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Showing 1 to 13 of 13 for “"DFTB"”.
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Quantenchemische Berechnungen zur enantioselektiv katalysierten Aldolreaktion
… Reaktion berechnet, wobei sich der Einsatz der DFTB-Methode (density-functional based tight-binding method) zur Berechnung des Systems als sehr gut geeignet erwies. Die Leistungsfähigkeit der DFTB Methode konnte im Vergleich mit den geometrischen Daten aus Röntgenkristallstrukturanalysen …
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Developing methods to construct ring pucker free energy hypersurfaces applied to the analysis of glycosidase enzyme catalytic mechanisms
… QM methods - AM1, PM3, PM3CARB-1 and SCC-DFTB. From this, the accessible puckering conformations and minimum free energy paths of puckering were reasoned An analysis of the furanose and pyranose free energy pucker surfaces and volumes compared with both Density Functional Theory …
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Structural, electronic and optical properties of cadmium sulfide nanoparticles
… density-functional based tight-binding method (DFTB) are overcome by a new SCF-DFTB method. Density-functional-based calculations employing linear-response theory have been performed on cadmium sulfide nanoparticles considering different stoichiometries, underlying crystal structures …
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COMPUTATIONAL STUDY OF THE INTERACTION BETWEEN MOLECULES OF TECHNOLOGICAL INTEREST AND MODIFIED NANOTUBULAR CLAYS
… the creation of Slater-Koster parameters set for DFTB calculation. The modus operandi used for the parametrization process has a general validity, namely it is applicable also to other type of materials. The new parameters allow, in future studies, the usage in a DFTB calculation of species that …
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Locality of forces in molecular systems
… the locality of the tight-binding model DFTB and quantified the extent to which chemical changes, such as bond conjugation and oxygen addition, introduce long-range effects within the more accurate DFT model. The results motivated the development of an intramolecular hydrocarbon potential …
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Characterizing the potential energy surface of two dimensional and bulk materials using high dimensional neural network potentials
… Theory method, Density Functional Tight Binding (DFTB+), is used to compute quantities required for the reference dataset. It is found that a network made up of linear activation functions in ænet is (almost) equivalent to a one-layer radial basis function network, and is sufficient to learn a …
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Mesoscopic Distinct Element Method for Multiscale Modeling of Carbon Nanotubes
… density functional theory-based tight-binding (DFTB) objective molecular modeling. Our mDEM model is capable of reproducing the atomistic elastic and frictional properties of CNTs. With the mDEM model, tensile tests of mesoscale CNT network were carried out, showing results in good agreement …
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Growth of unsaturated, cyclic, and polycyclic aromatic hydrocarbons: Reactions under the conditions of the interstellar medium
… level of theory was increased at each step from DFTB (tight-binding density-functional), to DFT, and finally to post-Hartree-Fock methods. Results on CH based hydrocarbon growth showed the transition from non-cyclic hydrocarbons to cyclic and aromatic structures and from cyclic to polycyclic …
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Atomistic simulations of semiconductor and metallic nanoparticles
… force field MD (DL POLY [1]), tightbinding DFT (DFTB+ [2]), conventional DFT (CASTEP [3]) and linear-scaling DFT (ONETEP [4]). A brief introduction regarding some basic principles of quantum mechanics (QM) and of solid state physics is presented in the first chapter; followed by a general chapter …
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Measuring the effects of reaction coordinate and electronic treatments in the QM/MM reaction dynamics of Trypanosoma cruzi trans-sialidase
… for B3LYP/6-31G(d), B3LYP/6-31G and SCC-DFTB/MIO point to the minimal basis set as the primary limitation in using self-consistent charge density functional tight binding as the quantum mechanical model for modeling of enzymatic reactions transforming sialic acid substrates.
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Theoretial studies of carbon-based nanostrutured materials with applications in hydrogen storage
The main goal of this work is to search for new stable porous carbon-based materials, which have the ability to accommodate and store hydrogen gas. Theoretical and experimental studies suggest a close relation between the nano-scale structure of the material and its storage capacity. In order to …
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Electron beam generation and structure of defects in carbon and boron nitride nanotubes
The nature and role of defects is of primary importance to understand the physical properties of C and BN single walled nanotubes. Transmission electron microscopy (TEM) is a well known powerful tool to study the structure of defects in materials. However, in the case of SWNTs, the electron …