[Pw_forum] smearing methods and relaxation

[rudra Banerjee]

hello friend
can you name a good resource on knowing what smearing is?

On 11/30/06, Nicola Marzari <marzari at mit.edu> wrote:
>
>
>
>
> Hi Jess, you should use a smearing instead (usually methfessel-paxton or
> marzari-vanderbilt). You need to use a small value - try 0.4 eV
> (remember, pwscf uses Ry, so divide by 13.6), and make sure
> that whatever you want to calculate is converged with respect
> to k-points.
>
> 0.4eV might be too large for a lot of critical properties - so decrease
> it (and increase, by a lot, the kpoints) and see if things change.
>
>                                 nicola
>
>
> Jess Kondor wrote:
> >
> >  Hello, everyone,
> >
> >  I have a question about smearing methods and relaxation, in
> > particularly  tetrahedron method and structural optimization  in case of
> > metals.  VASP manual recommends do not use tetrahedron method in
> > relaxation of metals because this method is not variational with respect
> > to the partial occupancies, which means, that the calculated forces are
> > wrong by 5 to 10 % in metals.  Is it applicable in pwscf case? I am
> > studying magnetic system (which is metal without U correction, and
> > should be insulator with LSDA+U) and I am not sure it is good idea to
> > use 'tetrahedra' in this case. What do you suggest?
> >
> >  Regards,
> >
> >   JK
>
>
> --
> ---------------------------------------------------------------------
> 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
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-- 
rudra
-------------------------
have a good time!
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