Optical Constants of Magnesium Oxide and Lithium Fluoride in the Far Ultraviolet*

Roessler, David M.; Walker, William C.

doi:10.1364/josa.57.000835

Cited by 113 publications

(57 citation statements)

References 7 publications

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“…LiF and argon have a low dielectric constant and therefore exhibit a crossing below the gap. However, the exciton binding energies, given by the difference between the energy of the fundamental quasiparticle gap and the exciton peak, are only 0.05 eV in LiF and 0.0 eV in Ar, much smaller than the experimental results (about 1.4 eV and 2.0 eV, respectively [39,40]), and in apparent contrast to [32]. The latter discrepancy cannot be explained with the use of Eq.…”

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confidence: 59%

Estimating Excitonic Effects in the Absorption Spectra of Solids: Problems and Insight from a Guided Iteration Scheme

et al. 2015

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A major obstacle for computing optical spectra of solids is the lack of reliable approximations for capturing excitonic effects within time-dependent density-functional theory. We show that the accurate prediction of strongly bound electron-hole pairs within this framework using simple approximations is still a challenge and that available promising results have to be revisited. Deriving a set of analytical formulae we analyze and explain the difficulties. We deduce an alternative approximation from an iterative scheme guided by previously available knowledge, significantly improving the description of exciton binding energies. Finally, we show how one can "read" exciton binding energies from spectra determined in the random phase approximation, without any further calculation.The response of materials to an electromagnetic field is a key to many properties and applications. In the frequency range from infrared to ultraviolet, the optical properties determine the color of materials, their ability to absorb the sunlight, and much more. They lay the ground for non-destructive spectroscopies such as ellipsometry, that can tell us much about the electronic or atomic structure of materials. However, theoretical tools are needed that allow one to analyze, understand and predict measured results and desired or undesired properties. These tools should be reliable and versatile, but simple enough to be applicable to systems of fundamental or technological interest, that are often rather complex. One of the major challenges is to design approximations for the ab initio calculation of optical spectra of extended systems such as solids and liquids [1].The state-of-the-art approach for the ab initio calculation of optical spectra consists in using the Kohn-Sham (KS) electronic structure coming from a density functional theory (DFT) calculation as starting point for a quasiparticle bandstructure calculation in the GW approximation, and the subsequent solution of the BetheSalpeter equation (BSE) to account for the electron-hole interaction [1][2][3][4][5]. The scheme is successful; in particular, excitonic effects are well described. However, calculations are computationally demanding, because of the two-particle (electron and hole) nature of the problem. Alternatively, time-dependent DFT (TDDFT) [1,6,7] formulates the response in terms of variations of local potentials that are functionals of the time-dependent density. This reduces the size of the problem, but raises the question of how to find a good approximation for the time-dependent exchange-correlation (xc) potential v xc and its first derivative, the xc kernel f xc (r, r ′ , t − t ′ ) = δv xc (r, t)/δn(r ′ , t ′ ), where n is the time-dependent electron density. Some simple but widely used approximations such as the adiabatic local density approximation [8,9], that are often successful for finite systems and for electron energy-loss spectra, yield disappointing results similar to the random phase approximation (f xc = 0) [7,10] for absorption spectra of solids.Many wo...

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confidence: 59%

Estimating Excitonic Effects in the Absorption Spectra of Solids: Problems and Insight from a Guided Iteration Scheme

et al. 2015

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“…3 with the experimental absorption spectrum. 57 The latter shows a sharp intense peak at about 12.6 eV -about 1.6 eV below the fundamental band gap -which has been identified as an exciton resonance. The position and intensity of the exciton resonance, and in general of all the absorption spectrum, is well reproduced at the G 0 W 0 +BSE level (top panel).…”

Section: B Lithium Fluoridementioning

confidence: 99%

Effect of ladder diagrams on optical absorption spectra in a quasiparticle self-consistent GW framework

Cunningham

Grüning

Azarhoosh

et al. 2018

Phys. Rev. Materials

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M. (2018). Effect of ladder diagrams on optical absorption spectra in a quasiparticle self-consistent GW framework. Physical Review Materials, 2(3), [034603] We present an approach to calculate the optical absorption spectra that combines the quasiparticle selfconsistent GW method [Phys. Rev. B, 76 165106 (2007)] for the electronic structure with the solution of the ladder approximation to the Bethe-Salpeter equation for the macroscopic dielectric function. The solution of the Bethe-Salpeter equation has been implemented within an all-electron framework, using a linear muffin-tin orbital basis set, with the contribution from the non-local self-energy to the transition dipole moments (in the optical limit) evaluated explicitly. This approach addresses those systems whose electronic structure is poorly described within the standard perturbative GW approaches with as a starting point density-functional theory calculations. The merits of this approach have been exemplified by calculating optical absorption spectra of a strongly correlated transition metal oxide, NiO, and a narrow gap semiconductor, Ge. In both cases, the calculated spectrum is in good agreement with the experiment. It is also shown that for systems whose electronic structure is well-described within the standard perturbative GW , such as Si, LiF and h-BN, the performance of the present approach is in general comparable to the standard GW plus Bethe-Salpeter equation. It is argued that both vertex corrections to the electronic screening and the electron-phonon interaction are responsible for the observed systematic overestimation of the fundamental bandgap and spectrum onset.

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“…4. The experimental data of the pure LiF crystal has been measured by Roessler and Walker [28]. For the calculated pure LiF crystal, there are three main peaks inε 2 (ω), which are 11.6, 17.2 and 20.0 eV.…”

Section: Resultsmentioning

confidence: 99%

Ab initio calculations of electronic and optical properties in O-doped LiF crystal

Guo

Zhang

et al. 2008

Open Physics

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Abstract:We present a first-principle study of electronic and optical properties in pure LiF and O-doped LiF crystals. The pure LiF crystal exhibits a wide band gap while the O-doped LiF crystal shows the less band gap due to the contribution of O 2p. Some optical constants, such as dielectric functions, reflectivity and the refractive index, have been performed. The calculated reflectivity and refractive index from the pure LiF crystal agree with the experimental and recently calculated results in the low-energy range. Meanwhile, the optical properties have also been predicted from the O-doped LiF crystal. The absorption band in 200 nm has been observed, which is relatively close to the experimental result.PACS (

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Optical Constants of Magnesium Oxide and Lithium Fluoride in the Far Ultraviolet*

Cited by 113 publications

References 7 publications

Estimating Excitonic Effects in the Absorption Spectra of Solids: Problems and Insight from a Guided Iteration Scheme

Estimating Excitonic Effects in the Absorption Spectra of Solids: Problems and Insight from a Guided Iteration Scheme

Effect of ladder diagrams on optical absorption spectra in a quasiparticle self-consistent GW framework

Ab initio calculations of electronic and optical properties in O-doped LiF crystal

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