1 / 16

Igor Reshetnyak , Lucia Reining

New starting point for the calculation of optical properties. Igor Reshetnyak , Lucia Reining. Outline. State of art methods Comparative analysis of TDLDA & BSE Analysis of the details Resonant only case Conclusions. Commonly used methods. TDDFT. BSE. Ground state. GW. f xc.

archie
Download Presentation

Igor Reshetnyak , Lucia Reining

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. New starting point for the calculation of optical properties Igor Reshetnyak, Lucia Reining

  2. Outline • State of art methods • Comparative analysis of TDLDA & BSE • Analysis of the details • Resonant only case • Conclusions

  3. Commonly used methods TDDFT BSE Ground state GW fxc They work in a completely different ways! + e.h.

  4. Comparison of real spectra Codes: Bulk Si, q= 0.75 (1,1,1) c.c. units of 2pi/a = 0.612217 a.u.; Exp. from [1] For Si EELS, the TDLDA & BSE results very similar Are the underlying objects connected? [1] H.C. Weissker et al. Phys. Rev. B, 81:085104, Feb 2010

  5. 4-point equations & Hamiltonian form BSE TDLDA

  6. 4-point equations & Hamiltonian form Formal solution Hamiltonian form Both formulated the same way • Comparative analysis • Mixed methods • Deeper understanding

  7. Underlying stuff Coefficient JDOS(ε) ε, eV ε, eV • For JDOS only difference – GW (scissor) • The vectors in transition space spread over a small range • For TDLDA spread larger than for BSE. Agrees with [2] [2] Z.-h. Yang and C.A. Ullrich Phys. Rev. B, 87:195204, May 2013

  8. Digging into details... Overlaps eigenvector, # Overlap ε, eV eigenvector, # Overlaps happen over a small range But how do we explain similarity in spectra? The JDOS is shifted. Are the eigenvectors making the opposite shift?

  9. Digging into details... • Interference is very important! Cancelations in • Not just , but also S is important

  10. Can we replace parts of BSE by smth? TDLDA BSE, width = dE • The dE required is smaller without coupling • For EELS not particularly good

  11. And for optics? TDLDA BSE, width = dE • The dE required is smaller without coupling • For optical properties should do better Usage for combined methods!

  12. Some good & bad news • Effect of coupling can be very important for large transferred momenta q. • One should not interpret results in a basis with positive energies only • Interference effects important • TDLDA and BSE give similar results for EELS • Space for combined methods & analysis possible

  13. Thank you! Question?

  14. Commonly used methods = = = (1) TDDFT BSE (2) (3) KS DFT GW fxc (1) (2) (3)

  15. Digging into details... (2) • Average shift practically 0 • Nothing specific around ε = 0 • Even if the effect !=0 cannot amount for the shift

More Related