[Pw_forum] about GGA implementation

[Axel Kohlmeyer]

On Tue, 30 May 2006, Nicola Marzari wrote:

hi,

[...]

NM> Notwithstanding this, hybrid functionals often seem to predict
NM> Kohn-Sham gaps in closer agreement with experiments. As far as I know,
NM> there aren't hybrid functionals implemented in pwscf yet.

to the best of my knowledge, exact exchange is an experimental
feature in the PW code, but needs to be ifdef'd in via -DEXX.
IIRC, it has been mentioned in this mailing list a couple of 
times. please search the mailing list archive.

NM> Gaussian03 has an extensive choice (e.g. the HSE hybrid),
NM> and I believe that now CPMD also has several of them.

correct. CPMD had exact exchange via ACM0/ACM1/ACM3
implemented for a while and as of the current version (3.11.1)
several hybrid functionals are implemented 
(B3LYP,X3LYP,B1LYP,PBE0,PBE1W).
note however, that this implementation has only seen
some limited testing and is computationally _extremely_
expensive (unlike in codes with gaussian basis sets). 

regards,
    axel.

NM> 
NM> Best luck,
NM> 
NM> 			nicola
NM> 
NM> Ezad Shojaee wrote:
NM> 
NM> > 
NM> > Hi
NM> > i want to implement GGA approximation in my performance for TiO2 & i 
NM> > have used GGA pseudopotentials .
NM> > i want to know what  can i do more?  ( in order to have a better band gap )
NM> > thanx
NM> > 
NM> ---------------------------------------------------------------------
NM> Prof Nicola Marzari   Department of Materials Science and Engineering
NM> 13-5066   MIT   77 Massachusetts Avenue   Cambridge MA 02139-4307 USA
NM> tel 617.4522758 fax 2586534 marzari at mit.edu http://quasiamore.mit.edu
NM> _______________________________________________
NM> Pw_forum mailing list
NM> Pw_forum at pwscf.org
NM> http://www.democritos.it/mailman/listinfo/pw_forum
NM> 

-- 
=======================================================================
Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
   Center for Molecular Modeling   --   University of Pennsylvania
Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
tel: 1-215-898-1582,  fax: 1-215-573-6233,  office-tel: 1-215-898-5425
=======================================================================
If you make something idiot-proof, the universe creates a better idiot.