Download or read book Density Functional Study on Quantum Point Contacts written by Peng-Jen Chen and published by . This book was released on 2008 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: ?Pub Inc The transport of electrons through a quantum point contact (QPC) has been intensively studied in the past decade both from experimental and theoretical points of view. In addition to the stepwise nature (at multiples of G=2e^2/h), the conductance G of a QPC system also exhibits a small plateau around G=0.7, varying at different temperatures and magnetic fields. This so-called "0.7 anomaly" remains an unsettled issue to date. In this work, we use density functional theory (DFT) based on the local density approximation (LDA) to study the spatial distribution of charge density of a QPC system. Periodic boundary condition is imposed in our calculations. Despite the neglect of spin effect, we show similar features of charge density distribution in comparison with other works. We also study the asymmetric potential modification of a QPC when a source-drain bias $V_sd$ is applied across the QPC. It is found that $\beta$, the ratio of potential drop between source and unbiased QPC to $V_{sd}$, depends on the magnitude of the confinement potential $V_{sg}$ produced by the split gates. Different chemical potentials are set at source and drain for some numerical reason to keep equal bulk density at both sides. Our focus on the biased calculations is in the pinch-off regime, and $\beta$ is about 0.45 from our results. However, experimental results show that $\beta$ is about 0.25 when pinched-off (higher $V_{sg}$) and about 0.5 at conducting state (lower $V_{sg}$). Discussion and comment on this inconsistency will be made at the end of this article.

Download or read book Recent Advances in Density Functional Methods written by Delano Pun Chong and published by World Scientific. This book was released on 1995 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt: Of all the different areas in computational chemistry, density functional theory (DFT) enjoys the most rapid development. Even at the level of the local density approximation (LDA), which is computationally less demanding, DFT can usually provide better answers than Hartree-Fock formalism for large systems such as clusters and solids. For atoms and molecules, the results from DFT often rival those obtained by ab initio quantum chemistry, partly because larger basis sets can be used. Such encouraging results have in turn stimulated workers to further investigate the formal theory as well as the computational methodology of DFT.This Part II expands on the methodology and applications of DFT. Some of the chapters report on the latest developments (since the publication of Part I in 1995), while others extend the applications to wider range of molecules and their environments. Together, this and other recent review volumes on DFT show that DFT provides an efficient and accurate alternative to traditional quantum chemical methods. Such demonstration should hopefully stimulate frutiful developments in formal theory, better exchange-correlation functionals, and linear scaling methodology.

Download or read book Density Functional Theory written by David S. Sholl and published by John Wiley & Sons. This book was released on 2011-09-20 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: Demonstrates how anyone in math, science, and engineering can master DFT calculations Density functional theory (DFT) is one of the most frequently used computational tools for studying and predicting the properties of isolated molecules, bulk solids, and material interfaces, including surfaces. Although the theoretical underpinnings of DFT are quite complicated, this book demonstrates that the basic concepts underlying the calculations are simple enough to be understood by anyone with a background in chemistry, physics, engineering, or mathematics. The authors show how the widespread availability of powerful DFT codes makes it possible for students and researchers to apply this important computational technique to a broad range of fundamental and applied problems. Density Functional Theory: A Practical Introduction offers a concise, easy-to-follow introduction to the key concepts and practical applications of DFT, focusing on plane-wave DFT. The authors have many years of experience introducing DFT to students from a variety of backgrounds. The book therefore offers several features that have proven to be helpful in enabling students to master the subject, including: Problem sets in each chapter that give readers the opportunity to test their knowledge by performing their own calculations Worked examples that demonstrate how DFT calculations are used to solve real-world problems Further readings listed in each chapter enabling readers to investigate specific topics in greater depth This text is written at a level suitable for individuals from a variety of scientific, mathematical, and engineering backgrounds. No previous experience working with DFT calculations is needed.

Download or read book Quantum Transport Calculations for Nanosystems written by Kenji Hirose and published by CRC Press. This book was released on 2014-04-11 with total page 532 pages. Available in PDF, EPUB and Kindle. Book excerpt: As electric devices become smaller and smaller, transport simulations based on the quantum mechanics become more and more important. There are currently numerous textbooks on the basic concepts of quantum transport, but few present calculation methods in detail. This book provides various quantum transport simulation methods and shows applications

Download or read book Finite ranged Interactions and Multiband Effects in Quantum Point Contacts written by Lukas Weidinger and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Chemist s Guide to Density Functional Theory written by Wolfram Koch and published by John Wiley & Sons. This book was released on 2015-11-18 with total page 378 pages. Available in PDF, EPUB and Kindle. Book excerpt: "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.

Download or read book Time Dependent Density Functional Theory written by Miguel A.L. Marques and published by Springer. This book was released on 2006-09-12 with total page 603 pages. Available in PDF, EPUB and Kindle. Book excerpt: The year 2004 was a remarkable one for the growing ?eld of time-dependent density functional theory (TDDFT). Not only did we celebrate the 40th - niversary of the Hohenberg-Kohn paper, which had laid the foundation for ground-state density functional theory (DFT), but it was also the 20th - niversary of the work by Runge and Gross, establishing a ?rm footing for the time-dependent theory. Because the ?eld has grown to such prominence, and has spread to so many areas of science (from materials to biochemistry), we feel that a volume dedicated to TDDFT is most timely. TDDFT is based on a set of ideas and theorems quite distinct from those governingground-stateDFT,butemployingsimilar techniques.Itisfarmore than just applying ground-state DFT to time-dependent problems, as it - volves its own exact theorems and new and di?erent density functionals. Presently,themostpopularapplicationistheextractionofelectronicexcit- state properties, especially transition frequencies. By applying TDDFT after thegroundstateofamoleculehasbeenfound,wecanexploreandunderstand the complexity of its spectrum, thus providing much more information about the species. TDDFT has a especially strong impact in the photochemistry of biological molecules, where the molecules are too large to be handled by t- ditional quantum chemical methods, and are too complex to be understood with simple empirical frontier orbital theory.

Download or read book Density Functional Methods In Physics written by Reiner M. Dreizler and published by Springer Science & Business Media. This book was released on 2013-11-11 with total page 530 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Density Functional Theory written by Reiner M. Dreizler and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt: Density Functional Theory is a rapidly developing branch of many-particle physics that has found applications in atomic, molecular, solid-state and nuclear physics. This book describes the conceptual framework of density functional theory and discusses in detail the derivation of explicit functionals from first principles as well as their application to Coulomb systems. Both non-relativistic and relativistic systems are treated. The connection of density functional theory with other many-body methods is highlighted. The presentation is self-contained; the book is, thus, well suited for a graduate course on density functional theory.

Download or read book Nonequilibrium Carrier Dynamics in Semiconductors written by Marco Saraniti and published by Springer Science & Business Media. This book was released on 2007-12-14 with total page 370 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Nonequilibrium Carrier Dynamics in Semiconductors" is a well-established, specialist conference, held every two years, covering a range of topics of current interest to R&D in semiconductor physics/materials, optoelectronics, nanotechnology, quantum information processing. Papers accepted for publication are selected and peer-reviewed by members of the Program Committee during the conference to ensure both rapid and high-quality processing.

Download or read book Advances in Density Functional Theory and Beyond for Computational Chemistry written by Wei Hu and published by Frontiers Media SA. This book was released on 2021-09-13 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Density Functional Theory in Quantum Chemistry written by Takao Tsuneda and published by Springer Science & Business Media. This book was released on 2014-02-18 with total page 207 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this book, density functional theory (DFT) is introduced within the overall context of quantum chemistry. DFT has become the most frequently used theory in quantum chemistry calculations. However, thus far, there has been no book on the fundamentals of DFT that uses the terminology and methodology of quantum chemistry, which is familiar to many chemists, including experimentalists. This book first reviews the basic concepts and historical background of quantum chemistry and then explains those of DFT, showing how the latter fits into the bigger picture. Recent interesting topics of DFT in chemistry are also targeted. In particular, the physical meanings of state-of-the-art exchange-correlation functionals and their corrections are described in detail. Owing to its unconventionality, this book is certain to be of great interest not only to chemists but also to solid state physicists.

Download or read book Recent Advances in Density Functional Methods written by Delano Pun Chong and published by World Scientific. This book was released on 1995 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the last few years, much attention has been given by theoretical chemists to the development of more accurate model functionals and faster computational techniques including excited electronic states. The 8th International Conference on the Applications of Density Functional Theory to Chemistry and Physics, held in Rome, Italy, on 6-10 September 1999, gathered chemists and physicists to present and discuss state-of-the-art methodological developments and applications of density functional theory (DFT) to increasingly complex systems. The scientists shared their knowledge and experience in DFT, enabling them to face the challenges posed by the needs of high level modeling and simulation in their disciplines. The meeting was opened with an exciting lecture delivered by Nobel laureate W Kohn. The growing use of DFT in studying organic, inorganic and organometallic molecules, clusters and solids provided the basis for the success of the conference, whose main contributions are collected in this invaluable book.

Download or read book Molecular Electronics written by Juan Carlos Cuevas and published by World Scientific. This book was released on 2010 with total page 724 pages. Available in PDF, EPUB and Kindle. Book excerpt: 1. The birth of molecular electronics. 1.1. Why molecular electronics?. 1.2. A brief history of molecular electronics. 1.3. Scope and structure of the book -- 2. Fabrication of metallic atomic-size contacts. 2.1. Introduction. 2.2. Techniques involving the scanning electron microscope (STM). 2.3. Methods using atomic force microscopes (AFM). 2.4. Contacts between macroscopic wires. 2.5. Transmission electron microscope. 2.6. Mechanically controllable break-junctions (MCBJ). 2.7. Electromigration technique. 2.8. Electrochemical methods. 2.9. Recent developments. 2.10. Electronic transport measurements. 2.11. Exercises -- 3. Contacting single molecules: Experimental techniques. 3.1. Introduction. 3.2. Molecules for molecular electronics. 3.3. Deposition of molecules. 3.4. Contacting single molecules. 3.5. Contacting molecular ensembles. 3.6. Exercises -- 4. The scattering approach to phase-coherent transport in nanocontacts. 4.1. Introduction. 4.2. From mesoscopic conductors to atomic-scale junctions. 4.3. Conductance is transmission : heuristic derivation of the Landauer formula. 4.4. Penetration of a potential barrier : tunnel effect. 4.5. The scattering matrix. 4.6. Multichannel Landauer formula. 4.7. Shot noise. 4.8. Thermal transport and thermoelectric phenomena. 4.9. Limitations of the scattering approach. 4.10. Exercises -- 5. Introduction to Green's function techniques for systems in equilibrium. 5.1. The Schrodinger and Heisenberg pictures. 5.2. Green's functions of a noninteracting electron system. 5.3. Application to tight-binding Hamiltonians. 5.4. Green's functions in time domain. 5.5. Exercises -- 6. Green's functions and Feynman diagrams. 6.1. The interaction picture. 6.2. The time-evolution operator. 6.3. Perturbative expansion of causal Green's functions. 6.4. Wick's theorem. 6.5. Feynman diagrams. 6.6. Feynman diagrams in energy space. 6.7. Electronic self-energy and Dyson's equation. 6.8. Self-consistent diagrammatic theory : the Hartree-Fock approximation. 6.9. The Anderson model and the Kondo effect. 6.10. Final remarks. 6.11. Exercises -- 7. Nonequilibrium Green's functions formalism. 7.1. The Keldysh formalism. 7.2. Diagrammatic expansion in the Keldysh formalism. 7.3. Basic relations and equations in the Keldysh formalism. 7.4. Application of Keldysh formalism to simple transport problems. 7.5. Exercises -- 8. Formulas of the electrical current : exploiting the Keldysh formalism. 8.1. Elastic current : microscopic derivation of the Landauer formula. 8.2. Current through an interacting atomic-scale junction. 8.3. Time-dependent transport in nanoscale junctions. 8.4. Exercises -- 9. Electronic structure I: Tight-binding approach. 9.1. Basics of the tight-binding approach. 9.2. The extended Huckel method. 9.3. Matrix elements in solid state approaches. 9.4. Slater-Koster two-center approximation. 9.5. Some illustrative examples. 9.6. The NRL tight-binding method. 9.7. The tight-binding approach in molecular electronics. 9.8. Exercises -- 10. Electronic structure II : density functional theory. 10.1. Elementary quantum mechanics. 10.2. Early density functional theories. 10.3. The Hohenberg-Kohn theorems. 10.4. The Kohn-Sham approach. 10.5. The exchange-correlation functionals. 10.6. The basic machinery of DFT. 10.7. DFT performance. 10.8. DFT in molecular electronics. 10.9. Exercises -- 11. The conductance of a single atom. 11.1. Landauer approach to conductance: brief reminder. 11.2. Conductance of atomic-scale contacts. 11.3. Conductance histograms. 11.4. Determining the conduction channels. 11.5. The chemical nature of the conduction channels of oneatom contacts. 11.6. Some further issues. 11.7. Conductance fluctuations. 11.8. Atomic chains : parity oscillations in the conductance. 11.9. Concluding remarks. 11.10. Exercises -- 12. Spin-dependent transport in ferromagnetic atomic contacts. 12.1. Conductance of ferromagnetic atomic contacts. 12.2. Magnetoresistance of ferromagnetic atomic contacts. 12.3. Anisotropic magnetoresistance in atomic contacts. 12.4. Concluding remarks and open problems -- 13. Coherent transport through molecular junctions I : basic concepts. 13.1. Identifying the transport mechanism in single-molecule junctions. 13.2. Some lessons from the resonant tunneling model. 13.3. A two-level model. 13.4. Length dependence of the conductance. 13.5. Role of conjugation in [symbol]-electron systems. 13.6. Fano resonances. 13.7. Negative differential resistance. 13.8. Final remarks. 13.9. Exercises -- 14. Coherent transport through molecular junctions II : test-bed molecules. 14.1. Coherent transport through some test-bed molecules. 14.2. Metal-molecule contact : the role of anchoring groups. 14.3. Tuning chemically the conductance : the role of side-groups. 14.4. Controlled STM-based single-molecule experiments. 14.5. Conclusions and open problems -- 15. Single-molecule transistors : Coulomb blockade and Kondo physics. 15.1. Introduction. 15.2. Charging effects in transport through nanoscale devices. 15.3. Single-molecule three-terminal devices. 15.4. Coulomb blockade theory : constant interaction model. 15.5. Towards a theory of Coulomb blockade in molecular transistors. 15.6. Intermediate coupling : cotunneling and Kondo effect. 15.7. Single-molecule transistors : experimental results. 15.8. Exercises -- 16. Vibrationally-induced inelastic current I : experiment. 16.1. Introduction. 16.2. Inelastic electron tunneling spectroscopy (IETS). 16.3. Highly conductive junctions : point-contact spectroscopy (PCS). 16.4. Crossover between PCS and IETS. 16.5. Resonant inelastic electron tunneling spectroscopy (RIETS). 16.6. Summary of vibrational signatures -- 17. Vibrationally-induced inelastic current II : theory. 17.1. Weak electron-phonon coupling regime. 17.2. Intermediate electron-phonon coupling regime. 17.3. Strong electron-phonon coupling regime. 17.4. Concluding remarks and open problems. 17.5. Exercises -- 18. The hopping regime and transport through DNA molecules. 18.1. Signatures of the hopping regime. 18.2. Hopping transport in molecular junctions : experimental examples. 18.3. DNA-based molecular junctions. 18.4. Exercises -- 19. Beyond electrical conductance : shot noise and thermal transport. 19.1. Shot noise in atomic and molecular junctions. 19.2. Heating and heat conduction. 19.3. Thermoelectricity in molecular junctions -- 20. Optical properties of current-carrying molecular junctions. 20.1. Surface-enhanced Raman spectroscopy of molecular junctions. 20.2. Transport mechanisms in irradiated molecular junctions. 20.3. Theory of photon-assisted tunneling. 20.4. Experiments on radiation-induced transport in atomic and molecular junctions. 20.5. Resonant current amplification and other transport phenomena in ac driven molecular junctions. 20.6. Fluorescence from current-carrying molecular junctions. 20.7. Molecular optoelectronic devices. 20.8. Final remarks. 20.9. Exercises -- 21. What is missing in this book?

Download or read book The Fundamentals of Electron Density Density Matrix and Density Functional Theory in Atoms Molecules and the Solid State written by N.I. Gidopoulos and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 233 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume records the proceedings of a Forum on The Fundamentals of Electron Density, Density Matrix and Density Functional Theory in Atoms, Molecules and the Solid State held at the Coseners' House, Abingdon-on-Thames, Oxon. over the period 31st May - 2nd June, 2002. The forum consisted of 26 oral and poster presentations followed by a discussion structure around questions and comments submitted by the participants (and others who had expressed an interest) in advance of the meeting. Quantum mechanics provides a theoretical foundation for our under standing of the structure and properties of atoms, molecules and the solid state in terms their component particles, electrons and nuclei. (Rel ativistic quantum mechanics is required for molecular systems contain ing heavy atoms.) However, the solution of the equations of quantum mechanics yields a function, a wave function, which depends on the co ordinates, both space and spin, of all of the particles in the system. This functions contains much more information than is required to yield the energy or other property.

Download or read book Handbook of Nanophysics written by Klaus D. Sattler and published by CRC Press. This book was released on 2010-09-17 with total page 770 pages. Available in PDF, EPUB and Kindle. Book excerpt: Intensive research on fullerenes, nanoparticles, and quantum dots in the 1990s led to interest in nanotubes and nanowires in subsequent years. Handbook of Nanophysics: Nanotubes and Nanowires focuses on the fundamental physics and latest applications of these important nanoscale materials and structures. Each peer-reviewed chapter contains a broad-

Download or read book Proceedings of the International Conference on Quantum Transport and Quantum Coherence Localisation 2002 written by Yoshiyuki Ono and published by . This book was released on 2003 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt: