Albrecht<i>et al.</i>Reply:

Albrecht, Stefan; Reining, Lucia; Onida, Giovanni; Olevano, Valério; Sole, R. Del

doi:10.1103/physrevlett.83.3971

Cited by 87 publications

(114 citation statements)

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“…Since the early applications of the BSE to the calculation of spectra of bulk systems, it was suggested that the use of M-P grids was likely responsible for the appearance of spurious peaks in the spectra 38 . It was also suggested that the use of grids shifted off the high symmetry directions 8 or randomly distributed k-points may help avoid the appearance of spurious spectral features.…”

Section: Applications To Bulk Silicon Carbon Diamond and Siliconmentioning

confidence: 99%

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Solution of the Bethe-Salpeter equation without empty electronic states: Application to the absorption spectra of bulk systems

et al. 2012

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An approach recently developed to solve the Bethe-Salpeter equation within density matrix perturbation theory is extended to the calculation of optical spectra of periodic systems. This generalization requires numerical integrations within the first Brillouin Zone, that are efficiently performed by exploiting point group symmetries. The technique is applied to the calculation of the optical spectra of bulk Si, diamond C and cubic SiC. Numerical convergence and the accuracy of the Tamm-Dancoff approximation are discussed in detail.

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Section: Applications To Bulk Silicon Carbon Diamond and Siliconmentioning

confidence: 99%

“…For example in Ref. 38 the example of an independent particle spectrum computed with 400000 k-points was presented, showing improved accuracy. However such a large mesh is not affordable in the solution of the BSE for realistic solids.…”

Section: Applications To Bulk Silicon Carbon Diamond and Siliconmentioning

confidence: 99%

Solution of the Bethe-Salpeter equation without empty electronic states: Application to the absorption spectra of bulk systems

et al. 2012

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“…Any single-particle excitation, associated to a transition of a single electron from an occupied to an empty state, should be apparent as a peak in Im(ε). The position of such an excitation corresponds to the transition energy between the two states of the band-like picture, eventually renormalized by electron-electron interaction effects (single-quasiparticle 39 excitations) and electronhole (excitonic 40,41 ) effects. On the other hand, collective plasmon excitations would manifest themselves as zero-crossings of the real part of the dielectric function Re(ε), when the imagi-nary part Im(ε) is small.…”

Section: 35mentioning

confidence: 99%

Screening inYBa2Cu3O7−δat large wave vectors

et al. 2010

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We present experimental inelastic x-ray scattering (IXS) and ab initio time-dependent densityfunctional-theory (TDDFT) studies of YBa2Cu3O 7−δ . The response of the low-lying Ba 5p and Y 4p core electrons is shown to interact strongly with the Cu 3d and O 2p excitations, with important consequences on screening. The agreement between IXS and TDDFT results is excellent, apart from a new type of excitations, mainly related to loosely bound Ba electrons and significantly affected by correlations. This points to correlation mechanisms not fully described by TDDFT that might have a role in giving rise to antiscreening.

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“…30 On the other hand, as pointed out above, the electronhole attraction can also lead to bound excitons in insu- 30 The present curve has been calculated by Olevano and Reining (2000) using an improved Brillouin-zone sampling with respect to the original publication of Albrecht et al (1998a). See also the discussions by Cardona et al (1999) and Albrecht et al (1999). lators, where the interaction is only weakly screened.…”

Section: The Effects Of the Electron-hole Interactionmentioning

confidence: 99%

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

2002

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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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Albrechtet al.Reply:

Cited by 87 publications

References 6 publications

Solution of the Bethe-Salpeter equation without empty electronic states: Application to the absorption spectra of bulk systems

Solution of the Bethe-Salpeter equation without empty electronic states: Application to the absorption spectra of bulk systems

Screening inYBa2Cu3O7−δat large wave vectors

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

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