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Effect of Correlation in SrRu03 Metal Sand LiF Insulators

Hadipour Siahmazgi, Hanif | 2012

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 42948 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Akhavan, Mohammad
  7. Abstract:
  8. There is no satisfactory agreement between theory and experiment in the Hartree-Fock (HF) and density functional theory (DFT) calculation for metals, semiconductors and metals. It is clear that this discrepancy is attributed to the neglecting of correlation. For example, experimentally
    LiF have the largest band gap about 13.6 eV among the alkali halides and show an exciton peak at 12.6 eV . Brener have obtained a value of 22.9 eV for LiF band gap in the HF approximation. DFT has been very successful tool in calculating the ground-state properties of materials. As
    we expect, the band gap in LiF are underestimated in the local density approximation (LDA) calculation (about 8.3 eV) . So, DFT can not explain excited states properties, like quasiparticle excitations or electron-hole excitations. The essential improvement has been obtained by the GW approximation over the Hartree-Fock equation and the quasiparticle band gap reach to 14.3 eV for LiF . Electron-hole interaction is dominant in the optical absorption of non-conducting materials which are described neither by LDA nor by GWA. With neglecting of the electron-hole interaction (for example LDA and GW), calculated optical absorption spectrum e(w) of bulk LiF show a peak at about 16 eV. There is a good agreement between theory and experiment with considering of electron-hole interaction. Solution of the Bethe-Salpeter equation (BSE) yields coupled excited electron-hole states with peak at 12.4 eV. In this text, we will discuss the excitonic effects on the dielectric function of LiF insulator in some detail. Also, for metals, we have investigated the role of electron-electron correlation in SrRuO3 and CaRuO3 bulk structures by GW approximation
  9. Keywords:
  10. Density Functional Theory (DFT) ; Ferromagnetic Model ; Electron Correlation ; Excited States ; Excited Electron-hole

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  • بررسي اثرات همبستگي در خواص الكتروني سيستم هاي فلزي SrRuO3 و عايق LiF
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