Relativistic Density Functional Studies on Ligated Transition Metal Clusters PDF Download
Are you looking for read ebook online? Search for your book and save it on your Kindle device, PC, phones or tablets. Download Relativistic Density Functional Studies on Ligated Transition Metal Clusters PDF full book. Access full book title Relativistic Density Functional Studies on Ligated Transition Metal Clusters by Alexander Genest. Download full books in PDF and EPUB format.
Author: Alexander Genest
Publisher:
ISBN:
Category :
Languages : en
Pages : 161
Get Book Here
Book Description
Author: Alexander Genest
Publisher:
ISBN:
Category :
Languages : en
Pages : 161
Get Book Here
Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
Get Book Here
Book Description
The influence of different ligands on small to medium size transition metal clusters was studied computationally by a scalar relativistic density functional method. For small metal clusters with main group atom impurities H, C, and O a large variety of structures was discovered, indicating the flexibility of the cluster framework. Thiolate ligands on M13 clusters (M = Cu, Au) were found to prefer bridge coordination. A QM/MM scheme was successfully tested on ligated clusters to reproduce results from full density functional calculations on Cu13 with thiolate ligands. For the first time, the compound Au55(PPh3)12Cl6 was studied computationally, using simple phosphanes as model ligands. From experiments chlorine has been suggested to exhibit terminal coordination, but higher coordination was calculated. In addition, instead of the often suggested cuboctahedral shape of the cluster core, a quasi-icosahedral structure was determined due to ligand-induced relaxation.
Author: Mohindar Seehra
Publisher: BoD – Books on Demand
ISBN: 1789232929
Category : Technology & Engineering
Languages : en
Pages : 432
Get Book Here
Book Description
The use of copper, silver, gold and platinum in jewelry as a measure of wealth is well known. This book contains 19 chapters written by international authors on other uses and applications of noble and precious metals (copper, silver, gold, platinum, palladium, iridium, osmium, rhodium, ruthenium, and rhenium). The topics covered include surface-enhanced Raman scattering, quantum dots, synthesis and properties of nanostructures, and its applications in the diverse fields such as high-tech engineering, nanotechnology, catalysis, and biomedical applications. The basis for these applications is their high-free electron concentrations combined with high-temperature stability and corrosion resistance and methods developed for synthesizing nanostructures. Recent developments in all these areas with up-to-date references are emphasized.
Author: Satyender Goel
Publisher:
ISBN:
Category : Density functionals
Languages : en
Pages : 140
Get Book Here
Book Description
This dissertation focuses on computational study of the geometry and energetics small molecules and nanoclusters involving transition metals (TM). These clusters may be used for various industrial applications including catalysis and photonics. Specifically, in this work we have studied hydrides and carbides of 3d-transition metal systems (Sc through Cu), small nickel and gold clusters. Qualitatively correct description of the bond dissociation is ensured by allowing the spatial and spin symmetry to break. We have tested applicability of new exchange-correlation functional and alternative theoretical descriptions (spin-contamination correction in broken symmetry DFT and ensemble Kohn-Sham (EKS)) as well. We studies TM hydrides and carbides systems to understand the importance of underlying phenomenon of bond breaking in catalytic processes. We have tested several exchange-correlation functionals including explicit dependence on kinetic energy density ([tau]-functionals) for the description of hydrides (both neutral and cationic) and carbides formed by 3d-transition metals. We find M05-2x and BMK dissociation energies are in better agreement with experiment (where available) than those obtained with high level wavefunction theory methods, published previously. This agreement with experiment deteriorates quickly for other functionals when the fraction of the Hartree-Fock exchange in DFT functional is decreased. Higher fraction of HF exchange is also essential in EKS formalism, but it does not help when spin-adapted unrestricted approach is employed. We analyze the electron spin densities using Natural Bond Orbital population analysis and find that simple description of 3d electrons as non-bonding in character is rarely correct. Unrestricted formalism results in appreciable spin-contamination for some of the systems at equilibrium, which motivated us to investigate it further in details. In order to correct the spin contamination effect on the energies, we propose a new scheme to correct for spin contamination arising in broken-symmetry DFT approach. Unlike conventional schemes, our spin correction is introduced for each spin-polarized electron pair individually and therefore is expected to yield more accurate energy values. We derive an expression to extract the energy of the pure singlet state from the energy of the broken-symmetry DFT description of the low spin state and the energies of the high spin states (pentuplet and two spin-contaminated triplets in the case of two spin-polarized electron pairs). We validate our spin-contamination correction approach by a simple example of H2 and applied to more complex MnH system. Ensemble KS formalism is also applied to investigate the dissociation of C2 molecule. We find that high fraction of HF exchange is essential to reproduce the results of EKS treatment with exact exchange-correlation functional. We analyze the geometry and energetics of small nickel clusters (Ni2-Ni5) for several lowest energy isomers. We also study all possible spin states of small nickel cluster isomers and report observed trends in energetics. Finally we determine the geometry and energetics of ten lowest energy isomers of four small gold clusters (Au2, Au4, Au6, and Au). We have also investigated the influence of cluster geometry, ligation, solvation and relativistic effects on electronic structure of these gold clusters. The effect of one-by-one ligand attachment in vacuum and solvent environment is also studied. Performance of five DFT functionals are tested as well; Local Spin Density Approximation (SVWN5), Generalized Gradient Approximation (PBE), kinetic energy density-dependent functional (TPSS), hybrid DFT (B3LYP), and CAM-B3LYP which accounts for long-range exchange effects believed to be important in the analysis of metal bonding in gold complexes and clusters. Our results exhibit the ligand induced stability enhancement of otherwise less stable isomers of Au4, Au6 and Au. Ligands are found to play a crucial role in determining the 2D[right arrow]3D transition realized in small gold clusters. In order to select an appropriate theory level to use in this study, we investigate the effect of attachment of four different ligands (NH3, NMe3, PH3, PMe3) on cluster geometry and energetics of Au2 and Au4 in vacuum and in solution. Our results benchmark the applicability of DFT functional model and polarization functions in the basis set for calculations of ligated gold cluster systems. We employ five different basis sets with increasing amount of polarization and diffuse functions; LANL2DZ, LANL2DZ-P, def2-SVP, def2-TZVP, and def2-QZVP. We obtain NMe3 [almost equal to]NH3 [less than] PH3 [less than] PMe3 order of ligand binding energies and observe shallow potential energy surfaces in all molecules. Our results suggest appropriate quantum-chemical methodologies to model small noble metal clusters in realistic ligand environment to provide reliable theoretical analysis in order to complement experiments.
Author: Sutjano Jusuf
Publisher:
ISBN:
Category :
Languages : en
Pages : 348
Get Book Here
Book Description
Author: Jean-François Halet
Publisher:
ISBN: 9783030251253
Category : Metal clusters
Languages : en
Pages :
Get Book Here
Book Description
This volume dedicated to the memory of Marcel Sergent who was a leader in this field for many years, addresses past achievements and recent developments in this vibrant area of research. Large classes of ligated transition metal clusters are produced either exclusively or most reliably by means of high-temperature solid-state reactions. Among them, the Chevrel-Sergent phases and related materials have generated enormous interest since their discovery in 1971. Today, these materials and their numerous derivatives still constitute a vivid area of research finding some applications not only in superconductivity, but also in catalysis, optics or thermoelectricity to mention a few. .
Author: Walter Ekardt
Publisher: John Wiley & Sons
ISBN:
Category : Science
Languages : en
Pages : 312
Get Book Here
Book Description
Metal Clusters Edited by Walter Ekardt Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany The current state of knowledge on these aggregated metal atoms, including both the fundamental principles and recent results, is presented here in a comprehensive form. Emphasis is placed on the theory linking it to the latest experimental results. Topics covered include: The Jellium Model; The Quantum Chemical Approach; Density Functional Theory and Car-Parrinello Molecular Dynamics; Dissociation, Fragmentation and Fission; Optical and Thermal Properties of Sodium Clusters; and Magnetic Properties of Transition Metal Clusters. Metal Clusters is set to become the standard reference work in this mature field and will be invaluable for all researchers in a broad range of disciplines from theoretical chemistry to condensed matter physics and materials science.
Author: Artem R Oganov
Publisher: Royal Society of Chemistry
ISBN: 1788015622
Category : Science
Languages : en
Pages : 470
Get Book Here
Book Description
New technologies are made possible by new materials, and until recently new materials could only be discovered experimentally. Recent advances in solving the crystal structure prediction problem means that the computational design of materials is now a reality. Computational Materials Discovery provides a comprehensive review of this field covering different computational methodologies as well as specific applications of materials design. The book starts by illustrating how and why first-principle calculations have gained importance in the process of materials discovery. The book is then split into three sections, the first exploring different approaches and ideas including crystal structure prediction from evolutionary approaches, data mining methods and applications of machine learning. Section two then looks at examples of designing specific functional materials with special technological relevance for example photovoltaic materials, superconducting materials, topological insulators and thermoelectric materials. The final section considers recent developments in creating low-dimensional materials. With contributions from pioneers and leaders in the field, this unique and timely book provides a convenient entry point for graduate students, researchers and industrial scientists on both the methodologies and applications of the computational design of materials.
Author: Shen Li
Publisher:
ISBN:
Category :
Languages : en
Pages : 210
Get Book Here
Book Description
Author: Alamgir Kabir
Publisher: LAP Lambert Academic Publishing
ISBN: 9783659900907
Category :
Languages : en
Pages : 216
Get Book Here
Book Description
In this book, Density Functional Theory (DFT) and Dynamical Mean-Field Theory (DMFT) approaches are applied to study the magnetic properties of transition metal nanosystems of different sizes and compositions. In particular, in order to take into account dynamical electron correlation effects (time-resolved local charge interactions), we have adopted the DFT+DMFT formalism and made it suitable for application to nanostructures. Preliminary application of this DFT+DMFT approach, using available codes, to study the magnetic properties of small (2 to 5-atom) Fe and FePt clusters provide meaningful results: dynamical effects lead to a reduction of the cluster magnetic moment as compared to that obtained from DFT or DFT+U (U being the Coulomb repulsion parameter). We have subsequently developed our own nanoDFT+DMFT code and applied it to examine the magnetization of iron particles containing10-147 atoms. Our results for the cluster magnetic moments are in a good agreement with experimental data. In particular, we are able to reproduce the oscillations in magnetic moment with size as observed in the experiments.
