1,721,362 research outputs found
All-electron CASPT2 study of Ce(eta(8)-C8H6)(2)
No full textCASSCF wave functions and CASPT2 energies are presented for the ground and 15 and 31 excited states of the D-2d and D-2h conformers respectively of the f-element sandwich molecule CePn(2) (Pn =eta(8)-C8H6) The ground states of both conformers are found to be strongly multiconfigurational, analogous to cerocene, CeCOT2 (COT = eta(8)-C8H8), as reported in Journal of Physical Chemistry A 113 (2009) 2896 Investigation of the nature of the multiconfigurational character shows that the analogy with cerocene is indeed strong It is shown that the occupations of the natural orbitals produce a more reliable description of the CePn(2) ground state than does the configurational admixture, and that these occupations can be used to deduce a value for the total f-density in the system. This density is found to be slightly lower than that of cerocene, and is in good agreement with that found experimentally. A density functional theory calculation of the same system is able to broadly capture the important features of the electronic structure, but is unable to replicate the experimental value of the total f-density CASPT2 calculations reproduce the energy of the first band in the UV/Vis spectrum of CePn*(2) (Pn* =eta(8)-(CMe6)-Me-8) to within 0 01 eV Although this extremely good agreement is probably somewhat fortuitous, it highlights the fact that multiconfigurational methods are required in order to model systems such as CePn(2) to a high level of accuracy. (C) 2010 Academie des sciences. Published by Elsevier Masson SAS. All rights reserve
Are the Ground States of the Later Actinocenes Multiconfigurational? All-Electron Spin-Orbit Coupled CASPT2 Calculations on An(eta(8)-C8H8)(2) (An = Th, U, Pu, Cm)
No full textSpin-orbit free and spin-orbit coupled CASPT2 wave functions and energies are presented for the ground and low-lying excited states of four actinide element sandwich molecules; thorocene (ThCOT2), uranocene (UCOT2), plutonocene (PuCOT2), and curocene (CmCOT2). Spin-orbit coupling is found to make little difference to the equilibrium geometry of uranocene and plutonocene but has a significant effect on the energy spectrum of all the systems considered here other than thorocene. In all cases, however, the spin-orbit free ground states make the dominant contribution to their spin-orbit coupled counterparts. Following work presented in J. Phys. Chem. A 2009, 113, 2896, the variation in the multiconfigurational character of the ground-state wave functions as the 5f series is crossed is quantified via the occupation of the a(u)/b(1u) (e(2u)) metal-ring bonding and antibonding natural orbitals. The ground state of plutonocene is found to be nondegenerate with vertical bar M-J vertical bar = 0, in agreement with its temperature-independent paramagnetism
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Is Cerocene Really a Ce(III) Compound? All-Electron Spin-Orbit Coupled CASPT2 Calculations on M(eta(8)-C8H8)(2) (M = Th, Pa, Ce)
No full textSpin-orbit free CASPT2 wave functions and energies are presented for the ground and 31 excited states of three f element sandwich Molecules; thorocene (ThCOT2), protactinocene (PaCOT2), and cerocene (CeCOT2). Ground-state metal-ring centroid distances are optimized at this level and show excellent agreement with experiment. The effects of spin-orbit coupling are included and are found to be negligible for the ground states of ThCOT2, and CeCOT2, for which comparison of the electronic excitation energies is made with experimental data. For PaCOT2, spin-orbit coupling is found to alter significantly the energies and nature of the ground and low-lying excited states, and good agreement is obtained with previous computational data. The ground state of CeCoT2 is found to be strongly multiconfigurational, though not in the same way as previously reported. The relationship of this result to previous computational and experimental data is discussed, as is the most appropriate way to view the electronic structure of CeCOT2. It is concluded that the occupations of the natural orbitals produce a more reliable description of the CeCOT2 ground state than does the configurational admixture
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