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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: The magnetocaloric effect, electronic structure and magnetic properties of high entropy alloys AlCo x Cr[Formula: see text]FeNi were calculated using the Monte Carlo simulation, the Korringa-Kohn-Rostoker method combined with the coherent potential approximation (KKR-CPA), method of linear augmented plane wave (FPLAPW) within generalized gradient approximation (GGA) and modified Becke-Johnson potential (TB-mBJ) as mentioned in this paper .
Abstract: The magnetocaloric effect, electronic structure and magnetic properties of High Entropy Alloys AlCo x Cr[Formula: see text]FeNi ([Formula: see text]) were calculated using the Monte Carlo simulation, the Korringa–Kohn–Rostoker method combined with the coherent potential approximation (KKR-CPA), method of linear augmented plane wave (FPLAPW) within generalized gradient approximation (GGA) and modified Becke–Johnson potential (TB-mBJ). Density of states of AlCo x Cr[Formula: see text]FeNi are studied and analyzed. The total magnetic moments of magnetic atoms were calculated and compared with theoretical and experimental results. On the other side, the magnetocaloric effect in AlCo x Cr[Formula: see text]FeNi was studied by first-principle calculations (FPCs) and Monte Carlo simulations. The magnetic phase transition temperature is estimated. The Curie temperature and exchange integrals were found to decrease with Co substitution. The magnetic entropy changes and relative cooling power are found.
01 Jan 2000
TL;DR: In this article, a polymorphous coherent potential approximation (PCPA) was proposed for the KKR-CPA, in which every atom in the supercell is different and the Madelung potential at each site must be zero.
Abstract: The coherent potential approximation (CPA) is a powerful mathematical technique for approximating the electronic structure of substitutional solid solution alloys. Most applications of the CPA to date have assumed an isomorphous model of the alloy in which all of the A atoms are assumed to be the same, as are all of the B atoms. The derivation of self-consistent potentials for the alloys within the framework of the CPA and the isomorphous model leads inevitably to the conclusion that the Madelung potential at each site must be zero. The approximate theory resulting from this derivation is called the KKR-CPA. The polymorphous CPA (PCPA) makes use of supercells that contain many atoms, and the Madelung potentials at all of the sites are calculated exactly. PCPA calculations produce a polymorphous alloy model in which every atom in the supercell is different. Tests will be shown that demonstrate the advantages of the PCPA over the KKR-CPA in explaining experiments that depend critically on the charge transfer in an alloy.
TL;DR: In this paper, the problem of motion of a single electron interacting with a periodic lattice of two-level systems was investigated within a spinless fermion model and the Green's function was calculated in a single-site dynamical coherent potential approximation which is equivalent to DMFT.
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TL;DR: In this paper, the quantum theory of the electron moving in a random environment is discussed and the many-body approach is used to derive the coherent-potential approximation and to show how it fits into the dynamical mean field theory.
Abstract: I review the quantum theory of the electron moving in a random environment. First, the quantum mechanics of individual particles scattered on a random potential is discussed. The quantum-mechanical description is extended to many-body systems by using many-body Green functions. The many-body approach is used to derive the coherent-potential approximation and to show how it fits into the dynamical mean-field theory. The generating functional of the coherent-potential approximation is obtained in an analytic form from the limit to infinite dimensions of the general many-body description of non-interacting electrons in random lattices. The analytic generating functional of the mean-field description of random systems is extended to the Falicov-Kimball model with thermally equilibrated scattering lattice potential. The many-body Green functions are then used to calculate transport properties. The electrical conductivity of the coherent-potential approximation is derived from the two-particle Green function calculated in infinite spatial dimensions. Finally, a perturbation theory for the vertex corrections to the mean-field conductivity is introduced. In particular, it is shown how to make the expansion beyond the local approximations conserving.
TL;DR: Graphene, as opposed to Al and Pd, is considered as a liner layer for thin Cu film with low-surface roughness using first principles calculation and the obtained results suggest that graphene is better than Al andPd as aliner material forthin Cu films.
Abstract: Surface scattering is a major issue in thin Cu films at reduced scales. The rise in the diffusive scattering due to the surface roughness causes the electrical resistance to increase remarkably. In this paper, graphene, as opposed to Al and Pd, is considered as a liner layer for thin Cu film with low-surface roughness using first principles calculation. The surface roughness is simulated using the nonequilibrium coherent potential approximation combined with the linear muffin-tin orbital formulation. The coherent potential approximation band structure shows that the graphene $\pi $ -bands is not significantly affected by the surface disorder at the Cu surface and that graphene acts as a parallel path to the electrons. On the other hand, the bands of Cu–Al/Pd around the Fermi level are substantially broadened due to the surface disorder. Moreover, the graphene-coated Cu shows less electrical resistance than Al/Pd-coated Cu for surface disorder $x\lessapprox 5$ % for thin films with 0.245 nm in width, and 1.23 nm in thickness. The enhancement in the transport properties in Cu–Gr is attributed to the weak electronic interaction at the interface. The obtained results suggest that graphene is better than Al and Pd as a liner material for thin Cu films.