This monograph reviews the subject of structural disorder in alloys and describes how structural information can be exploited to build sound theoretical descriptions in terms of modified Ising models. Scattering with thermal neutrons and x-rays prove to be complementary approaches to measure the weak diffuse scattering which provides detailed information about the disorder. The authors show how Monte Carlo methods are applied to determine the most realistic effective interactions among the alloying atoms. These results can be used as a benchmark for modern electronic structure calculations. Of more general interest, the limitations of scattering experiments in a determination of an interaction model, and thus also of the structure itself are discussed. Finally, simulations exhibit not only near-surface disordering due to frustration effects but also new possible surface - induced ordering phenomena. Accurate Monte Carlo simulations are used to test existing theories of wetting.
At present, there is an increasing interest in the prediction of properties of classical and new materials such as substitutional alloys, their surfaces, and metallic or semiconductor multilayers. A detailed understanding based on a thus of the utmost importance for fu microscopic, parameter-free approach is ture developments in solid state physics and materials science. The interrela tion between electronic and structural properties at surfaces plays a key role for a microscopic understanding of phenomena as diverse as catalysis, corrosion, chemisorption and crystal growth. Remarkable progress has been made in the past 10-15 years in the understand ing of behavior of ideal crystals and their surfaces by relating their properties to the underlying electronic structure as determined from the first principles. Similar studies of complex systems like imperfect surfaces, interfaces, and mul tilayered structures seem to be accessible by now. Conventional band-structure methods, however, are of limited use because they require an excessive number of atoms per elementary cell, and are not able to account fully for e.g. substitu tional disorder and the true semiinfinite geometry of surfaces. Such problems can be solved more appropriately by Green function techniques and multiple scattering formalism.
An introduction to the study of basic electronic and magnetic properties of complex materials such as alloys, their surfaces, interfaces, and extended defects. Part I explores theoretical background, with chapters on the linear muffin-tin orbital method, Green function method, coherent potential approximation, self- consistency within atomic sphere approximation, and relativistic theory. Part II is devoted to applications including magnetic properties, numerical implementation, and interatomic interactions in alloys. Of interest to researchers in solid state theory, surface science, and computational materials research. Annotation copyrighted by Book News, Inc., Portland, OR.
This book contains 18 invited contributions to the first Inter national Symposium on Order-Disorder Transformations in Alloys+. They cover the major aspects of this group of phase transformations. Although structural order-disorder transformations have been investigated for over 50 years the invited papers, the research papers - whose titles and authors are listed in the appendix - and the discussions at the Symposium have demonstrated very active continued interest and con siderable recent progress in the subject. This is true for theoretical work as weIl as for experimental studies and for the development of materials whose properties result from order-disorder transformations. + Some major national conferences on ordering were held in the USA and in the USSR in recent years; the proceedings are available in the following pUblications: Local Atomic Arrangements Studied by X-Ray Diffraction, Gordon & Breach, New York 1966 2 Ordered Alloys, Claitor's Publ. Div. , Baton Rouge, La. 1970 3 Summaries of the Proceedings of the 2nd Union Conference on Atomic Ordering and its Influence on the Properties of Alloys, Naukova Dumka, Kiev 1966 4 Atomic Ordering and its Influence on the Properties of Alloys, Naukova Dumka, Kiev 1968 5 Atomic Ordering and its Influence on the Properties of Alloys, TGU, Tomsk 1973 111 In assembling these papers it vas attempted to compile a systematic and approximately complete compendium of the sUbject.
This book focuses on the role of modeling in the design of alloys and intermetallic compounds. It includes an introduction to the most important and most used modeling techniques, such as CALPHAD and ab-initio methods, as well as a section devoted to the latest developments in applications of alloys. The book emphasizes the correlation between modeling and technological developments while discussing topics such as wettability of Ultra High Temperature Ceramics by metals, active brazing of diamonds to metals in cutting tools, surface issues in medicine, novel Fe-based superconductors, metallic glasses, high entropy alloys, and thermoelectric materials.
Disorder in crystalline materials can take different forms and originate from different sources. In particular, temperature introduces disorder in any kind of material. This can be observed as the appearance of vacant lattice sites in an otherwise perfect crystal, or as a random distribution of different elements on the same lattice in an alloy; at the same time, if the material is magnetic, temperature induces disorder also on the magnetic degrees of freedom. In this thesis, different levels of disorder associated to structure and magnetism are investigated by means of density functional theory and thermodynamic models. I start with diffusion of Ti vacancies in TiN, which is studied by means of nonequilibrium ab initio molecular dynamics using the color diffusion algorithm at different temperatures. The result is an Arrhenius behavior of Ti vacancy jump rates. A method to perform structural relaxations in magnetic materials in their hightemperature paramagnetic phase is then developed based on the disordered local moments approach in order to study vacancies, interstitial atoms, and combinations of defects in paramagnetic bcc Fe and B1 CrN, as well as the mixing enthalpy of bcc Fe1?xCrx random alloys. A correction to the energetics of every system due to the relaxation in the disordered magnetic state is observed in all cases. Not related to temperature and disorder, but very important for an accurate description of magnetic materials, is the choice of the exchange and correlation functional to be employed in the first principles calculations. We have investigated the performance of a recently developed meta-GGA functional, the strongly constrained and appropriately normed (SCAN) functional, in comparison with the more commonly used LDA and PBE on the ferromagnetic elemental solids bcc Fe, fcc Ni, and hcp Co, and SCAN it is found to give negligible improvements, if not a worsening, in the description of these materials. Finally, the coupling between vibrational and magnetic degrees of freedom is discussed by reviewing the literature and proposing an investigation of the influence of vibrations on longitudinal spin fluctuations. These excitations are here studied by means of thermodynamic models based on Landau expansion of the energy in even powers of the magnitude of the local magnetic moments. We find that vibrational and magnetic disorder alter the energy landscapes as a function of moment size also in bcc Fe, which is often considered a Heisenberg system, inducing a more itinerant electron behavior.
We present here the transcripts of lectures and talks which were delivered at the NATO ADVANCED STUDY INSTITUTE "Electrons in Disordered Hetals and at ~~etallic Surfaces" held at the State University of Ghent, Belgium between August 28 and September 9, 1978. The aim of these lectures was to highlight some of the current progress in our understanding of the degenerate electron 'liquid' in an external field which is neither uniform nor periodic. This theme brought together such topics as the electronic structure at metallic surfaces and in random metallic alloys, liquid metals and metallic glasses. As is the case in connection with infinite order ed crystals, the central issues to be discussed were the nature of the electronic spectra, the stability of the various phases and the occurrence of such phenomena as magnetism and supercon ductivity. In the theoretical lectures the emphasis was on detailed rea listic calculations based, more or less, on the density functional approach to the problem of the inhomogeneous electron liquid. How ever, where such calculations were not available, as in the case of magnetism in random alloys and that of metallic glasses, sim pler phenomenological models were used. The theoretical discussions were balanced by reviews of the most promising experimental techniques. Here the stress was on results and their relevance to the fundamental theory. lforeover, the attention had centered on those experiments which probe the electronic structure in the greatest detail.
This is the second volume in the NATO ASI series dealing with the topic of hydrogen in solids. The first (V. B76, Metal Hydrides) appeared five years ago and focussed primarily on crystalline phases of hydrided metallic systems. In the intervening period, the amorphous solid state has become an area of intense research activity, encompassing both metallic and non-metallic, e.g. semiconducting, systems. At the same time the problem of storage of hydrogen, which motivated the first ASI, continues to be important. In the case of metallic systems, there were early indications that metallic glasses and disordered alloys may be more corrosion resistant, less susceptible to embrittlement by hydrogen and have a higher hydrogen mobility than ordered metals or intermetallics. All of these properties are desirable for hydrogen storage. Subsequent research has shown that thermodynamic instability is a severe problem in many amorphous metal hydrides. The present ASI has provided an appropriate forum to focus on these issues.
Magnesium and magnesium alloys offer a wealth of valuable properties, making them of great interest for use across a wide range of fields. This has led to extensive research focused on understanding the properties of magnesium and how these can be controlled during processing. Fundamentals of magnesium alloy metallurgy presents an authoritative overview of all aspects of magnesium alloy metallurgy, including physical metallurgy, deformation, corrosion and applications.Beginning with an introduction to the primary production of magnesium, the book goes on to discuss physical metallurgy of magnesium and thermodynamic properties of magnesium alloys. Further chapters focus on understanding precipitation processes of magnesium alloys, alloying behaviour of magnesium, and alloy design. The formation, corrosion and surface finishing of magnesium and its alloys are reviewed, before Fundamentals of magnesium alloy metallurgy concludes by exploring applications across a range of fields. Aerospace, automotive and other structural applications of magnesium are considered, followed by magnesium-based metal matrix composites and the use of magnesium in medical applications.With its distinguished editors and international team of expert contributors, Fundamentals of magnesium alloy metallurgy is a comprehensive tool for all those involved in the production and application of magnesium and its alloys, including manufacturers, welders, heat-treatment and coating companies, engineers, metallurgists, researchers, designers and scientists working with these important materials. - Overviews all aspects of magnesium alloy metallurgy - Discusses physical metallurgy of magnesium and thermodynamic properties of magnesium alloys - Reviews the formation, corrosion and surface finishing of magnesium and its alloys
