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.

Theory of alloys, a coherent pseudopotential model

Abstract: The authors present a model for predicting the properties of a random alloy AxBy. A method is developed for finding an effective energy dependent potential, localized on a single site in the Wannier representation, to describe the effect of a B atom in an A host. A multiple scattering theory is then used to calculate the effect of many impurities, the model for this part of the calculation involving an iteration procedure which tends to the same solution of the formal problem as the 'coherent potential approximation' (CPA) of Soven and others. The most important feature of the calculation is that the input data are the density of states for both a pure A and a pure B crystal so that the model can be used easily for real physical systems whose densities of states are known; no other adjustable parameters are involved in this theory. The method is applied to the case of a silver-gold alloy and results are obtained for the specific heat and resistivity which compare favourably with experimental results.

Viscoelastic modeling of rocks saturated with heavy oil

Abstract: While properties of bulk heavy oil can be approximated by an appropriate viscoelastic model, only a few attempts to model properties of rocks saturated with heavy oil have been reported (Eastwood, 1993; Leurer and Dvorkin, 2006). Rock physics for heavy oil is different from rock physics for conventional fluids because its viscoelastic rheology makes Gassmann theory and all its extensions inapplicable in principle. In this paper, we estimate the properties of such rock-heavy oil mixtures by considering (1) a system of layers of solid and a viscoelastic medium and (2) by computing Hashin-Shtrikman bounds for this system. These two methods essentially give approximate bounds for the frequencyand temperature-dependent properties of these rocks. We also propose how to compute a realistic estimate of these properties that would lie between these bounds. This proposed estimate is based on one particular equivalent-medium approach known as coherent potential approximation (CPA) (Berryman, 1980). In a more general form, this approximation can be used for approximate fluid substitution for heavy oil.