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.

Spin-Polarized Relativistic Band Structure Calculations for Dilute and Concentrated Disordered Alloys

Abstract: Applications of the spin-polarized relativistic version of multiple scattering theory (SPRKKR) to study the electronic properties of dilute and concentrated disordered alloys are presented. This approach, developed recently, allows to investigate magnetic systems containing heavy elements and also gives access to a detailed discussion of phenomena, which are linked to the simultanous presence of spin-polarisation and spin-orbit coupling. This is demonstrated by discussing the hyperfine properties of 5d-transition metals dissolved substitutionally in Fe, where pronounced relativistic effects could be found. In addition the magnetic X-ray dichroism (MXD), denoting the difference in absorption of left and right circularly polarized radiation, is studied for these dilute alloys. To be able to deal also with concentrated alloys, we have combined the Coherent Potential Approximation (CPA) alloy theory with the SPRKKR-formalism. Results for the spin-orbit induced orbital contributions to the magnetic moments as well as the MXD in FexCol-x and CoxPtl-x clearly show that remarkable relativistic effects are present even for relatively light elements.

Breakdown of coherence in Kondo alloys: crucial role of concentration versus band filling.

Abstract: We study the low energy states of the Kondo alloy model (KAM) as function of the magnetic impurity concentration per site, x, and the conduction electron average site occupation, n c . In previous works, two different Fermi liquid regimes had been identified at strong Kondo coupling [Formula: see text], that may be separated by a transition at x = n c . Here, we analyze the KAM for finite [Formula: see text] on a Bethe lattice structure. First, using the mean-field coherent potential approximation (DMFT-CPA) which is exact at lattice coordination [Formula: see text], we show that the real part of the local potential scattering may be located outside the conduction electron band, revealing a possible breakdown of Luttinger theorem for intermediate values of impurity concentration x. Unusual physical signatures are expected, e.g. in ARPES experiments. In order to take into account fluctuations associated with finite dimensionality, i.e. finite Z, we extend this analysis by studying the KAM with an adaptation of the statistical-DMFT method that was developped elsewhere. We review the distributions of local potential scattering and their evolution with model parameters: concentration, strength of Kondo coupling, coordination number, local site neighborhood, connection with percolation issue. Relevence for Kondo alloys material with f -electrons is also discussed.

Electronic Structure of Thin Alloy Films

Abstract: The coherent potential approximation is adopted to the problem of an electron moving in a sub-stitutionally disordered alloy with thin film geometry (i.e. thin alloy film). The theory is formulated for a one-band tight-binding Hamiltonian of the alloy film consisting of N atomic planes. The numerical calculations illustrate the dependence of the local density of states for various layers on the parameters describing the alloy film. [Rusian Text Ignored]

Real-space electronic structure approach to transport in alloys

Abstract: We present a method for calculating dc and ac conductivities of alloys in the framework of a tight-binding description of their electronic structure. The method is entirely derived in real space, and thus requires no spatial symmetry of the underlying lattice on which the alloy is based. It also allows a calculation of conductivity in alloy cases where the chemical randomness is treated within the coherent potential approximation. Applications to simple model systems are given to illustrate the basic features, the advantages, and the range of applicability of the method.