1,720,975 research outputs found
TurboEELS - A code for the simulation of the electron energy loss and inelastic X-ray scattering spectra using the Liouville-Lanczos approach to time-dependent density-functional perturbation theory
No full textWe introduce turboEELS, an implementation of the Liouville-Lanczos approach to linearized time-dependent density-functional theory, designed to simulate electron energy loss and inelastic X-ray scattering spectra in periodic solids. turboEELS is open-source software distributed under the terms of the GPL as a component of Quantum ESPRESSO. As with other components, turboEELS is optimized to run on a variety of different platforms, from laptops to massively parallel architectures, using native mathematical libraries (LAPACK and FFTW) and a hierarchy of custom parallelization layers built on top of MPI. Program summary Program title: turboEELS Catalogue identifier: AEXB-v1-0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEXB-v1-0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU General Public License V 2.0 No. of lines in distributed program, including test data, etc.: 1371515 No. of bytes in distributed program, including test data, etc.: 37355712 Distribution format: tar.gz Programming language: Fortran 95. Computer: Any computer architecture. Operating system: GNU/Linux, AIX, IRIX, Mac OS X, and other UNIX-like OS's. Classification: 7.2. External routines: turboEELS is a tightly integrated component of the Quantum ESPRESSO distribution and requires the standard libraries linked by it: BLAS, LAPACK, FFTW, MPI. Nature of problem: Calculation of the electron energy loss and inelastic X-ray scattering spectra of periodic solids. Solution method: The charge-density susceptibility of a periodic system is expressed in terms of the resolvent of its Liouvillian superoperator within time-dependent density functional perturbation theory. It is calculated using non-Hermitian or pseudo-Hermitian variants of the Lanczos recursion scheme, whose implementation does not require the calculation of any virtual states. Pseudopotentials (both norm-conserving and ultrasoft) are used in conjunction with plane-wave basis sets and periodic boundary conditions. Relativistic effects (spin-orbit coupling) can be included in calculations. Restrictions: Linear-response regime. Adiabatic exchange-correlation kernels only. No hybrid functionals. Collinear spin-polarized formalism is not supported, only non-collinear spin-polarized case can be used. Spin-orbit coupling cannot be used with ultrasoft pseudopotentials. No magnetism. No Hubbard U formalism. No PAW pseudopotentials. Unusual features: No virtual orbitals are used, nor even calculated. A single Lanczos recursion gives access to the whole spectrum at fixed transferred momentum. Additional comments: The distribution file of this program can be downloaded from the Quantum ESPRESSO website: http://www.quantum-espresso.org/, and the development version of this program can be downloaded via SVN from the QE-forge website: http://qe-forge.org/gf/project/q-e/. !!!!! The distribution file for this program is over 37 Mbytes and therefore is not delivered directly when download or Email is requested. Instead a html file giving details of how the program can be obtained is sent. !!!!! Running time: From a few minutes for elemental bulk systems with a few atoms in the primitive unit cell on serial machines up to many hours on multiple processors for complex systems (e.g.; surfaces with high Miller indices) with dozens or hundreds of atoms
Improvement of Hydrogen Vacancy Diffusion Kinetics in MgH2 by Niobium- and Zirconium-Doping for Hydrogen Storage Applications
Full text linkTransition metal (TM) catalytic dopants are broadly used in hydrogen storage materials to increase H2 desorption and absorption kinetics. We have studied H vacancy formation energy in pure, Nb- or Zr- doped bulk magnesium hydride using density functional theory based calculations. The preferential dopant location was determined by means of occupation energy analysis. Both TM species prefer substitutional locations, Zr being more stable than Nb. Five different sites for H vacancy formation have been considered, all of them near the dopant. The vacancy formation energy decreases, especially in the interstitial Zr system in comparison with a pure one (from 1.35 to 0.51 eV). Concerning diffusion, we consider four paths in the pure and doped systems: the doping with TMs diminishes the activation energy barriers improving the diffusion kinetics, being more considerable for Zr. Effects of a possible spin polarization induced in the system by TM atoms and H vacancies generation have been considered as well.Fil: German, Estefania. The Abdus Salam. International Centre For Theoretical Physics; Italia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Gebauer, Ralph. The Abdus Salam. International Centre For Theoretical Physics; Itali
Why are MoS2 monolayers not a good catalyst for the oxygen evolution reaction?
Full text linkWe use density functional theory based calculations to study the energetics of the oxygen evolution reaction on a monolayer of MoS2. This material, a prototypical example of a layered transition metal dichalcogenide, is intensely studied in the context of many important catalytical applications, in particular for the hydrogen evolution reaction. The second half-reaction of the water-splitting process, the oxygen evolution reaction, is almost never considered on this material, due to its low activity. Based on our calculations, we explain this experimentally observed poor catalytic activity for the oxygen evolution by the weak binding of two key reaction intermediates (hydroxyl and hydroperoxyl) to the substrate. We explore substitutional doping with oxygen and phosphorous as means to facilitate the oxygen evolution on MoS2 layers. The oxygen substitution slightly increases the reaction´s overpotential, but does not significantly change the energetics. The doping with phosphorous, on the other hand, is not a promising way to promote the oxygen evolution on MoS2 layers. We also explore the role of the edges of MoS2 layers. We find that while the adsorption energies of reaction intermediates are strongly influenced by the presence of an edge, the final reaction overpotential remains nearly the same as on a pristine monolayer, meaning that the presence of edges is not favoring the OER.Fil: German, Estefania. Universidad de Valladolid; España. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Gebauer, Ralph. The Abdus Salam. International Centre for Theoretical Physics; Itali
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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