Coherent potential approximation experimental methods

Furthermore, a chapter which discusses different ways to perform calculations for disordered systems is presented, including a description of the Coherent Potential Approximation and the Screened Generalized Perturbation Method. A comparison between the Exact Muffin-Tin Orbital method and the Projector Augmented-Wave method in the case of systems exhibiting both compositional and magnetic disordered is included as well as a case study of the MoRu alloy, where the theoretical and experimental discrepancies are discussed. 

By using the tight-binding linearized muffin-tin orbital method combined with die coherent-potential approximation (TB-LMTO-CPA) the total energies, bulk moduli, equilibrium lattice parameters, magnetie moments, and hyperfine fields of bcc solid solution were ealeulated by [2000San], and are in qualitative agreement with experimental trends. 

An attempt to describe the concentration dependence of the DOS at the Fermi level in NbC Ni (x = 1.0, 0.75, 0.25, 0.12, and 0) was undertaken by Nikiforov and Kolpachev (1988) and Kolpachev and Nikiforov (1988). They used a multiple scattering method in the local coherent potential approximation. Variations in the solid solution composition caused the greatest changes in the nonmetal p-symmetry states and in the part of the d-band located close to the Fermi level. At the same time, comparison of the DOS of the calculated clusters and photoelectron spectra of Nb ternary alloys obtained by Ichara and Watanabe (1981) shows that the calculations only roughly reproduce the peculiarities of the NbC jNi c valence spectrum the energy separation of the p-d- and d-bands is considerably overestimated and there are some additional peaks in the DOS which are not seen in the experimental spectrum. 

The DFT studies represent a natural step towards a more detailed, parameter-free understanding of the properties of the DMS. One possibility is to employ the supercell approach , in which big cells are needed to simulate experimentally observed low concentrations of magnetic atoms and other impurities. Alternatively, one can employ the Green function methods combined with the coherent potential approximation (CP.A) in the framework of the Korringa-Kohn-Rostoker (KKR) method or the tight-binding... 

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