On the structure of Si(100) surface: importance of higher order correlations for buckled dimer

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  • Seoin Back
  • Johan Albrecht Schmidt
  • Hyunjun Ji
  • Jiyoung Heo
  • Yihan Shao
  • Yousung Jung
We revisit a dangling theoretical question of whether the surface reconstruction of the Si(100) surface would energetically favor the symmetric or buckled dimers on the intrinsic potential energy surfaces at 0 K. This seemingly simple question is still unanswered definitively since all existing density functional based calculations predict the dimers to be buckled, while most wavefunction based correlated treatments prefer the symmetric configurations. Here, we use the doubly hybrid density functional (DHDF) geometry optimizations, in particular, XYGJ-OS, complete active space self-consistent field theory, multi-reference perturbation theory, multi-reference configuration interaction (MRCI), MRCI with the Davidson correction (MRCI + Q), multi-reference average quadratic CC (MRAQCC), and multi-reference average coupled pair functional (MRACPF) methods to address this question. The symmetric dimers are still shown to be lower in energy than the buckled dimers when using the CASPT2 method on the DHDF optimized geometries, consistent with the previous results using B3LYP geometries [Y. Jung, Y. Shao, M. S. Gordon, D. J. Doren, and M. Head-Gordon, J. Chem. Phys. 119, 10917 (2003)]. Interestingly, however, the MRCI + Q, MRAQCC, and MRACPF results (which give a more refined description of electron correlation effects) suggest that the buckled dimer is marginally more stable than its symmetric counterpart. The present study underlines the significance of having an accurate description of the electron-electron correlation as well as proper multireference wave functions when exploring the extremely delicate potential energy surfaces of the reconstructed Si(100) surface. (C) 2013 AIP Publishing LLC.
Original languageEnglish
JournalJournal of Chemical Physics
Volume138
Issue number20
Number of pages5
ISSN0021-9606
DOIs
Publication statusPublished - 2013

ID: 117983531