Author: Alexander Lindmaa Publisher: Linköping University Electronic Press ISBN: 9176854868 Category : Languages : en Pages : 82
Book Description
The prediction of ground state properties of atomistic systems is of vital importance in technological advances as well as in the physical sciences. Fundamentally, these predictions are based on a quantum-mechanical description of many-electron systems. One of the hitherto most prominent theories for the treatment of such systems is density functional theory (DFT). The main reason for its success is due to its balance of acceptable accuracy with computational efficiency. By now, DFT is applied routinely to compute the properties of atomic, molecular, and solid state systems. The general approach to solve the DFT equations is to use a density-functional approximation (DFA). In Kohn-Sham (KS) DFT, DFAs are applied to the unknown exchangecorrelation (xc) energy. In orbital-free DFT on the other hand, where the total energy is minimized directly with respect to the electron density, a DFA applied to the noninteracting kinetic energy is also required. Unfortunately, central DFAs in DFT fail to qualitatively capture many important aspects of electronic systems. Two prime examples are the description of localized electrons, and the description of systems where electronic edges are present. In this thesis, I use a model system approach to construct a DFA for the electron localization function (ELF). The very same approach is also taken to study the non-interacting kinetic energy density (KED) in the slowly varying limit of inhomogeneous electron densities, where the effect of electronic edges are effectively included. Apart from the work on model systems, extensions of an exchange energy functional with an improved KS orbital description are presented: a scheme for improving its description of energetics of solids, and a comparison of its description of an essential exact exchange feature known as the derivative discontinuity with numerical data for exact exchange. An emerging alternative route towards the prediction of the properties of atomistic systems is machine learning (ML). I present a number of ML methods for the prediction of solid formation energies, with an accuracy that is on par with KS DFT calculations, and with orders-of-magnitude lower computational cost. Att kunna förutsäga egenskaper hos atomistiska system utgör en viktigdel av vår teknologiska utveckling, samt spelar en betydande roll i defysikaliska vetenskaperna. Sådana förutsägelser bygger på en kvantmekaniskbeskrivning av mångelektronsystem. En av de mest framståendeteorierna för att behandla den här typen av system är täthetsfunktionalteorin(DFT). Den främsta orsaken till dess framgång är attden lyckas kombinera skaplig noggrannhet med en bra beräkningseffektivitet.DFT används numera rutinmässigt för att beräkna storheterhos atomer, molekyler, och fasta kroppar. Generellt sett löses ekvationerna inom DFT genom att man inför entäthetsfunktionalapproximation (DFA). I Kohn-Sham (KS) DFT, användsDFAer för att approximera utbytes-korrelationsenergin. Inom orbitalfriDFT, där målet är att direkt minimera den totala energin med avseendepå elektrontätheten, så approximerar man också den icke-interageranderörelseenergin hos elektronerna. Dessvärre så fallerar många centralaDFAer att kvalitativt beskriva många viktiga aspekter hos elektronsystem.Två viktiga exempel är beskrivningen av lokaliserade elektroner,samt beskrivningen av system där det förekommer elektronytor. I denna avhandling använder jag modellsystem för att konstruera enDFAför elektronlokaliseringsfunktionen (ELF). Samma tillvägagångssättappliceras sedan för att studera den kinetiska energitätheten i gränsen avlångsamt varierande elektrontätheter, där effekten av elektronytor effektivtinkluderas. Förutom arbetet som berör modellsystem, så presenterasen utökad variant av en utbytes-energifunktional med en förbättrad KSorbitalbeskrivning: ett schema för att förbättra dess energiegenskaperför solida material, samt en jämförelse av dess beskrivning av en viktigegenskap hos den exakta utbytesenergin, vilket utgörs av diskontinuiteteri dess derivata. Ett mera nyligen uppkommet samt alternativt sätt att kunna förutsägaegenskaper hos atomistiska system utgörs av maskinlärning (ML).Jag presenterar ett antal ML-modeller för att kunna förutsäga formeringsenergierhos fasta material med en noggrannhet som är i linje medresultat som uppnås av beräkningar med hjälp av KS DFT, och med enberäkningseffektivitet som är flera storleksordningar snabbare.
Author: Pavlo O. Dral Publisher: Elsevier ISBN: 0323886043 Category : Science Languages : en Pages : 702
Book Description
Quantum chemistry is simulating atomistic systems according to the laws of quantum mechanics, and such simulations are essential for our understanding of the world and for technological progress. Machine learning revolutionizes quantum chemistry by increasing simulation speed and accuracy and obtaining new insights. However, for nonspecialists, learning about this vast field is a formidable challenge. Quantum Chemistry in the Age of Machine Learning covers this exciting field in detail, ranging from basic concepts to comprehensive methodological details to providing detailed codes and hands-on tutorials. Such an approach helps readers get a quick overview of existing techniques and provides an opportunity to learn the intricacies and inner workings of state-of-the-art methods. The book describes the underlying concepts of machine learning and quantum chemistry, machine learning potentials and learning of other quantum chemical properties, machine learning-improved quantum chemical methods, analysis of Big Data from simulations, and materials design with machine learning. Drawing on the expertise of a team of specialist contributors, this book serves as a valuable guide for both aspiring beginners and specialists in this exciting field. - Compiles advances of machine learning in quantum chemistry across different areas into a single resource - Provides insights into the underlying concepts of machine learning techniques that are relevant to quantum chemistry - Describes, in detail, the current state-of-the-art machine learning-based methods in quantum chemistry
Author: Wojciech Pietraszkiewicz Publisher: CRC Press ISBN: 1439859191 Category : Technology & Engineering Languages : en Pages : 686
Book Description
Shell Structures. Theory and Applications, Volume 2 contains 77 contributions from over 17 countries, reflecting a wide spectrum of scientific and engineering problems of shell structures. The papers are divided into six broad groups: 1. General lectures; 2. Theoretical modeling; 3. Stability; 4. Dynamics; 5. Numerical analysis; 6. Engineering
Author: Ali Reza Ashrafi Publisher: Springer Science & Business Media ISBN: 9400764138 Category : Science Languages : en Pages : 584
Book Description
Topological Modelling of Nanostructures and Extended Systems completes and expands upon the previously published title within this series: The Mathematics and Topology of Fullerenes (Vol. 4, 2011) by gathering the latest research and advances in materials science at nanoscale. It introduces a new speculative area and novel concepts like topochemical reactions and colored reactive topological indices and provides a better understanding of the physical-chemical behaviors of extended systems. Moreover, a charming new family of space-filling fullerenic crystals is here analyzed for the first time. Particular attention is given to the fundamental influences exercised by long-range connectivity topological mechanisms on the chemical and physical properties of carbon nanostructures. Systems consisting in graphenic layers with structural and topological defects are investigated in their electronic and magnetic behaviors also in presence of metallic particles. More specifically, the book focuses on: - Electronic Properties of low dimensional nanostructures including negatively-curved carbon surfaces; Pariser-Parr-Pople model hamiltonian approach to graphene studies; - Topochemistry and Toporeactcivity of extended sp2-nanocarbons: PAH, fullerenes, nanoribbons, Moebius-like nanoribbons, nanotubes and grapheme; - Novel class of crystal networks arising from spanning fullerenes; - Nanostructures and eigenvectors of matrices and an extended treatise of topological invariants; - Enumeration hetero-fullerenes by Polya theory. Topological Modelling of Nanostructures and Extended Systems represents a valuable resource to advances graduates and researchers working in mathematics, chemistry, physics and material science.
Author: Dipak Basu Publisher: Springer Nature ISBN: 3030270297 Category : Business & Economics Languages : en Pages : 275
Book Description
Using primarily Russian sources, this book explains the political and economic aspects of nuclear power. The nuclear fuel cycle is described, from the mining of natural uranium to the ultimate power generation, and to reprocessing to produce plutonium which is essential for both electricity generation and for weapons production. Historical aspects of nuclear developments in Germany, the USA, India, China and the Soviet Union are also considered and explained. The book then proceeds to argue that Russia is more powerful today in its nuclear weapons system and delivery than ever before, and that it is precisely this which has provoked President Trump to cancel the strategic nuclear weapons reduction treaty.
Author: Marek Niezgodka Publisher: CRC Press ISBN: 9780582305939 Category : Mathematics Languages : en Pages : 462
Book Description
Addressing various aspects of nonlinear partial differential equations, this volume contains papers and lectures presented at the Congress on Free boundary Problems, Theory and Application held in Zakopane, Poland in 1995. Topics include existence, uniqueness, asymptotic behavior, and regularity of solutions and interfaces.
Author: Robert A. Bell Publisher: Springer ISBN: 331919965X Category : Science Languages : en Pages : 178
Book Description
This thesis exploits the ability of the linear-scaling quantum mechanical code ONETEP to analyze systems containing many thousands of atoms. By implementing an electron transport capability to the code, it also investigates a range of phenomena associated with electrical conduction by nanotubes and, in particular, the process of transport electrons between tubes. Extensive work has been done on the conductivity of single carbon nanotubes. However, any realistic wire made of nanotubes will consist of a large number of tubes of finite length. The conductance of the resulting wire is expected to be limited by the process of transferring electrons from one tube to another.These quantum mechanical calculations on very large systems have revealed a number of incorrect claims made previously in the literature. Conduction processes that have never before been studied at this level of theory are also investigated.
Author: Sabu Thomas Publisher: William Andrew ISBN: 1455731609 Category : Technology & Engineering Languages : en Pages : 570
Book Description
Over 30% of commercial polymers are blends or alloys or one kind or another. Nanostructured blends offer the scientist or plastics engineer a new range of possibilities with characteristics including thermodynamic stablility; the potential to improve material transparency, creep and solvent resistance; the potential to simultaneously increase tensile strength and ductility; superior rheological properties; and relatively low cost. Nanostructured Polymer Blends opens up immense structural possibilities via chemical and mechanical modifications that generate novel properties and functions and high-performance characteristics at a low cost. The emerging applications of these new materials cover a wide range of industry sectors, encompassing the coatings and adhesives industry, electronics, energy (photovoltaics), aerospace and medical devices (where polymer blends provide innovations in biocompatible materials). This book explains the science of nanostructure formation and the nature of interphase formations, demystifies the design of nanostructured blends to achieve specific properties, and introduces the applications for this important new class of nanomaterial. All the key topics related to recent advances in blends are covered: IPNs, phase morphologies, composites and nanocomposites, nanostructure formation, the chemistry and structure of additives, etc. - Introduces the science and technology of nanostructured polymer blends – and the procedures involved in melt blending and chemical blending to produce new materials with specific performance characteristics - Unlocks the potential of nanostructured polymer blends for applications across sectors, including electronics, energy/photovoltaics, aerospace/automotive, and medical devices (biocompatible polymers) - Explains the performance benefits in areas including rheological properties, thermodynamic stablility, material transparency, solvent resistance, etc.
Author: Alexander Lindmaa
Author: Pavlo O. Dral
Author: Wojciech Pietraszkiewicz
Author: Ali Reza Ashrafi
Author: Richard M. Martin
Author: Dipak Basu
Author: Marek Niezgodka
Author: Robert A. Bell
Author: 
Author: Sabu Thomas