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.

The Slater–Pauling curve: First principles calculations of the moments of Fe1−cNic and V1−cFec

Abstract: We have performed calculations of the electronic structure of the random substitutional alloys Fe1−cNic and V1−cFec using the spin‐polarized, self‐consistent Korringa–Kohn–Rostoker coherent‐potential approximation (KKR‐CPA) method. This is a first principles method based on spin density functional theory and a local spin density approximation for the exchange and correlation functional. For fcc Fe1−cNic, a range of volumes were considered for 0.25

Exploring the XPS limit in soft and hard x-ray angle-resolved photoemission using a temperature-dependent one-step theory

Abstract: We present a theory of temperature-dependent photoemission which accurately describes phonon effects in soft and hard x-ray angle-resolved photoemission. Our approach is based on a fully relativistic one-step theory of photoemission that quantitatively reproduces the effects of phonon-assisted transitions beyond the usual $\mathbf{k}$-conserving dipole selection rules which lead to the so-called XPS limit in the hard x-ray and/or high temperature regime. Vibrational atomic displacements have been included using the coherent potential approximation in analogy to the treatment of disordered alloys. The applicability of this alloy analogy model is demonstrated by direct comparison to experimental soft x-ray data from W(110) showing very satisfying agreement.

Electronic states in Ag-Pd alloys

Abstract: Electronic densities of states functions are calculated for the random substitutional alloy system Ag-Pd for a number of compositions across the complete range of concentrations. The calculations are based on the coherent potential approximation. It was found necessary to extend the simple model Hamiltonian method previously used to describe Cu-Ni alloys because of the stronger dependence of the lattice constant on composition in the Ag-Pd system. It is shown that the results are consistent with published photoemission and optical absorption data, and low temperature specific heat and Pauli spin susceptibility experiments. The possibility of s-d charge transfer in this alloy system is discussed.

Electronic Transport in Alloys: Coherent-Potential Approximation

Abstract: The coherent-potential approximation, which has been successfully used to describe the electronic structure of a nondilute binary alloy ${A}_{x}{B}_{1\ensuremath{-}x}$, is reformulated in a diagrammatic way suitable for the calculation of more complicated transport coefficients. This approach is applied to the calculation of three elementary transport coefficients: the conductivity $\ensuremath{\sigma}$, the thermoelectric power $Q$, and the low-field Hall coefficient ${R}_{H}$. The appropriate response functions are evaluated for a simple cubic tight-binding model. The rigid-band limit is considered in detail, with emphasis on the role of critical points. As the random alloy potential increases, deviations from rigid-band behavior --- for example, Nordheim's rule --- become more pronounced for unexpectedly small scattering strengths. However, the usual relations among the transport coefficients, e.g., Mott's equation between $Q$ and $\ensuremath{\sigma}$, are maintained. The conductivity is no longer symmetrical with respect to electron and hole concentrations. Furthermore, the change in sign of $Q$ and ${R}_{H}$ may not occur when the band is half-full. Therefore, the identification of the carrier sign becomes ambiguous. For the model treated, numerical calculations are quite tractable. Examples are given which illustrate the behavior for a wide range of alloy parameters.

Phonons in random alloys: The itinerant coherent-potential approximation

Abstract: We present the itinerant coherent-potential approximation (ICPA), an analytic, translationally invariant, and tractable form of augmented-space-based multiple-scattering theory 1 8 in a single-site approximation for harmonic phonons in realistic random binary alloys with mass and force-constant disorder. We provide expressions for quantities needed for comparison with experimental structure factors such as partial and average spectral functions and derive the sum rules associated with them. Numerical results are presented for Ni 5 5 Pd 4 5 and Ni 5 0 Pt 5 0 alloys which serve as test cases the former for weak force-constant disorder and the latter for strong. We present results on dispersion curves and disorder-induced widths. Direct comparisons with the single-site coherent potential approximation (CPA) and experiment are made which provide insight into the physics of force-constant changes in random alloys. The CPA accounts well for the weak force-constant disorder case but fails for strong force-constant disorder where the ICPA succeeds.