Publisher Summary This chapter discusses statistical exchange-correlation in the self-consistent field. There are two sides to a self-consistent field calculation: the determination of the potential and the solution of Schrodinger's equation for the one-electron problem. The solution of Schrodinger's equation has fortunately advanced far enough through the application of the electronic digital computer so that it can be regarded for most purposes as being a standardized technique. The main point of the method of Gaspar, Kohn, and Sham is that they derive the approximate exchange correction from an approximate Hamiltonian for the system by varying the spin-orbitals to minimize the average value of this Hamiltonian for the ground state. The approximate Hamiltonian has many important and valuable features that are described in the chapter.

Statistical Exchange-Correlation in the Self-Consistent Field

Recently it has been shown that many traditional models used for a description of dilute magnetic alloys are completely integrable and may be solved exactly without any approximation. In this article we summarize the results which have been obtained in this way. The main part of the article is devoted to the consistent and detailed account of the Bethe-Ansatz technique for the s-d exchange (Kondo) model with arbitrary impurity spin, s-d model with anisotropic exchange, degenerate exchange model and for the canonical Anderson model. The thermodynamic properties of a magnetic impurity in a non-magnetic metal host obtained by the Bethe method are considered in detail. Mainly attention is paid to the analysis of singularities associated with the formation of a localized moment, Kondo effect and mixedvalence phenomenon, which can be treated analytically. In the introductory part of the article we discuss the applicability of the models which we study in the paper to the real alloys and consider some m...

Exact results in the theory of magnetic alloys

Alternative materials are required to enhance the efficacy of plasmonic devices. We discuss the optical properties of a number of alloys, doped metals, intermetallics, silicides, metallic glasses and high pressure materials. We conclude that due to the probability of low frequency interband transitions, materials with partially occupied d states perform poorly as plasmonic materials, ruling out many alloys, intermetallics and silicides as viable. The increased probability of electron-electron and electron-phonon scattering rules out many doped and glassy metals.

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A review of the optical properties of alloys and intermetallics for plasmonics

The properties of 3d transition metal impurities in simple metal hosts are summarized. There is a short discussion of the basic microscopic models, then the Anderson model is treated in some detail. The next section considers the s-d model and the Kondo effect. The main experimental features are reviewed and finally the question of dilute alloys is considered.

http://iopscience.iop.org/article/10.1088/0034-4885/37/12/001/pdf

Magnetic impurities in non-magnetic metals

Publisher Summary The chapter presents a discussion on the electronic properties of binary substitutional alloys within the single particle approximation. The transport and magnetic properties of such alloys have received a great deal of attention, the chapter presents a discussion on the didactic exposition of the equilibrium properties. The theoretical approach to be developed is that of multiple scattering theory. This approach has a long history, having been used extensively in earlier work dealing with acoustic and electromagnetic wave propagation in random media. Its application to the electronic properties of alloys has proceeded rapidly during recent years, beginning with several works. Of the various types of disordered systems, substitutional binary alloys are among the simplest. In the absence of short range order, the two constituents A and B of an alloy AxB1-x, having a concentration x of A atoms, are placed randomly on a periodic point lattice. Thus, even though Bloch's theorem does not apply, an effective medium theory akin to the Weiss theory of ferromagnetism can still be formulated. Within certain approximations, this theory retains some of the features of the periodic potential problem. However, in contrast to the perfect crystal, the electronic states have complex energies. This distinction is essential. The chapter begins by reviewing the early alloy theories and their relationship to some more recent experimental results, which illustrate their limitations.

The Electronic Structure of Alloys

Measurements of the transmission and reflection coefficients have been made on evaporated films of solid solutions of Pd in Cu, Ag and Au and Mn in Cu and Ag. In the ease of the Pd alloys additional absorption attributed to resonant bound states associated with the Pd d electrons has been observed. The location and breadth of these resonant levels have been determined for the Ag and Au alloys. In Cu the resonant state absorption overlaps the Cu absorption edge and is not separable. In the CuMn and AgMn alloys the bound d states of the Mn are known to be spin split. No evidence for the optical absorption due to these states has been found in CuMn which is interpreted as implying a very small splitting energy ∼0·25 ev per spin. Weak absorption is observed in the case of AgMn alloys and this is interpreted as indicating a spin splitting energy of ∼ 1 ev per spin. In all these alloys the absorption spectra of the matrix, particularly the characteristic edges of Cu, Ag and Au, are little affected by t...

Some optical properties of CuPd, AgPd, AuPd and CuMn, AgMn alloys

Etude des couches superficielles ordonnees de Sm sur Cu(001) par diffraction d'electrons de faible energie et spectroscopie photoelectronique avec excitation par RX. La valence du samarium varie lineairement de 2 a 2,7 au cours de la formation de la couche monomoleculaire

Homogeneous Intermediate Valence of Sm on Cu(001)

The valence of Sm in disordered monolayers formed on a Pd(001) substrate was determined from the 3d/sup 5/2/ x-ray photoemission spectrum. The valence of the isolated atom on this substrate is 3, but the valence decreases with coverage and saturates at the value 2.75. Work-function changes suggest that the behavior may be associated with charge transfer between adsorbate and substrate.

Valence of Sm adsorbed on Pd(001).

Ferromagnetic MnB 2

Samarium is found to form ordered overlayers when deposited on a clean Al(001) substrate. Annealing is necessary to produce the crystallographic order. The x-ray photoemission spectrum from the $3d$ level of Sm in such layers shows that the occurrence of the divalent initial state is dependent on the presence of structural disorder or large separations between Sm atoms. In annealed structurally ordered films we find an average valence of 2.95 for the samarium atom. Spectroscopic data for the $3d$ levels are presented.

H. P. Myers

Papers

Some optical properties of CuPd, AgPd, AuPd and CuMn, AgMn alloys

Homogeneous Intermediate Valence of Sm on Cu(001)

Valence of Sm adsorbed on Pd(001).

Ferromagnetic MnB 2

Mixed valence in Sm overlayers on Al(001)