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.

Interdependency between localization parameter and criterion of the coherent-potential-approximation applicability

Abstract: The proof is given that the potential-well analogy (PWA) can be used together with the coherent-potential approximation (CPA) at the low impurity concentration despite the fact that the CPA does not describe correctly the immediate vicinity of the band edge. The correspondent criterion of the CPA applicability for three-dimensional systems is presented. It is demonstrated that the CPA is reliable above the mobility edge position predicted by the PWA.

The Hubbard model on the kagome lattice

Abstract: In itinerant magnetically frustrated materials it is important to elucidate the effect of the electronic correlation on the band structure and how it evolves as a function of the electronic concentration n. In this work we address this problem by considering the Hubbard model on a kagome lattice with a single orbital per site, treating the local Coulomb repulsion U within the coherent potential approximation. A metal–insulator transition occurs in the half-filled band (n = 1) at Uc = 3.635t. A nearly flat band, characteristic of frustrated lattices, is present at the top of the band structure. For concentrations n>4/3, the chemical potential may be located in this very narrow band, and one obtains a significant enhancement of the γ coefficient of the specific heat depending on the value of U. This effect can be at the origin of the heavy fermion behaviour observed in LiV2O4.

Disordered Alloys and Their Surfaces: The Coherent Potential Approximation

Abstract: 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 linear muffin-tin orbital (TB-LMTO) method in the atomic sphere approximation which provides a physically transparent solution of the one-electron problem in metallic materials, (ii) the coherent potential approximation (CPA) for a mean- field treatment of the substitutional randomness, and (iii) the surface Green functions for a proper description of the true semi-infinite geometry of surfaces and interfaces. Theoretical formulation of fundamental electronic quantities, both site-diagonal (charge densities, densities of states) and site non-diagonal (the Bloch spectral functions) is presented. Transformation properties of the LMTO-CPA theory as well as specific problems of application of the local density approximation to random alloys are briefly discussed and basic algorithms employed in the numerical implementation of the formalism are described.

Effect of proton uptake on the structure of energy levels in the band-gap of Sr-doped LaScO3: diffuse reflectance spectroscopy and coherent potential approximation calculations.

Abstract: Features of the energy levels in the band-gap of La1−xSrxScO3−x/2 and the effect on those levels of proton uptake from H2 and H2O atmospheres were studied by diffuse reflectance spectroscopy and coherent potential approximation (CPA) calculations. It was shown that oxygen vacancies appearing due to acceptor doping with Sr form energy levels near the bottom of the conduction band that are strongly hybridized with the states of the nearest atoms. Excitation of electrons from the valence band to these vacancy levels gives rise to an additional absorption band which overlaps with the fundamental absorption edge. Proton incorporation from both H2 and H2O atmospheres leads to formation of proton levels below the valence band. However, during H2 uptake, electrons from hydrogen atoms occupy oxygen vacancy levels, and as a result additional absorption in the red-IR range appears due to electronic transitions from these levels to the conduction band. On the other hand, H2O uptake leads to the disappearance of oxygen vacancy levels. Experimental results obtained are similar to literature data on the optical absorption properties of some other proton-conducting perovskites, allowing the conclusion that findings from these CPA calculations on the nature of the energy levels could be extrapolated to some extent to those oxides.