Short-range correlations in disordered systems: nonlocal coherent-potential approximation

Rowlands, D A

doi:10.1088/0034-4885/72/8/086501

Cited by 32 publications

(39 citation statements)

References 196 publications

(426 reference statements)

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“…While it is certainly possible (and often necessary) to improve over the CPA, 95 in this work we aim at qualitative insight, and in Sec. VI B we present results obtained with the simple local formulation of CPA and the self-consistent set of equations Eqs.…”

Section: B the Coherent Potential Approximationmentioning

confidence: 99%

Interacting fermions in one-dimensional disordered lattices: Exploring localization and transport properties with lattice density-functional theories

et al. 2013

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We investigate the static and dynamical behavior of one-dimensional interacting fermions in disordered Hubbard chains contacted to semi-infinite leads. The chains are described via the repulsive Anderson-Hubbard Hamiltonian, using static and time-dependent lattice density-functional theory. The dynamical behavior of our quantum transport system is studied using an integration scheme available in the literature, which we modify via the recursive Lanczos method to increase its efficiency. To quantify the degree of localization due to disorder and interactions, we adapt the definition of the inverse participation ratio to obtain an indicator which is suitable for quantum transport geometries and can be obtained within density-functional theory. Lattice density-functional theories are reviewed and, for contacted chains, we analyze the merits and limits of the coherent-potential approximation in describing the spectral properties, with interactions included via lattice density-functional theory. Our approach appears to be able to capture complex features due to the competition between disorder and interactions. Specifically, we find a dynamical enhancement of delocalization in the presence of a finite bias and an increase of the steady-state current induced by interparticle interactions. This behavior is corroborated by results for the time-dependent densities and for the inverse participation ratio. Using short isolated chains with interaction and disorder, a brief comparative analysis between time-dependent density-functional theory and exact results is then given, followed by general concluding remarks.

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Section: B the Coherent Potential Approximationmentioning

confidence: 99%

Interacting fermions in one-dimensional disordered lattices: Exploring localization and transport properties with lattice density-functional theories

et al. 2013

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“…Although CPA is nowadays the most successful ab initio theory for the calculations of disordered alloys, the standard formulation of it neglects the effects of NNN environment. Along with the development of the ab initio methods (as non local CPA [37]), the understanding of the certain property of the specific compound can be reached in the framework of the suitable models with the parameters obtained from the ab initio calculations for a given compound. Namely such combination of the ab initio calculations with the multiorbital model one for the iron silicides was used in our work.…”

Section: Discussionmentioning

confidence: 99%

Self-consistent mapping: Effect of local environment on formation of magnetic moment in α−FeSi2

et al. 2017

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The Hohenberg-Kohn theorem establishes a basis for mapping of the exact energy functional to a model one provided that their charge densities coincide. We suggest here to use a mapping in a similar spirit: the parameters of the formulated multiorbital model should be determined from the requirement that the self-consistent charge and spin densities found from the ab initio and model calculations have to be as close to each other as possible. The analysis of the model allows for detailed understanding of the role played by different parameters of the model in the physics of interest. After finding the areas of interest in the phase diagram of the model we return to the ab initio calculations and check if the effects discovered are confirmed or not. Because of the last controlling step we call this approach as hybrid self-consistent mapping approach (HSCMA). As an example of the approach we present the study of the effect of silicon atoms substitution by the iron atoms and vice versa on the magnetic properties in the iron silicide α − F eSi2. The DFT+GGA calculations are mapped to the model with intraatomic Coulomb and exchange interactions, hoppings to nearest and next nearest atoms and exchange of the delocalized electrons between iron atoms; the magnetic moments on atoms and charge densities of the material are found self-consistently within the Hartree-Fock approximation.We find that while the stoichiometric α − F eSi2 is nonmagnetic, the substitutions generate different magnetic structures. For example, the substitution of three Si atoms by the F e atoms results in the ferrimagnetic structure whereas the substitution of four Si atoms by F e atoms gives rise to either the nonmagnetic or the ferromagnetic state depending on the type of local enviroment of the substitutional F e atoms. Besides, contrary to the commonly accepted statement that the destruction of the magnetic moment is controlled only by the number of F e − Si nearest neighbors, we find that actually it is controlled by the F e − F e next-nearest-neighbors' hopping parameter. This finding led us to the counterintuitive conclusion: an increase of Si concentration in F e1−xSi2+x ordered alloys may lead to a ferromagnetism. This conclusion is confirmed by the calculation within GGA-to-DFT.

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“…21 Furthermore, this coarse-graining of the Brillouin zone leads to discontinuities in the k -dependent integrand of Eq.12, whenever tile boundaries are crossed. 24,26 We note here however a recent suggestion to overcome such limitation through an additional averaging step over various phase choices, to reobtain a smooth k -dependence 18 .…”

Section: B the Non-local Cpa Solutionmentioning

confidence: 97%

“…14 Along the latter line of research, the non-local coherent potential approximation (NLCPA) has been recently developed based on insights provided by the Dynamical Cluster Approximation (DCA). 20 The method has shown its capability to describe SRO effects both within model Hamiltonian studies 18,[21][22][23][24] and when reimplemented within a completely self-consistent DFT-KKR framework for realistic systems. [25][26][27] This technique inherits however from its derivation a practical restriction to simple, one atom per unit cell lattices in Strukturberichte A h , A2 or A1 structures.…”

Section: Introductionmentioning

confidence: 99%

Generalized inclusion of short-range ordering effects in the coherent potential approximation for complex-unit-cell materials

et al. 2013

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The coherent potential approximation has historically allowed the efficient study of disorder effects over a variety of solid state systems. Its original formulation is however limited to a single-site or uncorrelated model of local substitutions. This neglects the effects of correlation and short range ordering, often found in realistic materials. Recent theoretical work has shown how to systematically address such shortcomings, for simple materials with only one element per unit cell. We briefly review the basic ideas of these developments within the framework of multiple scattering theory, and suggest their generalization to materials with complex lattices and possibly different types of disorder. We illustrate this extension with an example of local environment effects in the exotic Hapkeite F e − F e 37.5% Si 62.5% compound.

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Short-range correlations in disordered systems: nonlocal coherent-potential approximation

Cited by 32 publications

References 196 publications

Interacting fermions in one-dimensional disordered lattices: Exploring localization and transport properties with lattice density-functional theories

Interacting fermions in one-dimensional disordered lattices: Exploring localization and transport properties with lattice density-functional theories

Self-consistent mapping: Effect of local environment on formation of magnetic moment in α−FeSi2

Generalized inclusion of short-range ordering effects in the coherent potential approximation for complex-unit-cell materials

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