Coherent-potential approximation in a two band model



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Edition Notes

Statementby Pabitra Narayan Sen.
Classifications
LC ClassificationsMicrofilm 42585 (Q)
The Physical Object
FormatMicroform
Pagination15 p. in various pagings.
Number of Pages15
ID Numbers
Open LibraryOL1695197M
LC Control Number91954317

Books. Publishing Support. Login. Login. Forgotten password? Create account. Benefits of a My IOPscience account. Login via Athens/your Institution. Primary search Search. Article Lookup. Find article List of journal titles: Cited by: 7. Pages in category "Physics stubs" The following pages are in this category, out of approximately total. This list may not reflect recent changes (learn more). atoms by a vacancy, employing the coherent potential approximation. In addition the band structure of Li 3N, with and without vacancies, and the ordering of the magnetic moments is discussed. Section IV provides a discussion, and Section V gives a conclusion. II. . Abstract. This book presents the recent theoretical and experimental developments of neutron scattering by ferroelectrics. A model description of lattice dynamics of structurally unstable crystals (self consistent phonon approximation, pseudo-spin formalism, coherent potential approximation etc.) is formulated.

The basic theoretical aspects of the band anticrossing effects in highly electronegativity-mismatched semiconductor alloys are reviewed. The many-impurity Anderson model treated in the coherent potential approximation is applied to the semiconductor alloys, in which metallic anion atoms are. Abstract. Transport, as well as scattering, mean free paths are calculated within the weak-scattering approximation and within a recently developed extension of the well-known coherent-potential approximation for a random arrangement of dielectric sciroccowinds.com by: The index of physics articles is split into multiple pages due to its size.. To navigate by individual letter use the table of contents below. Jan 29,  · We generalize the typical medium dynamical cluster approximation (TMDCA) for systems with off-diagonal disorder. By applying our approach to the Anderson model we consider the effects of nonlocal correlations and typical environment beyond the local Blackman, Esterling, and Berk (BEB) method. %coherent potential approximation.

@article{osti_, title = {Self-consistent approximation beyond the CPA: Part II}, author = {Kaplan, T. and Gray, L.J.}, abstractNote = {In Part I, Professor Leath has described the substantial efforts to generalize the CPA. In this second part, a particular self-consistent approximation for random alloys developed by Kaplan, Leath, Gray, and Diehl is described. Get this from a library! Models of itinerant ordering in crystals: an introduction. [Jerzy Mizia; Grzegorz Górski] -- This book is devoted to the mathematical description of interesting phenomena which occur in solids, such as ferromagnetism, antiferromagnetism and superconductivity. Superconductivity and its. Alloys, Disordered Systems Introduction Order-Disorder Transformation and Bragg --Williams Approximation Bragg-Williams approximation Relation with the Band Model Transition Metal Alloys Different Types of Disorder in Bragg-Williams Approximation --References LDA+DMFT is a novel computational technique for ab initio investigations of real materials with strongly correlated electrons, such as transition metals and their oxides. It combines the strength of conventional band structure theory in the local density approximation (LDA) with a modern many-body approach, the dynamical mean-field theory (DMFT).

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Abstract The formalism of the coherent-potential approximation is extended to include the two-band case. The single-site energy of the one-band case is replaced by a 2 × 2 matrix which varies randomly from site to site according to the occupancy of the site. This fact was used to set up a simple model of alloying using the coherent potential approximation (CPA) in Chapter 6.

The model will be applied to binary transition metal alloys in Section One of the disorder measures is the residual electrical resistivity defined as. The CPA is applied to a two band separable pseudopotential model for a hot binary liquid alloy. The variation of the band gap with concentration is strictly linear, but the band broadening is found to be asymmetric about C = 50% and to depend in a complicated way on interband sciroccowinds.com: M.

Glasser, P. Sievert. The half- lled isotropic degenerate two-band Hubbard model is studied within coherent potential approximation. The model is characterized by an Ising-type Hunds exchange coupling, intra- and inter-orbital Coulomb parameters.

We found that the band degeneracy slightly reduces the Mott-Hubbard critical value UC. Interband Effects in the Coherent Potential Approximation: Simple Two Band Model Article (PDF Available) in Canadian Journal of Physics 53(11) · February with 23 Reads. This chapter describes one specific method for the configurational averaging of physical observables related to substitutionally random systems, the so-called coherent potential approximation (CPA).

The calculation of such averages is greatly simplified by expressing them in terms of the Green function G(z).Author: Ilja Turek, Václav Drchal, Václav Drchal, Josef Kudrnovský, Josef Kudrnovský, Mojmír Šob, Peter Wein.

Coherent potential approximation (CPA) is extended to a two-band model for diluted magnetic semiconductors (DMS). Coherent Potential Approximation November 29, 1 Green-function matrices in the TB formalism In the tight binding (TB) picture the matrix of a Hamiltonian His in the form H= Hij, where (1) Hij = ij" i + ij: (2) Single and double underlines denote matrices in angular momentum space and site-angular momentum space, respectively.

The coherent potential approximation (or CPA) is a method, in physics, of finding the Green's function of an effective medium.

It is a useful concept in understanding how sound waves scatter in a material which displays spatial inhomogeneity. One version of the CPA. The nonlocal coherent-potential approximation provides a systematic technique for the study of short-range ordering effects in a variety of disordered systems.

Site Index Path Coherent-potential approximation in a two band model book Coherent Potential Approximation Simple Lattice Additional Scattering These keywords were added by machine and not by the authors.

This process is experimental and the keywords may be updated as the learning algorithm improves. Formalism of the coherent potential approximation is extended to include the two band case.

Single site energy of the one band case is replaced by a 2 × 2 matrix which varies randomly from site to site according to the occupancy of the site. Cases treated explicitly correspond to Cited by: 1. Coherent potential approximation (CPA) has widely been used for studying residual resistivity of bulk alloys and electrical conductivity in inhomogeneous systems with structural disorder.

ADS Classic is now deprecated. It will be completely retired in October Please redirect your searches to the new ADS modern form or the classic sciroccowinds.com info can be found on our blog. The coherent potential approximation (CPA) is a useful method for describing the electron correlations as well as the effects of disorder on electrons.

Among the many-body theories using the CPA, the dynamical CPA, the many-body CPA, and the dynamical mean-field theory are reviewed to clarify how these theories use the CPA concept for the Author: Yoshiro Kakehashi.

Coherent potential approximation (CPA) is an effective method to describe the disorder alloy systems. Zhao et al. set up a model for describing the band gap energy of group III–V alloys by modifying simplified coherent potential approximation (MSCPA).

We consider that as the band gap energies of group III–V alloys can be estimated by MSCPA, the band gap energies of group II–VI alloys may Cited by: 3.

The coherent potential approximation (CPA) is applied to the problem of off-diagonal disorder caused by random spin orientations in the paramagnetic (PM) state of the double-exchange (DE) model.

The CPA calculations are supplemented by the variational mean-field approach for the Curie temperature (T C). Apr 28,  · This chapter details the coherent potential approximation (CPA) to describe the chemically and magnetically disordered phases for systems of arbitrary number of components.

Two widely used CPA implementations, namely, the exact muffin-tin orbitals (EMTO) and the Korringa–Kohn–Rostoker (KKR) methods, are briefly sciroccowinds.com by: 8. A recently developed ab initio approach to the electronic structure of substitutionally disordered alloys and their surfaces is reviewed.

It is based on (i) the tight-binding line. A two band system composed of a half-filled band and a almost fully filled band (hole band), with no charge transfer in between, is studied as a model system for high temperature superconductors.

The intraband electron-electron repulsions are assumed to be intermediate strength, while the interband repulsion V is assumed to be sciroccowinds.com: Keiichiro Nasu. Jul 15,  · This site uses cookies. By continuing to use this site you agree to our use of cookies.

To find out more, see our Privacy and Cookies sciroccowinds.com by: 2. For the stronger on-site interaction we use the coherent potential approximation (CPA). To describe the antiferromagnetic state we write the model Hamiltonian (2) taking into account the two interpenetrating magnetic sub-lattices α, β, with magnetic moments given by sciroccowinds.com: Jerzy Mizia, Grzegorz Górski, Krzysztof Kucab.

The theoretical study of magnetic semiconductors using the dynamical coherent potential approximation (dynamical CPA) is briefly reviewed. First, we give the results for ferromagnetic semiconductors (FMSs) such as EuO and EuS by applying the dynamical CPA to the s-f model. Next, applying the dynamical CPA to a simple model for A1−xMnxB-type diluted magnetic semiconductors (DMSs), we show the Cited by: 3.

The density of states function g (E) is defined as the number of electronic states per unit volume, per unit energy, for electron energies near E. The density of states function is important for calculations of effects based on band theory.

In Fermi's Golden Rule, a calculation for the rate of optical absorption. Chapter XI: Coherent Potential Approximation ; The Hubbard Model This volume also includes fifteen (15) fortran programs related to the topics discussed in.

Feb 01,  · We propose the two-band s-d model to describe theoretically a diffuse regime of the spin-dependent electron transport in magnetic tunnel junctions (MTJ's) of the form F/O/F where F's are 3d transition metal ferromagnetic layers and O is the insulating spacer.

We aim to explain the strong interface sensitivity of the tunneling properties of MTJ's and investigate the influence of electron Cited by: Coherent potential approximation.

The first scheme I consider is sometimes called the Coherent Potential Approximation (CPA) (Gubernatis and Krumhansl, ; Berryman, If the mixture were composed only of the two materials i and *, then the uniform expansion result would apply exactly.

and quantify two contributions to these shifts: a raise of the Fermi energy and an increase of the overall bandwidth. Alloy bands calculated using the first-principles Korringa–Kohn–Rostoker coherent-potential-approximation method accurately predict both of these effects.

As derived from the rigid band model,Cited by: 4. Abstract: We propose the two-band s-d model to describe theoretically a diffuse regime of the spin-dependent electron transport in magnetic tunnel junctions (MTJ's) of the form F/O/F where F's are 3d transition metal ferromagnetic layers and O is the insulating spacer.

We aim to explain the strong interface sensitivity of the tunneling properties of MTJ's and investigate the influence of Cited by: Table of Contents Introduction Augmented Wave Methods Linear Methods in Band Theory Questaal’s Basis Functions Augmentation Executable codes in the Questaal suite Input System Other Resources Introduction The Questaal suite consists of a collection of electronic structure codes based on the local-density approximation (LDA) to density-functional theory (DFT) to solids, with extensions to GW.

The muffin-tin approximation is a shape approximation of the potential well in a crystal lattice. It is most commonly employed in quantum mechanical simulations of the electronic band structure in solids. The approximation was proposed by John C.

Slater. Augmented plane wave method (APW) is a method which uses muffin-tin approximation.Books. Publishing Support. Login. A least-mean-squares fit to the data has been used to obtain the model parameters for a two band, multivalley, ellipsoidal Fermi surface.

The coherent potential approximation (CPA) has been generalized to describe spin waves in a dilute Heisenberg ferromagnet at T=0.

The full T matrix of an isolated.The study is concerned with two types of disordered epitaxial graphene: (i) graphene with randomly located carbon vacancies and (ii) structurally amorphous graphene.

The former type is considered in the coherent potential approximation, and for the latter type, a model of the density of states is proposed.