Dear Professor Giannozi and Marzari Many thanks for your helpful comments.
david grifith wrote: > > > yet I have not understood where is selected as zero energy > > in the Bulk graphite by QE ? or generally where is selected > > as zero energy in QE calculations? > > nothing is selected as "zero energy". One-electron energies, > including the Fermi energy, are calculated with respect to some > arbitrary reference energy (see the paper cited in the first of > the following links). If you want to set your zero of the energy > at the Fermi energy, you can do it in your preferred plotting > program. If instead you want to know how this arbitrary reference > level is calculatd in the code, see the notes in the last link. > > http://www.democritos.it/pipermail/pw_forum/2004-August/001240.html > http://www.democritos.it/pipermail/pw_forum/2007-April/006351.html > http://www.democritos.it/pipermail/pw_forum/2009-June/013231.html > http://www.democritos.it/pipermail/pw_forum/2009-June/013232.html > > P. > --- > Paolo Giannozzi, Dept of Chemistry&Physics, Univ. Udine > via delle Scienze 208, 33100 Udine, Italy > Phone +39-0432-558216, fax +39-0432-558222 > > > > > On this thread - let me also stress that lacking an absolute > scale of energies is an intrinsic feature of calculations > done in periodic-boundary conditions, and not a feature or a > defect of q-e. It's universal to any solid-state code (abinit, > vasp, castep...). it's also very instructive to understand > why it happens, and an extensive discussion of the issues related > to finding the position of the vacuum level and the electrostatic > averaging technique (Baldereschi et al Phys. Rev. Lett. 61, > 734 (1988)) can be found in Caspar Fall's thesis > http://library.epfl.ch/en/theses/?nr=1955 or in > Singh-Miller et al Phys. Rev. B 80, 235407 (2009), while the > issues related to electrostatics in periodic-boundary conditions > are discussed in Dabo et al Phys. Rev. B 77 115139 (2008). > > nicola > ? > > -- > --------------------------------------------------------------------- > Prof Nicola Marzari Department of Materials Science and Engineering > 13-5066 MIT 77 Massachusetts Avenue Cambridge MA 02139-4307 USA > tel 617.4522758 fax 2586534 marzari at mit.edu http://quasiamore.mit.edu > > > -- > Sincerely Yours > David G. > JCU > -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20101025/9f253e55/attachment.htm
