<i>Ab Initio</i>Calculation of Self-Energy Effects on Optical Properties of GaAs(110)

A subdivision of space into discrete cells underlies the traditional discrete dipole model. This model presumes that only nonlocal electric interactions between cells govern the electromagnetic response of a condensed matter system. Apart from the case of simple dielectrics, this is not realistic. Cells can also influence each other directly through the wave functions, when those extend across cell boundaries. In general, such nonlocal quantum mechanical interaction requires the use of nonlocal polarizabilities. In this paper it is shown how existing discrete dipole descriptions for clusters, slabs and (semi)-infinite systems have to be altered to incorporate the effects of nonlocal polarizabilities. The modified method is called discrete cellular method. r

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“…6. We compare these results with the results of Pulci et al [23], obtained by means of continuum theory. In the upper panel of Fig.…”

Section: Resultssupporting

confidence: 60%

“…The most remarkable result of nonlocality is the k-dependence of the planar polarizability in Eq. (23 …”

Section: Ij Are Called Interplanar Transfer Tensors If Iaj and Intrapmentioning

confidence: 99%

Nonlocality and discrete cellular methods in optics

Wijers

Boeij

2001

Physica B: Condensed Matter

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“…As pointed out earlier, such deviations could be corrected by improving the LDA with self-energy terms. 39,40 Qualitative theory-experiment differences are also visible in the FS maps of Fig. 10.…”

Section: Discussionmentioning

confidence: 76%

“…This limitation does not only apply to the excited states, since GWcorrected spectra for different systems have also shown large self-energy corrections for valence ͑occupied͒ states, particularly when they present a strong localization. 39,40 Furthermore, after the photoelectron excitation process, the electron has to surpass the attractive interaction with the hole just created before exiting, leading to a further renormalization of the energy bands. Although for metallic systems the magnitude of the LDA errors tends to be small, in semiconductors and insulators it may vary from a few hundredths of eV up to more than 1 eV.…”

Section: Arups Simulationsmentioning

confidence: 99%

Electronic structure and Fermi surface of two-dimensional rare-earth silicides epitaxially grown on Si(111)

et al. 2004

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The electronic structure and the Fermi surface of two-dimensional rare-earth silicides epitaxially grown on Si͑111͒, YSi 2 and GdSi 2 , have been studied by a combination of angle-resolved ultraviolet photoemission spectroscopy and density functional theory calculations. Both silicides present a very similar electronic structure, with two characteristic electronic bands below the Fermi energy. One crosses the Fermi energy near the ⌫ point of the surface Brillouin zone ͑hole pocket͒ and the other one close to the M point ͑electron pocket͒. These two bands arise from surface ͑localized͒ states and are responsible for all the Fermi surface features. The theoretical calculations are in good qualitative agreement with the experimental results, and also allow to examine the nature of the bonding between the rare earth and the neighboring silicon atoms. We have found a combination of sp metallic type bond together with covalent bonds involving the rare-earth d states and Si 3p states.

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“…26 The relevance of semicore states in the self-energy was also pointed out by Rohlfing et al (1995Rohlfing et al ( , 1998. 27 A typical bottleneck is given by the summations over the empty states , both for the determination of the screening and for G. Another difficulty comes from the convergence of Brillouin zone integrals (i.e., k-point sampling) of functions that have a factor ͉kϩG͉ 2 in the denominator as the exchange term (Pulci, 1998 (Marini et al, 2002); dashed line, DFT-LDA eigenvalues; ᭺, experimental data compiled by Courths and Hü fner (1984). A comparison to more recent experimental data (Strocov et al, 1998(Strocov et al, , 2001) yields the same agreement.…”

Section: A Evaluation Of the Green's Function Gmentioning

confidence: 99%

Electronic excitations: density-functional versus many-body Green’s-function approaches

2002

Self Cite

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Electronic excitations lie at the origin of most of the commonly measured spectra. However, the first-principles computation of excited states requires a larger effort than ground-state calculations, which can be very efficiently carried out within density-functional theory. On the other hand, two theoretical and computational tools have come to prominence for the description of electronic excitations. One of them, many-body perturbation theory, is based on a set of Green's-function equations, starting with a one-electron propagator and considering the electron-hole Green's function for the response. Key ingredients are the electron's self-energy ⌺ and the electron-hole interaction. A good approximation for ⌺ is obtained with Hedin's GW approach, using density-functional theory as a zero-order solution. First-principles GW calculations for real systems have been successfully carried out since the 1980s. Similarly, the electron-hole interaction is well described by the Bethe-Salpeter equation, via a functional derivative of ⌺. An alternative approach to calculating electronic excitations is the time-dependent density-functional theory (TDDFT), which offers the important practical advantage of a dependence on density rather than on multivariable Green's functions. This approach leads to a screening equation similar to the Bethe-Salpeter one, but with a two-point, rather than a four-point, interaction kernel. At present, the simple adiabatic local-density approximation has given promising results for finite systems, but has significant deficiencies in the description of absorption spectra in solids, leading to wrong excitation energies, the absence of bound excitonic states, and appreciable distortions of the spectral line shapes. The search for improved TDDFT potentials and kernels is hence a subject of increasing interest. It can be addressed within the framework of many-body perturbation theory: in fact, both the Green's functions and the TDDFT approaches profit from mutual insight. This review compares the theoretical and practical aspects of the two approaches and their specific numerical implementations, and presents an overview of accomplishments and work in progress. CONTENTS

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Ab InitioCalculation of Self-Energy Effects on Optical Properties of GaAs(110)

Cited by 96 publications

References 35 publications

Nonlocality and discrete cellular methods in optics

Nonlocality and discrete cellular methods in optics

Electronic structure and Fermi surface of two-dimensional rare-earth silicides epitaxially grown on Si(111)

Electronic excitations: density-functional versus many-body Green’s-function approaches

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