1,720,966 research outputs found
Dataset for Crystal Structure Prediction Dataset for: 'Resorcinol Crystallization from the Melt: A New Ambient Phase and New “Riddles”'
No full textResulting low energy crystal structures from a crystal structure prediction of resorcinol.
The .csv file contains the structure name, the volume per molecule in Ansgtom^3, and the relative energy of the structure in kJ/mol.
The .cif file contains the structural information for each structure in energy order. The naming convention of each structure is its relative energy (kJ/mol), the structure name, conformation index, space group index, and sobol seed it resulted from.</span
Background data set for "Convergence properties of crystal structure prediction by quasi-random sampling"
Full text linkThe attached .zip file named
Background data set for "Convergence properties of crystal structure prediction by quasi-random sampling"
contains
1. .cif files of the predicted crystal structures for artemisinin, CC1 and quinacridone for all variations of the search method described in the publication. The cifs contain the final calculated lattice energies for each structure.
2. pickle files of raw data, readable in Python, containing energies, crystal structural information and information on number of times each structure was located in the searches.</span
Improving density functional theory for crystal polymorph energetics
No full textWe show that the quality of density functional theory (DFT) predictions for the relative stabilities of polymorphs of crystalline para-diiodobenzene (PDIB) is dramatically improved through a simple two-body correction using wavefunction-based electronic structure theory. PDIB has two stable polymorphs under ambient conditions, and like Hongo et al. [J. Phys. Chem. Lett., 1, 1789 (2010)] we find that DFT makes wildly variable predictions of the relative stabilities, depending on the approximate functional used. The two-body corrected scheme, using Grimme's spin-scaled variant of second-order Moller-Plesset perturbation theory and any of the tested density functionals, predicts the a-polymorph to be more stable, consistent with experiment, and produces a relative stability that agrees with the benchmark quantum Monte-Carlo results of Hongo et al. within statistical uncertainty.</p
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
Rapid structure determination of molecular solids using chemical shifts directed by unambiguous prior constraints
No full textNMR based crystallography approaches involving the combination of crystal structure prediction methods, ab-initio calculated chemical shifts and solid-state NMR experiments are a powerful approach for crystal structure determination of microcrystalline powders. However, currently structural information obtained from solid state NMR is usually included only after a set of candidate crystal structures has already been independently generated, starting from a set of single molecule conformations. Here, we show with the case of ampicillin that this can lead to failure of structure determination. We propose a crystal structure determination method that includes experimental constraints during conformer selection. In order to overcome the problem that experimental measurements on the crystalline samples are not obviously translatable to restrict the single molecule conformational space, we propose constraints based on the analysis of absent cross-peaks in solidstate NMR correlation experiments. We show that these absences provide unambiguous structural constraints on both the crystal structure and the gas phase conformations, and therefore can be used for unambiguous selection. The approach is parameterized on the crystal structure determination of flutamide, flufenamic acid, and cocaine, where we reduce the computational cost by around 50%. Most importantly, the method is then shown to correctly determine the crystal structure of ampicillin, which would have failed using current methodsbecause it adopts a high energy conformer in its crystal structure. The average positional RMSE on the NMR powder structure is 〈푟_av〉 = 0.176 Å, which corresponds to an average equivalent displacement parameter 푈_eq = 0.0103 Å2
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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