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Author: Alamgir Kabir
Publisher: LAP Lambert Academic Publishing
ISBN: 9783659900907
Category :
Languages : en
Pages : 216
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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.
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.
Author: Alamgir Kabir
Publisher:
ISBN:
Category :
Languages : en
Pages : 189
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Book Description
In this thesis, 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.
Author: Steffen Backes
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: Vijay Kumar
Publisher: Springer Nature
ISBN: 9819956404
Category : Science
Languages : en
Pages : 515
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Book Description
This book highlights the optical properties of metal oxides at both the fundamental and applied level and their use in various applications. The book offers a basic understanding of the optical properties and related spectroscopic techniques essential for anyone interested in learning about metal oxide nanostructures. This is partly due to the fact that optical properties are closely associated with other properties and functionalities (e.g., electronic, magnetic, and thermal), which are of essential significance to many technological applications, such as optical data communications, imaging, lighting, and displays, life sciences, health care, security, and safety. The book also highlights the fundamentals and systematic developments in various optical techniques to achieve better characterization, cost-effective, user-friendly approaches, and most importantly, state-of-the-art developing methodologies for various scientific and technological applications. It provides an adequate understanding of the imposed limitations and highlights the prospects and challenges associated with optical analytical methods to achieve the desired performance in targeted applications.
Author: Falko P. Netzer
Publisher: Springer
ISBN: 3319283324
Category : Technology & Engineering
Languages : en
Pages : 403
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Book Description
This book summarizes the current knowledge of two-dimensional oxide materials. The fundamental properties of 2-D oxide systems are explored in terms of atomic structure, electronic behavior and surface chemistry. The concept of polarity in determining the stability of 2-D oxide layers is examined, charge transfer effects in ultrathin oxide films are reviewed as well as the role of defects in 2-D oxide films. The novel structure concepts that apply in oxide systems of low dimensionality are addressed, and a chapter giving an overview of state-of-the-art theoretical methods for electronic structure determination of nanostructured oxides is included. Special emphasis is given to a balanced view from the experimental and the theoretical side. Two-dimensional materials, and 2-D oxides in particular, have outstanding behavior due to dimensionality and proximity effects. Several chapters treat prototypical model systems as illustrative examples to discuss the peculiar physical and chemical properties of 2-D oxide systems. The chapters are written by renowned experts in the field.
Author: Daniel Glossman-Mitnik
Publisher: BoD – Books on Demand
ISBN: 178985167X
Category : Science
Languages : en
Pages : 168
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Book Description
Density Functional Theory (or DFT for short) is a potent methodology useful for calculating and understanding the molecular and electronic structure of atoms, molecules, clusters, and solids. Its use relies not only in the ability to calculate the molecular properties of the species of interest but also provides interesting concepts that allow a better comprehension of the chemical reactivity of the studied systems. This book represents an attempt to present examples on the utility of DFT for the understanding of the chemical reactivity through descriptors that constitute the basis of the so called Conceptual DFT (sometimes also named as Chemical Reactivity Theory) as well as the application of the theory and its related computational procedures in the determination of the molecular properties of different systems of academic and industrial interest.
Author: Johannes Ferber
Publisher:
ISBN:
Category :
Languages : en
Pages : 125
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Book Description
Author: Brian Patterson Neal
Publisher:
ISBN: 9781303792397
Category :
Languages : en
Pages :
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Book Description
The transition metal intermetallic compound NbFe2 displays a magnetic quantum critical point very near stoichiometry, unlike other Fe-based intermetallics, and no field or pressure tuning is required. In this compound we obtain an obvious candidate for the origin of quantum criticality: an accidental Fermi surface "hot stripe" centered on a point of vanishing quasiparticle velocity on the Fermi surface at an unconventional band critical point (uBCP) of NbFe2. Around this uBCP the dispersion is cubic ([epsilon](k) - [epsilon](f) [proportional to] k(superscript 3 over subscript x)) in one direction in the hexagonal basal plane and has a saddle point character in the orthogonal k(y), k(z) plane; both aspects have significant consequences. At such a uBCP Moriya's theory of weak magnetism breaks down due to divergent contributions to the dynamic bare susceptibility from the uBCP, both at Q (rigth arrow) 0 and at momenta spanning the uBCPs. These results are reminiscent of an earlier suggestion that anomalously low Fermi velocities are an essential aspect of the incipient or weak ferromagnetism of TiBe2, and strongly support the viewpoint that, for some quantum critical points, the mechanism may be identifiable in the underlying (mean field) electronic structure. Next, we study YMn2 in the cubic Laves phase (C15). With its highly frustrated pyrochlore type sublattice of Mn sites, it is one of a small but growing class of ordered magnets that lie close to a quantum critical point at stoichiometry. Its ground state displays long-spiral helical magnetic order that is highly sensitive to volume, disappearing due to the substitution of 3% Sc for the larger Y atom (chemical pressure), or by application of just 0.4 GPa pressure. The large change of volume (5%) upon ordering (T(N) = 100 K) argues for itinerant magnetism. In recentyears there have been developments in modeling magnetic fluctuations in itinerant magnets near the ordering point. We extend earlier results of Terao and Yamada on the first principles based energetics versus volume, and quantify the sensitivity of the magnetic state to pressure.Finally, we examine a tertiary nitride compound, Fe3Mo3N, which demonstrates quantum critical behavior and weak magnetism, with a structure consisting of a geometrically frustrated stella quadrangula lattice. Neutron scattering reveals antiferromagnetic ordering, but a 14 T magnetic field induces a ferromagnetic state, as does substitution of 5% Co on the Fe site. We present the energetics of a transition between these states with density functional based fixed spin moment studies. As the fixed spin moment in calculation is reduced, the ferromagnetic state switches to a ferrimagnetic state, approximately 0.2 eV higher in energy per formula unit.
Author:
Publisher:
ISBN:
Category : Dissertation abstracts
Languages : en
Pages : 816
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Book Description
Author: Wolfram Koch
Publisher: John Wiley & Sons
ISBN: 3527802819
Category : Science
Languages : en
Pages : 378
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Book Description
"Chemists familiar with conventional quantum mechanics will applaud and benefit greatly from this particularly instructive, thorough and clearly written exposition of density functional theory: its basis, concepts, terms, implementation, and performance in diverse applications. Users of DFT for structure, energy, and molecular property computations, as well as reaction mechanism studies, are guided to the optimum choices of the most effective methods. Well done!" Paul von Rague Schleyer "A conspicuous hole in the computational chemist's library is nicely filled by this book, which provides a wide-ranging and pragmatic view of the subject.[...It] should justifiably become the favorite text on the subject for practioneers who aim to use DFT to solve chemical problems." J. F. Stanton, J. Am. Chem. Soc. "The authors' aim is to guide the chemist through basic theoretical and related technical aspects of DFT at an easy-to-understand theoretical level. They succeed admirably." P. C. H. Mitchell, Appl. Organomet. Chem. "The authors have done an excellent service to the chemical community. [...] A Chemist's Guide to Density Functional Theory is exactly what the title suggests. It should be an invaluable source of insight and knowledge for many chemists using DFT approaches to solve chemical problems." M. Kaupp, Angew. Chem.
