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.

Developments of the local approximation for disordered systems

Abstract: The local approximation (LA) for the electronic structure of disordered systems, proposed by Butler and Kohn, is further developed. Analysis of the moments of the density of states and numerical application to the model of Velicky et al. allow comparison with the coherent potential approximation (CPA). The results of the two approximations differ substantially, the LA showing considerable structure where the CPA shows none. A preliminary discussion of this discrepancy is presented. The possibilities of using the LA for quantitative calculations of realistic alloy models are briefly discussed.

Electronic Structure of Nonstoichiometric Boron Nitride Films

Abstract: The density of states of π bands in boron nitride films is evaluated by assuming the films to be a substitutional disordered system in a two-dimensional hexagonal network. The Hamiltonian is described with a simple tight binding model and the calculations are carried out by using an extended version of the coherent potential approximation including atomic correlation. For completely disordered systems, no forbidden gap is found even in B/N=1, contrary to the experimental findings. When we start from periodic boron nitride (h-BN), on the other hand, where the energy gap is approximately 5 eV, the change in the composition ratio of B/N>1 turns out to narrow the gap due to the occurrence of new states. We suggest that the emergence of such a subband shows the crucial role of the decrease in the optical band gap of boron-rich films.

Influence of the short range order (SRO) on electrical resistivity of magnetic alloys

Abstract: The model of the magnetic binary alloy which contains interacting itinerant electrons and localized spins was considered. The interaction between both kinds of electrons was assumed in the simple local exchange form. The complicated many body problem was reduced to the one particle one with the help of Coherent Potential Approximation (CPA). Itinerant electron selfenergy was calculated using standard Green's function technique with taking into account short range order (SRO) within the localized spin system. Electron's states were strongly affected by the correlations (SRO, when T > T C ) within localized moments system. The DC electrical conductivity a in the paramagnetic region expressed by Kubo-Grennwood alloy formula was calculated. The resistivity p = 1/σ and its derivative over the temperature have the structure near T C , which depends on the number of the electrons in the band and the interaction strength between two subsystems. The quantities ρ,∂ρ ∂T were not constant vs. temperature as it is in the simple models. The influence of the important model parameters on the DC conductivity was also discussed.

Electronic Structure of bcc Cr-Ru Alloys in the Region of Coexisting Antiferromagnetism and Superconductivity

Abstract: The self-consistent Korringa-Kohn-Rostoker coherent potential approximation (KKR-CPA) method is applied to determine the changes in the Cr electronic structure due to addition of up to 30% Ru. The results provide an interpretation of the coexisting antiferromagnetism and superconductivity in terms of specific pieces of Fermi surface. The strong nesting which occurs for the Cr Fermi surface survives the addition of at least 20% Ru, in agreement with the observed persistence of antiferromagnetism into this region.