-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On 09/15/2015 08:36 PM, Lawal Mohammed wrote:
> I understand that in gga/lda the Kohn-Sham eigenstates are regarded
> as excited only when the scissors operator is non zero, is this
> correct? If yes then how valid is optical calculation when the
> scissors operator is set to zero? If no then what bring about the
> optical excitations that allow determination of some optical
> properties?

The “scissors operator” is simply a rigid shift of the unoccupied
bands in energy (where rigid means that the states themselves are not
changed).  This is done to “correct” band gaps which come out wrong
(usually too small) in DFT.  An optical excitation takes an electron
from an occupied to an unoccupied state.  This means that the scissors
operator will change the energies where these excitations are
possible, e.g. to adjust the optical gap in your calculation to the
experimental value.

HTH,

        Elias


-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1
Comment: Using GnuPG with Icedove - http://www.enigmail.net/
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=BART
-----END PGP SIGNATURE-----
_______________________________________________
Wien mailing list
Wien@zeus.theochem.tuwien.ac.at
http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
SEARCH the MAILING-LIST at:  
http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html

Reply via email to