The absorption of diamondoids from time-dependent density functional calculations

Márton Vörös, Tamás Demjén, Adam Gali

Research output: Conference contribution


Diamondoids are small diamond nanocrystals with perfect hydrogenated surfaces. Recent absorption measurements showed that the spectrum of diamondoids exhibit features that are not understood from the theoretical point of view, e.g. optical gaps are only slightly larger than the gap of bulk diamond which runs against the quantum confinement effect. Previous calculations, even beyond standard density functional theory (DFT), failed to obtain the experimental optical gaps (E g) of diamondoids. We show that all-electron time-dependent DFT (TD-DFT) calculations including the PBEO hybrid functional in the TD-DFT kernel are able to provide quantitatively accurate results. Our calculations demonstrate that Rydberg transitions govern the low energy part of the absorption spectrum, even for relatively large nanodiamonds resulting in low E g. Since the optical gap of these diamondoids lies in the ultraviolet spectral region, we investigated whether simple adsorbates of the surface are able to shift the gap towards the infrared region. We found that a double bonded sulfur atom at the surface results in a substantial gap reduction.

Original languageEnglish
Title of host publicationComputational Semiconductor Materials Science
Number of pages6
Publication statusPublished - dec. 23 2011
Event2011 MRS Spring Meeting - San Francisco, CA, United States
Duration: ápr. 25 2011ápr. 29 2011

Publication series

NameMaterials Research Society Symposium Proceedings
ISSN (Print)0272-9172


Other2011 MRS Spring Meeting
CountryUnited States
CitySan Francisco, CA

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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  • Cite this

    Vörös, M., Demjén, T., & Gali, A. (2011). The absorption of diamondoids from time-dependent density functional calculations. In Computational Semiconductor Materials Science (pp. 23-28). (Materials Research Society Symposium Proceedings; Vol. 1370).