Topic
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.
Papers published on a yearly basis
Papers
More filters
TL;DR: In this paper, the authors developed a theoretical scheme in which the local charge excesses for random alloys can be obtained as the responses to local external fields, and they showed that nonlinear charge rearrangements occur at the impurity site as a consequence of the complex phenomena related with the electronic screening of the external potential.
Abstract: Electronic structure calculations performed on very large supercells have shown that the local charge excesses in metallic alloys are related through simple linear relations to the local electrostatic field resulting from distribution of charges in the whole crystal. By including local external fields in the isomorphous coherent potential approximation theory, we develop a theoretical scheme in which the local charge excesses for random alloys can be obtained as the responses to local external fields. Our model maintains all the computational advantages of an isomorphous theory but allows for full charge relaxation at the impurity sites. Through applications to CuPd and CuZn alloys, we find that, as a general rule, nonlinear charge rearrangements occur at the impurity site as a consequence of the complex phenomena related with the electronic screening of the external potential. This notwithstanding, we observe that linear relations hold between charge excesses and external potentials, in quantitative agreement with the mentioned supercell calculations, and well beyond the limits of linearity for any other site property.
14 citations
TL;DR: In this article, a coherent potential approximation (CPA) treatment of positron annihilation in an alloy is presented, where simple formulae for the spatial and the momentum distributions of the positrons are derived.
Abstract: A coherent potential approximation (CPA) treatment of positron annihilation in an alloy is presented. Simple formulae for the spatial and the momentum distributions of the positrons are derived. Numerical computations are performed to illustrate the effects of the smearing of the positron momentum distribution and of the electron Fermi momentum of the annihilation photon momentum distribution.
14 citations
TL;DR: In this paper, the authors studied the correlation between a disordered random walk and a correlated random walk (CRW) and the effect these correlations have on the self-diffusion constant.
Abstract: A concentration c of particles undergo correlated random walks on a lattice. The random walks are constrained by only allowing the lattice sites to be singly occupied. This leads to the particles being 'dynamically' correlated. In addition to the dynamic correlations the hopping rates of the particles are disordered. The random hopping rates give rise to 'static' correlations. The resultant model is a many-body problem with disorder. Of principal interest are the new correlations that arise between a disordered random walk and a correlated random walk (CRW) and the effect these correlations have on the self-diffusion constant. The CRW is represented by a nonlinear master equation from which the diffusion constant is obtained by means of classical many-body Green functions. The dynamic correlations are represented by a two-particle Green function. The disorder is studied by means of the bond coherent potential approximation (BCPA). The disorder gives rise to a vertex correction to the two-particle Green function. The vertex correction is obtained by using the BCPA.
13 citations
TL;DR: In this article, a tight binding theory for d electrons at the surface of transition metal alloys which play an important role in catalysis is presented and an atomic layer dependent electronic self energy due to atomic disorder scattering is introduced and determined by using the continued fraction method and by using Bethe-Peierls approximation extension on the coherent potential approximation.
Abstract: A tight binding theory for d electrons at the surface of transition metal alloys which play an important role in catalysis is presented. An atomic layer dependent electronic self energy due to atomic disorder scattering is introduced and determined by using the continued fraction method and by using the Bethe-Peierls approximation extension on the coherent potential approximation. The authors also discuss s-d hybridization at the surface, and show how the electronic disturbance at the surface due to adatoms, can be determined.
13 citations
TL;DR: Abe et al. as discussed by the authors studied the self-trapping process of photo-created hot excitons which interact strongly with phonons in an effective medium approximation for Green functions.
Abstract: Dynamical self-trapping processes of photo-created hot excitons which interacts strongly with phonons are theoretically studied in an effective-medium approximation for Green functions. The previous formulation [S. Abe: J. Phys. Soc. Jpn. 57 (1988) 4029] of the resonant secondary-emission spectrum in the dynamical coherent potential approximation is extended in such a way that the effect of a finite band width of the phonon branch relevant to self-trapping is taken into account. Emission spectra calculated in this new method indicate that the intensity of hot luminescence from the metastable free state decreases with raising the incident-photon energy from the bottom of the free exciton band, suggesting that a part of hot excitons become self-trapped before they thermalize within the free exciton band states.
13 citations