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 KKR CPA study of electron states in TiCxN1-x

Abstract: An alloy TiCxN1−x has been studied for compositionx=0.4, 0.6 by the KKR CPA method. The local density of states (DOS) andL-emission spectra of Ti were calculated and compared to experiment. The comparison with the TB CPA calculation was also made.

Quantitative description of short-range order and its influence on the electronic structure in Ag-Pd alloys

Abstract: We investigate the effect of short-range order (SRO) on the electronic structure in alloys from the theoretical point of view using density of states (DOS) data. In particular, the interaction between the atoms at different lattice sites is affected by chemical disorder, which in turn is reflected in the fine structure of the DOS and, hence, in the outcome of spectroscopic measurements. We aim at quantifying the degree of potential SRO with a proper parameter. The theoretical modeling is done with the Korringa-Kohn-Rostoker Green's function method. Therein, the extended multi-sublattice non-local coherent potential approximation is used to include SRO. As a model system, we use the binary solid solution Ag$_c$Pd$_{1-c}$ at three representative concentrations $c=0.25$, $0.5$ and $0.75$. The degree of SRO is varied from local ordering to local segregation through an intermediate completely uncorrelated state. We observe some pronounced features, which change over the whole energy range of the valence bands as a function of SRO in the alloy. These spectral variations should be traceable in modern photoemission experiments.

Electronic transport properties of the Al0.5TiZrPdCuNi alloy in the high-entropy alloy and metallic glass forms

Abstract: High-entropy alloys (HEAs) are characterized by a simultaneous presence of a crystal lattice and an amorphous-type chemical (substitutional) disorder. In order to unravel the effect of crystal-glass duality on the electronic transport properties of HEAs, we performed a comparative study of the electronic transport coefficients of a 6-component alloy Al0.5TiZrPdCuNi that can be prepared either as a HEA or as a metallic glass (MG) at the same chemical composition. The HEA and the MG states of the Al0.5TiZrPdCuNi alloy both show large, negative-temperature-coefficient resistivity, positive thermopower, positive Hall coefficient and small thermal conductivity. The transport coefficients were reproduced analytically by the spectral conductivity model, using the Kubo-Greenwood formalism. For both modifications of the material (HEA and MG), contribution of phonons to the transport coefficients was found small, so that their temperature dependence originates predominantly from the temperature dependence of the Fermi-Dirac function and the variation of the spectral conductivity and the related electronic density of states with energy within the Fermi-level region. The very similar electronic transport coefficients of the HEA and the MG states point towards essential role of the immense chemical disorder.

Metal–insulator-like transition in the energy spectrum of a one-dimensional proton (ionic) conductor

Abstract: We propose a modification of the well-known coherent potential approximation (CPA) for fermionic systems with short-range interactions. We calculate the spectra of a one-dimensional proton (ionic) conductor described by the fermionic lattice model within this approach. Depending on correlation values we observe either quasi-metallic or dielectric behaviour of the system at half-filling. Away from half filling, the system is always in the quasi-metallic state.