Excitons in Solids from Time-Dependent Density-Functional Theory: Assessing the Tamm-Dancoff Approximation

In time-dependent density-functional theory, a family of exchange-correlation kernels, known as long-range-corrected (LRC) kernels, have shown promise in the calculation of excitonic effects in solids. We perform a systematic assessment of existing static LRC kernels (empirical LRC, Bootstrap, and jellium-with-a-gap model) for a range of semiconductors and insulators, focusing on optical spectra and exciton binding energies. We find that no LRC kernel is capable of simultaneously producing good optical spectra and quantitatively accurate exciton binding energies for both semiconductors and insulators. We propose a simple and universal, empirically scaled Bootstrap kernel which yields accurate exciton binding energies for all materials under consideration, with low computational cost.

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“…(7). However, we have found 30 that the TDA underestimates LRC E b of insulators significantly (i.e. by more than 100%) (e.g.…”

Section: A Linear-response Tddft For Solids: Dyson Equation Vs Casidmentioning

confidence: 78%

Assessment of long-range-corrected exchange-correlation kernels for solids: Accurate exciton binding energies via an empirically scaled bootstrap kernel

Byun

Ullrich

2017

Phys. Rev. B

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“…S3-S7, SI), thus saving computational time. 38,39 It is also worthwhile to note that for a long-range CT state in the time-dependent density functional theory (TDDFT) the B matrix vanishes, which is equivalent to applying the Tamm-Dancoff approximation. Thus, TDDFT and TDDFT/TDA yield identical results for the excitation energies of long-range CT states.…”

Section: General Methodsmentioning

confidence: 99%

Photoinduced Charge Shift in Li⁺-Doped Giant Nested Fullerenes

Stasyuk

Solà

et al. 2019

J. Phys. Chem. C

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Over the last years, carbon nano-onions (CNOs) have been in focus in material science research.Their red-shifted absorption allows utilizing CNOs as promising photosensitizers. We report here a systematic study of excited state properties of six double-layered Li + doped fullerenes of Ih symmetry:[[Li@C240@C960] + and [Li@C540@C960] + . On the basis of TDDFT calculations, we show that the long-wave absorption by the Li + doped species leads to charge transfer (CT) between the inner and the outer shells unlike their neutral double-layered precursors. The CT energy depends strongly on the size of the concentric fullerenes and it can easily be tuned by varying both the encapsulated metal ion and the size of the shells. Two types of low-lying excited states are identified (1)

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“…where A and B are defined in quasiparticle transition space (including excitations and deexcitations), (X n , Y n ) are the nth eigenvectors, and ω n is the nth excitation energy. The deexcitation effects are usually negligible in the BSE with momentum transfer q = 0 [28,60]. Therefore, we here adopt the Tamm-Dancoff approximation, which means B is set to zero [27,60].…”

Section: A Simplifying the Dielectric Screening In The Bsementioning

confidence: 99%

“…An alternative approach to the optical excitation problem is time-dependent density-functional theory (TDDFT) [18][19][20]. Using xc kernels with a proper long range, TDDFT can successfully describe excitonic effects and produce reasonable optical spectra for solids [21][22][23][24][25][26][27][28].…”

Section: Introductionmentioning

confidence: 99%

Low-cost alternatives to the Bethe-Salpeter equation: Towards simple hybrid functionals for excitonic effects in solids

Sun

Yang

Ullrich

2020

Phys. Rev. Research

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The Bethe-Salpeter equation (BSE) is the standard computational method for optical excitations in solids, including excitonic effects. In this paper we explore ways to reduce the computational cost of the BSE by simplifying the dielectrically screened Coulomb interaction: Instead of calculating the dielectric function from first principles, we replace it by a momentum-dependent model dielectric function or just by a single parameter. Combined with a semilocal exchange-correlation kernel, this defines an alternative class of hybrid functionals for solids within generalized time-dependent density-functional theory. We perform a systematic assessment of these simplified approaches and find that they yield optical absorption spectra and exciton binding energies of semiconductors and wide-gap insulators in close agreement with the standard BSE and with experiment. We also present applications to the perovskite material CsPbBr 3 as an example of a more complex system.

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Excitons in Solids from Time-Dependent Density-Functional Theory: Assessing the Tamm-Dancoff Approximation

Cited by 13 publications

References 39 publications

Assessment of long-range-corrected exchange-correlation kernels for solids: Accurate exciton binding energies via an empirically scaled bootstrap kernel

Assessment of long-range-corrected exchange-correlation kernels for solids: Accurate exciton binding energies via an empirically scaled bootstrap kernel

Photoinduced Charge Shift in Li⁺-Doped Giant Nested Fullerenes

Low-cost alternatives to the Bethe-Salpeter equation: Towards simple hybrid functionals for excitonic effects in solids

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Excitons in Solids from Time-Dependent Density-Functional Theory: Assessing the Tamm-Dancoff Approximation

Cited by 13 publications

References 39 publications

Assessment of long-range-corrected exchange-correlation kernels for solids: Accurate exciton binding energies via an empirically scaled bootstrap kernel

Assessment of long-range-corrected exchange-correlation kernels for solids: Accurate exciton binding energies via an empirically scaled bootstrap kernel

Photoinduced Charge Shift in Li+-Doped Giant Nested Fullerenes

Low-cost alternatives to the Bethe-Salpeter equation: Towards simple hybrid functionals for excitonic effects in solids

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Photoinduced Charge Shift in Li⁺-Doped Giant Nested Fullerenes