[Pw_forum] Smearing the occupations or not?

Ari P Seitsonen Ari.P.Seitsonen at iki.fi
Thu Aug 18 11:40:10 CEST 2011

Dear Musari, (or how do you want to be called?)

   The safest is to start with broadening, calculate the band structure, 
and reduce the broadening: If the system remains a metal or semi-metal (ie 
the occupation numbers are not integers), the system is most likely such 
(at least at the level of DFT or DFT-HF that you have used for the 
exchange-correlation). Of course there are dangers that your material is 
strongly-correlated etc (LDA/GGA+U or hybrid functionals might help). In 
general the GW calculation should be closer to the experiments, if the 
system decides to be semi-conducting or insulating.

   Hopefully this helps you a bit.

     Greetings from Sunny Zurich,


   Ari P Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/
   Physikalisch-Chemisches Institut der Universitaet Zuerich
   Tel: +41 44 63 54 497  /  Mobile: +41 79 71 90 935

On Thu, 18 Aug 2011, Abolore Musari wrote:

> Dear all, pls just want to calculate the band structure of a compound,
> but l dont know if its a metal, insulator, semiconductor or semi metal
> so l want to ask if l can use smearing for occupations in the &system
> card? in other word l am asking that how do we know when to use
> smearing for the accupations or tetrahedra or others. thanks for your
> usual assistance. Musari A A. UNAAB Nigeria
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