-level interactions further revealed the origin of the breathing of MIL-53(Sc) upon temperature variation and CO2 adsorption. These simulations illustrate the power of the AIMD method for the prediction and understanding of the behavior of flexible microporous solids.
Continuity of phenomenology and (in)consistency of content of meaningful autobiographical memories.

Science.gov (United States)

Luchetti, Martina; Rossi, Nicolino; Montebarocci, Ornella; Sutin, Angelina R

2016-05-01

Phenomenology is a critical component of autobiographical memory retrieval; it reflects both (a) memory-specific features and (b) stable individual differences. Few studies have tested phenomenology longitudinally. The present work examined the continuity of memory phenomenology in a sample of Italians adults (N=105) over a 4-week period. Participants retrieved two 'key' personal memories, a Turning Point and an Early Childhood Memory, rated the phenomenology of each memory, and completed measures of personality, psychological distress and subjective well-being. Phenomenological ratings were moderately stable over time (median correlation >.40), regardless of memory content. Personality traits, psychological distress and well-being were associated with phenomenology cross-sectionally and with changes in phenomenology over time. These results suggest that how individuals re-experience their most important personal memories is relatively consistent over time and shaped by both trait and state aspects of psychological functioning. Copyright © 2016 Elsevier Inc. All rights reserved.
Ab initio calculations of 3H(d,n)4He fusion

International Nuclear Information System (INIS)

Navratil, Petr; Quaglioni, Sofia

2012-01-01

We build a new ab initio many-body approach capable of describing simultaneously both bound and scattering states in light nuclei, by combining the resonating-group method with the ab initio no-core shell model. In this way, we complement a microscopic-cluster technique with the use of realistic interactions, and a microscopic and consistent description of the nucleon clusters. We will present the first results of the d- 3 H and d- 3 He fusion calculation obtained within our ab initio approach. We will also discuss our d- 4 He, 3 H- 4 He and 3 H- 3 H scattering calculations and the outline of the extension of the formalism to include three-cluster final states with the goal to calculate the 3 H( 3 H,2n) 4 He cross section
The cruel and unusual phenomenology of solitary confinement

Directory of Open Access Journals (Sweden)

Shaun eGallagher

2014-06-01

Full Text Available What happens when subjects are deprived of intersubjective contact? This paper looks closely at the phenomenology and psychology of one example of that deprivation: solitary confinement. It also puts the phenomenology and psychology of solitary confinement to use in the legal context. Not only is there no consensus on whether solitary confinement is a cruel and unusual punishment, there is no consensus on the definition of the term ‘cruel’ in the use of that legal phrase. I argue that we can find a moral consensus on the meaning of ‘cruelty’ by looking specifically at the phenomenology and psychology of solitary confinement.
Merleau-Ponty's Phenomenology of Language and General Semantics.

Science.gov (United States)

Lapointe, Francois H.

A survey of Maurice Merleau-Ponty's views on the phenomenology of language yields insight into the basic semiotic nature of language. Merleau-ponty's conceptions stand in opposition to Saussure's linguistic postulations and Korzybski's scientism. That is, if language is studied phenomenologically, the acts of speech and gesture take on greater…
Structure of the glass-forming metallic liquids by ab-initio and classical molecular dynamics, a case study: Quenching the Cu{sub 60}Ti{sub 20}Zr{sub 20} alloy

Energy Technology Data Exchange (ETDEWEB)

Amokrane, S.; Ayadim, A.; Levrel, L. [Groupe “Physique des Liquides et Milieux Complexes,” Faculté des Sciences et Technologie, Université Paris-Est (Créteil), 61 av. du Général de Gaulle, 94010 Créteil Cedex (France)

2015-11-21

We consider the question of the amorphization of metallic alloys by melt quenching, as predicted by molecular dynamics simulations with semi-empirical potentials. The parametrization of the potentials is discussed on the example of the ternary Cu-Ti-Zr transition metals alloy, using the ab-initio simulation as a reference. The pair structure in the amorphous state is computed from a potential of the Stillinger-Weber form. The transferability of the parameters during the quench is investigated using two parametrizations: from solid state data, as usual and from a new parametrization on the liquid structure. When the adjustment is made on the pair structure of the liquid, a satisfactory transferability is found between the pure components and their alloys. The liquid structure predicted in this way agrees well with experiment, in contrast with the one obtained using the adjustment on the solid. The final structure, after quenches down to the amorphous state, determined with the new set of parameters is shown to be very close to the ab-initio one, the latter being in excellent agreement with recent X-rays diffraction experiments. The corresponding critical temperature of the glass transition is estimated from the behavior of the heat capacity. Discussion on the consistency between the structures predicted using semi-empirical potentials and ab-initio simulation, and comparison of different experimental data underlines the question of the dependence of the final structure on the thermodynamic path followed to reach the amorphous state.
Kantian Feeling: Empirical Psychology, Transcendental Critique, and Phenomenology

Directory of Open Access Journals (Sweden)

Patrick Frierson

2016-06-01

Full Text Available This paper explores the relationship between empirical psychology, transcendental critique, and phenomenology in Kant’s discussion of respect for the moral law, particularly as that is found in the Critique of Practical Reason. I first offer an empirical-psychological reading of moral respect, in the context of which I distinguish transcendental and empirical perspectives on moral action and defend H. J. Paton’s claim that moral motivation can be seen from two points of view, where “from one point of view, [respect] is the cause of our action, but from another point of view the moral law is its ground.” Then, after a discussion of a distinction between first- and second-order transcendental/practical perspectives where reasons for action are first-order practical judgments while the conditions of possibility for those reasons’ authority are expressed in second-order judgments, I turn to a third kind of perspective: the properly phenomenological one. I explain the general notion of Kantian phenomenology with an example of the experience of time from Kant’s Anthropology before applying this to a phenomenological reading of the discussion of respect in the Critique of Practical Reason. I end by noting that on my account, in contrast to that of Jeanine Grenberg, the distinctive phenomenology of respect is not systematically important for grounding claims in moral philosophy.

Observing the amorphous-to-crystalline phase transition in Ge{sub 2}Sb{sub 2}Te{sub 5} non-volatile memory materials from ab initio molecular-dynamics simulations

Energy Technology Data Exchange (ETDEWEB)

Lee, T.H.; Elliott, S.R. [Department of Chemistry, University of Cambridge, Lensfield Road, CB2 1EW Cambridge (United Kingdom)

2012-10-15

Phase-change memory is a promising candidate for the next generation of non-volatile memory devices. This technology utilizes reversible phase transitions between amorphous and crystalline phases of a recording material, and has been successfully used in rewritable optical data storage, revealing its feasibility. In spite of the importance of understanding the nucleation and growth processes that play a critical role in the phase transition, this understanding is still incomplete. Here, we present observations of the early stages of crystallization in Ge{sub 2}Sb{sub 2}Te{sub 5} materials through ab initio molecular-dynamics simulations. Planar structures, including fourfold rings and planes, play an important role in the formation and growth of crystalline clusters in the amorphous matrix. At the same time, vacancies facilitate crystallization by providing space at the glass-crystalline interface for atomic diffusion, which results in fast crystal growth, as observed in simulations and experiments. The microscopic mechanism of crystallization presented here may deepen our understanding of the phase transition occurring in real devices, providing an opportunity to optimize the memory performance of phase-change materials. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Supersymmetry and Superstring Phenomenology

Energy Technology Data Exchange (ETDEWEB)

Gaillard, Mary K; Gaillard, Mary K.; Zumino, Bruno

2008-05-05

We briefly cover the early history of supersymmetry, describe the relation of SUSY quantum field theories to superstring theories and explain why they are considered a likely tool to describe the phenomenology of high energy particle theory beyond the Standard Model.
R-parity breaking phenomenology

International Nuclear Information System (INIS)

Vissani, F.

1996-02-01

We review various features of the R-parity breaking phenomenology, with particular attention to the low energy observables, and to the patterns of the R-parity breaking interactions that arise in Grand Unified models. (author). 22 refs, 1 fig., 3 tabs
Phenomenology and hermeneutics - poles apart?

DEFF Research Database (Denmark)

Keller, Kurt Dauer; Feilberg, Casper

A key dispute within qualitative methodology is the choice between top-down (deductive) and bottom-up (inductive) research approaches. Abduction, on the other hand, has received little attention, even though it would often seem to be a more promising methodology. The phenomenological tradition is...... to qualitative methodology. Thus, like abductive approaches, Ricoeur argues for the necessity of an interplay between explanatory theory and description of the lived understanding of the informant in the development of interpretation....... is marked by a similar dichotomy, whereas hermeneutical phenomenologists argue for the necessity of preunderstanding and theorethical perspectives (van Manen), Husserlian phenomenologists insist on the importance of the epoché together with reduction. The existential phenomenology of Heidegger and Merleau...
Ab Initio Nuclear Structure and Reaction Calculations for Rare Isotopes

Energy Technology Data Exchange (ETDEWEB)

Draayer, Jerry P. [Louisiana State Univ., Baton Rouge, LA (United States)

2014-09-28

We have developed a novel ab initio symmetry-adapted no-core shell model (SA-NCSM), which has opened the intermediate-mass region for ab initio investigations, thereby providing an opportunity for first-principle symmetry-guided applications to nuclear structure and reactions for nuclear isotopes from the lightest p-shell systems to intermediate-mass nuclei. This includes short-lived proton-rich nuclei on the path of X-ray burst nucleosynthesis and rare neutron-rich isotopes to be produced by the Facility for Rare Isotope Beams (FRIB). We have provided ab initio descriptions of high accuracy for low-lying (including collectivity-driven) states of isotopes of Li, He, Be, C, O, Ne, Mg, Al, and Si, and studied related strong- and weak-interaction driven reactions that are important, in astrophysics, for further understanding stellar evolution, X-ray bursts and triggering of s, p, and rp processes, and in applied physics, for electron and neutrino-nucleus scattering experiments as well as for fusion ignition at the National Ignition Facility (NIF).
Ab Initio Nuclear Structure and Reaction Calculations for Rare Isotopes

International Nuclear Information System (INIS)

Draayer, Jerry P.

2014-01-01

We have developed a novel ab initio symmetry-adapted no-core shell model (SA-NCSM), which has opened the intermediate-mass region for ab initio investigations, thereby providing an opportunity for first-principle symmetry-guided applications to nuclear structure and reactions for nuclear isotopes from the lightest p-shell systems to intermediate-mass nuclei. This includes short-lived proton-rich nuclei on the path of X-ray burst nucleosynthesis and rare neutron-rich isotopes to be produced by the Facility for Rare Isotope Beams (FRIB). We have provided ab initio descriptions of high accuracy for low-lying (including collectivity-driven) states of isotopes of Li, He, Be, C, O, Ne, Mg, Al, and Si, and studied related strong- and weak-interaction driven reactions that are important, in astrophysics, for further understanding stellar evolution, X-ray bursts and triggering of s, p, and rp processes, and in applied physics, for electron and neutrino-nucleus scattering experiments as well as for fusion ignition at the National Ignition Facility (NIF).
Researching Embodiment in Movement Contexts: A Phenomenological Approach

Science.gov (United States)

Standal, Oyvind F.; Engelsrud, Gunn

2013-01-01

This article takes a phenomenological approach to understanding embodiment in relation to teaching and learning taking place in movement contexts. Recently a number of studies have pointed to the potential that phenomenology has to understand the meanings and experiences of moving subjects. By presenting two examples of our own work on embodied…
Ab initio study on the dynamics of furfural at the liquid-solid interfaces

Science.gov (United States)

Dang, Hongli; Xue, Wenhua; Shields, Darwin; Liu, Yingdi; Jentoft, Friederike; Resasco, Daniel; Wang, Sanwu

2013-03-01

Catalytic biomass conversion sometimes occurs at the liquid-solid interfaces. We report ab initio molecular dynamics simulations at finite temperatures for the catalytic reactions involving furfural at the water-Pd and water-Cu interfaces. We found that, during the dynamic process, the furan ring of furfural prefers to be parallel to the Pd surface and the aldehyde group tends to be away from the Pd surface. On the other hand, at the water-Cu(111) interface, furfural prefers to be tilted to the Cu surface while the aldehyde group is bonded to the surface. In both cases, interaction of liquid water and furfural is identified. The difference of dynamic process of furfural at the two interfaces suggests different catalytic reaction mechanisms for the conversion of furfural, consistent with the experimental investigations. Supported by DOE (DE-SC0004600). Simulations and calculations were performed on XSED's and NERSC's supercomputers
Phenomenological and mechanistic modeling of melt-structure-water interactions in a light water reactor severe accident

International Nuclear Information System (INIS)

Bui, V.A.

1998-01-01

The objective of this work is to address the modeling of the thermal hydrodynamic phenomena and interactions occurring during the progression of reactor severe accidents. Integrated phenomenological models are developed to describe the accident scenarios, which consist of many processes, while mechanistic modeling, including direct numerical simulation, is carried out to describe separate effects and selected physical phenomena of particular importance
An ab initio and TD DFT

Indian Academy of Sciences (India)

The photophysical behaviour of N-(2-hydroxy benzylidene) aniline or most commonly known as salicylideneaniline (SA) has been investigated using the ab initio and DFT levels of theory. The quantum chemical calculations show that the optimized non planar enol (1) form of the SA molecule is the most stable conformer ...
Understanding the Key Tenets of Heidegger’s Philosophy for Interpretive Phenomenological Research

OpenAIRE

Marcella Horrigan-Kelly; Michelle Millar; Maura Dowling

2016-01-01

Martin Heidegger’s phenomenology provides methodological guidance for qualitative researchers seeking to explicate the lived experience of study participants. However, most phenomenological researchers apply his philosophy loosely. This is not surprising because Heidegger’s phenomenological philosophy is challenging and the influence of his philosophy in shaping the conduct of interpretive phenomenological research is broadly debated. This article presents an exploration of Dasein, a key tene...
Phenomenology and Qualitative Data Analysis Software (QDAS): A Careful Reconciliation

OpenAIRE

Brian Kelleher Sohn

2017-01-01

An oft-cited phenomenological methodologist, Max VAN MANEN (2014), claims that qualitative data analysis software (QDAS) is not an appropriate tool for phenomenological research. Yet phenomenologists rarely describe how phenomenology is to be done: pencil, paper, computer? DAVIDSON and DI GREGORIO (2011) urge QDAS contrarians such as VAN MANEN to get over their methodological loyalties and join the digital world, claiming that all qualitative researchers, whatever their methodology, perform p...
A classic case of Jahn–Teller effect theory revisited: Ab initio simulation of hyperfine coupling and pseudorotational tunneling in the 1"2E′ state of Na_3

International Nuclear Information System (INIS)

Hauser, Andreas W.; Pototschnig, Johann V.; Ernst, Wolfgang E.

2015-01-01

Highlights: • Multireference and Coupled Cluster methods are applied to Na_3. • The PES is characterized by an analytical function fitted to ab initio data. • An effective rovibrational Hamiltonian is set up, with all parameters derived ab initio. • The coupling of pseudorotational tunneling and hyperfine interactions is investigated. • The theoretical predictions are compared to microwave spectra. - Abstract: The predictive capabilities of current ab initio approaches are tested in a benchmark study on the well known case of the Na_3 ground state. This molecule is small enough to be treated with computationally demanding methods, but also shows an interesting interplay between Jahn–Teller-, spin-orbit-, rovibrational- and hyperfine-interactions. The necessary parameters for the effective Hamiltonian are derived from the potential energy surface of the 1"2E′ ground state and from spin density evaluations at selected geometries, without any fitting adjustments to experimental data. We compare our results to highly resolved microwave spectra, with the aim to improve previous assignment attempts, where some parameters had to be estimated from fits to measured spectra.
Nonadiabatic ab initio molecular dynamics of photoisomerization reaction between 1,3-cyclohexadiene and 1,3,5-cis-hexatriene

International Nuclear Information System (INIS)

Ohta, Ayumi; Kobayashi, Osamu; Danielache, Sebastian O.; Nanbu, Shinkoh

2015-01-01

Highlights: • The photoisomerization between cyclohexadiene and hexatriene was simulated. • Nonadiabatic ab initio MD simulations were employed to elucidate the mechanism. • Each excitations to S_1 and S_2 were simulated using full-dimensional model. • Specific molecular motions at CoIns and molecular vibrations on S_1 PES were found. • The one-sided product branching ratio was obtained at the photoexcitation to S_2. - Abstract: The photoisomerization process between 1,3-cyclohexadiene (CHD) and 1,3,5-cis-hexatriene (HT) has been studied by nonadiabatic ab initio molecular dynamics based on trajectory surface-hopping approach with a full-dimensional reaction model. The quantum chemical calculations were treated at MS-MR-CASPT2 level for 8 electrons in 8 orbitals with the cc-pVDZ basis set. The Zhu–Nakamura formula was employed to evaluate nonadiabatic transition probabilities. S_1 and S_2 states were included in the photoisomerization dynamics. Lifetimes and CHD:HT branching ratios were computationally estimated on the basis of statistical analysis of multiple executed trajectories. The analysis of trajectories suggested that the nonadiabatic transitions at the S_0/S_1 and S_1/S_2 conical intersections (CoIn) are correlated to the Kekulé-type vibration and the C3–C4–C5 bending motion, respectively. The one-sided branching ratio was obtained by excitations to the S_2 state; 70:30. The critical branching process was found to be dominated by the location of CoIn in potential energy hypersurface of the excited state.
Resonant diphoton phenomenology simplified

International Nuclear Information System (INIS)

Panico, Giuliano; Vecchi, Luca; Wulzer, Andrea

2016-01-01

A framework is proposed to describe resonant diphoton phenomenology at hadron colliders in full generality. It can be employed for a comprehensive model-independent interpretation of the experimental data. Within the general framework, few benchmark scenarios are defined as representative of the various phenomenological options and/or of motivated new physics scenarios. Their usage is illustrated by performing a characterization of the 750 GeV excess, based on a recast of available experimental results. We also perform an assessment of which properties of the resonance could be inferred, after discovery, by a careful experimental study of the diphoton distributions. These include the spin J of the new particle and its dominant production mode. Partial information on its CP-parity can also be obtained, but only for J≥2. The complete determination of the resonance CP properties requires studying the pattern of the initial state radiation that accompanies the resonant diphoton production.
Elastic dipoles of point defects from atomistic simulations

Science.gov (United States)

Varvenne, Céline; Clouet, Emmanuel

2017-12-01

The interaction of point defects with an external stress field or with other structural defects is usually well described within continuum elasticity by the elastic dipole approximation. Extraction of the elastic dipoles from atomistic simulations is therefore a fundamental step to connect an atomistic description of the defect with continuum models. This can be done either by a fitting of the point-defect displacement field, by a summation of the Kanzaki forces, or by a linking equation to the residual stress. We perform here a detailed comparison of these different available methods to extract elastic dipoles, and show that they all lead to the same values when the supercell of the atomistic simulations is large enough and when the anharmonic region around the point defect is correctly handled. But, for small simulation cells compatible with ab initio calculations, only the definition through the residual stress appears tractable. The approach is illustrated by considering various point defects (vacancy, self-interstitial, and hydrogen solute atom) in zirconium, using both empirical potentials and ab initio calculations.
Superstring inspired phenomenology

International Nuclear Information System (INIS)

Binetruy, P.

1988-01-01

Recent progress in superstring model building is reviewed with an emphasis on the general features of the models obtained. The problems associated with supersymmetry breaking and intermediate gauge symmetry breaking (M W I GUT ) are described. Finally, the phenomenology of these models is summarized, with a discussion of the role that new experimental results could play to help clearing up the above difficulties
Brane vector phenomenology

International Nuclear Information System (INIS)

Clark, T.E.; Love, S.T.; Nitta, Muneto; Veldhuis, T. ter; Xiong, C.

2009-01-01

Local oscillations of the brane world are manifested as massive vector fields. Their coupling to the Standard Model can be obtained using the method of nonlinear realizations of the spontaneously broken higher-dimensional space-time symmetries, and to an extent, are model independent. Phenomenological limits on these vector field parameters are obtained using LEP collider data and dark matter constraints
Difficulties Encountered in the Application of the Phenomenological ...

African Journals Online (AJOL)

While it is heartening to see that more researchers in the field of the social sciences are using some version of the phenomenological method, it is also disappointing to see that very often some of the steps employed do not follow phenomenological logic. In this paper, several dissertations are reviewed in order to point out ...
Thermodynamic properties by equation of state and from Ab initio molecular dynamics of liquid potassium under pressure

Science.gov (United States)

Li, Huaming; Tian, Yanting; Sun, Yongli; Li, Mo; Nonequilibrium materials; physics Team; Computational materials science Team

In this work, we apply a general equation of state of liquid and Ab initio molecular-dynamics method to study thermodynamic properties in liquid potassium under high pressure. Isothermal bulk modulus and molar volume of molten sodium are calculated within good precision as compared with the experimental data. The calculated internal energy data and the calculated values of isobaric heat capacity of molten potassium show the minimum along the isothermal lines as the previous result obtained in liquid sodium. The expressions for acoustical parameter and nonlinearity parameter are obtained based on thermodynamic relations from the equation of state. Both parameters for liquid potassium are calculated under high pressure along the isothermal lines by using the available thermodynamic data and numeric derivations. Furthermore, Ab initio molecular-dynamics simulations are used to calculate some thermodynamic properties of liquid potassium along the isothermal lines. Scientific Research Starting Foundation from Taiyuan university of Technology, Shanxi Provincial government (``100-talents program''), China Scholarship Council and National Natural Science Foundation of China (NSFC) under Grant No. 51602213.

Coding considerations for standalone molecular dynamics simulations of atomistic structures

Science.gov (United States)

Ocaya, R. O.; Terblans, J. J.

2017-10-01

The laws of Newtonian mechanics allow ab-initio molecular dynamics to model and simulate particle trajectories in material science by defining a differentiable potential function. This paper discusses some considerations for the coding of ab-initio programs for simulation on a standalone computer and illustrates the approach by C language codes in the context of embedded metallic atoms in the face-centred cubic structure. The algorithms use velocity-time integration to determine particle parameter evolution for up to several thousands of particles in a thermodynamical ensemble. Such functions are reusable and can be placed in a redistributable header library file. While there are both commercial and free packages available, their heuristic nature prevents dissection. In addition, developing own codes has the obvious advantage of teaching techniques applicable to new problems.
Ab initio velocity-field curves in monoclinic β-Ga2O3

Science.gov (United States)

Ghosh, Krishnendu; Singisetti, Uttam

2017-07-01

We investigate the high-field transport in monoclinic β-Ga2O3 using a combination of ab initio calculations and full band Monte Carlo (FBMC) simulation. Scattering rate calculation and the final state selection in the FBMC simulation use complete wave-vector (both electron and phonon) and crystal direction dependent electron phonon interaction (EPI) elements. We propose and implement a semi-coarse version of the Wannier-Fourier interpolation method [Giustino et al., Phys. Rev. B 76, 165108 (2007)] for short-range non-polar optical phonon (EPI) elements in order to ease the computational requirement in FBMC simulation. During the interpolation of the EPI, the inverse Fourier sum over the real-space electronic grids is done on a coarse mesh while the unitary rotations are done on a fine mesh. This paper reports the high field transport in monoclinic β-Ga2O3 with deep insight into the contribution of electron-phonon interactions and velocity-field characteristics for electric fields ranging up to 450 kV/cm in different crystal directions. A peak velocity of 2 × 107 cm/s is estimated at an electric field of 200 kV/cm.
Why natural science needs phenomenological philosophy.

Science.gov (United States)

Rosen, Steven M

2015-12-01

Through an exploration of theoretical physics, this paper suggests the need for regrounding natural science in phenomenological philosophy. To begin, the philosophical roots of the prevailing scientific paradigm are traced to the thinking of Plato, Descartes, and Newton. The crisis in modern science is then investigated, tracking developments in physics, science's premier discipline. Einsteinian special relativity is interpreted as a response to the threat of discontinuity implied by the Michelson-Morley experiment, a challenge to classical objectivism that Einstein sought to counteract. We see that Einstein's efforts to banish discontinuity ultimately fall into the "black hole" predicted in his general theory of relativity. The unavoidable discontinuity that haunts Einstein's theory is also central to quantum mechanics. Here too the attempt has been made to manage discontinuity, only to have this strategy thwarted in the end by the intractable problem of quantum gravity. The irrepressible discontinuity manifested in the phenomena of modern physics proves to be linked to a merging of subject and object that flies in the face of Cartesian philosophy. To accommodate these radically non-classical phenomena, a new philosophical foundation is called for: phenomenology. Phenomenological philosophy is elaborated through Merleau-Ponty's concept of depth and is then brought into focus for use in theoretical physics via qualitative work with topology and hypercomplex numbers. In the final part of this paper, a detailed summary is offered of the specific application of topological phenomenology to quantum gravity that was systematically articulated in The Self-Evolving Cosmos (Rosen, 2008a). Copyright © 2015. Published by Elsevier Ltd.
Ab-initio calculations of superconducting properties of YBa2Cu3O7

International Nuclear Information System (INIS)

Zhao, G.L.; Bagayoko, D.

1999-01-01

The authors present ab-initio calculations for the electronic structure and superconducting properties of YBa 2 Cu 3 O 7 (YBCO). The electronic structure was calculated using a self-consistent ab-initio LCAO method. They solved the anisotropic Eliashberg gap equation numerically. The strong coupling of the high energy optical phonons around 60--73 meV, with the electrons at the Fermi surface, leads to a high Tc in YBCO. The calculated Tc is about 89 K for μ* = 0.1. The good agreement of the calculated results with experimental measurements and the ab-initio nature of the calculations support the scenario of an anisotropic s-wave superconductor for YBCO
[An existential-phenomenological approach to consciousness].

Science.gov (United States)

Langle, A

2014-01-01

The human beings are characterized as subjects. Their essence is understood as Person. A treatment which does not consider the subjective and the Person would not correspond their essence. For a feeling and autonomous being, consciousness plays a role but cannot fully correspond the being a person. This has a therapeutic impact on the treatment of unconscious patients and gives the treatment a specific access. Some instructions for the therapeutic application of the phenomenological-existential concept and the phenomenological attitude towards unconscious or brain traumatized patients are given. The role of consciousness for being human is briefly reflected from an existential perspective.
Use of ab initio quantum chemical methods in battery technology

Energy Technology Data Exchange (ETDEWEB)

Deiss, E [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1997-06-01

Ab initio quantum chemistry can nowadays predict physical and chemical properties of molecules and solids. An attempt should be made to use this tool more widely for predicting technologically favourable materials. To demonstrate the use of ab initio quantum chemistry in battery technology, the theoretical energy density (energy per volume of active electrode material) and specific energy (energy per mass of active electrode material) of a rechargeable lithium-ion battery consisting of a graphite electrode and a nickel oxide electrode has been calculated with this method. (author) 1 fig., 1 tab., 7 refs.
Energetic, electronic and optical properties of lanthanide doped TiO2: An ab initio LDA+U study

CSIR Research Space (South Africa)

Mulwa, WM

2016-05-01

Full Text Available potential, J. Chem. Phys. 118 (2003) 8207. doi:10.1063/1.1564060. [23] X. Ren, Beyond LDA and GGA - Tackling exact exchange , hybrid functional , MP2 , and RPA with numeric atom-centered orbitals The Fritz-Haber-Institute ab initio molecular simulations.... Calzolari, A. Ruini, A. Catellani, Anchor Group versus Conjugation: Toward the Gap-State Engineering of Functionalized ZnO (101̅0) Surface for Optoelectronic Applications, J. Am. Chem. Soc. 133 (2011) 5893–5899. [36] R. Gillen, S.J. Clark, J. Robertson...
Ab Initio molecular dynamics with excited electrons

NARCIS (Netherlands)

Alavi, A.; Kohanoff, J.; Parrinello, M.; Frenkel, D.

1994-01-01

A method to do ab initio molecular dynamics suitable for metallic and electronically hot systems is described. It is based on a density functional which is costationary with the finite-temperature functional of Mermin, with state being included with possibly fractional occupation numbers.
Strong influence of coadsorbate interaction on CO desorption dynamics on Ru(0001) probed by ultrafast x-ray spectroscopy and ab initio simulations

Energy Technology Data Exchange (ETDEWEB)

Xin, H. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., Stanford, CA (United States); LaRue, J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Oberg, H. [Stockholm Univ., Stockholm (Sweden); Beye, M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Helmholtz Zentrum Berlin fur Materialien und Energie GmbH, Berlin (Germany); Dell' Angela, M. [Univ. of Hamburg and Center for Free Electron Laser Science, Hamburg (Germany); Turner, J. J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Gladh, J. [Stockholm Univ., Stockholm (Sweden); Ng, M. L. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Sellberg, J. A. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Helmholtz Zentrum Berlin fur Materialien und Energie GmbH, Berlin (Germany); Kaya, S. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Mercurio, G. [Univ. of Hamburg and Center for Free Electron Laser Science, Hamburg (Germany); Hieke, F. [Univ. of Hamburg and Center for Free Electron Laser Science, Hamburg (Germany); Nordlund, D. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Schlotter, W. F. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Dakovski, G. L. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Minitti, M. P. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Fohlisch, A. [Helmholtz Zentrum Berlin fur Materialien und Energie GmbH, Berlin (Germany); Univ. Potsdam, Potsdam (Germany); Wolf, M. [Fritz-Haber Institute of the Max-Planck-Society, Berlin (Germany); Wurth, W. [Univ. of Hamburg and Center for Free Electron Laser Science, Hamburg (Germany); DESY Photon Science, Hamburg (Germany); Ogasawara, H. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Norskov, J. K. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., Stanford, CA (United States); Ostrom, H. [Stockholm Univ., Stockholm (Sweden); Pettersson, L. G. M. [Stockholm Univ., Stockholm (Sweden); Nilsson, A. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stockholm Univ., Stockholm (Sweden); Ablid-Pedersen, F. [SLAC National Accelerator Lab., Menlo Park, CA (United States)

2015-04-16

We show that coadsorbed oxygen atoms have a dramatic influence on the CO desorption dynamics from Ru(0001). In contrast to the precursor-mediated desorption mechanism on Ru(0001), the presence of surface oxygen modifies the electronic structure of Ru atoms such that CO desorption occurs predominantly via the direct pathway. This phenomenon is directly observed in an ultrafast pump-probe experiment using a soft x-ray free-electron laser to monitor the dynamic evolution of the valence electronic structure of the surface species. This is supported with the potential of mean force along the CO desorption path obtained from density-functional theory calculations. Charge density distribution and frozen-orbital analysis suggest that the oxygen-induced reduction of the Pauli repulsion, and consequent increase of the dative interaction between the CO 5σ and the charged Ru atom, is the electronic origin of the distinct desorption dynamics. Ab initio molecular dynamics simulations of CO desorption from Ru(0001) and oxygen-coadsorbed Ru(0001) provide further insights into the surface bond-breaking process.
Ab Initio Calculations Of Light-Ion Reactions

International Nuclear Information System (INIS)

Navratil, P.; Quaglioni, S.; Roth, R.; Horiuchi, W.

2012-01-01

The exact treatment of nuclei starting from the constituent nucleons and the fundamental interactions among them has been a long-standing goal in nuclear physics. In addition to the complex nature of nuclear forces, one faces the quantum-mechanical many-nucleon problem governed by an interplay between bound and continuum states. In recent years, significant progress has been made in ab initio nuclear structure and reaction calculations based on input from QCD employing Hamiltonians constructed within chiral effective field theory. In this contribution, we present one of such promising techniques capable of describing simultaneously both bound and scattering states in light nuclei. By combining the resonating-group method (RGM) with the ab initio no-core shell model (NCSM), we complement a microscopic cluster approach with the use of realistic interactions and a microscopic and consistent description of the clusters. We discuss applications to light nuclei scattering, radiative capture and fusion reactions.
Phenomenological and mechanistic modeling of melt-structure-water interactions in a light water reactor severe accident

Energy Technology Data Exchange (ETDEWEB)

Bui, V.A

1998-10-01

The objective of this work is to address the modeling of the thermal hydrodynamic phenomena and interactions occurring during the progression of reactor severe accidents. Integrated phenomenological models are developed to describe the accident scenarios, which consist of many processes, while mechanistic modeling, including direct numerical simulation, is carried out to describe separate effects and selected physical phenomena of particular importance 88 refs, 54 figs, 7 tabs
Simulation of the microstructural evolution under irradiation of dilute Fe-CuNiMnSi alloys by atomic kinetic monte Carlo model based on ab initio data

International Nuclear Information System (INIS)

Vincent, E.; Domain, C.; Vincent, E.; Becquart, C.S.

2008-01-01

Full text of publication follows. The embrittlement and the hardening of pressure vessel steels under radiation has been correlated with the presence solutes such as Cu, Ni, Mn and Si. Indeed it has been observed that under irradiation, these solutes tend to gather to form more or less dilute clusters. The interactions of these solutes with radiation induced point defects thus need to be characterised properly in order to understand the elementary mechanisms behind the formation of these clusters. Ab initio calculations based on the density functional theory have been performed to determine the interactions of point defects (vacancies as well as interstitials) with solute atoms in dilute FeX alloys (X Cu, Mn, Ni or Si) in order to build a database used to parameterize an atomic kinetic Monte Carlo model. The model has been applied to simulate thermal ageing as well as irradiation conditions in dilute Fe-CuNiMnSi alloys. Results obtained with this model will be presented. (authors)
Cooperative effects in the structuring of fluoride water clusters: Ab initio hybrid quantum mechanical/molecular mechanical model incorporating polarizable fluctuating charge solvent

Science.gov (United States)

Bryce, Richard A.; Vincent, Mark A.; Malcolm, Nathaniel O. J.; Hillier, Ian H.; Burton, Neil A.

1998-08-01

A new hybrid quantum mechanical/molecular mechanical model of solvation is developed and used to describe the structure and dynamics of small fluoride/water clusters, using an ab initio wave function to model the ion and a fluctuating charge potential to model the waters. Appropriate parameters for the water-water and fluoride-water interactions are derived, with the fluoride anion being described by density functional theory and a large Gaussian basis. The role of solvent polarization in determining the structure and energetics of F(H2O)4- clusters is investigated, predicting a slightly greater stability of the interior compared to the surface structure, in agreement with ab initio studies. An extended Lagrangian treatment of the polarizable water, in which the water atomic charges fluctuate dynamically, is used to study the dynamics of F(H2O)4- cluster. A simulation using a fixed solvent charge distribution indicates principally interior, solvated states for the cluster. However, a preponderance of trisolvated configurations is observed using the polarizable model at 300 K, which involves only three direct fluoride-water hydrogen bonds. Ab initio calculations confirm this trisolvated species as a thermally accessible state at room temperature, in addition to the tetrasolvated interior and surface structures. Extension of this polarizable water model to fluoride clusters with five and six waters gave less satisfactory agreement with experimental energies and with ab initio geometries. However, our results do suggest that a quantitative model of solvent polarization is fundamental for an accurate understanding of the properties of anionic water clusters.
Molecular dynamics simulation, ab initio calculation, and size-selected anion photoelectron spectroscopy study of initial hydration processes of calcium chloride.

Science.gov (United States)

He, Zhili; Feng, Gang; Yang, Bin; Yang, Lijiang; Liu, Cheng-Wen; Xu, Hong-Guang; Xu, Xi-Ling; Zheng, Wei-Jun; Gao, Yi Qin

2018-06-14

To understand the initial hydration processes of CaCl 2 , we performed molecular simulations employing the force field based on the theory of electronic continuum correction with rescaling. Integrated tempering sampling molecular dynamics were combined with ab initio calculations to overcome the sampling challenge in cluster structure search and refinement. The calculated vertical detachment energies of CaCl 2 (H 2 O) n - (n = 0-8) were compared with the values obtained from photoelectron spectra, and consistency was found between the experiment and computation. Separation of the Cl-Ca ion pair is investigated in CaCl 2 (H 2 O) n - anions, where the first Ca-Cl ionic bond required 4 water molecules, and both Ca-Cl bonds are broken when the number of water molecules is larger than 7. For neutral CaCl 2 (H 2 O) n clusters, breaking of the first Ca-Cl bond starts at n = 5, and 8 water molecules are not enough to separate the two ion pairs. Comparing with the observations on magnesium chloride, it shows that separating one ion pair in CaCl 2 (H 2 O) n requires fewer water molecules than those for MgCl 2 (H 2 O) n . Coincidentally, the solubility of calcium chloride is higher than that of magnesium chloride in bulk solutions.
Interpretive and Critical Phenomenological Crime Studies: A Model Design

Science.gov (United States)

Miner-Romanoff, Karen

2012-01-01

The critical and interpretive phenomenological approach is underutilized in the study of crime. This commentary describes this approach, guided by the question, "Why are interpretive phenomenological methods appropriate for qualitative research in criminology?" Therefore, the purpose of this paper is to describe a model of the interpretive…
Edmund Husserl's Phenomenology of Habituality and Habitus

OpenAIRE

Moran, Dermot

2011-01-01

Habit is a key concept in Husserl’s genetic phenomenology. In this paper, I want to flesh out Husserl’s conception of habit (for which he employs a wide variety of terms including: Habitus, Habitualität, Gewohnheit, das Habituelle, Habe, Besitz, Sitte, Tradition) to illustrate the complexity, range and depth of the phenomenological treatment of habit. I shall show that Husserl was by no means offering a limited Cartesian intellectualist explication of habitual action, rather he attempted to c...
Ab initio nuclear structure - the large sparse matrix eigenvalue problem

Energy Technology Data Exchange (ETDEWEB)

Vary, James P; Maris, Pieter [Department of Physics, Iowa State University, Ames, IA, 50011 (United States); Ng, Esmond; Yang, Chao [Computational Research Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Sosonkina, Masha, E-mail: jvary@iastate.ed [Scalable Computing Laboratory, Ames Laboratory, Iowa State University, Ames, IA, 50011 (United States)

2009-07-01

The structure and reactions of light nuclei represent fundamental and formidable challenges for microscopic theory based on realistic strong interaction potentials. Several ab initio methods have now emerged that provide nearly exact solutions for some nuclear properties. The ab initio no core shell model (NCSM) and the no core full configuration (NCFC) method, frame this quantum many-particle problem as a large sparse matrix eigenvalue problem where one evaluates the Hamiltonian matrix in a basis space consisting of many-fermion Slater determinants and then solves for a set of the lowest eigenvalues and their associated eigenvectors. The resulting eigenvectors are employed to evaluate a set of experimental quantities to test the underlying potential. For fundamental problems of interest, the matrix dimension often exceeds 10{sup 10} and the number of nonzero matrix elements may saturate available storage on present-day leadership class facilities. We survey recent results and advances in solving this large sparse matrix eigenvalue problem. We also outline the challenges that lie ahead for achieving further breakthroughs in fundamental nuclear theory using these ab initio approaches.
Ab initio nuclear structure - the large sparse matrix eigenvalue problem

International Nuclear Information System (INIS)

Vary, James P; Maris, Pieter; Ng, Esmond; Yang, Chao; Sosonkina, Masha

2009-01-01

The structure and reactions of light nuclei represent fundamental and formidable challenges for microscopic theory based on realistic strong interaction potentials. Several ab initio methods have now emerged that provide nearly exact solutions for some nuclear properties. The ab initio no core shell model (NCSM) and the no core full configuration (NCFC) method, frame this quantum many-particle problem as a large sparse matrix eigenvalue problem where one evaluates the Hamiltonian matrix in a basis space consisting of many-fermion Slater determinants and then solves for a set of the lowest eigenvalues and their associated eigenvectors. The resulting eigenvectors are employed to evaluate a set of experimental quantities to test the underlying potential. For fundamental problems of interest, the matrix dimension often exceeds 10 10 and the number of nonzero matrix elements may saturate available storage on present-day leadership class facilities. We survey recent results and advances in solving this large sparse matrix eigenvalue problem. We also outline the challenges that lie ahead for achieving further breakthroughs in fundamental nuclear theory using these ab initio approaches.
Hydration structure and dynamics of a hydroxide ion in water clusters of varying size and temperature: Quantum chemical and ab initio molecular dynamics studies

International Nuclear Information System (INIS)

Bankura, Arindam; Chandra, Amalendu

2012-01-01

Highlights: ► A theoretical study of hydroxide ion-water clusters is carried for varying cluster size and temperature. ► The structures of OH − (H 2 O) n are found out through quantum chemical calculations for n = 4, 8, 16 and 20. ► The finite temperature behavior of the clusters is studied through ab initio dynamical simulations. ► The spectral features of OH modes (deuterated) and their dependence on hydrogen bonding states of water are discussed. ► The mechanism and kinetics of proton transfer processes in these anionic clusters are also investigated. - Abstract: We have investigated the hydration structure and dynamics of OH − (H 2 O) n clusters (n = 4, 8, 16 and 20) by means of quantum chemical and ab initio molecular dynamics calculations. Quantum chemical calculations reveal that the solvation structure of the hydroxide ion transforms from three and four-coordinated surface states to five-coordinated interior state with increase in cluster size. Several other isomeric structures with energies not very different from the most stable isomer are also found. Ab initio simulations show that the most probable configurations at higher temperatures need not be the lowest energy isomeric structure. The rates of proton transfer in these clusters are found to be slower than that in bulk water. The vibrational spectral calculations reveal distinct features for free OH (deuterated) stretch modes of water in different hydrogen bonding states. Effects of temperature on the structural and dynamical properties are also investigated for the largest cluster considered here.
Phenomenology of BWR fuel assembly degradation

Science.gov (United States)

Kurata, Masaki; Barrachin, Marc; Haste, Tim; Steinbrueck, Martin

2018-03-01

Severe accidents occurred at the Fukushima-Daiichi Nuclear Power Station (FDNPS) which required an immediate re-examination of fuel degradation phenomenology. The present paper reviews the updated knowledge on the phenomenology of the fuel degradation, focusing mainly on the BWR fuel assembly degradation at the macroscopic scale and that of the individual interactions at the meso-scale. Oxidation of boron carbide (B4C) control rods potentially generates far larger amounts of heat and hydrogen under BWR accident conditions. All integral tests with B4C control rods or control blades have shown early failure, liquefaction, relocation and oxidation of B4C starting at temperatures around 1250 °C, well below the significant interaction temperatures of UO2-Zry. These interactions or reactions potentially influence the progress of fuel degradation in the early phase. The steam-starved conditions, which are being discussed as a likely scenario at the FDNPS accident, highly influence the individual interactions and potentially lead the fuel degradation in non-prototypical directions. The detailed phenomenology of individual interactions and their influence on the transient and on the late phase of the severe accidents are also discussed.

The end of what? Phenomenology vs. speculative realism

DEFF Research Database (Denmark)

Zahavi, Dan

2016-01-01

Phenomenology has recently come under attack from proponents of speculative realism. In this paper, I present and assess the criticism, and argue that it is either superficial and simplistic or lacks novelty.......Phenomenology has recently come under attack from proponents of speculative realism. In this paper, I present and assess the criticism, and argue that it is either superficial and simplistic or lacks novelty....
Looking Inward: Philosophical and Methodological Perspectives on Phenomenological Self-Reflection.

Science.gov (United States)

Pool, Natalie M

2018-07-01

Engaging in early and ongoing self-reflection during interpretive phenomenological research is critical for ensuring trustworthiness or rigor. However, the lack of guidelines and clarity about the role of self-reflection in this methodology creates both theoretical and procedural confusion. The purpose of this article is to describe key philosophical underpinnings, characteristics, and hallmarks of the process of self-reflection in interpretive phenomenological investigation and to provide a list of guidelines that facilitate this process. Excerpts from an interpretive phenomenological study are used to illustrate characteristics of quality self-reflection. The guidelines are intended to be particularly beneficial for novice researchers who may find self-reflective writing to be daunting and unclear. Facilitating use of self-reflection may strengthen both the interpretive phenomenological body of work as well as that of all qualitative research.
Introducing Postphenomenological Research: A Brief and Selective Sketch of Phenomenological Research Methods

Science.gov (United States)

Aagaard, Jesper

2017-01-01

In time, phenomenology has become a viable approach to conducting qualitative studies in education. Popular and well-established methods include descriptive and hermeneutic phenomenology. Based on critiques of the essentialism and receptivity of these two methods, however, this article offers a third variation of empirical phenomenology:…
In-medium no-core shell model for ab initio nuclear structure calculations

International Nuclear Information System (INIS)

Gebrerufael, Eskendr

2017-01-01

In this work, we merge two successful ab initio nuclear-structure methods, the no-core shell model (NCSM) and the multi-reference in-medium similarity renormalization group (IM-SRG), to define a novel many-body approach for the comprehensive description of ground and excited states of closed- and open-shell medium-mass nuclei. Building on the key advantages of the two methods - the decoupling of excitations at the many-body level in the IM-SRG, and the exact diagonalization in the NCSM applicable up to medium-light nuclei - their combination enables fully converged no-core calculations for an unprecedented range of nuclei and observables at moderate computational cost. The efficiency and rapid model-space convergence of the new approach make it ideally suited for ab initio studies of ground and low-lying excited states of nuclei up to the medium-mass regime. Interactions constructed within the framework of chiral effective field theory provide an excellent opportunity to describe properties of nuclei from first principles, i.e., rooted in quantum chromodynamics, they overcome the lack of predictive power of phenomenological potentials. The hard core of these interactions causes strong short-range correlations, which we soften by using the similarity-renormalization-group transformation that accelerates the model-space convergence of many-body calculations. Three-nucleon effects, which are mandatory for the correct description of bulk properties of nuclei, are included in our calculations by using the normal-ordered two-body approximation, which has been shown to be sufficient to capture the main effects of the three-nucleon interaction. Using these interactions, we analyze energies of ground and excited states in the carbon and oxygen isotopic chains, where conventional NCSM calculations are still feasible and provide an important benchmark. Furthermore, we study the Hoyle state in 12 C - a three-alpha cluster state that cannot be converged in standard NCSM
Towards a Relational Phenomenology of Violence.

Science.gov (United States)

Staudigl, Michael

This article elaborates a relational phenomenology of violence. Firstly, it explores the constitution of all sense in its intrinsic relation with our embodiment and intercorporality. Secondly, it shows how this relational conception of sense and constitution paves the path for an integrative understanding of the bodily and symbolic constituents of violence. Thirdly, the author addresses the overall consequences of these reflections, thereby identifying the main characteristics of a relational phenomenology of violence. In the final part, the paper provides an exemplification of the outlined conception with regard to a concrete phenomenon of violence, i.e., slapping, and a concluding reflection upon its overall significance for research on violence.
Light Higgs bosons in phenomenological NMSSM

International Nuclear Information System (INIS)

Mahmoudi, F.; Rathsman, J.; Zeune, L.; Goettingen Univ.

2010-12-01

We consider scenarios in the next-to-minimal supersymmetric model (NMSSM) where the CP-odd and charged Higgs bosons are very light. As we demonstrate, these can be obtained as simple deformations of existing phenomenological MSSM benchmarks scenarios with parameters defined at the weak scale. This offers a direct and meaningful comparison to the MSSM case. Applying a wide set of up-to-date constraints from both high-energy collider and flavour physics, the Higgs boson masses and couplings are studied in viable parts of parameter space. The LHC phenomenology of the light Higgs scenario for neutral and charged Higgs boson searches is discussed. (orig.)
Light Higgs bosons in phenomenological NMSSM

Energy Technology Data Exchange (ETDEWEB)

Mahmoudi, F. [CERN, Geneva (Switzerland); Clermont Univ., CNRS/IN2P3, LPC, Clermont-Ferrand (France); Rathsman, J. [Uppsala Univ. (Sweden). High-Energy Physics; Lund Univ. (Sweden). Theoretical High Energy Physics; Staal, O. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Zeune, L. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Goettingen Univ. (Germany). II. Physikalisches Inst.

2010-12-15

We consider scenarios in the next-to-minimal supersymmetric model (NMSSM) where the CP-odd and charged Higgs bosons are very light. As we demonstrate, these can be obtained as simple deformations of existing phenomenological MSSM benchmarks scenarios with parameters defined at the weak scale. This offers a direct and meaningful comparison to the MSSM case. Applying a wide set of up-to-date constraints from both high-energy collider and flavour physics, the Higgs boson masses and couplings are studied in viable parts of parameter space. The LHC phenomenology of the light Higgs scenario for neutral and charged Higgs boson searches is discussed. (orig.)
Sarnet lecture notes on nuclear reactor severe accident phenomenology

International Nuclear Information System (INIS)

Trambauer, K.; Adroguer, B.; Fichot, F.; Muller, C.; Meyer, L.; Breitung, W.; Magallon, D.; Journeau, C.; Alsmeyer, H.; Housiadas, C.; Clement, B.; Ang, M.L.; Chaumont, B.; Ivanov, I.; Marguet, S.; Van Dorsselaere, J.P.; Fleurot, J.; Giordano, P.; Cranga, M.

2008-01-01

The 'Severe Accident Phenomenology Short Course' is part of the Excellence Spreading activities of the European Severe Accident Research NETwork of Excellence SARNET (project of the EURATOM 6. Framework programme). It was held at Cadarache, 9-13 January 2006. The course was divided in 14 lectures covering all aspects of severe accident phenomena that occur during a scenario. It also included lectures on PSA-2, Safety Assessment and design measures in new LWR plants for severe accident mitigation (SAM). This book presents the lecture notes of the Severe Accident Phenomenology Short Course and condenses the essential knowledge on severe accident phenomenology in 2008. (authors)
Double-walled silicon nanotubes: an ab initio investigation

Science.gov (United States)

Lima, Matheus P.

2018-02-01

The synthesis of silicon nanotubes realized in the last decade demonstrates multi-walled tubular structures consisting of Si atoms in {{sp}}2 and the {{sp}}3 hybridizations. However, most of the theoretical models were elaborated taking as the starting point {{sp}}2 structures analogous to carbon nanotubes. These structures are unfavorable due to the natural tendency of the Si atoms to undergo {{sp}}3. In this work, through ab initio simulations based on density functional theory, we investigated double-walled silicon nanotubes proposing layered tubes possessing most of the Si atoms in an {{sp}}3 hybridization, and with few {{sp}}2 atoms localized at the outer wall. The lowest-energy structures have metallic behavior. Furthermore, the possibility to tune the band structure with the application of a strain was demonstrated, inducing a metal-semiconductor transition. Thus, the behavior of silicon nanotubes differs significantly from carbon nanotubes, and the main source of the differences is the distortions in the lattice associated with the tendency of Si to make four chemical bonds.
The Pu–U–Am system: An ab initio informed CALPHAD thermodynamic study

International Nuclear Information System (INIS)

Perron, A.; Turchi, P.E.A.; Landa, A.; Söderlind, P.; Ravat, B.; Oudot, B.; Delaunay, F.

2015-01-01

Highlights: • The ab initio informed CALPHAD assessment of the Am–U system has been realized. • A strong tendency toward phase separation across the whole composition range is predicted. • The ab initio informed Pu–U–Am thermodynamic database has been developed. • The solubility of Am and U in the liquid phase is improved by adding Pu. • The δ-Pu (fcc) phase is strongly stabilized by Am, on the contrary to the bcc phase. - Abstract: Phase diagram and thermodynamic properties of the Am–U system, that are experimentally unknown, are calculated using the CALPHAD method with input from ab initio electronic-structure calculations for the fcc and bcc phases. A strong tendency toward phase separation across the whole composition range is predicted. In addition, ab initio informed Pu–U and Am–Pu thermodynamic assessments are combined to build a Pu–U–Am thermodynamic database. Regarding the Pu-rich corner of the ternary system, predictions indicate that Am acts as a powerful δ-Pu (fcc) stabilizer. In the U-rich corner, similar predictions are made but to a lesser extent. In both cases, the bcc phase is destabilized and the fcc phase is enhanced. Finally, results and methodology are discussed and compared with previous assessments and guidelines are provided for further experimental studies
The Pu–U–Am system: An ab initio informed CALPHAD thermodynamic study

Energy Technology Data Exchange (ETDEWEB)

Perron, A., E-mail: perron1@llnl.gov [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Turchi, P.E.A.; Landa, A.; Söderlind, P. [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Ravat, B.; Oudot, B.; Delaunay, F. [CEA-Centre de Valduc, 21120 Is sur Tille (France)

2015-03-15

Highlights: • The ab initio informed CALPHAD assessment of the Am–U system has been realized. • A strong tendency toward phase separation across the whole composition range is predicted. • The ab initio informed Pu–U–Am thermodynamic database has been developed. • The solubility of Am and U in the liquid phase is improved by adding Pu. • The δ-Pu (fcc) phase is strongly stabilized by Am, on the contrary to the bcc phase. - Abstract: Phase diagram and thermodynamic properties of the Am–U system, that are experimentally unknown, are calculated using the CALPHAD method with input from ab initio electronic-structure calculations for the fcc and bcc phases. A strong tendency toward phase separation across the whole composition range is predicted. In addition, ab initio informed Pu–U and Am–Pu thermodynamic assessments are combined to build a Pu–U–Am thermodynamic database. Regarding the Pu-rich corner of the ternary system, predictions indicate that Am acts as a powerful δ-Pu (fcc) stabilizer. In the U-rich corner, similar predictions are made but to a lesser extent. In both cases, the bcc phase is destabilized and the fcc phase is enhanced. Finally, results and methodology are discussed and compared with previous assessments and guidelines are provided for further experimental studies.
PHENOMENOLOGICAL INTERPRETATION OF BIOETHICAL REALITY (THE SOCIOLOGICAL ANALYSIS)

OpenAIRE

Nikulina Marina Alekseevna

2012-01-01

The interpretation of social reality is a classical problem of sociology, which solution helps perception and understanding of social phenomena. In the article phenomenological interpretation of bioethical reality is shown. Phenomenological sociology, being one of the perspective directions of development of social knowledge, it is characterized by aspiration to show «artificial», that is designed, nature of bioethical reality, its semantic structure, and thus, to «humanize» bioethical realit...
Ab Initio Atomistic Thermodynamics for Surfaces: A Primer

National Research Council Canada - National Science Library

Rogal, Jutta; Reuter, Karsten

2006-01-01

.... These techniques are referred to as first-principles (or in latin: ab initio) to indicate that they do not rely on empirical or fitted parameters, which then makes them applicable for a wide range of realistic conditions...
Examining the Lived World: The Place of Phenomenology in ...

African Journals Online (AJOL)

This paper aims to explore the validity of phenomenology in the psychiatric setting. The phenomenological method - as a mode of research, a method of engagement between self and other, and a framework for approaching what it means to know - has found a legitimate home in therapeutic practice. Over the last century, ...
Global sensitivity analysis of a phenomenological wastewater treatment plant influent generator. 8th IWA Symposium on Systems Analysis and Integrated Assessment

DEFF Research Database (Denmark)

Flores-Alsina, Xavier; Gernaey, Krist; Jeppsson, Ulf

2011-01-01

The objective of this paper is to present the results of a global sensitivity analysis (GSA) of a phenomenological model that generates wastewater treatment plant (WWTP) dynamic influent disturbance scenarios. This influent model is part of the Benchmark Simulation Model no 2 (BSM2) and creates r...
The Phenomenology of Democracy

Science.gov (United States)

Shaw, Robert

2009-01-01

Human beings originate votes, and democracy constitutes decisions. This is the essence of democracy. A phenomenological analysis of the vote and of the decision reveals for us the inherent strength of democracy and its deficiencies. Alexis de Tocqueville pioneered this form of enquiry into democracy and produced positive results from it.…
Phenomenology and Neuroaesthetics

Directory of Open Access Journals (Sweden)

Elio Franzini

2015-05-01

Full Text Available Phenomenology is not the simple description of a fact, but rather the description of an intentional immanent moment, and it presents itself as a science of essences, and not of matter of facts. The Leib, the lived body of the phenomenological tradition, is not a generic corporeal reality, but rather an intentional subject, a transcendental reference point, on the base of which the connections between physical body and psychic body should be grasped. So, the reduction of empathy to mirror neurons amounts to an “objectivisation”, with the consequent absolutisation of a process that is a function of the Leib as intentional subject, not as a physical reality. The main task of the philosophical research, bracketed by the new “neuro” researches, thus emphasizing their theoretical limits as soon as they depart from experimental enquiries, is then to understand the conditions of possibility of cognitive procedures, that is to say, in other words, the genesis of consciousness, that in aesthetics becomes “the genesis of aesthetic consciousness”. Interdisciplinarity is already an ancient and out of fashion word, now it is the time of “dialogue”, being aware however that the “logoi” not always require synthesis, and that the unity of the corporeal reality implies, as Husserl emphasizes, very different descriptive behaviours.
Electronic Structure of Hydrogenated and Surface-Modified GaAs Nanocrystals: Ab Initio Calculations

Directory of Open Access Journals (Sweden)

Hamsa Naji Nasir

2012-01-01

Full Text Available Two methods are used to simulate electronic structure of gallium arsenide nanocrystals. The cluster full geometrical optimization procedure which is suitable for small nanocrystals and large unit cell that simulates specific parts of larger nanocrystals preferably core part as in the present work. Because of symmetry consideration, large unit cells can reach sizes that are beyond the capabilities of first method. The two methods use ab initio Hartree-Fock and density functional theory, respectively. The results show that both energy gap and lattice constant decrease in their value as the nanocrystals grow in size. The inclusion of surface part in the first method makes valence band width wider than in large unit cell method that simulates the core part only. This is attributed to the broken symmetry and surface passivating atoms that split surface degenerate states and adds new levels inside and around the valence band. Bond length and tetrahedral angle result from full geometrical optimization indicate good convergence to the ideal zincblende structure at the centre of hydrogenated nanocrystal. This convergence supports large unit cell methodology. Existence of oxygen atoms at nanocrystal surface melts down density of states and reduces energy gap.
Supersymmetry and supergravity: Phenomenology and grand unification

International Nuclear Information System (INIS)

Arnowitt, R.; Nath, P.

1993-01-01

A survey is given of supersymmetry and supergravity and their phenomenology. Some of the topics discussed are the basic ideas of global supersymmetry, the minimal supersymmetric Standard Model (MSSM) and its phenomenology, the basic ideas of local supersymmetry (supergravity), grand unification, supersymmetry breaking in supergravity grand unified models, radiative breaking of SU(2) x U(1), proton decay, cosmological constraints, and predictions of supergravity grand unified models. While the number of detailed derivations are necessarily limited, a sufficient number of results are given so that a reader can get a working knowledge of this field
Time-resolved photoelectron spectroscopy and ab initio multiple spawning studies of hexamethylcyclopentadiene

DEFF Research Database (Denmark)

Wolf, T. J. A.; Kuhlman, Thomas Scheby; Schalk, O.

2014-01-01

Time-resolved photoelectron spectroscopy and ab initio multiple spawning were applied to the ultrafast non-adiabatic dynamics of hexamethylcyclopentadiene. The high level of agreement between experiment and theory associates wavepacket motion with a distinct degree of freedom.......Time-resolved photoelectron spectroscopy and ab initio multiple spawning were applied to the ultrafast non-adiabatic dynamics of hexamethylcyclopentadiene. The high level of agreement between experiment and theory associates wavepacket motion with a distinct degree of freedom....

Liquid Segregation Phenomenological Behaviors of Ti14 Alloy during Semisolid Deformation

Directory of Open Access Journals (Sweden)

Y. N. Chen

2014-05-01

Full Text Available The liquid segregation phenomenon and its effect on deformation mechanism of Ti14 alloy in semisolid metal processing were investigated by thermal simulation test. Microstructure of depth profile was determined by cross-section quantitative metallography, and liquid segregation phenomenon was described by Darcy's law. The results show that segregation phenomenon was affected by solid fraction, strain rate, and deformation rate. More liquid segregated from center to edge portion with high strain rate and/or deformation ratio as well as low solid fraction, which caused different distribution of dominating deformation mechanism. The relationship between liquid segregation and main deformation mechanism was also discussed by phenomenological model.
[Social actors and phenomenologic modelling].

Science.gov (United States)

Laflamme, Simon

2012-05-01

The phenomenological approach has a quasi-monopoly in the individual and subjectivity analyses in social sciences. However, the conceptual apparatus associated with this approach is very restrictive. The human being has to be understood as rational, conscious, intentional, interested, and autonomous. Because of this, a large dimension of human activity cannot be taken into consideration: all that does not fit into the analytical categories (nonrational, nonconscious, etc.). Moreover, this approach cannot really move toward a relational analysis unless it is between individuals predefined by its conceptual apparatus. This lack of complexity makes difficult the establishment of links between phenomenology and systemic analysis in which relation (and its derivatives such as recursiveness, dialectic, correlation) plays an essential role. This article intends to propose a way for systemic analysis to apprehend the individual with respect to his complexity.
Phenomenology of unified gauge theories

International Nuclear Information System (INIS)

Ellis, J.

1983-01-01

Part I of these lectures treats the standard Glashow-Weinberg-Salam model of weak and electromagnetic interactions, discussing in turn its basic structure and weak neutral currents, charged currents, mixing angles and CP violation, and the phenomenology of weak vector and Higgs bosons. Part II of the lectures discusses the structure of theories of dynamical symmetry breaking such as technicolour, phenomenological consequences, frustrations and alternatives. The third part of these lectures offers the standard menu of grand unified theories (GUTs) of the strong, weak and electromagnetic interactions, including an hors d'oeuvre of constraints on the parameters of the standard model, a main course of baryon number violating processes, and desserts which violate lepton number and CP. The fourth and final part goes through different attempts to remedy the inadequacies of previous theories by invoking supersymmetry and reaching out towards gravitation. (orig./HSI)
Phenomenological aspects of mirage mediation

Energy Technology Data Exchange (ETDEWEB)

Loewen, Valeri

2009-07-15

We consider the possibility that string theory vacua with spontaneously broken supersymmetry and a small positive cosmological constant arise due to hidden sector matter interactions, known as F-uplifting/F-downlifting. We analyze this procedure in a model-independent way in the context of type IIB and heterotic string theory. Our investigation shows that the uplifting/downlifting sector has very important consequences for the resulting phenomenology. Not only does it adjust the vacuum energy, but it can also participate in the process of moduli stabilization. In addition, we find that this sector is the dominant source of supersymmetry breaking. It leads to a hybrid mediation scheme and its signature is a relaxed mirage pattern of the soft supersymmetry breaking terms. The low energy spectra exhibit distinct phenomenological properties and di er from conventional schemes considered so far. (orig.)
Phenomenological aspects of mirage mediation

International Nuclear Information System (INIS)

Loewen, Valeri

2009-07-01

We consider the possibility that string theory vacua with spontaneously broken supersymmetry and a small positive cosmological constant arise due to hidden sector matter interactions, known as F-uplifting/F-downlifting. We analyze this procedure in a model-independent way in the context of type IIB and heterotic string theory. Our investigation shows that the uplifting/downlifting sector has very important consequences for the resulting phenomenology. Not only does it adjust the vacuum energy, but it can also participate in the process of moduli stabilization. In addition, we find that this sector is the dominant source of supersymmetry breaking. It leads to a hybrid mediation scheme and its signature is a relaxed mirage pattern of the soft supersymmetry breaking terms. The low energy spectra exhibit distinct phenomenological properties and di er from conventional schemes considered so far. (orig.)
Supplementary Material for Finding the Stable Structures of N1-xWX with an Ab-initio High-Throughput Approach

Science.gov (United States)

2015-05-08

Supplementary material for “Finding the stable structures of N1−xWX with an ab - initio high-throughput approach” Michael J. Mehl∗ Center for...AND SUBTITLE Supplementary Material for ’Finding the Stable Structures of N1-xWX with an ab - initio High-throughput Approach’ 5a. CONTRACT NUMBER 5b...and J. Hafner, Ab initio molecular dynamics for open-shell transition metals, Phys. Rev. B 48, 13115–13118 (1993). 2 G. Kresse and J. Hafner, Ab initio
The Silica-Water Interface from the Analysis of Molecular Dynamic Simulations

KAUST Repository

Lardhi, Sheikha F.

2013-01-01

detailed understanding of the silica-water interface. In this study, we investigate the details of this interaction at microscopic level by analyzing trajectories obtained with ab initio molecular dynamic simulations. The system we consider consists of bulk
Ab initio interionic potentials for NaCl by multiple lattice inversion

International Nuclear Information System (INIS)

Zhang Shuo; Chen Nanxian

2002-01-01

Based on the Chen-Moebius lattice inversion and a series of pseudopotential total-energy curves, a different method is presented to derive the ab initio interionic pair potentials for B1-type ionic crystals. Comparing with the experimental data, the static properties of B1- and B2-type NaCl are well reproduced by the interionic potentials. Moreover, the phase stability of B1-NaCl has been described by the energy minimizations from the global deformed and disturbed states. The molecular-dynamics simulations for the molten NaCl indicate that the calculated mean-square displacements, radial distribution function, and diffusion coefficients gain good agreements with the experimental results. It can be concluded that the inversion pair potentials are valid over a wide range of interionic separations for describing the structural properties of B1-type ionic crystals
Phenomenology of School Leaders' Experiences of Ethical Dilemmas

OpenAIRE

Guy, Timothy Michael

2016-01-01

This research study explores the intersection of school leadership and ethics. This study used the hermeneutic phenomenological approach described by Max Van Manen (1990, 2014) to explore the question: How do school leaders experience ethical dilemmas in their role as school leaders? Hermeneutic phenomenology seeks to find the meaning of a phenomenon, which in this case is the experience of an ethical dilemma. Hermeneutic refers to the interpretive-reflective-analytical component and phenom...
Foregrounding the relational domain - phenomenology, enactivism and care ethics

Czech Academy of Sciences Publication Activity Database

Urban, Petr

2016-01-01

Roč. 5, č. 1 (2016), s. 171-182 ISSN 2226-5260 R&D Projects: GA ČR(CZ) GA16-23046S Institutional support: RVO:67985955 Keywords : phenomenology * care ethics * phenomenological ethics * enactivism * the lived body * intersubjectivity * relationality Subject RIV: AA - Philosophy ; Religion http://horizon.spb.ru/index.php?option=com_content&view=article&id=1038&lang=en
Atomic carbon chains as spin-transmitters: An ab initio transport study

DEFF Research Database (Denmark)

Fürst, Joachim Alexander; Brandbyge, Mads; Jauho, Antti-Pekka

2010-01-01

An atomic carbon chain joining two graphene flakes was recently realized in a ground-breaking experiment by Jin et al. (Phys. Rev. Lett., 102 (2009) 205501). We present ab initio results for the electron transport properties of such chains and demonstrate complete spin-polarization of the transmi......An atomic carbon chain joining two graphene flakes was recently realized in a ground-breaking experiment by Jin et al. (Phys. Rev. Lett., 102 (2009) 205501). We present ab initio results for the electron transport properties of such chains and demonstrate complete spin...
Indo-Pacific Journal of Phenomenology - Vol 1, No 1 (2001)

African Journals Online (AJOL)

Phenomenological Research Method, Design and Procedure: A Phenomenological Investigation of the Phenomenon of Being-in-Community as Experienced by Two Individuals Who Have Participated in a Community Building Workshop · EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT · DOWNLOAD FULL TEXT ...
On Being a Juror: A Phenomenological Self-Study | Fortune | Indo ...

African Journals Online (AJOL)

Phenomenological inquiry offers a vehicle for transcending conventional disciplinary boundaries and investigative settings. Van Manen's protocol writing offers a hermeneutic tool for human scientific phenomenological research that is ideal for the empirical realm of everyday lived experience. Underlying this approach is ...
Phenomenology beyond the standard model

Energy Technology Data Exchange (ETDEWEB)

Lykken, Joseph D.; /Fermilab

2005-03-01

An elementary review of models and phenomenology for physics beyond the Standard Model (excluding supersymmetry). The emphasis is on LHC physics. Based upon a talk given at the ''Physics at LHC'' conference, Vienna, 13-17 July 2004.
Augmented wave ab initio EFG calculations: some methodological warnings

International Nuclear Information System (INIS)

Errico, Leonardo A.; Renteria, Mario; Petrilli, Helena M.

2007-01-01

We discuss some accuracy aspects inherent to ab initio electronic structure calculations in the understanding of nuclear quadrupole interactions. We use the projector augmented wave method to study the electric-field gradient (EFG) at both Sn and O sites in the prototype cases SnO and SnO 2 . The term ab initio is used in the standard context of the also called first principles methods in the framework of the Density Functional Theory. As the main contributions of EFG calculations to problems in condensed matter physics are related to structural characterizations on the atomic scale, we discuss the 'state of the art' on theoretical EFG calculations and make a brief critical review on the subject, calling attention to some fundamental theoretical aspects
Augmented wave ab initio EFG calculations: some methodological warnings

Energy Technology Data Exchange (ETDEWEB)

Errico, Leonardo A. [Departamento de Fisica-IFLP (CONICET), Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CC67 (1900) La Plata (Argentina); Renteria, Mario [Departamento de Fisica-IFLP (CONICET), Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CC67 (1900) La Plata (Argentina); Petrilli, Helena M. [Instituto de Fisica-DFMT, Universidade de Sao Paulo, C.P. 66318, 05315-970 Sao Paulo, SP (Brazil)]. E-mail: hmpetril@macbeth.if.usp.br

2007-02-01

We discuss some accuracy aspects inherent to ab initio electronic structure calculations in the understanding of nuclear quadrupole interactions. We use the projector augmented wave method to study the electric-field gradient (EFG) at both Sn and O sites in the prototype cases SnO and SnO{sub 2}. The term ab initio is used in the standard context of the also called first principles methods in the framework of the Density Functional Theory. As the main contributions of EFG calculations to problems in condensed matter physics are related to structural characterizations on the atomic scale, we discuss the 'state of the art' on theoretical EFG calculations and make a brief critical review on the subject, calling attention to some fundamental theoretical aspects.
Formation Dynamics of Potassium-Based Graphite Intercalation Compounds: An Ab Initio Study

Science.gov (United States)

Jiang, Xiankai; Song, Bo; Tománek, David

2018-04-01

This paper is a contribution to the Physical Review Applied collection in memory of Mildred S. Dresselhaus. We use ab initio molecular dynamics simulations to study the microscopic dynamics of potassium intercalation in graphite. Upon adsorbing on graphite from the vapor phase, K atoms transfer their valence charge to the substrate. K atoms adsorbed on the surface diffuse rapidly along the graphene basal plane and eventually enter the interlayer region following a "U -turn" across the edge, gaining additional energy. This process is promoted at higher coverages associated with higher K pressure, leading to the formation of a stable intercalation compound. We find that the functionalization of graphene edges is an essential prerequisite for intercalation since bare edges reconstruct and reconnect, closing off the entry channels for the atoms.
Interpretation of the U L3-edge EXAFS in uranium dioxide using molecular dynamics and density functional theory simulations

International Nuclear Information System (INIS)

Bocharov, Dmitry; Chollet, Melanie; Krack, Matthias; Bertsch, Johannes; Grolimund, Daniel; Martin, Matthias; Kuzmin, Alexei; Purans, Juris; Kotomin, Eugene

2016-01-01

X-ray absorption spectroscopy is employed to study the local structure of pure and Cr-doped UO 2 at 300 K. The U L 3 -edge EXAFS spectrum is interpreted within the multiplescattering (MS) theory using the results of the classical and ab initio molecular dynamics simulations, allowing us to validate the accuracy of theoretical models. The Cr K-edge XANES is simulated within the full-multiple-scattering formalism considering a substitutional model (Cr at U site). It is shown that both unrelaxed and relaxed structures, produced by ab initio density functional theory (DFT) calculations, fail to describe the experiment. (paper)
Bullies and Victims: A Phenomenological Study

Science.gov (United States)

Omizo, Michael M.; Omizo, Sharon A.; Baxa, Gari-Vic C. O.; Miyose, Ross J.

2006-01-01

This study presents the results of a phenomenological study with sixteen elementary school children identified as bullies or victims. Implications for school counselors and educators are also discussed.
AB INITIO Modeling of Thermomechanical Properties of Mo-Based Alloys for Fossil Energy Conversion

Energy Technology Data Exchange (ETDEWEB)

Ching, Wai-Yim

2013-12-31

In this final scientific/technical report covering the period of 3.5 years started on July 1, 2011, we report the accomplishments on the study of thermo-mechanical properties of Mo-based intermetallic compounds under NETL support. These include computational method development, physical properties investigation of Mo-based compounds and alloys. The main focus is on the mechanical and thermo mechanical properties at high temperature since these are the most crucial properties for their potential applications. In particular, recent development of applying ab initio molecular dynamic (AIMD) simulations to the T1 (Mo{sub 5}Si{sub 3}) and T2 (Mo{sub 5}SiB{sub 2}) phases are highlighted for alloy design in further improving their properties.

Study of hydrogen-molecule guests in type II clathrate hydrates using a force-matched potential model parameterised from ab initio molecular dynamics

Science.gov (United States)

Burnham, Christian J.; Futera, Zdenek; English, Niall J.

2018-03-01

The force-matching method has been applied to parameterise an empirical potential model for water-water and water-hydrogen intermolecular interactions for use in clathrate-hydrate simulations containing hydrogen guest molecules. The underlying reference simulations constituted ab initio molecular dynamics (AIMD) of clathrate hydrates with various occupations of hydrogen-molecule guests. It is shown that the resultant model is able to reproduce AIMD-derived free-energy curves for the movement of a tagged hydrogen molecule between the water cages that make up the clathrate, thus giving us confidence in the model. Furthermore, with the aid of an umbrella-sampling algorithm, we calculate barrier heights for the force-matched model, yielding the free-energy barrier for a tagged molecule to move between cages. The barrier heights are reasonably large, being on the order of 30 kJ/mol, and are consistent with our previous studies with empirical models [C. J. Burnham and N. J. English, J. Phys. Chem. C 120, 16561 (2016) and C. J. Burnham et al., Phys. Chem. Chem. Phys. 19, 717 (2017)]. Our results are in opposition to the literature, which claims that this system may have very low barrier heights. We also compare results to that using the more ad hoc empirical model of Alavi et al. [J. Chem. Phys. 123, 024507 (2005)] and find that this model does very well when judged against the force-matched and ab initio simulation data.
AB INITIO calculations of magneto-optical effects

Czech Academy of Sciences Publication Activity Database

Kuneš, Jan; Oppeneer, P. M.

2002-01-01

Roč. 2, - (2002), s. 141-146 ISSN 1346-7948 R&D Projects: GA AV ČR IAA1010214 Institutional research plan: CEZ:AV0Z1010914 Keywords : electronic structure * ab initio calculation * polar magneto-optical Kerr effect * transitiom metal * uranium intermetallics * CrO 2 Subject RIV: BM - Solid Matter Physics ; Magnetism
Unraveling the structure of the h-BN/Rh(111) nanomesh with ab initio calculations

International Nuclear Information System (INIS)

Laskowski, R; Blaha, P

2008-01-01

The properties of a single layer of h-BN on top of a Rh(111) surface are discussed in terms of an ab initio generated force field approach as well as by direct ab initio density-functional theory (DFT) calculations. A single-layer model for the h-BN/Rh(111) nanomesh, in contrast to a previously considered (incomplete) double-layer model of h-BN, can explain the experimental data. The main focus of this work is to compare a force field approach described earlier in (Laskowski et al 2007 Phys. Rev. Lett. 98 106802) with direct ab initio calculations. The calculated geometry of the h-BN layer is very similar to the structure predicted by the force field approach. The ab initio calculated density of states projected on N-p x,y of BN corresponding to 'low' and 'high' regions with respect to the Rh surface shows a 1 eV splitting and thus explains the observed σ-band splitting. Moreover, we find good agreement between calculated and experimental scanning tunneling microscope (STM) images of this system
Computer simulations of small semiconductor and metal clusters

International Nuclear Information System (INIS)

Andreoni, W.

1991-01-01

A brief survey is presented of recent simulations of small clusters, made with both ab-initio and classical approaches, with particular emphasis on the application of the Car-Parrinello method. The discussion mainly focusses on the structural properties of a variety of materials and on the effects of temperature. (orig.)
The Cure for Civiliter Mortuus: Complementary Values of Phenomenology and Democracy

Directory of Open Access Journals (Sweden)

Mindaugas Briedis

2011-03-01

Full Text Available The core of this article is the ancient question concerning the individual person in relation to his/her society. This fundamental question of ethics and political philosophy is approached from the perspective of phenomenological philosophy. Hence, this article is an attempt to conjoin two prima facie inconsistent (because of category mistake types of attitude towards reality and action, e.g. democracy and phenomenology. The thesis states that there is a common ground between the basic features of phenomenological method and the fundamental values of democracy. This paper explores the arguments that establish this parallelism between the values of democracy and phenomenology. One of the outcomes of this analysis will be the sketch of a new kind of virtue ethics and a new type of citizen, concerning new approaches to identity problem. In this respect method of phenomenology can be used as a technique (phronesis for a future citizenship. On the other hand, this perspective helps to reevaluate the treasures of antique democracy and compare them with contemporary transformations of democracy in political, social and everyday spheres.
Digital simulation of an enrichment process for solutions by means of an advection-diffusion chamber

International Nuclear Information System (INIS)

Artucio, G.; Suarez, R.; Uruguay Catholic University)

1995-01-01

An ab-initio digital simulation of the space-time dynamics of the concentration field of a solute in an advection-diffusion chamber is done. Some questions related to the digital simulation of the concentration field using the analytical solution obtained in a previous paper are discussed
Phenomenology and the Empirical Turn

NARCIS (Netherlands)

Zwier, Jochem; Blok, Vincent; Lemmens, Pieter

2016-01-01

This paper provides a phenomenological analysis of postphenomenological philosophy of technology. While acknowledging that the results of its analyses are to be recognized as original, insightful, and valuable, we will argue that in its execution of the empirical turn, postphenomenology forfeits
Phenomenological characteristics of autobiographical memory in Korsakoff's syndrome.

Science.gov (United States)

El Haj, Mohamad; Nandrino, Jean-Louis

2017-10-01

A body of research suggests compromise of autobiographical memory in Korsakoff's syndrome (KS). The present paper extends this literature by investigating the subjective experience of autobiographical recall in the syndrome. Patients with KS and controls were asked to retrieve autobiographical memories. After memory retrieval, participants were asked to rate phenomenological characteristics of their memories (i.e., reliving, back in time, remembering, realness, visual imagery, auditory imagery, language, emotion, rehearsal, importance, spatial recall and temporal recall). Analysis showed lower "Mean Phenomenological Experience" in the Korsakoff patients than in controls. However, the Korsakoff patients attributed relatively high emotional value and importance to their memories. Although our findings suggest compromised phenomenological reliving of autobiographical memory in patients with KS, affective characteristics such as emotion and importance are likely to play a main role in the subjective experience of the past in these patients. Copyright © 2017 Elsevier Inc. All rights reserved.
Phenomenological study of in the minimal model at LHC

Indian Academy of Sciences (India)

K M Balasubramaniam

2017-10-05

Oct 5, 2017 ... Phenomenological study of Z in the minimal B − L model at LHC ... The phenomenological study of neutral heavy gauge boson (Z. B−L) of the ...... JHEP10(2015)076, arXiv:1506.06767 [hep-ph] ... [15] ATLAS Collaboration: G Aad et al, Phys. Rev. D 90(5) ... [19] C W Chiang, N D Christensen, G J Ding and T.
Phenomenological two-nucleon interaction operator

International Nuclear Information System (INIS)

Lagaris, I.E.; Pandharipande, V.R.

1981-01-01

We report a phenomenological two-nucleon interaction operator obtained by fitting the nucleon-nucleon phase shifts up to 425 MeV in S, P, D and F waves, and the deuteron properties. The operator has the standard eight potentials associated with the two-body operators 1, sigma 1 x sigma 2 , tau 1 x tau 2 , sigma 1 x sigma 2 tau 1 x tau 2 , S 12 , S 12 tau 1 x tau 2 , L x S and L x Stau 2 ; and six phenomenological potentials associated with operators L 2 , L 2 sigma 1 x sigma 2 , L 2 tau 1 x tau 2 , L 2 sigma 1 x sigma 2 tau 1 xtau 2 (L x S) 2 tau 1 x tau 2 . The six quadratic L terms are relatively weak, and are chosen in order to make many-body calculations with this operator simpler. (orig.)
The Role of Phenomenology of Merleau- ponty in Medicine

Directory of Open Access Journals (Sweden)

Somayeh Rafighi

2017-07-01

Full Text Available Today, phenomenology, with an emphasis on direct explanations with regard to the lived experience of people is interest of different areas. With emphasis on body, Merleau- Ponty's phenomenology is considered in medical science. In his phenomenology, Merleau- Ponty gives new definition of body and names it lived body. Lived body is against of mechanical body and is the central of subjectivity and being- in- the – world and included all of existential aspects of man. Such definition enable doctors to consider all of existential aspects of man besides his physiological and same understanding of the disease based on the patient lived experience. This paper attempts to examine the implications of this new concept of the body as it is described in the medical field.
Dominant Modes in Light Nuclei - Ab Initio View of Emergent Symmetries

International Nuclear Information System (INIS)

Draayer, J P; Dytrych, T; Launey, K D; Dreyfuss, A C; Langr, D

2015-01-01

An innovative symmetry-guided concept is discussed with a focus on emergent symmetry patterns in complex nuclei. In particular, the ab initio symmetry-adapted no-core shell model (SA-NCSM), which capitalizes on exact as well as partial symmetries that underpin the structure of nuclei, provides remarkable insight into how simple symmetry patterns emerge in the many-body nuclear dynamics from first principles. This ab initio view is complemented by a fully microscopic no-core symplectic shell-model framework (NCSpM), which, in turn, informs key features of the primary physics responsible for the emergent phenomena of large deformation and alpha-cluster substructures in studies of the challenging Hoyle state in Carbon-12 and enhanced collectivity in intermediate-mass nuclei. Furthermore, by recognizing that deformed configurations often dominate the low-energy regime, the SA-NCSM provides a strategy for determining the nature of bound states of nuclei in terms of a relatively small subspace of the symmetry-reorganized complete model space, which opens new domains of nuclei for ab initio investigations, namely, the intermediate-mass region, including isotopes of Ne, Mg, and Si
Investigation of the binding mode of a novel cruzain inhibitor by docking, molecular dynamics, ab initio and MM/PBSA calculations

Science.gov (United States)

Martins, Luan Carvalho; Torres, Pedro Henrique Monteiro; de Oliveira, Renata Barbosa; Pascutti, Pedro Geraldo; Cino, Elio A.; Ferreira, Rafaela Salgado

2018-05-01

Chagas disease remains a major health problem in South America, and throughout the world. The two drugs clinically available for its treatment have limited efficacy and cause serious adverse effects. Cruzain is an established therapeutic target of Trypanosoma cruzi, the protozoan that causes Chagas disease. Our group recently identified a competitive cruzain inhibitor (compound 1) with an IC50 = 15 µM that is also more synthetically accessible than the previously reported lead, compound 2. Prior studies, however, did not propose a binding mode for compound 1, hindering understanding of the structure-activity relationship and optimization. Here, the cruzain binding mode of compound 1 was investigated using docking, molecular dynamics (MD) simulations with ab initio derived parameters, ab initio calculations, and MM/PBSA. Two ligand protonation states and four binding poses were evaluated. A careful ligand parameterization method was employed to derive more physically meaningful parameters than those obtained by automated tools. The poses of unprotonated 1 were unstable in MD, showing large conformational changes and diffusing away from the binding site, whereas the protonated form showed higher stability and interaction with negatively charged residues Asp161 and Cys25. MM/PBSA also suggested that these two residues contribute favorably to binding of compound 1. By combining results from MD, ab initio calculations, and MM/PBSA, a binding mode of 1 is proposed. The results also provide insights for further optimization of 1, an interesting lead compound for the development of new cruzain inhibitors.
Using Transcendental Phenomenology to Explore the “Ripple Effect” in a Leadership Mentoring Program

OpenAIRE

Tammy Moerer-Urdahl; John W. Creswell

2004-01-01

Several approaches exist for organizing and analyzing data in a phenomenological qualitative study. Transcendental phenomenology, based on principles identified by Husserl (1931) and translated into a qualitative method by Moustakas (1994), holds promise as a viable procedure for phenomenological research. However, to best understand the approach to transcendental phenomenology, the procedures need to be illustrated by a qualitative study that employs this approach. This article first discuss...
A phenomenological attempt at understanding otherness

Directory of Open Access Journals (Sweden)

A. KOVÁCS

2017-12-01

Full Text Available The phenomenology of otherness is not satisfied with the reductionist definitions of the classical anthropological conceptions. The latter have identified the essence of man in his rationality, morality, createdness, or the possibility of moral and aesthetic self-perfection. The monolithic definition of human essence, based on uniform criteria, seems today one-sided and outdated. The parallel effects of cultural diversification, the pluralized political and social system, and multilingualism have directly and inevitably confronted us with otherness and strangeness. We could even say that we can understand our identity primarily through the experience of otherness. We will reach our conclusions related to the phenomenological constitutive of otherness by way of the interpretation of the relevant ideas of Baudrillad, Guillaume and Lévinas.
Ab initio lattice dynamics of metal surfaces

International Nuclear Information System (INIS)

Heid, R.; Bohnen, K.-P.

2003-01-01

Dynamical properties of atoms on surfaces depend sensitively on their bonding environment and thus provide valuable insight into the local geometry and chemical binding at the boundary of a solid. Density-functional theory provides a unified approach to the calculation of structural and dynamical properties from first principles. Its high accuracy and predictive power for lattice dynamical properties of semiconductor surfaces has been demonstrated in a previous article by Fritsch and Schroeder (Phys. Rep. 309 (1999) 209). In this report, we review the state-of-the-art of these ab initio approaches to surface dynamical properties of metal surfaces. We give a brief introduction to the conceptual framework with focus on recent advances in computational procedures for the ab initio linear-response approach, which have been a prerequisite for an efficient treatment of surface dynamics of noble and transition metals. The discussed applications to clean and adsorbate-covered surfaces demonstrate the high accuracy and reliability of this approach in predicting detailed microscopic properties of the phonon dynamics for a wide range of metallic surfaces
Theoretical Frameworks, Methods, and Procedures for Conducting Phenomenological Studies in Educational Settings

OpenAIRE

Pelin Yüksel; Soner Yıldırım

2015-01-01

The main purposes of phenomenological research are to seek reality from individuals’ narratives of their experiences and feelings, and to produce in-depth descriptions of the phenomenon. Phenomenological research studies in educational settings generally embody lived experience, perception, and feelings of participants about a phenomenon. This study aims to provide a general framework for researchers who are interested in phenomenological studies especially in educational setting. Additionall...
Interpretive Hermeneutic Phenomenology: Clarifying Understanding ...

African Journals Online (AJOL)

The philosophical orientation of Gadamerian hermeneutic phenomenology is explored in this paper. Gadamer offers a hermeneutics of the humanities that differs significantly from models of the human sciences historically rooted in scientific methodologies. In particular, Gadamer proposes that understanding is first a mode ...
Investigation of the impact of defect models on Monte Carlo simulations of RBS/C spectra

International Nuclear Information System (INIS)

Kovac, D.; Hobler, G.

2006-01-01

We compare the impact on the RBS/C spectra of defect configurations in silicon obtained from either empirical interatomic potentials or ab initio calculations. Using the Tersoff potential as the empirical potential and the VASP code for ab initio calculations we have determined the coordinates of the split- interstitial, of the di-, tri- and four-interstitial cluster, and of the tetrahedral interstitial as well as the strain on neighboring atoms induced by the presence of these defects. Using these coordinates in binary collision RBS/C simulations we find differences in the RBS/C yields of up to 30%. The dependence of the backscattering yield on the assumed defect type is larger with the defect coordinates obtained by the empirical potential than by the ab initio calculations
AAMQS: a non-linear phenomenological tool

International Nuclear Information System (INIS)

Milhano, Jose Guilherme; Albacete, Javier L.; Armesto, Nestor; Quiroga-Arias, Paloma; Salgado, Carlos A.

2011-01-01

We demonstrate the phenomenological potential of the Balitsky-Kovchegov equation with running coupling by showing its ability to accurately describe the combined H1/ZEUS data for DIS reduced cross section.

AAMQS: a non-linear phenomenological tool

Energy Technology Data Exchange (ETDEWEB)

Milhano, Jose Guilherme, E-mail: guilherme.milhano@ist.utl.p [CENTRA, Departamento de Fisica, Instituto Superior Tecnico (IST), Av. Rovisco Pais 1, P-1049-001 Lisboa (Portugal); Physics Department, Theory Unit, CERN, CH-1211 Geneve 23 (Switzerland); Albacete, Javier L. [Institut de Physique Theorique, CEA/Saclay, 91191 Gif-sur-Yvette cedex (France); URA 2306, unite de recherche associee au CNRS (France); Armesto, Nestor; Quiroga-Arias, Paloma; Salgado, Carlos A. [Departamento de Fisica de Particulas and IGFAE, Universidade de Santiago de Compostela 15706 Santiago de Compostela (Spain)

2011-04-01

We demonstrate the phenomenological potential of the Balitsky-Kovchegov equation with running coupling by showing its ability to accurately describe the combined H1/ZEUS data for DIS reduced cross section.
Transversity: Theory and phenomenology

Energy Technology Data Exchange (ETDEWEB)

D' Alesio, Umberto [Dipartimento di Fisica, Universita di Cagliari, Cittadella Universitaria, and Istituto Nazionale di Fisica Nucleare, Sezione di Cagliari, C. P. 170, I-09042 Monserrato (Italy)

2013-04-15

The distribution of transversely polarized quarks inside a transversely polarized nucleon, known as transversity, encodes a basic piece of information on the nucleon structure, sharing the same status with the more familiar unpolarized and helicity distributions. I will review its properties and discuss different ways to access it, with highlights and limitations. Recent phenomenological extractions and perspectives are also presented.
Transversity: Theory and phenomenology

International Nuclear Information System (INIS)

D'Alesio, Umberto

2013-01-01

The distribution of transversely polarized quarks inside a transversely polarized nucleon, known as transversity, encodes a basic piece of information on the nucleon structure, sharing the same status with the more familiar unpolarized and helicity distributions. I will review its properties and discuss different ways to access it, with highlights and limitations. Recent phenomenological extractions and perspectives are also presented.
Four Generations in Phenomenology

Energy Technology Data Exchange (ETDEWEB)

Kribs, Graham D. [Department of Physics, University of Oregon, Eugene, OR 97403 (United States); Plehn, Tilman [SUPA, School of Physics, University of Edinburgh, Edinburgh EH9 3JZ, Scotland (HCP speaker) (United Kingdom); Spannowsky, Michael [ASC, Department fuer Physik, Ludwig-Maximilians-Universitaet Muenchen, 80333 Muenchen (Germany); Tait, Tim M.P. [HEP Division, Argonne National Laboratory, 9700 Cass Ave., Argonne, IL 60439 (United States)

2008-03-15

In four-generation models Higgs masses of 115-315 GeV are perfectly allowed by electroweak precision data. In this mass range we find dramatic effects on Higgs phenomenology at hadron colliders: production rates are enhanced, weak-boson-fusion channels are suppressed, angular distributions are modified, Higgs pairs can be observed, and Higgs decays to Majorana neutrinos can lead to exotic signals.
The cruel and unusual phenomenology of solitary confinement

OpenAIRE

Shaun eGallagher; Shaun eGallagher; Shaun eGallagher

2014-01-01

What happens when subjects are deprived of intersubjective contact? This paper looks closely at the phenomenology and psychology of one example of that deprivation: solitary confinement. It also puts the phenomenology and psychology of solitary confinement to use in the legal context. Not only is there no consensus on whether solitary confinement is a cruel and unusual punishment, there is no consensus on the definition of the term ‘cruel’ in the use of that legal phrase. I argue that we ...
Ab initio study of alanine polypeptide chain twisting

DEFF Research Database (Denmark)

Solov'yov, Ilia; Yakubovich, Alexander V.; Solov'yov, Andrey V.

2006-01-01

chains. These particular degrees of freedom are essential for the characterization of the proteins folding process. Calculations have been carried out within the ab initio theoretical framework based on the density functional theory and accounting for all the electrons in the system. We have determined...
Tip-of-the-tongue phenomena: an introductory phenomenological analysis.

Science.gov (United States)

Brown, S R

2000-12-01

The issue of meaningful yet unexpressed background-to language and to our experiences of the body-is one whose exploration is still in its infancy. There are various aspects of "invisible," implicit, or background experiences which have been investigated from the viewpoints of phenomenology, cognitive psychology, and linguistics. I will argue that James's concept of the phenomenon of fringes, as explicated by Gurwitsch, provides a structural framework from which to investigate and better understand ideas and concepts that are indeterminate, particularly those experienced in the sense of being sought-after. Johnson's conception of the image-schematic gestalt (ISG) provides an approach to bridging the descriptive gap between phenomenology and cognitive psychology. Starting from an analysis of the fringes, I will turn to a consideration of the tip-of-tongue (TOT) state, as a kind of feeling-of-knowing (FOK) state, from a variety of approaches, focusing mainly on cognitive psychology and phenomenology. I will then integrate a phenomenological analysis of these experiences, from the James/Gurwitsch structural viewpoint, with a cognitive/phenomenological analysis in terms of ISGs, and further integrate that with a cognitive/functional analysis of the relation between consciousness and retrieval, employing Anderson et al's theory of inhibitory mechanisms in cognition. This synthesis of these viewpoints will be employed to explore the thesis that the TOT state and similar experiences may relate to the gestalt nature of schemas, and that figure/ground and other contrast-enhancing structures may be both explanatory and descriptive characterizations of the field of consciousness. Copyright 2000 Academic Press.
Simple and accurate model for voltage-dependent resistance of metallic carbon nanotube interconnects: An ab initio study

International Nuclear Information System (INIS)

Yamacli, Serhan; Avci, Mutlu

2009-01-01

In this work, development of a voltage dependent resistance model for metallic carbon nanotubes is aimed. Firstly, the resistance of metallic carbon nanotube interconnects are obtained from ab initio simulations and then the voltage dependence of the resistance is modeled through regression. Self-consistent non-equilibrium Green's function formalism combined with density functional theory is used for calculating the voltage dependent resistance of metallic carbon nanotubes. It is shown that voltage dependent resistances of carbon nanotubes can be accurately modeled as a polynomial function which enables rapid integration of carbon nanotube interconnect models into electronic design automation tools.
Effects of spin orbital coupling on atomic and electronic structures in Al2Cu and Al2Au crystal and liquid phases via ab initio molecular dynamics simulations

International Nuclear Information System (INIS)

Wang, Y.; Lu, Y.H.; Wang, X.D.; Cao, Q.P.; Zhang, D.X.; Jiang, J.Z.

2014-01-01

Highlights: • The SOC effect affects the cohesion energy of crystal phase. • The effect of SOC was reduced due to random local atomic structures in liquids. • The local geometrical structures also affect the melting points. • Both SOC effect and local atomic structures are important for melting point difference. - Abstract: The origin of different melting points between Al 2 Cu and Al 2 Au has been studied using ab initio molecular dynamics simulations. Cohesive energy, electronic structures and structure information of both crystal and liquid phases have been analyzed. It is found that spin orbital coupling (SOC) plays an important role on the cohesive energy of crystal phase, consistent with the different melting points of these two alloys. Whereas, it seems that SOC has no effect on the formation energy and structure of liquid phase. Possible mechanism of reduced SOC effect at liquid phase is proposed. Our results are helpful to understand the glass formation ability difference between Al 2 Cu and Al 2 Au
Steel — ab Initio: Quantum Mechanics Guided Design of New Fe-Based Materials

Science.gov (United States)

Prahl, Ulrich; Bleck, Wolfgang; Saeed-Akbari, Alireza

This contribution reports the results of the collaborative research unit SFB 761 "Steel — ab initio", a cooperative project between RWTH Aachen University and the Max-Planck-Institute for Iron Research in Düsseldorf (MPIE) financed by the German Research Foundation (DFG). For the first time, it is exploited how ab initio approaches may lead to a detailed understanding and thus to a specific improvement of material development. The challenge lies in the combination of abstract natural science theories with rather engineering-like established concepts. Aiming at the technological target of the development of a new type of structural materials based on Fe-Mn-C alloys, the combination of ab initio and engineering methods is new, but could be followed quite successfully. Three major topics are treated in this research unit: a) development of a new method for material- and process-development based on ab initio calculations; b) design of a new class of structural materials with extraordinary property combinations; c) acceleration of development time and reduction of experimental efforts and complexity for material- and process-development. In the present work, an overview of the results of the first five years as well as an outlook for the upcoming three-year period is given.
A Review of Solid-Solution Models of High-Entropy Alloys Based on Ab Initio Calculations

Directory of Open Access Journals (Sweden)

Fuyang Tian

2017-11-01

Full Text Available Similar to the importance of XRD in experiments, ab initio calculations, as a powerful tool, have been applied to predict the new potential materials and investigate the intrinsic properties of materials in theory. As a typical solid-solution material, the large degree of uncertainty of high-entropy alloys (HEAs results in the difficulty of ab initio calculations application to HEAs. The present review focuses on the available ab initio based solid-solution models (virtual lattice approximation, coherent potential approximation, special quasirandom structure, similar local atomic environment, maximum-entropy method, and hybrid Monte Carlo/molecular dynamics and their applications and limits in single phase HEAs.
Light Condensation and Localization in Disordered Photonic Media: Theory and Large Scale ab initio Simulations

KAUST Repository

Toth, Laszlo Daniel

2013-05-07

Disordered photonics is the study of light in random media. In a disordered photonic medium, multiple scattering of light and coherence, together with the fundamental principle of reciprocity, produce a wide range of interesting phenomena, such as enhanced backscattering and Anderson localization of light. They are also responsible for the existence of modes in these random systems. It is known that analogous processes to Bose-Einstein condensation can occur in classical wave systems, too. Classical condensation has been studied in several contexts in photonics: pulse formation in lasers, mode-locking theory and coherent emission of disordered lasers. All these systems have the common theme of possessing a large ensemble of waves or modes, together with nonlinearity, dispersion or gain. In this work, we study light condensation and its connection with light localization in a disordered, passive dielectric medium. We develop a theory for the modes inside the disordered resonator, which combines the Feshbach projection technique with spin-glass theory and statistical physics. In particular, starting from the Maxwell’s equations, we map the system to a spherical p-spin model with p = 2. The spins are replaced by modes and the temperature is related to the fluctuations in the environment. We study the equilibrium thermodynamics of the system in a general framework and show that two distinct phases exist: a paramagnetic phase, where all the modes are randomly oscillating and a condensed phase, where the energy condensates on a single mode. The thermodynamic quantities can be explicitly interpreted and can also be computed from the disorder-averaged time domain correlation function. We launch an ab initio simulation campaign using our own code and the Shaheen supercomputer to test the theoretical predictions. We construct photonic samples of varying disorder and find computationally relevant ways to obtain the thermodynamic quantities. We observe the phase transition
The Phenomenology of Emotion Experience in First-Episode Psychosis

DEFF Research Database (Denmark)

Vodušek, V V; Parnas, J; Tomori, M

2014-01-01

-depth interviews were conducted twice with each of the 20 participants (firstly at admission and secondly 6 months later). Data collection and analysis were guided by the principles of phenomenological study of lived experience. RESULTS: The emotion experiences described by our participants vary greatly in both......BACKGROUND: Although it has been suggested that disturbances in emotion experience and regulation play a central role in the aetiology and psychopathology of schizophrenia spectrum disorders, the phenomenology of emotion experience in schizophrenia remains under-researched. SAMPLING AND METHODS: In...... quality and intensity, but appear to have a common phenomenology. Anxiety is reported as the basic emotion which buffers, transforms and sometimes supplants all others. Emotions in general are experienced as foreign, unstable and perturbing, thereby contributing greatly to feelings of ambivalence...
Ab Initio Calculations and Raman and SERS Spectral Analyses of Amphetamine Species

DEFF Research Database (Denmark)

Berg, Rolf W.; Nørbygaard, Thomas; White, Peter C.

2011-01-01

For the first time, the differences between the spectra of amphetamine and amphetamine-H+ and between different conformers are thoroughly studied by ab initio model calculations, and Raman and surface-enhanced Raman spectroscopy (SERS) spectra are measured for different species of amphetamine....... The spectra of amphetamine and amphetamine-H+ sampleswere obtained and assigned according to a comparison of the experimental spectra and the ab initio MO calculations, performed using the Gaussian 03W program (Gaussian, Inc., Pittsburgh, PA). The analyses were based on complete geometry minimization...
The problem of arriving at a phenomenological description of memory loss.

Science.gov (United States)

Moyle, W; Clinton, M

1997-07-01

This paper discusses a methodological difficulty that arose when uncovering the conscious experience of being nurtured as an in-patient with depression on a psychiatric ward. It considers the problem of arriving at a phenomenological description of memory loss in a patient who had undergone electroconvulsive therapy (ECT). The paper begins by describing the prevalence of depression and its significance for nurses working in in-patient settings. Examples of empirical research into memory loss in depression are used to show what researchers must set aside if they are to arrive at a phenomenological description of memory loss. The choice of a phenomenological approach to the wider study from which the methodological problem discussed here arose is then justified. The phenomena of memory is introduced to show the methodological significance of attempting to arrive at a phenomenological description of the statement made by one of the participants, a woman being treated as an in-patient for major depression. A possible description of the phenomena of memory loss based on the existential phenomenology of Sartre is offered to call into question the ability of researchers to bracket their assumptions. The significance for nurses of the wider study from which our example is taken is then described. Finally it is argued that despite the methodological difficulty described, a phenomenological perspective based on the philosophy of Husserl can point nurses in the direction of meeting the human needs of their patients.
Ab initio modeling of Al adsorption on CaF2 surfaces

International Nuclear Information System (INIS)

Barzilai, S.; Argaman, N.; Froumin, N.; Fuks, D.; Frage, N.

2008-01-01

Ab initio simulations of the adsorption of Al atoms on CaF 2 (0 0 1) and (1 1 1) surfaces have been performed for supercells with 7 different atomic configurations, using density functional theory. For (1 1 1) surfaces, a repulsive interaction was observed for most configurations, while a weak attraction was obtained when the Al atom was placed above F atoms. For the Ca-terminated (0 0 1) surface, the adsorption energy was about 5 times larger, whereas for the F-terminated (0 0 1) surface it was about 20 times greater. The comparative analysis indicates that the (0 0 1) surfaces are reactive and have a strong Al adatom bonding (chemisorption), especially for the F-terminated substrate. On the contrary, the (1 1 1) plane may be considered as non-reactive (physisorption), having a weak bonding of the Al adatom above the F site
Phenomenology between Pathos and Response

Directory of Open Access Journals (Sweden)

Bernhard Waldenfels

2011-03-01

Full Text Available The author calls phenomenological intentionality, into question while taking it, nevertheless, as a starting point. From the analysis of the meaning of phenomena he goes back to a pathic dimension which precedes them. What happens to us or affects us and to what we respond in different ways cannot be reduced to previous horizons. Between pathos and response, there is an irreducible cleft which constitutes a special sort of time-lag. What happens to us comes is always too early; our responses always come too late. Our experience is never completely up to date. In order to explore this pre-semantic and pre-pragmatic depth of experience we need a sort of responsive reduction, which guides all meaning toward something we respond to. In conclusion, the author evokes some areas in which such a revision of phenomenology shows its effects, namely the genesis of life in bioethics, the historical elaboration of memory and the experience of the Other.
Phenomenological three center model

CERN Document Server

Poenaru, D N; Gherghescu, R A; Nagame, Y; Hamilton, J H; Ramayya, A V

2001-01-01

Experimental results on ternary fission of sup 2 sup 5 sup 2 Cf suggest the existence of a short-lived quasi-molecular state. We present a three-center phenomenological model able to explain such a state by producing a new minimum in the deformation energy at a separation distance very close to the touching point. The shape parametrization chosen by us allows to describe the essential geometry of the systems in terms of one independent coordinate, namely, the distance between the heavy fragment centers. The shell correction (also treated phenomenologically) only produces quantitative effects; qualitatively it is not essential for the new minimum. Half-lives of some quasi-molecular states which could be formed in sup 1 sup 0 B accompanied fission of sup 2 sup 3 sup 6 U, sup 2 sup 3 sup 6 Pu, sup 2 sup 4 sup 6 Cm, sup 2 sup 5 sup 2 Cf, sup 2 sup 5 sup 2 sup , sup 2 sup 5 sup 6 Fm, sup 2 sup 5 sup 6 sup , sup 2 sup 6 sup 0 No, and sup 2 sup 6 sup 2 Rf are roughly estimated. (authors)
Method development at Nordic School of Public Health NHV: Phenomenology and Grounded Theory.

Science.gov (United States)

Strandmark, Margaretha

2015-08-01

Qualitative methods such as phenomenology and grounded theory have been valuable tools in studying public health problems. A description and comparison of these methods. Phenomenology emphasises an inside perspective in form of consciousness and subjectively lived experiences, whereas grounded theory emanates from the idea that interactions between people create new insights and knowledge. Fundamental aspects of phenomenology include life world, consciousness, phenomenological reduction and essence. Significant elements in grounded theory are coding, categories and core categories, which develop a theory. There are differences in the philosophical approach, the name of the concept and the systematic tools between the methods. Thus, the phenomenological method is appropriate when studying emotional and existential research problems, and grounded theory is a method more suited to investigate processes. © 2015 the Nordic Societies of Public Health.
Idols of the psychologist: Johannes Linschoten and the demise of phenomenological psychology in the Netherlands.

Science.gov (United States)

van Hezewijk, René; Stam, Henderikus J

2008-08-01

Before and after World War II, a loose movement within Dutch psychology solidified as a nascent phenomenological psychology. Dutch phenomenological psychologists attempted to generate an understanding of psychology that was based on Husserlian interpretations of phenomenological philosophy. This movement came to a halt in the 1960s, even though it had been exported to North America and elsewhere as "phenomenological psychology." Frequently referred to as the "Utrecht school," most of the activity of the group was centered at Utrecht University. In this article, the authors examine the role played by Johannes Linschoten in both aspects of the development of a phenomenological psychology: its rise in North America and Europe, and its institutional demise. By the time of his early death in 1964, Linschoten had cast considerable doubt on the possibilities of a purely phenomenological psychology. Nonetheless, his own empirical work, especially his 1956 dissertation published in German, can be seen to be a form of empiricism inspired by phenomenology but that clearly distanced itself from the more elitist and esoteric aspects of Dutch phenomenological psychology.

Integration of QUARK and I-TASSER for Ab Initio Protein Structure Prediction in CASP11.

Science.gov (United States)

Zhang, Wenxuan; Yang, Jianyi; He, Baoji; Walker, Sara Elizabeth; Zhang, Hongjiu; Govindarajoo, Brandon; Virtanen, Jouko; Xue, Zhidong; Shen, Hong-Bin; Zhang, Yang

2016-09-01

We tested two pipelines developed for template-free protein structure prediction in the CASP11 experiment. First, the QUARK pipeline constructs structure models by reassembling fragments of continuously distributed lengths excised from unrelated proteins. Five free-modeling (FM) targets have the model successfully constructed by QUARK with a TM-score above 0.4, including the first model of T0837-D1, which has a TM-score = 0.736 and RMSD = 2.9 Å to the native. Detailed analysis showed that the success is partly attributed to the high-resolution contact map prediction derived from fragment-based distance-profiles, which are mainly located between regular secondary structure elements and loops/turns and help guide the orientation of secondary structure assembly. In the Zhang-Server pipeline, weakly scoring threading templates are re-ordered by the structural similarity to the ab initio folding models, which are then reassembled by I-TASSER based structure assembly simulations; 60% more domains with length up to 204 residues, compared to the QUARK pipeline, were successfully modeled by the I-TASSER pipeline with a TM-score above 0.4. The robustness of the I-TASSER pipeline can stem from the composite fragment-assembly simulations that combine structures from both ab initio folding and threading template refinements. Despite the promising cases, challenges still exist in long-range beta-strand folding, domain parsing, and the uncertainty of secondary structure prediction; the latter of which was found to affect nearly all aspects of FM structure predictions, from fragment identification, target classification, structure assembly, to final model selection. Significant efforts are needed to solve these problems before real progress on FM could be made. Proteins 2016; 84(Suppl 1):76-86. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.
The cruel and unusual phenomenology of solitary confinement

OpenAIRE

Gallagher, Shaun

2014-01-01

What happens when subjects are deprived of intersubjective contact? This paper looks closely at the phenomenology and psychology of one example of that deprivation: solitary confinement. It also puts the phenomenology and psychology of solitary confinement to use in the legal context. Not only is there no consensus on whether solitary confinement is a “cruel and unusual punishment,” there is no consensus on the definition of the term “cruel” in the use of that legal phrase. I argue that we ca...
Summary of workshop 'Theory Meets Industry' - the impact of ab initio solid state calculations on industrial materials research

International Nuclear Information System (INIS)

Wimmer, E

2008-01-01

A workshop, 'Theory Meets Industry', was held on 12-14 June 2007 in Vienna, Austria, attended by a well balanced number of academic and industrial scientists from America, Europe, and Japan. The focus was on advances in ab initio solid state calculations and their practical use in industry. The theoretical papers addressed three dominant themes, namely (i) more accurate total energies and electronic excitations (ii) more complex systems, and (iii) more diverse and accurate materials properties. Hybrid functionals give some improvements in energies, but encounter difficulties for metallic systems. Quantum Monte Carlo methods are progressing, but no clear breakthrough is on the horizon. Progress in order-N methods is steady, as is the case for efficient methods for exploring complex energy hypersurfaces and large numbers of structural configurations. The industrial applications were dominated by materials issues in energy conversion systems, the quest for hydrogen storage materials, improvements of electronic and optical properties of microelectronic and display materials, and the simulation of reactions on heterogeneous catalysts. The workshop is a clear testimony that ab initio computations have become an industrial practice with increasingly recognized impact
Phenomenology and qualitative research: combining the transcendetal orientation of phenomenology with the diversities of lived experience

DEFF Research Database (Denmark)

Ravn, Susanne

research, researchers involve in describing lived bodies and lived experiences to further explore and understand the diversities of our embodied practices and experiences. The aim of this paper is to present and discus some of the methodological challenges of combining phenomenology and qualitative...... methodologies. I will specifically focus on discussing how the transcendental orientation of phenomenological descriptions has the potential to work through difference by approaching lived bodies according to their lived situation. The discussion will fall in three parts focusing on: a) how the research design...... in the practices; c) how the researcher can handle and ‘go beyond’ the subjective and situated descriptions in analyses when aiming at accounting for the structure of subjective experiences. In descriptions and discussions I draw on my current research of movement practices related to different kinds and genre...
(4)He Thermophysical Properties: New Ab Initio Calculations.

Science.gov (United States)

Hurly, John J; Mehl, James B

2007-01-01

Since 2000, atomic physicists have reduced the uncertainty of the helium-helium "ab initio" potential; for example, from approximately 0.6 % to 0.1 % at 4 bohr, and from 0.8 % to 0.1 % at 5.6 bohr. These results led us to: (1) construct a new inter-atomic potential ϕ 07, (2) recalculate values of the second virial coefficient, the viscosity, and the thermal conductivity of (4)He from 1 K to 10,000 K, and (3), analyze the uncertainties of the thermophysical properties that propagate from the uncertainty of ϕ 07 and from the Born-Oppenheimer approximation of the electron-nucleon quantum mechanical system. We correct minor errors in a previous publication [J. J. Hurly and M. R. Moldover, J. Res. Nat. Inst. Standards Technol. 105, 667 (2000)] and compare our results with selected data published after 2000. The ab initio results tabulated here can serve as standards for the measurement of thermophysical properties.
Matrix product operators, matrix product states, and ab initio density matrix renormalization group algorithms

Science.gov (United States)

Chan, Garnet Kin-Lic; Keselman, Anna; Nakatani, Naoki; Li, Zhendong; White, Steven R.

2016-07-01

Current descriptions of the ab initio density matrix renormalization group (DMRG) algorithm use two superficially different languages: an older language of the renormalization group and renormalized operators, and a more recent language of matrix product states and matrix product operators. The same algorithm can appear dramatically different when written in the two different vocabularies. In this work, we carefully describe the translation between the two languages in several contexts. First, we describe how to efficiently implement the ab initio DMRG sweep using a matrix product operator based code, and the equivalence to the original renormalized operator implementation. Next we describe how to implement the general matrix product operator/matrix product state algebra within a pure renormalized operator-based DMRG code. Finally, we discuss two improvements of the ab initio DMRG sweep algorithm motivated by matrix product operator language: Hamiltonian compression, and a sum over operators representation that allows for perfect computational parallelism. The connections and correspondences described here serve to link the future developments with the past and are important in the efficient implementation of continuing advances in ab initio DMRG and related algorithms.
Ab-initio calculations for dilute magnetic semiconductors

Energy Technology Data Exchange (ETDEWEB)

Belhadji, Brahim

2008-03-03

This thesis focusses on ab-initio calculations for the electronic structure and the magnetic properties of dilute magnetic semiconductors (DMS). In particular we aim at the understanding of the complex exchange interactions in these systems. Our calculations are based on density functional theory, being ideally suited for a description of the material specific properties of the considered DMS. Moreover we use the KKR Green function method in connection with the coherent potential approximation (CPA), which allows to include the random substitutional disorder in a mean field-like approximation for the electronic structure. Finally we calculate the exchange coupling constants J{sub ij} between two impurities in a CPA medium by using the Lichtenstein formula and from this calculate the Curie temperature by a numerically exact Monte Carlo method. Based on this analysis we found and investigated four different exchange mechanisms being of importance in DMS systems: Double exchange, p-d exchange, antiferromagnetic superexchanges, and ferromagnetic superexchange. A second topic we have investigated in this thesis is the pressure dependence of the exchange interactions and the Curie temperatures in (Ga,Mn)As and (In,Mn)As, using the LDA and the LDA+U approximations. Exact calculations of T{sub C} by Monte Carlo simulations show a somehow different behavior. (orig.)
A new method for finding vacua in string phenomenology

Energy Technology Data Exchange (ETDEWEB)

Gray, James [Institut d' Astrophysique de Paris and APC, Universite de Paris 7, 98 bis, Bd. Arago 75014, Paris (France); He, Yang-Hui [Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP (United Kingdom)]|[Merton College, Oxford, OX1 4JD and Mathematical Institute, Oxford University, Oxford (United Kingdom); Ilderton, Anton [School of Mathematics and Statistics, University of Plymouth, Drake Circus, Plymouth PL4 8AA (United Kingdom); Lukas, Andre [Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP (United Kingdom)

2007-05-15

One of the central problems of string-phenomenology is to find stable vacua in the four dimensional effective theories which result from compactification. We present an algorithmic method to find all of the vacua of any given string-phenomenological system in a huge class. In particular, this paper reviews and then extends hep-th/0606122 to include various nonperturbative effects. These include gaugino condensation and instantonic contributions to the superpotential. (authors)
Identification of nickel-vacancy defects by combining experimental and ab initio simulated photocurrent spectra

Science.gov (United States)

Londero, E.; Bourgeois, E.; Nesladek, M.; Gali, A.

2018-06-01

There is a continuous search for solid state spin qubits operating at room temperature with excitation in the infrared communication bandwidth. Recently, we have introduced the photoelectric detection of magnetic resonance (PDMR) to read the electron spin state of nitrogen-vacancy (NV) centers in diamond, a technique which is promising for applications in quantum information technology. By measuring the photoionization spectra on a diamond crystal, we found two ionization thresholds of unknown origin. On the same sample we also observed absorption and photoluminescence signatures that were identified in the literature as Ni-associated defects. We performed ab initio calculations of the photoionization cross section of the nickel split-vacancy complex (NiV) and N-related defects in their relevant charge states and fitted the concentration of these defects to the measured photocurrent spectrum, which led to a surprising match between experimental and calculated spectra. This study enabled us to identify the two unknown ionization thresholds with the two acceptor levels of NiV. Because the excitation of NiV is in the infrared, the photocurrent detected from the paramagnetic NiV color centers is a promising way towards the design of electrically readout qubits.
Water-mediated tautomerization of cytosine to the rare imino form: An ab initio dynamics study

Energy Technology Data Exchange (ETDEWEB)

Fogarasi, Geza [Institute of Chemistry, Eotvos University, H-1518 Budapest, Pf. 32. (Hungary)], E-mail: fg@chem.elte.hu

2008-06-16

Tautomerism in nucleotide bases is one of the possible mechanisms of mutation of DNA. In spite of numerous studies on the structure and energy of cytosine tautomers, little information is available on the process of proton transfer itself. We present here Born-Oppenheimer dynamics calculations, with the potential surface obtained 'on the fly' from ab initio quantum chemistry (QC) and the atoms moving classically. In search for water-mediated tautomerization the monohydrated complex was studied, running about 300 trajectories each of 3000-5000 points of 1 fs steps. One single trajectory has been found to lead to tautomerization. Although the QC method used in the simulations was inevitably modest (B3LYP/3-21G), higher-level test calculations along the same trajectory suggest that the simulation grasped the basic mechanism of proton transfer: a concerted, synchronous process characterized by strong coupling between the motions of the two participating hydrogen atoms.
Using Transcendental Phenomenology to Explore the “Ripple Effect” in a Leadership Mentoring Program

Directory of Open Access Journals (Sweden)

Tammy Moerer-Urdahl

2004-06-01

Full Text Available Several approaches exist for organizing and analyzing data in a phenomenological qualitative study. Transcendental phenomenology, based on principles identified by Husserl (1931 and translated into a qualitative method by Moustakas (1994, holds promise as a viable procedure for phenomenological research. However, to best understand the approach to transcendental phenomenology, the procedures need to be illustrated by a qualitative study that employs this approach. This article first discusses the procedures for organizing and analyzing data according to Moustakas (1994. Then it illustrates each step in the data analysis procedure of transcendental phenomenology using a study of reinvestment or the “ripple effect” for nine individuals who have participated in a youth leadership mentoring program from the 1970s to the present. Transcendental phenomenology works well for this study as this methodology provides logical, systematic, and coherent design elements that lead to an essential description of the experience.
The Concept of Motivation in Young Heidegger’s Hermeneutical Phenomenology

Directory of Open Access Journals (Sweden)

Rocío Garcés Ferrer

2018-05-01

Full Text Available This paper deals with the methodological role played by the term «motivation» in young Heidegger’s early hermeneutic transformation of phenomenology. To that effect, I shall start analyzing the concept of motivation in Husserl’s phenomenology so as to better understand its hermeneutical variation in young Heidegger’s philosophy. Subsequently, I will pay special attention to the relevance exhibited by motivation in the emergence of the most important methodological notions of hermeneutical phenomenology as «destruction» (Destruktion, «formal indication» (formale Anzeige and «preconception» (Vorgriff. To conclude, I shall explore the possibility of reshaping the phenomenological problem of the motivation to reduction in hermeneutical terms. That is to say: a motivation to reduction in factical life experience is always needed to access to the primordial sphere of meaning. Accordingly, I will finally suggest that the philosophical basic experience of radical questioning (Fraglichkeit can be read as a hermeneutical epoche, which is, however, directly linked to the concern for one’s own existence.
Phenomenology and Qualitative Data Analysis Software (QDAS: A Careful Reconciliation

Directory of Open Access Journals (Sweden)

Brian Kelleher Sohn

2017-01-01

Full Text Available An oft-cited phenomenological methodologist, Max VAN MANEN (2014, claims that qualitative data analysis software (QDAS is not an appropriate tool for phenomenological research. Yet phenomenologists rarely describe how phenomenology is to be done: pencil, paper, computer? DAVIDSON and DI GREGORIO (2011 urge QDAS contrarians such as VAN MANEN to get over their methodological loyalties and join the digital world, claiming that all qualitative researchers, whatever their methodology, perform processes aided by QDAS: disaggregation and recontextualization of texts. Other phenomenologists exemplify DAVIDSON and DI GREGORIO's observation that arguments against QDAS often identify problems more closely related to the researchers than QDAS. But the concerns about technology of McLUHAN (2003 [1964], HEIDEGGER (2008 [1977], and FLUSSER (2013 cannot be ignored. In this conceptual article I answer the questions of phenomenologists and the call of QDAS methodologists to describe how I used QDAS to carry out a phenomenological study in order to guide others who choose to reconcile the use of software to assist their research. URN: http://nbn-resolving.de/urn:nbn:de:0114-fqs1701142
Inelastic neutron scattering an ab-initio calculation of negative thermal expansion in Ag2O

International Nuclear Information System (INIS)

Gupta, M.K.; Mittal, R.; Rols, S.; Chaplot, S.L.

2012-01-01

The compound Ag 2 O undergoes large and isotropic negative thermal expansion over 0-500 K. We report temperature dependent inelastic neutron scattering measurements and ab-initio calculations of the phonon spectrum. The temperature dependence of the experimental phonon spectrum shows strong anharmonic nature of phonon modes of energy around 2.4 meV. The ab-initio calculations reveal that the maximum negative Grüneisen parameter, which is a measure of the relevant anharmonicity, occurs for the transverse phonon modes that involve bending motions of the Ag 4 O tetrahedra. The thermal expansion is evaluated from the ab-initio calculation of the pressure dependence of the phonon modes, and found in good agreement with available experimental data.
Reve{a,i}ling the risks: a phenomenology of information security

NARCIS (Netherlands)

Pieters, Wolter

2010-01-01

In information security research, perceived security usually has a negative meaning, when it is used in contrast to actual security. From a phenomenological perspective, however, perceived security is all we have. This paper develops a phenomenological account of information security, in which a
Light front quantum chromodynamics: Towards phenomenology

Indian Academy of Sciences (India)

Light front dynamics; quantum chromodynamics; deep inelastic scattering. PACS Nos 11.10. ... What makes light front dynamics appealing from high energy phenomenology point of view? .... given in terms of Poincarй generators by. MВ = W P ...
Stop, look, listen: the need for philosophical phenomenological perspectives on auditory verbal hallucinations

Science.gov (United States)

McCarthy-Jones, Simon; Krueger, Joel; Larøi, Frank; Broome, Matthew; Fernyhough, Charles

2013-01-01

One of the leading cognitive models of auditory verbal hallucinations (AVHs) proposes such experiences result from a disturbance in the process by which inner speech is attributed to the self. Research in this area has, however, proceeded in the absence of thorough cognitive and phenomenological investigations of the nature of inner speech, against which AVHs are implicitly or explicitly defined. In this paper we begin by introducing philosophical phenomenology and highlighting its relevance to AVHs, before briefly examining the evolving literature on the relation between inner experiences and AVHs. We then argue for the need for philosophical phenomenology (Phenomenology) and the traditional empirical methods of psychology for studying inner experience (phenomenology) to mutually inform each other to provide a richer and more nuanced picture of both inner experience and AVHs than either could on its own. A critical examination is undertaken of the leading model of AVHs derived from phenomenological philosophy, the ipseity disturbance model. From this we suggest issues that future work in this vein will need to consider, and examine how interdisciplinary methodologies may contribute to advances in our understanding of AVHs. Detailed suggestions are made for the direction and methodology of future work into AVHs, which we suggest should be undertaken in a context where phenomenology and physiology are both necessary, but neither sufficient. PMID:23576974
Phenomenology of colour exotic fermions

International Nuclear Information System (INIS)

Luest, D.

1986-01-01

The authors discuss the phenomenological consequences of a dynamical scenario according to which the electroweak symmetry breaking and generation of fermion masses is due to fermions that transform under high colour representations. Particular emphasis is given to the predictions for rare processes and to the spectrum of high colour boundstates. (Auth.)
Age differences in autobiographical memory across the adult lifespan: older adults report stronger phenomenology.

Science.gov (United States)

Luchetti, Martina; Sutin, Angelina R

2018-01-01

As an individual's life story evolves across adulthood, the subjective experience (phenomenology) of autobiographical memory likely changes. In addition to age at retrieval, both the recency of the memory and the age when a memory is formed may be particularly important to its phenomenology. The present work examines the effect of three temporal factors on phenomenology ratings: (a) age of the participant, (b) age at the event reported in the memory, and (c) memory age (recency). A large sample of Americans (N = 1120), stratified by chronological age, recalled and rated two meaningful memories, a Turning Point and an Early Childhood Memory. Ratings of phenomenology (e.g., vividness of turning points) were higher among older adults compared to younger adults. Memories of events from the reminiscence bump were more positive in valence than events from other time periods but did not differ on other phenomenological dimensions; recent memories had stronger phenomenology than remote memories. In contrast to phenomenology, narrative content was generally unrelated to participant age, age at the event, or memory age. Overall, the findings indicate age-related differences in how meaningful memories are re-experienced.
Phenomenological 'Verstehen' and interactionist 'sympathetic understanding': similarities and differences

OpenAIRE

Verhoeven, Jef

1991-01-01

Herbert Blumer, albeit accepting some similarities, did see clear differences between "symbolic interactionism" and "phenomenology". His main criticisms concerned the introspection of phenomenology and consequently the solipsism of this approach. Unfortunately, there was no opportunity in this interview to go into this problem more thoroughly. I want to resume this discussion here. As far as I have been abie to determine, the topic has not yet been treated in detail elsewhere. There has been ...

Geometry optimization of supersymmetrical molecules in quantum chemical ab-initio calculations

International Nuclear Information System (INIS)

Gruenbichler, H.

1985-01-01

One-dimensional geometry optimizations in ab-initio SCF-calculations are investigated. It is shown, that the well known standard algorithms are sometimes too expensive and can be replaced or accompanied by more recent algorithms. Two alternatives were realized in the molecule calculating program GAUSSIAN 80, basing on the Fibonacci algorithm and Kryachco potential adjustment. The algorithms were compared in terms of accuracy of results, CPU-time used and reliability of the method. The results are presented in various tables, showing the efficiency of the various methods. A survey of the usual model potentials is given and the compatibility with ab-initio data is evaluated. (Author, shortened and translated by A.N.)
Hermeneutic phenomenological analysis: the 'possibility' beyond 'actuality' in thematic analysis.

Science.gov (United States)

Ho, Ken H M; Chiang, Vico C L; Leung, Doris

2017-07-01

This article discusses the ways researchers may become open to manifold interpretations of lived experience through thematic analysis that follows the tradition of hermeneutic phenomenology. Martin Heidegger's thinking about historical contexts of understandings and the notions of 'alētheia' and 'techne' disclose what he called meaning of lived experience, as the 'unchanging Being of changing beings'. While these notions remain central to hermeneutic phenomenological research, novice phenomenologists usually face the problem of how to incorporate these philosophical tenets into thematic analysis. Discussion paper. This discussion paper is based on our experiences of hermeneutic analysis supported by the writings of Heidegger. Literature reviewed for this paper ranges from 1927 - 2014. We draw on data from a study of foreign domestic helpers in Hong Kong to demonstrate how 'dwelling' in the language of participants' 'ek-sistence' supported us in a process of thematic analysis. Data were collected from December 2013 - February 2016. Nurses doing hermeneutic phenomenology have to develop self-awareness of one's own 'taken-for-granted' thinking to disclose the unspoken meanings hidden in the language of participants. Understanding the philosophical tenets of hermeneutic phenomenology allows nurses to preserve possibilities of interpretations in thinking. In so doing, methods of thematic analysis can uncover and present the structure of the meaning of lived experience. We provide our readers with vicarious experience of how to begin cultivating thinking that is aligned with hermeneutic phenomenological philosophical tenets to conduct thematic analysis. © 2017 John Wiley & Sons Ltd.
SPASER as a complex system: femtosecond dynamics traced by ab-initio simulations

KAUST Repository

Gongora, J. S. Totero; Miroshnichenko, Andrey E.; Kivshar, Yuri S.; Fratalocchi, Andrea

2016-01-01

Integrating coherent light sources at the nanoscale with spasers is one of the most promising applications of plasmonics. A spaser is a nano-plasmonic counterpart of a laser, with photons replaced by surface plasmon polaritons and the resonant cavity replaced by a nanoparticle supporting localized plasmonic modes. Despite the large body of experimental and theoretical studies, the understanding of the fundamental properties of the spaser emission is still challenging. In this work, we investigated the ultrafast dynamics of the emission from a core-shell spaser by developing a rigorous first-principle numerical model. Our results show that the spaser is a highly nonlinear system with many interacting degrees of freedom, whose emission sustain a rich manifold of different spatial phases. In the regime of strong interaction we observed that the spaser emission manifests an irreversible ergodic evolution, where energy is equally shared among all the available degrees of freedom. Under this condition, the spaser generates ultrafast vortex lasing modes that are spinning on the femtosecond scale, acquiring the character of a nanoparticle with an effective spin. Interestingly, the spin orientation is defined by spontaneous symmetry breaking induced by quantum noise, which is a fundamental component of our ab-initio model. This opens up interesting possibilities of achieving unidirectional emission from a perfectly spherical nanoparticle, stimulating a broad range of applications for nano-plasmonic lasers as unidirectional couplers, random information sources and novel form of photonics neural-networks. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
SPASER as a complex system: femtosecond dynamics traced by ab-initio simulations

KAUST Repository

Gongora, J. S. Totero

2016-03-14

Integrating coherent light sources at the nanoscale with spasers is one of the most promising applications of plasmonics. A spaser is a nano-plasmonic counterpart of a laser, with photons replaced by surface plasmon polaritons and the resonant cavity replaced by a nanoparticle supporting localized plasmonic modes. Despite the large body of experimental and theoretical studies, the understanding of the fundamental properties of the spaser emission is still challenging. In this work, we investigated the ultrafast dynamics of the emission from a core-shell spaser by developing a rigorous first-principle numerical model. Our results show that the spaser is a highly nonlinear system with many interacting degrees of freedom, whose emission sustain a rich manifold of different spatial phases. In the regime of strong interaction we observed that the spaser emission manifests an irreversible ergodic evolution, where energy is equally shared among all the available degrees of freedom. Under this condition, the spaser generates ultrafast vortex lasing modes that are spinning on the femtosecond scale, acquiring the character of a nanoparticle with an effective spin. Interestingly, the spin orientation is defined by spontaneous symmetry breaking induced by quantum noise, which is a fundamental component of our ab-initio model. This opens up interesting possibilities of achieving unidirectional emission from a perfectly spherical nanoparticle, stimulating a broad range of applications for nano-plasmonic lasers as unidirectional couplers, random information sources and novel form of photonics neural-networks. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Experimental and ab initio investigations on textured Li–Mn–O spinel thin film cathodes

Energy Technology Data Exchange (ETDEWEB)

Fischer, J., E-mail: Julian.Fischer@kit.edu [Karlsruhe Institute of Technology (KIT), Institute for Applied Materials (IAM), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Music, D. [RWTH Aachen University, Materials Chemistry, Kopernikusstrasse 10, 52074 Aachen (Germany); Bergfeldt, T.; Ziebert, C.; Ulrich, S.; Seifert, H.J. [Karlsruhe Institute of Technology (KIT), Institute for Applied Materials (IAM), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)

2014-12-01

This paper describes the tailored preparation of nearly identical lithium–manganese–oxide thin film cathodes with different global grain orientations. The thin films were synthesized by rf magnetron sputtering from a LiMn{sub 2}O{sub 4}-target in a pure argon plasma. Under appropriate processing conditions, thin films with a cubic spinel structure and a nearly similar density and surface topography but different grain orientation, i.e. (111)- and (440)-textured films, were achieved. The chemical composition was determined by inductively coupled plasma optical emission spectroscopy and carrier gas hot extraction. The constitution- and microstructure were evaluated by X-ray diffraction and Raman spectroscopy. The surface morphology and roughness were investigated by scanning electron and atomic force microscopy. The differently textured films represent an ideal model system for studying potential effects of grain orientation on the lithium ion diffusion and electrochemical behavior in LiMn{sub 2}O{sub 4}-based thin films. They are nearly identical in their chemical composition, atomic bonding behavior, surface-roughness, morphology and thickness. Our initial ab initio molecular dynamics data indicate that Li ion transport is faster in (111)-textured structure than in (440)-textured one. - Highlights: • Thin film model system of differently textured cubic Li–Mn–O spinels. • Investigation of the Li–Mn–O thin film mass density by X-ray reflectivity. • Ab initio molecular dynamics simulation on Li ion diffusion in LiMn{sub 2}O{sub 4}.
Experimental and ab initio investigations on textured Li–Mn–O spinel thin film cathodes

International Nuclear Information System (INIS)

Fischer, J.; Music, D.; Bergfeldt, T.; Ziebert, C.; Ulrich, S.; Seifert, H.J.

2014-01-01

This paper describes the tailored preparation of nearly identical lithium–manganese–oxide thin film cathodes with different global grain orientations. The thin films were synthesized by rf magnetron sputtering from a LiMn 2 O 4 -target in a pure argon plasma. Under appropriate processing conditions, thin films with a cubic spinel structure and a nearly similar density and surface topography but different grain orientation, i.e. (111)- and (440)-textured films, were achieved. The chemical composition was determined by inductively coupled plasma optical emission spectroscopy and carrier gas hot extraction. The constitution- and microstructure were evaluated by X-ray diffraction and Raman spectroscopy. The surface morphology and roughness were investigated by scanning electron and atomic force microscopy. The differently textured films represent an ideal model system for studying potential effects of grain orientation on the lithium ion diffusion and electrochemical behavior in LiMn 2 O 4 -based thin films. They are nearly identical in their chemical composition, atomic bonding behavior, surface-roughness, morphology and thickness. Our initial ab initio molecular dynamics data indicate that Li ion transport is faster in (111)-textured structure than in (440)-textured one. - Highlights: • Thin film model system of differently textured cubic Li–Mn–O spinels. • Investigation of the Li–Mn–O thin film mass density by X-ray reflectivity. • Ab initio molecular dynamics simulation on Li ion diffusion in LiMn 2 O 4
Sphinx: merging knowledge-based and ab initio approaches to improve protein loop prediction.

Science.gov (United States)

Marks, Claire; Nowak, Jaroslaw; Klostermann, Stefan; Georges, Guy; Dunbar, James; Shi, Jiye; Kelm, Sebastian; Deane, Charlotte M

2017-05-01

Loops are often vital for protein function, however, their irregular structures make them difficult to model accurately. Current loop modelling algorithms can mostly be divided into two categories: knowledge-based, where databases of fragments are searched to find suitable conformations and ab initio, where conformations are generated computationally. Existing knowledge-based methods only use fragments that are the same length as the target, even though loops of slightly different lengths may adopt similar conformations. Here, we present a novel method, Sphinx, which combines ab initio techniques with the potential extra structural information contained within loops of a different length to improve structure prediction. We show that Sphinx is able to generate high-accuracy predictions and decoy sets enriched with near-native loop conformations, performing better than the ab initio algorithm on which it is based. In addition, it is able to provide predictions for every target, unlike some knowledge-based methods. Sphinx can be used successfully for the difficult problem of antibody H3 prediction, outperforming RosettaAntibody, one of the leading H3-specific ab initio methods, both in accuracy and speed. Sphinx is available at http://opig.stats.ox.ac.uk/webapps/sphinx. deane@stats.ox.ac.uk. Supplementary data are available at Bioinformatics online. © The Author 2017. Published by Oxford University Press.
Reve{a,i}ling the risks: a phenomenology of information security

NARCIS (Netherlands)

Pieters, Wolter

2009-01-01

In information security research, perceived security usually has a negative meaning, when it is used in contrast to actual security. From a phenomenological perspective, however, perceived security is all we have. In this paper, we develop a phenomenological account of information security, where we
Phenomenology and Mathematics

CERN Document Server

Hartimo, Mirja

2010-01-01

During Edmund Husserl,s lifetime, modern logic and mathematics rapidly developed toward their current outlook and Husserl,s writings can be fruitfully compared and contrasted with both 19th century figures (Boole, Schroder, Weierstrass) as well as the 20th century characters (Heyting, Zermelo, Godel). Besides the more historical studies, the internal ones on Husserl alone and the external ones attempting to clarify his role in the more general context of the developing mathematics and logic, Husserl,s phenomenology offers also a systematically rich but little researched area of investigation.
Indo-Pacific Journal of Phenomenology

African Journals Online (AJOL)

The journal is an initiative of the Phenomenology Research Group based at Edith ... The journal is published by NISC SA (IPJP on NISC) and has its own website online here: http://www.ipjp.org/ ... Beyond support: Exploring support as existential phenomenon in the context of young people and mental health · EMAIL FREE ...
Superstring inspired models and phenomenology

International Nuclear Information System (INIS)

Ross, G.G.

1987-01-01

An investigation of the effective low-energy theory resulting from the superstring is given. The possible light gauge and chiral super-multiplet structure is considered and a specific model leading to a SU(3)xSU(2)xU(1) gauge group is presented. Phenomenological implications for such models are briefly discussed
PHENOMENOLOGY, IT’S USE IN NURSING SCIENTIFIC PRODUCTION: BIBLIOMETRIC STUDY 2010-2014

Directory of Open Access Journals (Sweden)

Raúl Fernando Guerrero-Castañeda

2015-07-01

Full Text Available Phenomenology emerges as a philosophy with Husserl; It´s the study of phenomena, it provides access to human consciousness in nursing, to understand the meaning of being human. The bibliometric analysis is useful to describe and evaluate scientific products reported in scientific journals. The objective is to analyze the use of phenomenology in nursing production with bibliometric indicators. Materials and methods. Retrospective descriptive bibliometric study. Articles published in indexed journals in databases Scielo and CUIDEN Foundation Index. Descriptors: "Fenomenología" "Enfermería" (Spanish, “Fenomenología” “Enfermagem” (Portuguese, "Phenomenology" "Nursing" (English, lapse 2010-2014, search performed in February 2015. Results and Discussion. Sample (n = 142. Journals with more publications: Revista Paraninfo Digital (9.2%, Ciência, Cuidado e Saúde, Revista Latino-Americana de Enfermagem and Texto & Contexto Enfermagem (7%. Knowledge Area: Adult Nursing (18.3%; Topics: Teaching in nursing (14.7%, Cancer and Discipline of Nursing (9.8%, Care (7.7%; Population: Nurses (25%. Country: Brazil (69.2%; Keywords: Nursing (11.73%, Qualitative Research (6.9%; Language: Portuguese (50%; Original articles (88%; Phenomenological approach: Social Alfred Schütz (33.5%; Sampling: Intentional (64.62%; Technique used: Interview (42.9%. The phenomenology is a method and a philosophy, seeks the truth of phenomena in the deep variety of reality identifying Brazil development in the use of phenomenology. The social approaches are used as superior form of intersubjectivity (subject-phenomenon-society, referring to Alfred Schütz. Conclusions. The use of bibliometrics is an assessment of scientific activity, it is an instrument to approach to use given in nursing to phenomenology as philosophy and method.
Ab initio study of point defects in magnesium oxide

International Nuclear Information System (INIS)

Gilbert, C. A.; Kenny, S. D.; Smith, R.; Sanville, E.

2007-01-01

Energetics of a variety of point defects in MgO have been considered from an ab initio perspective using density functional theory. The considered defects are isolated Schottky and Frenkel defects and interstitial pairs, along with a number of Schottky defects and di-interstitials. Comparisons were made between the density functional theory results and results obtained from empirical potential simulations and these generally showed good agreement. Both methodologies predicted the first nearest neighbor Schottky defects to be the most energetically favorable of the considered Schottky defects and that the first, second, and fifth nearest neighbor di-interstitials were of similar energy and were favored over the other di-interstitial configurations. Relaxed structures of the defects were analyzed, which showed that empirical potential simulations were accurately predicting the displacements of atoms surrounding di-interstitials, but were overestimating O atom displacement for Schottky defects. Transition barriers were computed for the defects using the nudged elastic band method. Vacancies and Schottky defects were found to have relatively high energy barriers, the majority of which were over 2 eV, in agreement with conclusions reached using empirical potentials. The lowest barriers for di-interstitial transitions were found to be for migration into a first nearest neighbor configuration. Charges were calculated using a Bader analysis and this found negligible charge transfer during the defect transitions and only small changes in the charges on atoms surrounding defects, indicating why fixed charge models work as well as they do
[Phenomenological anthropological social psychiatry--paving the way for a theoretical reanimation].

Science.gov (United States)

Thoma, Samuel

2012-11-01

This article tries to link the present lack of theoretical discussion within German Social Psychiatry with a loss of phenomenological and anthropological thought. The so-called Phenomenological Psychiatry used to play a very important role in German psychiatry during the 50 ies until the 70 ies and had strong influences on the first reformers of German psychiatry, such as Walter Ritter von Baeyer, Heinz Häfner, Caspar Kulenkampff, Karl Peter Kisker and Erich Wulff. Their reforms were not only founded by a social criticism put forth by theories such as marxism (Basaglia, Wulff) or structuralism (Foucault) but also by a concrete notion of what it is like to suffer from mental illness and what kind of needs are linked to such suffering. This very notion was given by the phenomenological approach. Finally the article tries to give reasons for today's reciprocal loss of connection of the phenomenological and the socio-psychiatric school. © Georg Thieme Verlag KG Stuttgart · New York.
Shear stiffness in nanolaminar Ti3SiC2 challenges ab initio calculations

International Nuclear Information System (INIS)

Kisi, E H; Zhang, J F; Kirstein, O; Riley, D P; Styles, M J; Paradowska, A M

2010-01-01

Nanolaminates such as the M n+1 AX n (MAX) phases are a material class with ab initio derived elasticity tensors published for over 250 compounds. We have for the first time experimentally determined the full elasticity tensor of the archetype MAX phase, Ti 3 SiC 2 , using polycrystalline samples and in situ neutron diffraction. The experimental elastic constants show extreme shear stiffness, with c 44 more than five times greater than expected for an isotropic material. Such shear stiffness is quite rare in hexagonal materials and strongly contradicts the predictions of all published MAX phase elastic constants derived from ab initio calculations. It is concluded that second order properties such as elastic moduli derived from ab initio calculations require careful experimental verification. The diffraction technique used currently provides the only method of verification for the elasticity tensor for the majority of new materials where single crystals are not available. (fast track communication)
Proper construction of ab initio global potential surfaces with accurate long-range interactions

International Nuclear Information System (INIS)

Ho, Tak-San; Rabitz, Herschel

2000-01-01

An efficient procedure based on the reproducing kernel Hilbert space interpolation method is presented for constructing intermolecular potential energy surfaces (PES) using not only calculated ab initio data but also a priori information on long-range interactions. Explicitly, use of the reciprocal power reproducing kernel on the semiinfinite interval [0,∞) yields a set of exact linear relations between dispersion (multipolar) coefficients and PES data points at finite internuclear separations. Consequently, given a combined set of ab initio data and the values of dispersion (multipolar) coefficients, the potential interpolation problem subject to long-range interaction constraints can be solved to render globally smooth, asymptotically accurate ab initio potential energy surfaces. Very good results have been obtained for the one-dimensional He-He potential curve and the two-dimensional Ne-CO PES. The construction of the Ne-CO PES was facilitated by invoking a new reproducing kernel for the angular coordinate based on the optimally stable and shape-preserving Bernstein basis functions. (c) 2000 American Institute of Physics
Internal force corrections with machine learning for quantum mechanics/molecular mechanics simulations.

Science.gov (United States)

Wu, Jingheng; Shen, Lin; Yang, Weitao

2017-10-28

Ab initio quantum mechanics/molecular mechanics (QM/MM) molecular dynamics simulation is a useful tool to calculate thermodynamic properties such as potential of mean force for chemical reactions but intensely time consuming. In this paper, we developed a new method using the internal force correction for low-level semiempirical QM/MM molecular dynamics samplings with a predefined reaction coordinate. As a correction term, the internal force was predicted with a machine learning scheme, which provides a sophisticated force field, and added to the atomic forces on the reaction coordinate related atoms at each integration step. We applied this method to two reactions in aqueous solution and reproduced potentials of mean force at the ab initio QM/MM level. The saving in computational cost is about 2 orders of magnitude. The present work reveals great potentials for machine learning in QM/MM simulations to study complex chemical processes.
Summary of workshop 'Theory Meets Industry'—the impact of ab initio solid state calculations on industrial materials research

Science.gov (United States)

Wimmer, E.

2008-02-01

A workshop, 'Theory Meets Industry', was held on 12-14 June 2007 in Vienna, Austria, attended by a well balanced number of academic and industrial scientists from America, Europe, and Japan. The focus was on advances in ab initio solid state calculations and their practical use in industry. The theoretical papers addressed three dominant themes, namely (i) more accurate total energies and electronic excitations, (ii) more complex systems, and (iii) more diverse and accurate materials properties. Hybrid functionals give some improvements in energies, but encounter difficulties for metallic systems. Quantum Monte Carlo methods are progressing, but no clear breakthrough is on the horizon. Progress in order-N methods is steady, as is the case for efficient methods for exploring complex energy hypersurfaces and large numbers of structural configurations. The industrial applications were dominated by materials issues in energy conversion systems, the quest for hydrogen storage materials, improvements of electronic and optical properties of microelectronic and display materials, and the simulation of reactions on heterogeneous catalysts. The workshop is a clear testimony that ab initio computations have become an industrial practice with increasingly recognized impact.
Refinement of homology-based protein structures by molecular dynamics simulation techniques

NARCIS (Netherlands)

Fan, H; Mark, AE

The use of classical molecular dynamics simulations, performed in explicit water, for the refinement of structural models of proteins generated ab initio or based on homology has been investigated. The study involved a test set of 15 proteins that were previously used by Baker and coworkers to
Calibration and validation of a phenomenological influent pollutant disturbance scenario generator using full-scale data

DEFF Research Database (Denmark)

Flores Alsina, Xavier; Saagi, Ramesh; Lindblom, Erik Ulfson

2014-01-01

The objective of this paper is to demonstrate the full-scale feasibility of the phenomenological dynamic influent pollutant disturbance scenario generator (DIPDSG) that was originally used to create the influent data of the International Water Association (IWA) Benchmark Simulation Model No. 2 (BSM...... rainfall patterns (climate change) or influent biodegradability (process uncertainty) on the generated time series; 2) a demonstration of how to reduce the cost/workload of measuring campaigns by filling the gaps due to missing data in the influent profiles; and, 3) a critical discussion of the presented...

Pi-nucleon phenomenology at high energies

International Nuclear Information System (INIS)

Kogitz, S.

1973-01-01

A brief introduction to the phenomenology of strong interactions at high energy is presented. This includes discussion of the topics including absorption, finite energy sum rules, and duality. The application of these ideas to two-particle inelastic reactions is examined. (author)
The Possibility of Phenomenology in Heidegger

African Journals Online (AJOL)

denise

“democracy to come has always been suicidal” (read: not “life-assured”) .... Plato and Aristotle: “Phenomenology radicalized in ... of Plato and Aristotle brought back to life: the repetition, the ..... notwithstanding, simply to fight the fight is to lose it.
New perspectives on phenomenological decoherence

International Nuclear Information System (INIS)

Melo, Fernando Vaz de; Guzzo, Marcelo Moraes; Peres, Orlando Luis Goulart

2001-01-01

Decoherence showed to be a powerful tool in helping to solve the atmospheric Neutrino problem. However a complete analysis was not yet done. In this work we present all the possibilities concerning phenomenological decoherence linked to Neutrino 'problem'. Its possibilities and differences are stressed out in a effort to clarify the whole phenomena. (author)
Computational methods for ab initio detection of microRNAs

Directory of Open Access Journals (Sweden)

Malik eYousef

2012-10-01

Full Text Available MicroRNAs are small RNA sequences of 18-24 nucleotides in length, which serve as templates to drive post transcriptional gene silencing. The canonical microRNA pathway starts with transcription from DNA and is followed by processing via the Microprocessor complex, yielding a hairpin structure. Which is then exported into the cytosol where it is processed by Dicer and then incorporated into the RNA induced silencing complex. All of these biogenesis steps add to the overall specificity of miRNA production and effect. Unfortunately, their modes of action are just beginning to be elucidated and therefore computational prediction algorithms cannot model the process but are usually forced to employ machine learning approaches. This work focuses on ab initio prediction methods throughout; and therefore homology-based miRNA detection methods are not discussed. Current ab initio prediction algorithms, their ties to data mining, and their prediction accuracy are detailed.
Phenomenological aspects of unified theories

International Nuclear Information System (INIS)

Peccei, R.D.

1987-01-01

The author briefly discusses two new phenomena of recent interest, the 5/sup th/ force and variant axions. The former, for its elucidation, will require further gravitational experiments, but the author concludes that variant axions are now definitely rules out experimentally. Various aspects of superstring phenomenology are then addressed, including some of the generic predictions of superstrings and some of its generic problems. In particular, he discusses some of the phenomenological consequences of having an extra Z 0 boson and the circumstances under which this excitation is a genuine prediction of superstrings. Since it is likely that a more reliable relic of superstrings will be provided by the presence of superpartners at low energy (≤ TeV), he discusses some of the bounds for squarks and gluinos obtained at the SppS collider and the expectations for their production at the Tevatron. As a final topic, he touches upon some of the consequences that result from having the Fermi scale arise from an underlying theory. Some aspects of the composite Higgs model and of the strongly coupled standard model are briefly reviewed
Phenomenological modeling of abradable wear in turbomachines

Science.gov (United States)

Berthoul, Bérenger; Batailly, Alain; Stainier, Laurent; Legrand, Mathias; Cartraud, Patrice

2018-01-01

Abradable materials are widely used as coatings within compressor and turbine stages of modern aircraft engines in order to reduce operating blade-tip/casing clearances and thus maximize energy efficiency. However, rubbing occurrences between blade tips and coating liners may lead to high blade vibratory levels and endanger their structural integrity through fatigue mechanisms. Accordingly, there is a need for a better comprehension of the physical phenomena at play and for an accurate modeling of the interaction, in order to predict potentially unsafe events. To this end, this work introduces a phenomenological model of the abradable coating removal based on phenomena reported in the literature and accounting for key frictional and wear mechanisms including plasticity at junctions, ploughing, micro-rupture and machining. It is implemented within an in-house software solution dedicated to the prediction of full three-dimensional blade/abradable coating interactions within an aircraft engine low pressure compressor. Two case studies are considered. The first one compares the results of an experimental abradable test rig and its simulation. The second one deals with the simulation of interactions in a complete low-pressure compressor. The consistency of the model with experimental observations is underlined, and the impact of material parameter variations on the interaction and wear behavior of the blade is discussed. It is found that even though wear patterns are remarkably robust, results are significantly influenced by abradable coating material properties.
A phenomenological model for pre-stressed piezoelectric ceramic stack actuators

International Nuclear Information System (INIS)

Wang, D H; Zhu, W

2011-01-01

In order to characterize the hysteretic characteristics between the output displacement and applied voltage of pre-stressed piezoelectric ceramic stack actuators (PCSAs), this paper considers that a linear force and a hysteretic force will be generated by a linear extension and a hysteretic extension, respectively, due to the applied voltage to a pre-stressed PCSA and the total force will result in the forced vibration of the single-degree-of-freedom (DOF) system composed of the mass of the pre-stressed PCSA and the equivalent spring and damper of the pre-stressed mechanism, which lets the PCSA be pre-stressed to endure enough tension. On this basis, the phenomenological model to characterize the hysteretic behavior of the pre-stressed PCSA is put forward by using the Bouc–Wen hysteresis operator to model the hysteretic extension. The parameter identification method in a least-squares sense is established by identifying the parameters for the linear and hysteretic components separately with the step and periodic responses of the pre-stressed PCSA, respectively. The performance of the proposed phenomenological model with the corresponding parameter identification method is experimentally verified by the established experimental set-up. The research results show that the phenomenological model for the pre-stressed PCSA with the corresponding parameter identification method can accurately portray the hysteretic characteristics of the pre-stressed PCSA. In addition, the phenomenological model for PCSAs can be deduced from the phenomenological model for pre-stressed PCSAs by removing the terms related to the pre-stressed mechanisms
Theoretical Frameworks, Methods, and Procedures for Conducting Phenomenological Studies in Educational Settings

Directory of Open Access Journals (Sweden)

Pelin Yüksel

2015-01-01

Full Text Available The main purposes of phenomenological research are to seek reality from individuals’ narratives of their experiences and feelings, and to produce in-depth descriptions of the phenomenon. Phenomenological research studies in educational settings generally embody lived experience, perception, and feelings of participants about a phenomenon. This study aims to provide a general framework for researchers who are interested in phenomenological studies especially in educational setting. Additionally, the study provides a guide for researchers on how to conduct a phenomenological research and how to collect and analyze phenomenal data. The first part of the paper explains the underpinnings of the research methodology consisting of methodological framework and key phenomenological concepts. The second part provides guidance for a phenomenological research in education settings, focusing particularly on phenomenological data collection procedure and phenomenological data analysis methods.Keywords: Phenomenology, phenomenological inquiry, phenomenological data analysis Eğitim Ortamlarında Fenomenal Çalışmaları Yürütmek İçin Teorik Çerçeveler, Yöntemler ve ProsedürlerÖzFenomenolojik araştırmaların temel amacı, bireyin deneyimlerinden ve duygularından yola çıkarak belli bir fenomenan üzerinde yaptığı anlatılarında gerçeği aramak ve bu fenomenana yönelik derinlemesine açıklamalar üretmektir. Eğitim ortamlarında fenomenolojik araştırmalar genellikle araştırmaya katılanların belli bir fenomenan hakkında yaşantıları, deneyimleri, algıları ve duyguları somutlaştırmak için kullanılır. Bu çalışma, özellikle eğitim ortamlarında fenomenolojik çalışmalarla ilgilenen araştırmacılar için genel bir çerçeve sunmayı amaçlamaktadır. Ayrıca, çalışmada fenomenolojik araştırmalar için veri toplamak ve bu fenomenal verileri analiz yapmak için araştırmacılara yön gösterici bir k
Multiscale simulation of mechanical properties of TiNb alloy

Science.gov (United States)

Nikonov, A. Yu.

2017-12-01

The article presents a numerical simulation of the mechanical properties of a Ti-Nb β-alloy on three different scales. The ab-initio approach is used to estimate the concentrations of the Ti alloy with required elastic properties. On the basis of molecular dynamics simulation, we calculate the adhesive force between individual particles of the alloy. The calculated dependence is implemented within the movable cellular automata method to determine the mechanical properties of Ti-Nb depending on the interparticle free space.
Phenomenological model of an electron flow with a virtual cathode

International Nuclear Information System (INIS)

Koronovskij, A.A.; Khramov, A.E.; Anfinogenov, V.G.

1999-01-01

A phenomenological model of electron flow with a virtual cathode in diode space, which is a modification of cellular automation, is suggested. The type of models, called cellular conveyer, permits making allowance for distribution and delay in a beam with a virtual cathode. A good agreement between results of numerical study of electron flow dynamics and results obtained using the phenomenological model described has been achieved [ru
Large-scale ab initio configuration interaction calculations for light nuclei

International Nuclear Information System (INIS)

Maris, Pieter; Potter, Hugh; Vary, James P; Aktulga, H Metin; Ng, Esmond G; Yang Chao; Caprio, Mark A; Çatalyürek, Ümit V; Saule, Erik; Oryspayev, Dossay; Sosonkina, Masha; Zhou Zheng

2012-01-01

In ab-initio Configuration Interaction calculations, the nuclear wavefunction is expanded in Slater determinants of single-nucleon wavefunctions and the many-body Schrodinger equation becomes a large sparse matrix problem. The challenge is to reach numerical convergence to within quantified numerical uncertainties for physical observables using finite truncations of the infinite-dimensional basis space. We discuss strategies for constructing and solving the resulting large sparse matrix eigenvalue problems on current multicore computer architectures. Several of these strategies have been implemented in the code MFDn, a hybrid MPI/OpenMP Fortran code for ab-initio nuclear structure calculations that can scale to 100,000 cores and more. Finally, we will conclude with some recent results for 12 C including emerging collective phenomena such as rotational band structures using SRG evolved chiral N3LO interactions.
More Wounding Than Wounds: Hysterectomy, Phenomenology, and the Pain(s of Excorporation

Directory of Open Access Journals (Sweden)

Heather Hill-Vásquez

2016-06-01

Full Text Available Focusing on the pain experience of hysterectomy, this article applies and interrogates the foundational descriptive process on which phenomenology is based and suggests that feminism and phenomenology are more compatible than previously asserted. Building upon the work of feminist philosophers who have also explored how feminist and phenomenological approaches share similar methods and intentions—especially in connection with the former’s significant attention to lived experience as a source for the theory feminism employs—the article engages with the philosophies of Maurice Merleau-Ponty and Samuel Mallin who maintain a consistent attention to the body in their phenomenological approaches. Arguing that Mallin’s method of “body hermeneutics” is especially valuable for constructing a feminist phenomenological approach, the article applies Mallin’s theories to the hysterectomy experience, thus revealing how other female-coded experiences of pain, intrusion, shame, and vulnerability are intertwined with hysterectomy. Moreover, the article posits the pain experience of hysterectomy as a particularly emphatic form of phenomenological excorporation in which hidden and habituated assumptions—in this case, the previously unnoticed and unexamined association of a woman’s womb with what it means to be a woman—are painfully brought to light. As the womb becomes more present in the notion and reality of its absence, what does this mean for the many women who experience the shared phenomenon of hysterectomy—including feminist women who enter the experience with a more explicit understanding of themselves as gendered subjects?
Ab initio modeling of plasticity in HCP metals: pure zirconium and titanium and effect of oxygen

International Nuclear Information System (INIS)

Chaari, Nermine

2015-01-01

We performed atomistic simulations to determine screw dislocations properties in pure zirconium and titanium and to explain the hardening effect attributed to oxygen alloying in both hexagonal close-packed transition metals. We used two energetic models: ab initio calculations based on the density functional theory and calculations with an empirical potential. The complete energetic profile of the screw dislocation when gliding in the different slip planes is obtained in pure Zr. Our calculations reveal the existence of a metastable configuration of the screw dislocation partially spread in the first order pyramidal plane. This configuration is responsible for the cross slip of screw dislocations from prismatic planes, the easiest glide planes, to pyramidal or basal planes. This energy profile is affected by oxygen addition. Ab initio calculations reveal two main effects: oxygen enhances pyramidal cross slip by modifying the dislocation core structure, and pins the dislocation in its metastable sessile configuration. The same modeling approach is applied to titanium. In pure Ti, the same configurations of the screw dislocation in Zr are obtained, but with different energy levels. This leads to a different gliding mechanism. The same way as in Zr, oxygen enhances pyramidal glide in Ti by modifying the dislocation core structure. Besides, oxygen atom lowers the energy of the metastable configuration but not enough to pin the dislocation in this sessile configuration. (author) [fr
Ab initio calculations and modelling of atomic cluster structure

DEFF Research Database (Denmark)

Solov'yov, Ilia; Lyalin, Andrey G.; Solov'yov, Andrey V.

2004-01-01

The optimized structure and electronic properties of small sodium and magnesium clusters have been investigated using it ab initio theoretical methods based on density-functional theory and post-Hartree-Fock many-body perturbation theory accounting for all electrons in the system. A new theoretical...
Modeling of nuclear glasses by classical and ab initio molecular dynamics

International Nuclear Information System (INIS)

Ganster, P.

2004-01-01

A calcium aluminosilicate glass of molar composition 67 % SiO 2 - 12 % Al 2 O 3 - 21 % CaO was modelled by classical and ab initio molecular dynamics. The size effect study in classical MD shows that the systems of 100 atoms are more ordered than the larger ones. These effects are mainly due to the 3-body terms in the empirical potentials. Nevertheless, these effects are small and the structures generated are in agreement with experimental data. In such kind of glass, we denote an aluminium avoidance and an excess of non bridging oxygens which can be compensated by tri-coordinated oxygens. When the dynamics of systems of 100 and 200 atoms is followed by ab initio MD, some local arrangements occurs (bond length, angular distributions). Thus, more realistic vibrational properties are obtained in ab initio MD. The modelling of thin films shows that aluminum atoms extend to the most external part of the surface and they are all tri-coordinated. Calcium atoms are set in the sub layer part of the surface and they produce a depolymerization of the network. In classical MD, tri-coordinated aluminium atoms produce an important electric field above the surface. With non bridging oxygens, they constitute attractive sites for single water molecules. (author) [fr
Modelling of nuclear glasses by classical and ab initio molecular dynamics

International Nuclear Information System (INIS)

Ganster, P.

2004-10-01

A calcium aluminosilicate glass of molar composition 67 % SiO 2 - 12 % Al 2 O 3 - 21 % CaO was modelled by classical and ab initio molecular dynamics. The size effect study in classical MD shows that the systems of 100 atoms are more ordered than the larger ones. These effects are mainly due to the 3-body terms in the empirical potentials. Nevertheless, these effects are small and the structures generated are in agreement with experimental data. In such kind of glass, we denote an aluminium avoidance and an excess of non bridging oxygens which can be compensated by tri coordinated oxygens. When the dynamics of systems of 100 and 200 atoms is followed by ab initio MD, some local arrangements occurs (bond length, angular distributions). Thus, more realistic vibrational properties are obtained in ab initio MD. The modelling of thin films shows that aluminium atoms extend to the most external part of the surface and they are all tri-coordinated. Calcium atoms are set in the sub layer part of the surface and they produce a depolymerization of the network. In classical MD, tri-coordinated aluminium atoms produce an important electric field above the surface. With non bridging oxygens, they constitute attractive sites for single water molecules. (author)
Ab Initio Modeling of Structure and Properties of Single and Mixed Alkali Silicate Glasses.

Science.gov (United States)

Baral, Khagendra; Li, Aize; Ching, Wai-Yim

2017-10-12

A density functional theory (DFT)-based ab initio molecular dynamics (AIMD) has been applied to simulate models of single and mixed alkali silicate glasses with two different molar concentrations of alkali oxides. The structural environments and spatial distributions of alkali ions in the 10 simulated models with 20% and 30% of Li, Na, K and equal proportions of Li-Na and Na-K are studied in detail for subtle variations among the models. Quantum mechanical calculations of electronic structures, interatomic bonding, and mechanical and optical properties are carried out for each of the models, and the results are compared with available experimental observation and other simulations. The calculated results are in good agreement with the experimental data. We have used the novel concept of using the total bond order density (TBOD), a quantum mechanical metric, to characterize internal cohesion in these glass models. The mixed alkali effect (MAE) is visible in the bulk mechanical properties but not obvious in other physical properties studied in this paper. We show that Li doping deviates from expected trend due to the much stronger Li-O bonding than those of Na and K doping. The approach used in this study is in contrast with current studies in alkali-doped silicate glasses based only on geometric characterizations.
Growth of nitrogen-doped graphene on copper: Multiscale simulations

Science.gov (United States)

Gaillard, P.; Schoenhalz, A. L.; Moskovkin, P.; Lucas, S.; Henrard, L.

2016-02-01

We used multiscale simulations to model the growth of nitrogen-doped graphene on a copper substrate by chemical vapour deposition (CVD). Our simulations are based on ab-initio calculations of energy barriers for surface diffusion, which are complemented by larger scale Kinetic Monte Carlo (KMC) simulations. Our results indicate that the shape of grown doped graphene flakes depends on the temperature and deposition flux they are submitted during the process, but we found no significant effect of nitrogen doping on this shape. However, we show that nitrogen atoms have a preference for pyridine-like sites compared to graphite-like sites, as observed experimentally.
Exploring the speed and performance of molecular replacement with AMPLE using QUARK ab initio protein models

Energy Technology Data Exchange (ETDEWEB)

Keegan, Ronan M. [STFC Rutherford Appleton Laboratory, Didcot OX11 0FA (United Kingdom); Bibby, Jaclyn; Thomas, Jens [University of Liverpool, Liverpool L69 7ZB (United Kingdom); Xu, Dong [Sanford-Burnham Medical Research Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037 (United States); Zhang, Yang [University of Michigan, Ann Arbor, MI 48109 (United States); Mayans, Olga [University of Liverpool, Liverpool L69 7ZB (United Kingdom); Winn, Martyn D. [Science and Technology Facilities Council Daresbury Laboratory, Warrington WA4 4AD (United Kingdom); Rigden, Daniel J., E-mail: drigden@liv.ac.uk [University of Liverpool, Liverpool L69 7ZB (United Kingdom); STFC Rutherford Appleton Laboratory, Didcot OX11 0FA (United Kingdom)

2015-02-01

Two ab initio modelling programs solve complementary sets of targets, enhancing the success of AMPLE with small proteins. AMPLE clusters and truncates ab initio protein structure predictions, producing search models for molecular replacement. Here, an interesting degree of complementarity is shown between targets solved using the different ab initio modelling programs QUARK and ROSETTA. Search models derived from either program collectively solve almost all of the all-helical targets in the test set. Initial solutions produced by Phaser after only 5 min perform surprisingly well, improving the prospects for in situ structure solution by AMPLE during synchrotron visits. Taken together, the results show the potential for AMPLE to run more quickly and successfully solve more targets than previously suspected.
Non-equilibrium dynamics in disordered materials: Ab initio molecular dynamics simulations

International Nuclear Information System (INIS)

Ohmura, Satoshi; Nagaya, Kiyonobu; Yao, Makoto; Shimojo, Fuyuki

2015-01-01

The dynamic properties of liquid B 2 O 3 under pressure and highly-charged bromophenol molecule are studied by using molecular dynamics (MD) simulations based on density functional theory (DFT). Diffusion properties of covalent liquids under high pressure are very interesting in the sense that they show unexpected pressure dependence. It is found from our simulation that the magnitude relation of diffusion coefficients for boron and oxygen in liquid B 2 O 3 shows the anomalous pressure dependence. The simulation clarified the microscopic origin of the anomalous diffusion properties. Our simulation also reveals the dissociation mechanism in the coulomb explosion of the highly-charged bromophenol molecule. When the charge state n is 6, hydrogen atom in the hydroxyl group dissociates at times shorter than 20 fs while all hydrogen atoms dissociate when n is 8. After the hydrogen dissociation, the carbon ring breaks at about 100 fs. There is also a difference on the mechanism of the ring breaking depending on charge states, in which the ring breaks with expanding (n = 6) or shrink (n = 8)

Dynamics of ligand exchange mechanism at Cu(II) in water: an ab initio quantum mechanical charge field molecular dynamics study with extended quantum mechanical region.

Science.gov (United States)

Moin, Syed Tarique; Hofer, Thomas S; Weiss, Alexander K H; Rode, Bernd M

2013-07-07

Ab initio quantum mechanical charge field molecular dynamics (QMCF-MD) were successfully applied to Cu(II) embedded in water to elucidate structure and to understand dynamics of ligand exchange mechanism. From the simulation studies, it was found that using an extended large quantum mechanical region including two shells of hydration is required for a better description of the dynamics of exchanging water molecules. The structural features characterized by radial distribution function, angular distribution function and other analytical parameters were consistent with experimental data. The major outcome of this study was the dynamics of exchange mechanism and reactions in the first hydration shell that could not be studied so far. The dynamical data such as mean residence time of the first shell water molecules and other relevant data from the simulations are close to the results determined experimentally. Another major characteristic of hydrated Cu(II) is the Jahn-Teller distortion which was also successfully reproduced, leading to the final conclusion that the dominating aqua complex is a 6-coordinated species. The ab initio QMCF-MD formalism proved again its capabilities of unraveling even ambiguous properties of hydrated species that are far difficult to explore by any conventional quantum mechanics/molecular mechanics (QM/MM) approach or experiment.
Dynamics of ligand exchange mechanism at Cu(II) in water: An ab initio quantum mechanical charge field molecular dynamics study with extended quantum mechanical region

International Nuclear Information System (INIS)

Moin, Syed Tarique; Hofer, Thomas S.; Weiss, Alexander K. H.; Rode, Bernd M.

2013-01-01

Ab initio quantum mechanical charge field molecular dynamics (QMCF-MD) were successfully applied to Cu(II) embedded in water to elucidate structure and to understand dynamics of ligand exchange mechanism. From the simulation studies, it was found that using an extended large quantum mechanical region including two shells of hydration is required for a better description of the dynamics of exchanging water molecules. The structural features characterized by radial distribution function, angular distribution function and other analytical parameters were consistent with experimental data. The major outcome of this study was the dynamics of exchange mechanism and reactions in the first hydration shell that could not be studied so far. The dynamical data such as mean residence time of the first shell water molecules and other relevant data from the simulations are close to the results determined experimentally. Another major characteristic of hydrated Cu(II) is the Jahn-Teller distortion which was also successfully reproduced, leading to the final conclusion that the dominating aqua complex is a 6-coordinated species. The ab initio QMCF-MD formalism proved again its capabilities of unraveling even ambiguous properties of hydrated species that are far difficult to explore by any conventional quantum mechanics/molecular mechanics (QM/MM) approach or experiment
Ab initio modeling of the motional Stark effect on MAST

International Nuclear Information System (INIS)

De Bock, M. F. M.; Conway, N. J.; Walsh, M. J.; Carolan, P. G.; Hawkes, N. C.

2008-01-01

A multichord motional Stark effect (MSE) system has recently been built on the MAST tokamak. In MAST the π and σ lines of the MSE spectrum overlap due to the low magnetic field typical for present day spherical tokamaks. Also, the field curvature results in a large change in the pitch angle over the observation volume. The measured polarization angle does not relate to one local pitch angle but to an integration over all pitch angles in the observation volume. The velocity distribution of the neutral beam further complicates the measurement. To take into account volume effects and velocity distribution, an ab initio code was written that simulates the MSE spectrum on MAST. The code is modular and can easily be adjusted for other tokamaks. The code returns the intensity, polarized fraction, and polarization angle as a function of wavelength. Results of the code are presented, showing the effect on depolarization and wavelength dependence of the polarization angle. The code is used to optimize the design and calibration of the MSE diagnostic.
Low energy phenomenology

CERN Document Server

Schmid, C

1972-01-01

The following topics are discussed: theoretical tools; models; Pade approximants; theoretical predictions of pi pi S-waves; pi pi phase shifts from K/sub e4/; Chew Low extrapolation in pi p to pi /sup -/ pi /sup +/n; the KK cusp in pi pi to pi pi ; K pi phase shifts. (25 refs) . For pt. I see ibid., 265. The following topics are discussed: patterns of resonance couplings from exchange degeneracy; Reggeon couplings; clash of t and s channel structure in pole model; B/sub 4/ phenomenology; Odorico zeros; Barrelet zeros and phase shift ambiguities. (29 refs).
Phenomenology of chromostatics

International Nuclear Information System (INIS)

Pervushin, V.N.; Kallies, W.; Sarikov, N.A.

1988-01-01

For the description of hadrons as bound states the physical perturbation theory (PPT) on the spatial components of the gluon field over the exact solution, defined by the temporal one, is proposed. A quntization method is used, which in each order of the PPT is relativistic-covariant, and an elimination of the infrared divergences with the help of the phenomenological redefinition of the Coulomb potential. The main elements of the PPT: the Green functions of quarks and gluons, the effective coupling constant are found; and the functional, unifying the meson spectroscopy, dual amplitudes and chiral Lagrangians, is constructed
Intentionality and Narrativity in Phenomenological Psychological ...

African Journals Online (AJOL)

Christopher R Stones

2014-10-02

Oct 2, 2014 ... ... analysis. Likewise, it is argued that Ricoeur's work on narrativity and narrative ... method of Husserl's static phenomenological analysis .... the possibility of description in a qualitative research ... theoretical perspective, assumption, hypothesis, and so on” .... every case the noetic constitution of the object is.
Should phenomenological approaches to illness really be wary of naturalism

OpenAIRE

Ferry-Danini , Juliette

2018-01-01

In some quarters within philosophy of medicine, more particularly in the phenomenological approaches, naturalism is looked upon with suspicion. This paper argues, first, that it is necessary to distinguish between two expressions of this attitude towards naturalism: phenomenological approaches to illness disagree with naturalism regarding various theoretical claims and they disapprove of naturalism on an ethical level. Second, this paper argues that both the disagreement with and the disappro...
Auroral phenomenology and magnetospheric processes earth and other planets

CERN Document Server

Keiling, Andreas; Bagenal, Fran; Karlsson, Tomas

2013-01-01

Published by the American Geophysical Union as part of the Geophysical Monograph Series. Many of the most basic aspects of the aurora remain unexplained. While in the past terrestrial and planetary auroras have been largely treated in separate books, Auroral Phenomenology and Magnetospheric Processes: Earth and Other Planets takes a holistic approach, treating the aurora as a fundamental process and discussing the phenomenology, physics, and relationship with the respective planetary magnetospheres in one volume. While there are some behaviors common in auroras of the diffe
Ab initio screening methodology applied to the search for new permanent magnetic materials

International Nuclear Information System (INIS)

Drebov, Nedko; Gumbsch, Peter; Elsässer, Christian; Martinez-Limia, Alberto; Kunz, Lothar; Gola, Adrien; Eckl, Thomas; Shigematsu, Takashi

2013-01-01

In this paper a computational high-throughput screening (HTS) approach to the search for alternative permanent magnetic materials is presented. Systems considered for a start are binary intermetallic compounds composed of rare-earth (RE) and transition metal (TM) elements. With the tight-binding-linear muffin-tin-orbital-atomic-sphere-approximation (TB-LMTO-ASA) method of density functional theory (DFT) a variety of RE–TM intermetallic phases is investigated and their magnetic properties are obtained at rather low computational costs. Next, interstitial elements such as boron, carbon and nitrogen in these phases are considered. For promising candidate phases with high and stable spontaneous ferromagnetic polarization, the calculated local magnetic moments and exchange coupling parameters, as obtained from TB-LMTO-ASA calculations, are then used for Monte Carlo simulations to identify candidates with sufficiently high Curie temperatures (T c ). Finally, magnetocrystalline anisotropy constants (K 1 ) of the most promising candidate phases are calculated with accurate, potential-shape-unrestricted DFT calculations using the Vienna ab initio simulation package. The computational HTS procedure is illustrated by results for a selection of hard-magnetic RE–TM phases like RETM 5 , RE 2 TM 17 and RE 2 TM 14 B. (paper)
Scanning the phenomenological MSSM

CERN Document Server

Wuerzinger, Jonas

2017-01-01

A framework to perform scans in the 19-dimensional phenomenological MSSM is developed and used to re-evaluate the ATLAS experiments' sensitivity to R-parity-conserving supersymmetry with LHC Run 2 data ($\\sqrt{s}=13$ TeV), using results from 14 separate ATLAS searches. We perform a $\\tilde{t}_1$ dedicated scan, only considering models with $m_{\\tilde{t}_1}<1$ TeV, while allowing both a neutralino ($\\tilde{\\chi}_1^0$) and a sneutrino ($\\tilde{\
The Classification of Hysteria and Related Disorders: Historical and Phenomenological Considerations

Science.gov (United States)

North, Carol S.

2015-01-01

This article examines the history of the conceptualization of dissociative, conversion, and somatoform syndromes in relation to one another, chronicles efforts to classify these and other phenomenologically-related psychopathology in the American diagnostic system for mental disorders, and traces the subsequent divergence in opinions of dissenting sectors on classification of these disorders. This article then considers the extensive phenomenological overlap across these disorders in empirical research, and from this foundation presents a new model for the conceptualization of these disorders. The classification of disorders formerly known as hysteria and phenomenologically-related syndromes has long been contentious and unsettled. Examination of the long history of the conceptual difficulties, which remain inherent in existing classification schemes for these disorders, can help to address the continuing controversy. This review clarifies the need for a major conceptual revision of the current classification of these disorders. A new phenomenologically-based classification scheme for these disorders is proposed that is more compatible with the agnostic and atheoretical approach to diagnosis of mental disorders used by the current classification system. PMID:26561836
Delirium phenomenology: what can we learn from the symptoms of delirium?

Science.gov (United States)

Gupta, Nitin; de Jonghe, Jos; Schieveld, Jan; Leonard, Maeve; Meagher, David

2008-09-01

This review focuses on phenomenological studies of delirium, including subsyndromal and prodromal concepts, and their relevance to other elements of clinical profile. A Medline search using the keywords delirium, phenomenology, and symptoms for new data articles published in English between 1998 and 2008 was utilized. The search was supplemented by additional material not identified by Medline but known to the authors. Understanding of prodromal and subsyndromal concepts is still in its infancy. The characteristic profile can differentiate delirium from other neuropsychiatric disorders. Clinical (motoric) subtyping holds potential but more consistent methods are needed. Studies are almost entirely cross-sectional in design and generally lack comprehensive symptom assessment. Multiple assessment tools are available but are oriented towards hyperactive features and few have demonstrated ability to distinguish delirium from dementia. There is insufficient evidence linking specific phenomenology with etiology, pathophysiology, management, course, and outcome. Despite the major advancements of the past decade in many aspects of delirium research, further phenomenological work is crucial to targeting studies of causation, pathophysiology, treatment, and prognosis. We identified eight key areas for future studies.
The Classification of Hysteria and Related Disorders: Historical and Phenomenological Considerations

Directory of Open Access Journals (Sweden)

Carol S. North

2015-11-01

Full Text Available This article examines the history of the conceptualization of dissociative, conversion, and somatoform syndromes in relation to one another, chronicles efforts to classify these and other phenomenologically-related psychopathology in the American diagnostic system for mental disorders, and traces the subsequent divergence in opinions of dissenting sectors on classification of these disorders. This article then considers the extensive phenomenological overlap across these disorders in empirical research, and from this foundation presents a new model for the conceptualization of these disorders. The classification of disorders formerly known as hysteria and phenomenologically-related syndromes has long been contentious and unsettled. Examination of the long history of the conceptual difficulties, which remain inherent in existing classification schemes for these disorders, can help to address the continuing controversy. This review clarifies the need for a major conceptual revision of the current classification of these disorders. A new phenomenologically-based classification scheme for these disorders is proposed that is more compatible with the agnostic and atheoretical approach to diagnosis of mental disorders used by the current classification system.
Ab initio protein structure assembly using continuous structure fragments and optimized knowledge-based force field.

Science.gov (United States)

Xu, Dong; Zhang, Yang

2012-07-01

Ab initio protein folding is one of the major unsolved problems in computational biology owing to the difficulties in force field design and conformational search. We developed a novel program, QUARK, for template-free protein structure prediction. Query sequences are first broken into fragments of 1-20 residues where multiple fragment structures are retrieved at each position from unrelated experimental structures. Full-length structure models are then assembled from fragments using replica-exchange Monte Carlo simulations, which are guided by a composite knowledge-based force field. A number of novel energy terms and Monte Carlo movements are introduced and the particular contributions to enhancing the efficiency of both force field and search engine are analyzed in detail. QUARK prediction procedure is depicted and tested on the structure modeling of 145 nonhomologous proteins. Although no global templates are used and all fragments from experimental structures with template modeling score >0.5 are excluded, QUARK can successfully construct 3D models of correct folds in one-third cases of short proteins up to 100 residues. In the ninth community-wide Critical Assessment of protein Structure Prediction experiment, QUARK server outperformed the second and third best servers by 18 and 47% based on the cumulative Z-score of global distance test-total scores in the FM category. Although ab initio protein folding remains a significant challenge, these data demonstrate new progress toward the solution of the most important problem in the field. Copyright © 2012 Wiley Periodicals, Inc.
Ab initio results for intermediate-mass, open-shell nuclei

Science.gov (United States)

Baker, Robert B.; Dytrych, Tomas; Launey, Kristina D.; Draayer, Jerry P.

2017-01-01

A theoretical understanding of nuclei in the intermediate-mass region is vital to astrophysical models, especially for nucleosynthesis. Here, we employ the ab initio symmetry-adapted no-core shell model (SA-NCSM) in an effort to push first-principle calculations across the sd-shell region. The ab initio SA-NCSM's advantages come from its ability to control the growth of model spaces by including only physically relevant subspaces, which allows us to explore ultra-large model spaces beyond the reach of other methods. We report on calculations for 19Ne and 20Ne up through 13 harmonic oscillator shells using realistic interactions and discuss the underlying structure as well as implications for various astrophysical reactions. This work was supported by the U.S. NSF (OCI-0904874 and ACI -1516338) and the U.S. DOE (DE-SC0005248), and also benefitted from the Blue Waters sustained-petascale computing project and high performance computing resources provided by LSU.
Ab initio theory and calculations of X-ray spectra

International Nuclear Information System (INIS)

Rehr, J.J.; Kas, J.J.; Prange, M.P.; Sorini, A.P.; Takimoto, Y.; Vila, F.

2009-01-01

There has been dramatic progress in recent years both in the calculation and interpretation of various x-ray spectroscopies. However, current theoretical calculations often use a number of simplified models to account for many-body effects, in lieu of first principles calculations. In an effort to overcome these limitations we describe in this article a number of recent advances in theory and in theoretical codes which offer the prospect of parameter free calculations that include the dominant many-body effects. These advances are based on ab initio calculations of the dielectric and vibrational response of a system. Calculations of the dielectric function over a broad spectrum yield system dependent self-energies and mean-free paths, as well as intrinsic losses due to multielectron excitations. Calculations of the dynamical matrix yield vibrational damping in terms of multiple-scattering Debye-Waller factors. Our ab initio methods for determining these many-body effects have led to new, improved, and broadly applicable x-ray and electron spectroscopy codes. (authors)
Ab Initio Many-Body Calculations Of Nucleon-Nucleus Scattering

Energy Technology Data Exchange (ETDEWEB)

Quaglioni, S; Navratil, P

2008-12-17

We develop a new ab initio many-body approach capable of describing simultaneously both bound and scattering states in light nuclei, by combining the resonating-group method with the use of realistic interactions, and a microscopic and consistent description of the nucleon clusters. This approach preserves translational symmetry and Pauli principle. We outline technical details and present phase shift results for neutron scattering on {sup 3}H, {sup 4}He and {sup 10}Be and proton scattering on {sup 3,4}He, using realistic nucleon-nucleon (NN) potentials. Our A = 4 scattering results are compared to earlier ab initio calculations. We find that the CD-Bonn NN potential in particular provides an excellent description of nucleon-{sup 4}He S-wave phase shifts. We demonstrate that a proper treatment of the coupling to the n-{sup 10}Be continuum is successful in explaining the parity-inverted ground state in {sup 11}Be.
Moral Education: Its Historical and Phenomenological Foundations.

Science.gov (United States)

Skorpen, Erling

1984-01-01

Presents a historically based outline of six stages of human normative development. Elucidates this outline phenomenologically and derives a hierarchical scheme of normative behavior from which to develop programs of moral education. (SK)
Ab initio multiple cloning algorithm for quantum nonadiabatic molecular dynamics

Energy Technology Data Exchange (ETDEWEB)

Makhov, Dmitry V.; Shalashilin, Dmitrii V. [Department of Chemistry, University of Leeds, Leeds LS2 9JT (United Kingdom); Glover, William J.; Martinez, Todd J. [Department of Chemistry and The PULSE Institute, Stanford University, Stanford, California 94305, USA and SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States)

2014-08-07

We present a new algorithm for ab initio quantum nonadiabatic molecular dynamics that combines the best features of ab initio Multiple Spawning (AIMS) and Multiconfigurational Ehrenfest (MCE) methods. In this new method, ab initio multiple cloning (AIMC), the individual trajectory basis functions (TBFs) follow Ehrenfest equations of motion (as in MCE). However, the basis set is expanded (as in AIMS) when these TBFs become sufficiently mixed, preventing prolonged evolution on an averaged potential energy surface. We refer to the expansion of the basis set as “cloning,” in analogy to the “spawning” procedure in AIMS. This synthesis of AIMS and MCE allows us to leverage the benefits of mean-field evolution during periods of strong nonadiabatic coupling while simultaneously avoiding mean-field artifacts in Ehrenfest dynamics. We explore the use of time-displaced basis sets, “trains,” as a means of expanding the basis set for little cost. We also introduce a new bra-ket averaged Taylor expansion (BAT) to approximate the necessary potential energy and nonadiabatic coupling matrix elements. The BAT approximation avoids the necessity of computing electronic structure information at intermediate points between TBFs, as is usually done in saddle-point approximations used in AIMS. The efficiency of AIMC is demonstrated on the nonradiative decay of the first excited state of ethylene. The AIMC method has been implemented within the AIMS-MOLPRO package, which was extended to include Ehrenfest basis functions.
The outside of phenomenology: Jean-Luc Nancy on world and sense

African Journals Online (AJOL)

In this essay, I examine Jean-Luc Nancy's notion of the sense of the world in relation to the phenomenological investigation of the life-world in Husserl and the worldhood of the world in Heidegger. My aim is to address the reasons why Nancy stresses the need for a different thinking that goes beyond the phenomenological ...

Raman spectroscopy, ab-initio model calculations, and conformational, equilibria in ionic liquids

DEFF Research Database (Denmark)

Berg, Rolf W.

2009-01-01

spectroscopy and ab-initio molecular orbital calculations. A discussion is given, based mainly on some recent FT- Raman spectroscopic results on the model ionic liquid system of 1-butyl-3-methyl-imidazolium ([C4C1Im]+X-) salts. The rotational isomerism of the [C4C1Im]+ cation is described: the presence of anti.......3 Brief introduction to ab-initio model calculations .... 312 12.4 Case study on Raman spectroscopy and structure of imidazolium-based ionic liquids ..... 312 12.5 Raman spectra and structure of [C4C1Im]+ liquids ..... 315 12.6 Normal mode analysis and rotational isomerism of the [C4C1Im]+ cation...
The ionic structure of liquid sodium obtained by numerical simulation from 'first principles' and ab initio 'norm-conserving' pseudopotentials

International Nuclear Information System (INIS)

Harchaoui, N; Hellal, S; Grosdidier, B; Gasser, J G

2008-01-01

The physical properties of disordered matter depend on the 'atomic structure' i.e. the arrangement of the atoms. This arrangement is described by the structure factor S (q) in reciprocal space and by the pair correlation function g(r) in real space. The structure factor is obtained experimentally while the numerical simulation enables us to obtain the pair correlation function. Liquid sodium is one of the elements the most studied and one can wonder about new scientific contribution appropriateness. The majority of theoretical calculations are compared with the experiment of Waseda. However two other posterior measurements have been published and give different results, in particular with regard to the height of the first peak of the structure factor. Three models of pseudopotential are considered to describe the electron-ion interaction. The first is a local pseudopotential with the alternative known as 'individual' of the model suggested by Fiolhais et al. The second model considered is that of Bachelet et al. This one, ab-initio and 'norm conserving', is non local. The last model is that proposed by Shaw known as 'first principles' and 'energy dependent'. Various static dielectric functions characteristic of the effects of exchange and correlation have been used and developed by Hellal et al. We calculated the form factors (pseudopotential in reciprocal space) and deduce the normalized energy-wave-number characteristic F N (q), the interatomic pair potential V eff (r), then the pair correlation function g(r) by molecular dynamics. The structure factor S(q) is obtained by Fourier transform and is compared with the experiment. Our calculations with the Bachelet and Shaw pseudopotentials are close to the last experiments of Greenfield et al. and of Huijben et al. Our results are discussed
[How to think a phenomenological clinic].

Science.gov (United States)

Rovaletti, María L

2016-01-01

The emergence of Phenomenology cannot to be understood outside the context of naturalism, the crisis affecting the philosophy and the scientific foundation of psychology toward the end of the 19th century. Binswanger thinks Husserl's attempt to found the experience of the things themselves in intentional living structures can to be useful to guide the psychiatric examination. For that, he seeks in the fundamental dimensions of existence, the conditions of possibility of being sick, which are also those of the same psychiatry. While the phenomenological psycho(patho)logy has not born of direct confrontation with patients, it doesn't mean that it doesn't have internal references with practice. It's proposed then a semiological Eidetic founded in multiple modes of intentionality, or "basic categories", opposite of semiology supported on psychic functions. From etiology to the anthropological a priori of mental illnesses, from the symptom to the phenomenon, here are two possible readings in the field of the clinic.
Ab initio and empirical studies on the asymmetry of molecular current-voltage characteristics

International Nuclear Information System (INIS)

Hoft, R C; Armstrong, N; Ford, M J; Cortie, M B

2007-01-01

We perform theoretical calculations of the tunnelling current through various small organic molecules sandwiched between gold electrodes by using both a tunnel barrier model and an ab initio transport code. The height of the tunnelling barrier is taken to be the work function of gold as modified by the adsorbed molecule and calculated from an ab initio electronic structure code. The current-voltage characteristics of these molecules are compared. Asymmetry is introduced into the system in two ways: an asymmetric molecule and a gap between the molecule and the right electrode. The latter is a realistic situation in scanning probe experiments. The asymmetry is also realized in the tunnel barrier model by two distinct work functions on the left and right electrodes. Significant asymmetry is observed in the ab initio i(V) curves. The tunnel barrier i(V) curves show much less pronounced asymmetry. The relative sizes of the currents through the molecules are compared. In addition, the performance of the WKB approximation is compared to the results obtained from the exact Schroedinger solution to the tunnelling barrier problem
The accuracy of ab initio calculations without ab initio calculations for charged systems: Kriging predictions of atomistic properties for ions in aqueous solutions

Science.gov (United States)

Di Pasquale, Nicodemo; Davie, Stuart J.; Popelier, Paul L. A.

2018-06-01

Using the machine learning method kriging, we predict the energies of atoms in ion-water clusters, consisting of either Cl- or Na+ surrounded by a number of water molecules (i.e., without Na+Cl- interaction). These atomic energies are calculated following the topological energy partitioning method called Interacting Quantum Atoms (IQAs). Kriging predicts atomic properties (in this case IQA energies) by a model that has been trained over a small set of geometries with known property values. The results presented here are part of the development of an advanced type of force field, called FFLUX, which offers quantum mechanical information to molecular dynamics simulations without the limiting computational cost of ab initio calculations. The results reported for the prediction of the IQA components of the energy in the test set exhibit an accuracy of a few kJ/mol, corresponding to an average error of less than 5%, even when a large cluster of water molecules surrounding an ion is considered. Ions represent an important chemical system and this work shows that they can be correctly taken into account in the framework of the FFLUX force field.
Towards an ab initio evaluation of the wave - vector- and frequency-dependent dielectric response function for crystalline water

Energy Technology Data Exchange (ETDEWEB)

Zaider, M [Columbia Univ., New York, NY (USA). Radiological Research Labs.; Fry, J L; Orr, D E [Texas Univ., Arlington, TX (USA)

1990-01-01

We describe an ab initio calculation of the properties of energy loss by electrons in crystalline water using its dielectric response function, {epsilon}(q,{omega}), where q and {omega} are, respectively, the wave vector and frequency. The calculation was performed on a model system (cubic ice) in order to take advantage of its ordered structure (i.e. Block's theorem), but also because of evidence that liquid water in biological systems ('structured' water) contains residues with tetrahedral structure (i.e. ice) over time scales of at least 10{sup -11} s. The main features of the calculation are (a) {epsilon}(q,{omega}) is evaluated in the random phase approximation (we used the expression given by Ehrenreich and Cohen), (b) the crystal potential is expressed as a sum of water-molecule self-consistent potentials, and (c) wave functions are expanded using tight binding functions (ultimately employing a Gaussian base set). A total of seven states (bands), five occupied and two conduction, are considered. We report the band structure and the density of states of the crystal, as well as values of {epsilon}(q,{omega}) at selected values of q and {omega}. Results are compared with energy loss measurements and with absorption spectra (XPS, UPS, and VUV data). The possibility of using an empirical combination of molecular potentials as a phenomenological Hamiltonian is also examined. (author).
The Role of Aesthetics for Design Phenomenology

DEFF Research Database (Denmark)

Folkmann, Mads Nygaard

The aim of the paper is to conceptualize the means and effects of different dimensions of aesthetic meaning in relation to the experience of design. In doing so, the paper combines two philosophical interests in design, design phenomenology and design aesthetics, in order to promote a framework...... for discussing the impact of aesthetic meaning construction on experience. First, the paper raises the phenomenological question of the relationship between design and experience, specifically, how design conditions experience. Second, in looking at aesthetics in terms of a) the sensual appeal of design, b...... our experience: We can look at sensual, conceptual, and contextual aesthetic dimensions of design and examine their contribution to the framing of experience, that is, how different dimensions of meaning articulation in design offer different framings of the experiences promoted by design objects...
Phenomenological perspectives of self-care in healthcare professionals' continuing education

Directory of Open Access Journals (Sweden)

Daniele Bruzzone

2014-12-01

Full Text Available Healthcare professionals, daily confronted with existential failty, feel themselves emotionally vulnerable too. For this reason, they need knowledge and tools in order to take care for themselves. Phenomenology provides an epistemological model that includes subjective and affective dimensions and legitimates lived experience as a source of cognition. In the undergraduate and continuing education of healthcare professionals, the phenomenological approach can represent a way of promoting self-care through personal narrative and reflection.
Responsibility and the Moral Phenomenology of Using Self-Driving Cars

OpenAIRE

Coeckelbergh, Mark

2016-01-01

This paper explores how the phenomenology of using self-driving cars influences conditions for exercising and ascribing responsibility. First, a working account of responsibility is presented, which identifies two classic Aristotelian conditions for responsibility and adds a relational one, and which makes a distinction between responsibility for (what one does) and responsibility to (others). Then, this account is applied to a phenomenological analysis of what happens when we use a self-driv...
Structure and dynamics of hydrated Fe(II) and Fe(III) ions. Quantum mechanical and molecular mechanical simulations

International Nuclear Information System (INIS)

Remsungnen, T.

2002-11-01

Classical molecular dynamics (MD) and combined em ab initio quantum mechanical/molecular mechanical molecular dynamics (QM/MM-MD) simulations have been performed to investigate structural, dynamical and energetical properties of Fe(II), and Fe(III) transition metal ions in aqueous solution. In the QM/MM-MD simulations the ion and its first hydration sphere were treated at the Hartree-Fock ab initio quantum mechanical level, while ab initio generated pair plus three-body potentials were employed for the remaining system. For the classical MD simulation the pair plus three-body potential were employed for all ion-water interactions. The coordination number of the first hydration shell is 100 % of 6 in both cases. The number of waters in the second hydration shell obtained from classical simulations are 13.4 and 15.1 for Fe(II) and Fe(III), respectively, while QM/MM-MD gives the values of 12.4 and 13.4 for Fe(II) and Fe(III). The energies of hydration obtained from MD and QM/MM-MD for Fe(II) are 520 and 500 kcal/mol, and for Fe(III) 1160 and 1100 kcal/mol respectively. The mean residence times of water in the second shell obtained from QM/MM-MD are 24 and 48 ps for Fe(II) and Fe(III), respectively. In contrast to the data obtained from classical MD simulation, the QM/MM-MD values are all in good agreement with the experimental data available. These investigations and results clearly indicate that many-body effects are essential for the proper description of all properties of the aqueous solution of both Fe(II) and Fe(III) ions. (author)
A Hermeneutic Phenomenological Approach to Understanding ...

African Journals Online (AJOL)

User

focus in a new way, it enables us to glimpse the phenomenon anew, with the prospect of .... three girls (Claudia, Sarah and Kamille) and three ... were registered in the enriched school programme. .... phenomenological dynamic offers an original and ..... is a registered nurse and Professor in the Department of Education,.
Alternative Education Completers: A Phenomenological Study

Science.gov (United States)

Murray, Becky L.; Holt, Carleton R.

2014-01-01

The purpose of this study was to explore the elements of the alternative education experience significant to successful completion of the program. This phenomenological paradigm provided the framework for all aspects of the qualitative study. Students, parents, administrators, and staff members of two alternative programs in the southeast Kansas…
Phenomenological modeling of critical heat flux: The GRAMP code and its validation

International Nuclear Information System (INIS)

Ahmad, M.; Chandraker, D.K.; Hewitt, G.F.; Vijayan, P.K.; Walker, S.P.

2013-01-01

Highlights: ► Assessment of CHF limits is vital for LWR optimization and safety analysis. ► Phenomenological modeling is a valuable adjunct to pure empiricism. ► It is based on empirical representations of the (several, competing) phenomena. ► Phenomenological modeling codes making ‘aggregate’ predictions need careful assessment against experiments. ► The physical and mathematical basis of a phenomenological modeling code GRAMP is presented. ► The GRAMP code is assessed against measurements from BARC (India) and Harwell (UK), and the Look Up Tables. - Abstract: Reliable knowledge of the critical heat flux is vital for the design of light water reactors, for both safety and optimization. The use of wholly empirical correlations, or equivalently “Look Up Tables”, can be very effective, but is generally less so in more complex cases, and in particular cases where the heat flux is axially non-uniform. Phenomenological models are in principle more able to take into account of a wider range of conditions, with a less comprehensive coverage of experimental measurements. These models themselves are in part based upon empirical correlations, albeit of the more fundamental individual phenomena occurring, rather than the aggregate behaviour, and as such they too require experimental validation. In this paper we present the basis of a general-purpose phenomenological code, GRAMP, and then use two independent ‘direct’ sets of measurement, from BARC in India and from Harwell in the United Kingdom, and the large dataset embodied in the Look Up Tables, to perform a validation exercise on it. Very good agreement between predictions and experimental measurements is observed, adding to the confidence with which the phenomenological model can be used. Remaining important uncertainties in the phenomenological modeling of CHF, namely the importance of the initial entrained fraction on entry to annular flow, and the influence of the heat flux on entrainment rate
Style as a Symptom: A Phenomenological Perspective.

Science.gov (United States)

Gregorc, Anthony F.

1984-01-01

Findings from early and current phenomenological studies indicate that stylistic characteristics are indicators of psychological forces that guide interactions with the world. Implications of how this theory relates to learning and teaching styles are discussed. (DF)
Modelling of nuclear glasses by classical and ab initio molecular dynamics; Modelisation de verres intervenant dans le conditionnement des dechets radioactifs par dynamiques moleculaires classique et ab initio

Energy Technology Data Exchange (ETDEWEB)

Ganster, P

2004-10-15

A calcium aluminosilicate glass of molar composition 67 % SiO{sub 2} - 12 % Al{sub 2}O{sub 3} - 21 % CaO was modelled by classical and ab initio molecular dynamics. The size effect study in classical MD shows that the systems of 100 atoms are more ordered than the larger ones. These effects are mainly due to the 3-body terms in the empirical potentials. Nevertheless, these effects are small and the structures generated are in agreement with experimental data. In such kind of glass, we denote an aluminium avoidance and an excess of non bridging oxygens which can be compensated by tri coordinated oxygens. When the dynamics of systems of 100 and 200 atoms is followed by ab initio MD, some local arrangements occurs (bond length, angular distributions). Thus, more realistic vibrational properties are obtained in ab initio MD. The modelling of thin films shows that aluminium atoms extend to the most external part of the surface and they are all tri-coordinated. Calcium atoms are set in the sub layer part of the surface and they produce a depolymerization of the network. In classical MD, tri-coordinated aluminium atoms produce an important electric field above the surface. With non bridging oxygens, they constitute attractive sites for single water molecules. (author)
An ab initio study of the structure and dynamics of bulk liquid Cd and its liquid-vapor interface

International Nuclear Information System (INIS)

Calderín, L; González, L E; González, D J

2013-01-01

Several static and dynamic properties of bulk liquid Cd at a thermodynamic state near its triple point have been calculated by means of ab initio molecular dynamics simulations. The calculated static structure shows a very good agreement with the available experimental data. The dynamical structure reveals collective density excitations with an associated dispersion relation which points to a small positive dispersion. Results are also reported for several transport coefficients. Additional simulations have also been performed at a slightly higher temperature in order to study the structure of the free liquid surface. The ionic density profile shows an oscillatory behavior with two different wavelengths, as the spacing between the outer and first inner layer is different from that between the other inner layers. The calculated reflectivity shows a marked maximum whose origin is related to the surface layering, along with a shoulder located at a much smaller wavevector transfer.
Phenomenology of cosmic phase transitions

International Nuclear Information System (INIS)

Kaempfer, B.; Lukacs, B.; Paal, G.

1989-11-01

The evolution of the cosmic matter from Planck temperature to the atomic combination temperature is considered from a phenomenological point of view. Particular emphasis is devoted to the sequence of cosmic phase transitions. The inflationary era at the temperature of the order of the grand unification energy scale and the quantum chromodynamic confinement transition are dealt with in detail. (author) 131 refs.; 26 figs
Conclusions for the Xth moriond conference on the phenomenology of hadronic structure

International Nuclear Information System (INIS)

Yokosawa, A.

A summary is presented of the talks presented on the phenomenology of hadronic structure including diffractive, elastic, and diffractive--dissociation data, correlation experiments, multiplicity at large transverse momentum, high and low energy phenomenology, results from the proton synchrotron, psi production, and the np charge-exchange reaction. (U.S.)
van Manen's method and reduction in a phenomenological hermeneutic study.

Science.gov (United States)

Heinonen, Kristiina

2015-03-01

To describe van Manen's method and concept of reduction in a study that used a phenomenological hermeneutic approach. Nurse researchers have used van Manen's method in different ways. Participants' lifeworlds are described in depth, but descriptions of reduction have been brief. The literature and knowledge review and manual search of research articles. Databases Web Science, PubMed, CINAHL and PsycINFO, without applying a time period, to identify uses of van Manen's method. This paper shows how van Manen's method has been used in nursing research and gives some examples of van Manen's reduction. Reduction enables us to conduct in-depth phenomenological hermeneutic research and understand people's lifeworlds. As there are many variations in adapting reduction, it is complex and confusing. This paper contributes to the discussion of phenomenology, hermeneutic study and reduction. It opens up reduction as a method for researchers to exploit.
Vantage perspective during encoding: The effects on phenomenological memory characteristics.

Science.gov (United States)

Mooren, Nora; Krans, Julie; Näring, Gérard W B; Moulds, Michelle L; van Minnen, Agnes

2016-05-01

The vantage perspective from which a memory is retrieved influences the memory's emotional impact, intrusiveness, and phenomenological characteristics. This study tested whether similar effects are observed when participants were instructed to imagine the events from a specific perspective. Fifty student participants listened to a verbal report of car-accidents and visualized the scenery from either a field or observer perspective. There were no between-condition differences in emotionality of memories and the number of intrusions, but imagery experienced from a relative observer perspective was rated as less self-relevant. In contrast to earlier studies on memory retrieval, vantage perspective influenced phenomenological memory characteristics of the memory representation such as sensory details, and ratings of vividness and distancing of the memory. However, vantage perspective is most likely not a stable phenomenological characteristic itself. Implications and suggestions for future research are discussed. Copyright © 2016 Elsevier Inc. All rights reserved.

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