Dear Nicola, Thank you very much for your reply, Helen ----- Original Message ----- From: "Nicola Marzari" <[email protected]> To: "PWSCF Forum" <pw_forum at pwscf.org> Sent: Monday, March 31, 2008 1:15 PM Subject: Re: [Pw_forum] band energies
> > > > Dear Helen, > > there are several ways to look at this - most thorough discussion would > be Caspar Fall PhD thesis at EPFL (www.epfl.ch) - it's available on the > web. Also, for a recent review, citing most of the relevant literature, > you could look at http://arxiv.org/abs/0801.1077 . The papers > by Baldereschi/Baroni/Resta/Peressi from the late '80s onwards on > homo and heterosemiconductor junctions contain the original discussion > of these issues. > > In short - you can refer the homo of your bulk semiconductor to another > property that is easy to transfer across non-bulk environment - often > the average value of the Hartree or of the Kohn-Sham potentials. Suppose > the HOMO were 3.5 eV above the Hartree bulk average. > > Then, in a slab calculation, you can find out what is the average > Hartree well inside the slab (where it is bulk-like), and well outside > the slab, what it reaches the vacuum level. Suppose this difference > is 5eV. Then, the HOMO is 1.5eV below the vacuum level - i.e. it takes > 1.5eV to bring the top valence electron well outside the solid (across > the surface used in your slab calculation - these quantities are surface > dependent). > > nicola > > > > Helen wrote: >> Hello, >> So far I've been calculating bandgaps and so have been using the >> differences in band-energies, now I want to compare the absolute value >> of the HOMO in semiconductors with experimental workfunctions. How can I >> know what the absolute zero value of the bandenergies is? Is there any >> meaning to the absolute values given in the output file or are only the >> band energy differences relevant? >> Thanks for your help, >> Dr. Helen Eisenberg, >> Fritz Haber Center, Hebrew University. >> >> >> ------------------------------------------------------------------------ >> >> _______________________________________________ >> Pw_forum mailing list >> Pw_forum at pwscf.org >> http://www.democritos.it/mailman/listinfo/pw_forum > > > -- > --------------------------------------------------------------------- > 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 > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum >
