Accelrys is a software company headquartered in the United States, with representation in Europe and Asia. It provides software for chemical, materials and bioscience research for the pharmaceutical, biotechnology, consumer packaged goods, aerospace, energy and chemical industries.It is a wholly owned subsidiary of Dassault Systèmes after an April 2014 acquisition. Wikipedia.
Rogers D.,3429 North Mountain View Drive |
Journal of Chemical Information and Modeling | Year: 2010
Extended-connectivity fingerprints (ECFPs) are a novel class of topological fingerprints for molecular characterization. Historically, topological fingerprints were developed for substructure and similarity searching. ECFPs were developed specifically for structure-activity modeling. ECFPs are circular fingerprints with a number of useful qualities: they can be very rapidly calculated; they are not predefined and can represent an essentially infinite number of different molecular features (including stereochemical information); their features represent the presence of particular substructures, allowing easier interpretation of analysis results; and the ECFP algorithm can be tailored to generate different types of circular fingerprints, optimized for different uses. While the use of ECFPs has been widely adopted and validated, a description of their implementation has not previously been presented in the literature. © 2010 American Chemical Society.
Friedrich A.,Goethe University Frankfurt |
Winkler B.,Goethe University Frankfurt |
Refson K.,Rutherford Appleton Laboratory |
Physical Review B - Condensed Matter and Materials Physics | Year: 2010
We report the elastic, electronic, and vibrational properties of hexagonal Re3 N rhenium nitride from experiment and theory using density-functional-theory-based atomistic model calculations. Re3 N was formed at 12 and 20 GPa at about 2000 K in a laser-heated diamond-anvil cell and recovered at ambient conditions. The structural model proposed recently is confirmed by a comparison of the vibrational properties obtained from Raman spectroscopy and from theory, which are in very good agreement. The mode Grüneisen parameters are reported from the pressure-dependent shift of the vibrational modes. The calculated density of electronic states at the Fermi level shows that Re3 N is metallic in the pressure range 0-20 GPa. © 2010 The American Physical Society.
Carlsson J.M.,Accelrys |
Carlsson J.M.,Fritz Haber Institute |
Ghiringhelli L.M.,Fritz Haber Institute |
Fasolino A.,Radboud University Nijmegen
Physical Review B - Condensed Matter and Materials Physics | Year: 2011
Several experiments have revealed the presence of grain boundaries in graphene that may change its electronic and elastic properties. Here, we present a general theory for the structure of  tilt grain boundaries in graphene based on the coincidence site lattice (CSL) theory. We show that the CSL theory uniquely classifies the grain boundaries in terms of the misorientation angle θ and periodicity d using two grain-boundary indices (m,n), similar to the nanotube indices. The structure and formation energy of a large set of grain boundaries generated by the CSL theory for 0<θ<60 (up to 15 608 atoms) were optimized by a hierarchical methodology and validated by density functional calculations. We find that low-energy grain boundaries in graphene can be identified as dislocation arrays. The dislocations form hillocks like those observed by scanning tunneling microscopy in graphene grown on Ir(111) for small θ that flatten out at larger misorientation angles. We find that, in contrast to three-dimensional materials, the strain created by the grain boundary can be released via out-of-plane distortions that lead to an effective attractive interaction between dislocation cores. Therefore, the dependence on θ of the formation energy parallels that of the out-of-plane distortions, with a secondary minimum at θ=32.2 where the grain boundary is made of a flat zigzag array of only 5 and 7 rings. For θ>32.2, other nonhexagonal rings are also possible. We discuss the importance of these findings for the interpretation of recent experimental results. © 2011 American Physical Society.
Bjork J.,Linkoping University |
Chemistry - A European Journal | Year: 2014
The covalent molecular assembly on metal surfaces is explored, outlining the different types of applicable reactions. Density functional calculations for on-surface reactions are shown to yield valuable insights into specific reaction mechanisms and trends across the periodic table. Finally, it is shown how design rules could be derived for nanostructures on metal surfaces. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
International Journal of Quantum Chemistry | Year: 2011
This study aims to use the concept of ground-state reactivity index formalism within density functional theory (DFT) to predict the behavior of the excited state through the response function produced by weak electric field on chlorinated methanes and chlorinated benzenes. A comparison was made between the geometry of ground state and the excited state for those moieties through configuration interaction (CI) method with Austin Model 1 Hamiltonian over the optimized geometry of DFT at the ground state. Results obtained through these two methodologies suggested that in terms of polarizability and heat of formation, DFT can reproduce the excited state qualitatively. Again, those results can be further validated through UV spectral data, generated using CI method. The reactivity index proposition at ground state shows the potential of DFT to simulate excitation. © 2010 Wiley Periodicals, Inc.