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.

Electronic properties of surfaces of disordered alloys.

Abstract: An approach to the electronic properties of surfaces of disordered metals is developed that combines the tight-binding linear-muffin-tin-orbital method with the surface Green's-function formalism and the coherent-potential approximation. The actual composition in the top surface layers can differ from that in the bulk layers. The method is applied to evaluate component- and layer-projected densities of states for the ${\mathrm{Ag}}_{50}$${\mathrm{Pd}}_{50}$(001) surface, assuming both uniform and nonuniform concentration profiles in the sample surface.

The effect of non-orthogonality and previously neglected diagonal terms in the tight-binding approximation for the electronic structure of liquid metals and alloys

Abstract: The averaged Green's function for an electron in non-simple liquid metals and alloys is evaluated in the tight-binding approximation (LCAO) when the effect of non-orthogonality and previously neglected diagonal terms are taken into account. The actual formalism is given on the basis of self-consistent single-site approximations (SSSA)-particularly of the coherent potential approximation (CPA) for liquid metals and of the Ishida-Yonezawa theory. The averaged Green's function is well known to be related to one-electron properties such as the density of states and, within SSSA assumptions, even to the electric conductivity, the Hall coefficient, etc. Calculated densities of states with and without non-orthogonal terms are given for comparison and discussion.

Lattice vibrations in Rb/sub 1-c/K/sub c/ alloys: Shortcomings of a single-site coherent potential approximation

Abstract: A single-site coherent potential approximation (CPA) including force constant changes in the additive limit (designated the CPA-F) is applied to phonons in Rb/sub 1-c/K/sub c/ alloys. The CPA-F results are in better overall agreement with the neutron scattering measurements of Kamitakahara and Copley than mass-defect CPA results. However, marked discrepancies in the concentration, branch, and wave-vector dependence and in the line shapes remain between CPA-F and experimental neutron scattering cross sections. These discrepancies suggest the need to include multiple scattering from pairs and larger clusters in the theoretical treatment.

CPA theory for jump diffusion of particles in periodic lattices

Abstract: The incoherent dynamical structure factor and the diffusion coefficient of the nearest neighbour (NN) jump diffusion model is studied. Diffusion of a specific particle in a static but random arrangement of background particles is considered. The virtual crystal approximation and coherent potential approximation procedures are used to find solutions. First five exact frequency moments of the spectral density are calculated and compared with those given by these theories. In simple cubic and body-centred cubic lattices four first moments are exactly reproduced by the CPA solution.

Composition-dependent band gaps and indirect–direct band gap transitions of group-IV semiconductor alloys

Abstract: We used the coherent potential approximation to investigate the band structures of group-IV semiconductor alloys, including SixGe1−x, Ge1−ySny and SixGe1−x−ySny. The calculations for SixGe1−x prove the reliability and accuracy of the method we used. For Ge1−ySny, the direct band gap optical bowing parameter we obtained is 2.37 eV and the indirect–direct band gap transition point is at y = 0.067, both consistent with the existing experimental data. For SixGe1−x−ySny, with the increase of the Si concentration, the compositional dependency of the band gap becomes complex. An indirect–direct band gap transition is found in SixGe1−x−ySny in the range of 0 < x ≤ 0.20, and the indirect–direct crossover line in the compositional space has the quadratic form of y = 3.4x2 + 1.11x + 0.07, not the linear form as suggested before. Furthermore, for the Ge lattice-matched alloy Ge1−x(Si0.79Sn0.21)X, our results show that those with 0.18 < X < 0.253 have band gaps larger than 0.8 eV at room temperature.