2 research outputs found
Dielectric anisotropy in the GW space-time method
Excited-state calculations, notably for quasiparticle band structures, are nowadays routinely performed within the GW approximation for the electronic self-energy. Nevertheless, certain numerical approximations and simplifications are still employed in practice to make the computations feasible. An important aspect for periodic systems is the proper treatment of the singularity of the screened Coulomb interaction in reciprocal space, which results from the slow 1/r decay in real space. This must be done without introducing artificial interactions between the quasiparticles and their periodic images in repeated cells, which occur when integrals of the screened Coulomb interaction are discretised in reciprocal space. An adequate treatment of both aspects is crucial for a numerically stable computation of the self-energy. In this article we build on existing schemes for isotropic screening and present an extension for anisotropic systems. We also show how the contributions to the dielectric function arising from the non-local part of the pseudopotentials can be computed efficiently. These improvements are crucial for obtaining a fast convergence with respect to the number of points used for the Brillouin zone integration and prove to be essential to make GW calculations for strongly anisotropic systems, such as slabs or multilayers, efficient. (C) 2006 Elsevier B.V. All rights reserved
Electronic and optical properties of core-shell InAlN nanorods: a comparative study via LDA, LDA-1/2, mBJ and methods
Currently, self-induced InAlN core-shell nanorods enjoy an advanced stage of
accumulation of experimental data from their growth and characterization as
well as a comprehensive understanding of their formation mechanism by the ab
initio modeling based on Synthetic Growth Concept. However, their electronic
and optical properties, on which most of their foreseen applications are
expected to depend, have not been investigated comprehensively. is
currently regarded as a gold-standard methodology with quasi-particle
corrections to calculate electronic properties of materials in general. It is
also the starting point for higher-order methods that study excitonic effects,
such as those based on the Bethe-Salpeter equation. One major drawback of
, however, is its computational cost, much higher than
density-functional theory (DFT). Therefore, in many applications, it is highly
desirable to answer the question of how well approaches based on DFT, such as
e. g. LDA, LDA-1/2, and mBJ, can approximately reproduce results with
respect to the electronic and optical properties. Thus, the purpose of the
present paper is to investigate how the DFT-based methodologies LDA, LDA-1/2,
and mBJ can be used as tools to approximate in studies of the
electronic and optical properties of scaled down models of core-shell InAlN
nanorods. For these systems, we observed that band gaps, density of states,
dielectric functions, refractive indexes, absorption and reflectance
coefficients are reasonably well described by LDA-1/2 and mBJ when compared to
, however, at a much more favorable computational cost.Comment: The following article has been submitted to The Journal of Chemical
Physics. After it is published, it will be found at
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