1,721,010 research outputs found
Applications of a variational coupled-electron pair approach to the calculation of intermolecular interaction in the framework of the VB theory: Study of the van der Waals complex He-CH4 Source: JOURNAL OF CHEMICAL PHYSICS Volume: 113 Issue: 16 Pages: 6724-6735 Published: OCT 22 2000 Times Cited: 10
No full textA general nonorthogonal coupled electron pair approach for the evaluation of electron correlation contribution is presented in details. The self-consistent field for molecular interactions wave function is used as reference state for a multistructure valence bond (VB) calculation. The central idea of the method is the optimization of the virtual space of the VB wave function by means of a procedure very close to the independent electron pair approach (IEPA) scheme. All the orbitals employed are expanded in the basis set of their fragment so as to exclude the basis set superposition error (BSSE) in a priori fashion. As an example, the application to the study of the van der Waals complex He–CH4 is reported. The equilibrium geometry of the system occurs at a He–C distance of 3.6 Å , with the He atom pointing to the center of one of the faces of the CH4 molecule, with a well depth of 19 cm−1. The potential energy surface of the He–CH4 complex is used to determine the parameters of a potential model which is employed in close-coupling calculations of integral state-to-state cross sections for rotationally inelastic scattering of methane molecules with helium atoms. The predicted values are compared with the available experimental data
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
Cover Image, Volume 116, Issue 21
No full textOn page 1575, Matteo Bonfanti and Rocco Martinazzo examine reactions at surfaces under a magnifying glass. Fruitful combination of theory, modelling, and simulations provides a powerful tool to understand the dynamics of atoms and molecules at the gas‐solid interface. This is pictured on the cover with a simple illustration of two prototypical recombination processes, the Eley‐Rideal (left) and the Langmuir‐Hinshelwood (right) reactions. Image credit goes to Matteo Bonfanti. (DOI: 10.1002/qua.25192
The Local Coherent-State approach to system-bath quantum dynamics
No full textThe recently introduced Local Coherent-State Approximation (LCSA) method (R. Martinazzo, M. Nest, P. Saalfrank and G.F. Tantardini, J. Chem. Phys. 125, 194102 (2006)) is a time-dependent, multiconfiguration method of the general G-MCTDH type which has been specifically tailored to deal with system-bath dynamical problems. In the usual system-bath picture, it uses discrete variable representation (DVR) states for the subsystem and Hartree products of coherent-states (CSs) for local bath states, in such a way to capture the important system-bath correlations and to scale linearly with respect to the number of bath degrees of freedom. Some generalizations of the method are introduced, ranging from locally multiconfigurational variants to generalized mixed quantum-classical schemes. In the multiconfiguration variants the Hartree approximation is relaxed while preserving the linear scaling property, and local bath states are described by superposition of CSs products. In the generalized mixed quantum-classical approaches, locality is reduced and each bath configuration is used for groups of subsystem DVR states. These extensions include a DVR-based, full G-MCTDH method and the traditional mixed quantum-classical approach as limiting cases. Applications to model system-bath problems at T=0 K (e.g. vibrational relaxation, tunneling and surface sticking) are discussed and results are compared with exact MCTDH ones in systems with 50-100 bath degrees of freedom
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
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