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.

One Step Model Description of HARPES: Inclusion of Disorder and Temperature Effects

Abstract: Angle integrated as well as angle resolved photoemission in the soft and hard X-ray regime became a very important tool to investigate the bulk properties of various materials. In practise enhanced bulk sensitivity can be achieved by so called threshold photoemission. Increased bulk sensitivity may suggest that LSDA band structure or density of states calculations can be directly compared to the measured spectra. However, various important effects, like matrix elements, the photon momentum or phonon excitations, are this way neglected. Here, we present a generalization of the one-step model that describes the excitation of the photoelectron, its transport to the surface and the escape into the vacuum in a coherent way. First, a short introduction to the main features of the one-step model implementation within the Munich SPR-KKR program package is given. The capability to account for correlation effects and chemical disorder using the LSDA+DMFT (dynamical mean field theory) scheme in combination with the coherent potential approximation (CPA) method will be demonstrated by various examples. Special emphasis is put on the description of phonon-assisted transitions which lead to the so-called XPS-limit in the hard X-ray and/or high temperature regime.

Electronic Structure and Magnetic Properties of Zinc-Blende Co-Doped GaN with N Vacancies

Abstract: The electronic structure and magnetic properties of zinc-blende structure of (Ga,Co)N phase with N vacancy defects are investigated using the Korringa–Kohn–Rostoker (KKR) method combined with coherent potential approximation (CPA). The results show that (Ga,Co)N phase is ferromagnetically polarized with an enhancement of the polarization and that the electronic structure can be modified simply by changing the concentration of N vacancies. Moreover, the (Ga,Co)N with high density of N vacancies shows a drastic increase of the magnetic moment of cobalt in the parent GaN compound, to reach a maximum value of 1.7 μB/Co at 8 at.%, which is in good agreement with the experimental values reported in the literature.

Disorder effects on tunneling through one-dimensional double-barrier quantum-well structures: A coherent-potential approximation.

Abstract: We present a formalism for studying the disorder effects on electron tunneling through one-dimensional double-barrier quantum-well structures based on the coherent-potential approximation. This formalism enables us to calculate the configuration-averaged transmission coefficients in a nonperturbative way. It is shown that elastic scattering reduces and broadens the resonance peak, and also destroys its Lorentzian behavior. For sharp resonance structures, the transmission coefficient directly reflects the structures in the density of states within the well. The result obtained using this method agrees well with direct numerical simulation

First-Principles Calculations of the Instabilities in Fe-(Ni, Co, Pt) Alloys

Abstract: First-principles calculations using the Korringa-Kohn-Rostocker method and the Coherent-Potential Approximation for Fe-Ni, Fe-Ni-Co and Fe-Pt alloys show that several features are responsible for the Invar anomalies. Atomic short range ordering in the alloys is responsible for the appearance of antiferromagnetic and non-colinear magnetic moments. The antiferromagnetic contributions are responsible for two effects, the negative anharmonicity due to the tendency of the alloys to have a smaller lattice constant, as well as the tendency to have a larger lattice constant because of additional density of states of antibonding majority-spin orbitals at the Fermi level, which simultaneously stabilizes the antiferromagnetic moments.

Electronic states in some disordered noble metal—transition metal alloys

Abstract: It is shown that the coherent potential approximation is capable of explaining the densities of states functions as observed in the photoemission experiment for noble metal rich alloys of CuPd, CuNi and AgPd. The analysis reveals the importance of the separation in energy between the d-scattering resonances associated with each of the constituent atomic species in these alloys. In all of these alloys the separation between the d-scattering resonances is sufficient to render both the rigid band and the virtual crystal approximations in capable of explaining the observed photoemission data.