Nature of the 5f states in actinide metals
TL;DR: In this article, a review compiles and analyzes progress in the understanding of the electronic and magnetic structure of the $5f$ states in actinide metals, focusing on electron energy-loss spectroscopy and many-electron atomic spectral calculations.
Abstract: Actinide elements produce a plethora of interesting physical behaviors due to the $5f$ states. This review compiles and analyzes progress in the understanding of the electronic and magnetic structure of the $5f$ states in actinide metals. Particular interest is given to electron energy-loss spectroscopy and many-electron atomic spectral calculations, since there is now an appreciable library of core $d\ensuremath{\rightarrow}\text{valence}$ $f$ transitions for Th, U, Np, Pu, Am, and Cm. These results are interwoven and discussed against published experimental data, such as x-ray photoemission and absorption spectroscopy, transport measurements, and electron, x-ray, and neutron diffraction, as well as theoretical results, such as density-functional theory and dynamical mean-field theory.
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TL;DR: The experimental status of the study of the superconducting phases of $f$-electron compounds is reviewed in this paper, where superconductivity has been found at the border of magnetic order as well as deep within ferromagnetic and antiferromagnetically ordered states.
Abstract: Intermetallic compounds containing $f$-electron elements display a wealth of superconducting phases, which are prime candidates for unconventional pairing with complex order parameter symmetries. For instance, superconductivity has been found at the border of magnetic order as well as deep within ferromagnetically and antiferromagnetically ordered states, suggesting that magnetism may promote rather than destroy superconductivity. Superconducting phases near valence transitions or in the vicinity of magnetopolar order are candidates for new superconductive pairing interactions such as fluctuations of the conduction electron density or the crystal electric field, respectively. The experimental status of the study of the superconducting phases of $f$-electron compounds is reviewed.
529 citations
TL;DR: The literature on vibrational thermodynamics of materials is reviewed in this article, with a focus on metals and alloys, especially on the progress over the last decade in understanding differences in the vibrational entropy of different alloy phases and phase transformations.
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373 citations
TL;DR: A review of the 25-year quest to understand the continuous (second-order), mean-field-like phase transition occurring at 17.5 K is given in this paper.
Abstract: This Colloquium reviews the 25 year quest to understand the continuous (second-order), mean-field-like phase transition occurring at 17.5 K in ${\mathrm{URu}}_{2}{\mathrm{Si}}_{2}$. About ten years ago, the term ``hidden order'' (HO) was coined and has since been utilized to describe the unknown ordered state, whose origin cannot be disclosed by conventional solid-state probes, such as x rays, neutrons, or muons. The HO is able to support superconductivity at lower temperatures (${T}_{c}\ensuremath{\approx}1.5\text{ }\text{ }\mathrm{K}$), and when magnetism is developed with increasing pressure both the HO and the superconductivity are destroyed. Other ways of probing the HO are via Rh doping and large magnetic fields. During the last few years a variety of advanced techniques have been tested to probe the HO state and these attempts will be summarized. A digest of recent theoretical developments is also included. It is the objective of this Colloquium to shed additional light on the HO state and its associated phases in other materials.
307 citations
TL;DR: An overview of different chemical complexes studied by X-ray magnetic circular dichroism (XMCD) is presented in this article, where the possibilities of this technique for the characterization of magnetically interesting systems are discussed.
265 citations
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01 Jan 1989TL;DR: In this paper, a review of current studies in density functional theory and density matrix functional theory is presented, with special attention to the possible applications within chemistry, including the concept of an atom in a molecule, calculation of electronegativities from the Xα method, pressure, Gibbs-Duhem equation, Maxwell relations and stability conditions.
Abstract: Current studies in density functional theory and density matrix functional theory are reviewed, with special attention to the possible applications within chemistry. Topics discussed include the concept of electronegativity, the concept of an atom in a molecule, calculation of electronegativities from the Xα method, the concept of pressure, Gibbs-Duhem equation, Maxwell relations, stability conditions, and local density functional theory.
14,008 citations
01 Sep 1951
TL;DR: In this paper, an attempt is made to explain the observed phenomena in the yielding and ageing of mild steel, described in two previous papers, in the general terms of a grain-boundary theory.
Abstract: An attempt is made here to explain the observed phenomena in the yielding and ageing of mild steel, described in two previous papers, in the general terms of a grain-boundary theory. On this hypothesis, a satisfactory explanation of the variation of the lower yield point with grain size may be developed. It is shown that strain-ageing must involve two processes: a healing of the grain-boundary films, coupled with a hardening in the grains themselves. A discussion of the possible nature of the grain-boundary film is also undertaken.
5,893 citations
TL;DR: The dynamical mean field theory of strongly correlated electron systems is based on a mapping of lattice models onto quantum impurity models subject to a self-consistency condition.
Abstract: We review the dynamical mean-field theory of strongly correlated electron systems which is based on a mapping of lattice models onto quantum impurity models subject to a self-consistency condition. This mapping is exact for models of correlated electrons in the limit of large lattice coordination (or infinite spatial dimensions). It extends the standard mean-field construction from classical statistical mechanics to quantum problems. We discuss the physical ideas underlying this theory and its mathematical derivation. Various analytic and numerical techniques that have been developed recently in order to analyze and solve the dynamical mean-field equations are reviewed and compared to each other. The method can be used for the determination of phase diagrams (by comparing the stability of various types of long-range order), and the calculation of thermodynamic properties, one-particle Green's functions, and response functions. We review in detail the recent progress in understanding the Hubbard model and the Mott metal-insulator transition within this approach, including some comparison to experiments on three-dimensional transition-metal oxides. We present an overview of the rapidly developing field of applications of this method to other systems. The present limitations of the approach, and possible extensions of the formalism are finally discussed. Computer programs for the numerical implementation of this method are also provided with this article.
5,230 citations
TL;DR: In this article, Murnaghan's theory of finite strain is developed for a medium of cubic symmetry subjected to finite hydrostatic compression, plus an arbitrary homogeneous infinitesimal strain.
Abstract: Murnaghan's theory of finite strain is developed for a medium of cubic symmetry subjected to finite hydrostatic compression, plus an arbitrary homogeneous infinitesimal strain. The free energy is developed for cubic symmetry to include terms of the third order in the strain components. The effect of pressure upon the second-order elastic constants is found and compared with experiment, with particular reference to the compressibility; the pressure-volume relation in several approximations is compared with the measurements to 100,000 kg/${\mathrm{cm}}^{2}$. The simplest approximation is shown to give a satisfactory account of most of the experimental data. The results are also compared with some of the calculations based on Born's lattice theory.
4,834 citations
TL;DR: In this article, the authors proposed a method to improve our understanding of the behavior of real solids by using calculations of the electronic structure of real molecules and solids in order to improve the search for new and better materials.
Abstract: We would like to improve our understanding of the behaviour of real solids. Why do atoms combine into molecules and solids in the way they do and what is the response of these aggregates of atoms to external fields, stress, temperature, etc. ? Answers to such questions would, for instance, be a useful guide in our, so far mostly empirical, search for new and better materials Stronger materials, materials which corrode less, better catalysts, better magnets, better semi- or superconductors, and, materials with properties unknown today. I expect that future advances in this field will be aided by insight obtained from calculations of the electronic structure.
4,733 citations