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Coherent potential approximation

About: Coherent potential approximation is a research topic. Over the lifetime, 1930 publications have been published within this topic receiving 36805 citations.


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TL;DR: In this paper, the electronic and magnetic properties of HgSe doped by chromium (Cr) were investigated and the lattice parameter was optimized to be 6.5/6.5
Abstract: Ab-initio calculations have been performed based on the Korringa-Kohn-Rostoker (KKR) Green's function method combined with coherent potential approximation (CPA) in order to investigate the electronic and magnetic properties of HgSe doped by chromium (Cr). The lattice parameter has been optimized to be 6.5 A which is close to the experimental value of 6.085 A. The pure HgSe compound is found to be a semimetal, whereas the Cr dopant introduces an itinerant ferromagnetic moment with the spin polarization at the Fermi surface of around 90%. The Curie temperature (TC) has been estimated using the mean field theory and is found to vary from 326/313 to 485/585 (K) for 8% and 24% of Cr concentration, against the lattice parameter of 6.5/6.085 (A), respectively. The double exchange is suggested to be the most responsible interaction of ferromagnetism in the system.

11 citations

Journal Article
TL;DR: In this article, a dynamical coherent potential approximation (CPA) to correlated electrons has been extended to a system with realistic Hamiltonian which consists of the first-principles tight-binding linear muffintin orbital (LMTO) bands and intraatomic Coulomb interactions.
Abstract: Dynamical coherent-potential approximation (CPA) to correlated electrons has been extended to a system with realistic Hamiltonian which consists of the first-principles tight-binding linear muffintin orbital (LMTO) bands and intraatomic Coulomb interactions. Thermodynamic potential and self-consistent equations for Green function are obtained on the basis of the functional integral method and the harmonic approximation which neglects the mode–mode couplings between the dynamical potentials with different frequency. Numerical calculations have been performed for Fe and Ni within the second-order dynamical corrections to the static approximation. The band narrowing of the quasiparticle states and the 6 eV satellite are obtained for Ni at finite temperatures. The theory leads to the Curie–Weiss law for both Fe and Ni. Calculated effective Bohr magneton numbers are 3.0 µ B for Fe and 1.2 µ B for Ni, explaining the experimental data. But calculated Curie temperatures are 2020 K for Fe and 1260 K for Ni, being ...

11 citations

Journal ArticleDOI
TL;DR: A combination of ab initio density functional perturbation theory (DFPT) and the itinerant coherent potential approximation (ICPA), an analytic, self-consistent method for performing configuration averaging in random alloys, is used to model the inter-atomic force constants for Pd( 0.96)Fe(0.04) and Pd (0.1) alloys based upon the ab-initio results and intuitive arguments.
Abstract: Understanding the role of the inter-atomic force constants in lattice dynamics of random binary alloys is a challenging problem. Addressing these inter-atomic interactions accurately is a necessity to obtain an accurate phonon spectrum and to calculate properties from them. Using a combination of ab initio density functional perturbation theory (DFPT) and the itinerant coherent potential approximation (ICPA), an analytic, self-consistent method for performing configuration averaging in random alloys, we model the inter-atomic force constants for Pd0.96Fe0.04 and Pd0.9Fe0.1 alloys based upon the ab initio results and intuitive arguments. The calculated phonon dispersion curves and elastic constants agree very well with the experimental results. Comparison of our results with those obtained in a model potential scheme is also done. The modeling of inter-atomic interactions in random alloys and their roles regarding the phonon-related properties are also discussed in light of these results.

11 citations

Journal ArticleDOI
TL;DR: In this paper, a first-principles approach to magnetic properties of diluted magnetic semiconductors (DMS) is presented that is based on the local spin density approximation (LSDA) as implemented in the framework of the tight-binding linear muffin-tin orbital method, while the effect of randomness is described by the coherent potential approximation.
Abstract: A first-principles approach to magnetic properties of diluted magnetic semiconductors (DMS) is presented that is based on the local spin-density approximation (LSDA) as implemented in the framework of the tight-binding linear muffin-tin orbital method, while the effect of randomness is described by the coherent potential approximation. Application of a real-space Green-function formalism yields the exchange pair interactions between distant magnetic atoms that are needed for quantitative studies of magnetic excitations including the Curie temperatures. We have found that the pair exchange interactions exhibit a strong directional dependence and are exponentially damped with increasing distance between magnetic atoms due to disorder and the half-metallic character of the DMS. As a case study we consider (Ga, Mn) As, (Ga, Mn)N, and (Zn, Cr)Te alloys. The calculations demonstrate that inclusion of disorder and, in particular, realistic distances among magnetic impurities, are needed to obtain critical temperatures which are in good agreement with available experiments.

11 citations

Journal ArticleDOI
TL;DR: Etude d'une serie d'echantillons dans le domaine x=0,5-1 (ou x=1 correspond a CdTe).
Abstract: The composition dependence of the ${\ensuremath{\Gamma}}_{8}$-${\ensuremath{\Gamma}}_{6}$ transition in mercury cadmium telluride (MCT) has long been classified apart among all disordered alloy systems. The nonconstant bowing parameter reported in this case could only be accounted for in terms of a finite departure from the virtual-crystal approximation but was not clearly reflected in the properties of carriers and/or the characteristics of the alloys. Moreover this nonconstant bowing appears to be a unique feature of MCT. First, it departs from all reports concerning standard II-VI and III-V materials which, even for structurally disordered systems like In-Ga-As, still exhibit a constant bowing and a parabolic dependence of the fundamental absorption edge on alloy composition. Second, it is not easily reflected in many band-structure calculations. Most of the time, even if they have been performed in the light of the coherent-potential approximation (CPA), they fail to reproduce such a complicated scheme.As a matter of fact, because of the closer lattice matching achieved in Hg-Cd-Te than in Hg-Zn-Te, these calculations suggest that less deviation (or bowing) from the straight-line average between the two binary compounds should exist in Hg-Cd-Te than in Hg-Zn-Te. In both cases, they predict a parabolic (or nearly parabolic) behavior. This rather large discrepancy between the experimental results and the theoretical calculation is one of the characteristics of MCT. To clear up this point, we have investigated a series of samples with concentrations in the range x=0.5--1 (where x=1 corresponds to CdTe). We resolve a series of excitonic features and get a clear, unambiguous determination of the first interband transition at different alloy compositions. This gives a constant bowing parameter (i.e., a simple parabolic dependence) with a maximum departure from linearity of 33 meV at x=0.5. We discuss these results in the light of the virtual-crystal approximation, using the empirical pseudopotential method, and compare them with recent CPA predictions where both diagonal and off-diagonal disorder terms had been included. We find a surprisingly good agreement which demonstrates, on a purely experimental basis, the near-cancellation of disorder effects expected at the band edge in mercury cadmium telluride.

11 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20234
202222
202127
202030
201930
201840