[Pw_forum] smearing methods and relaxation

[degironc]

dear rudra Banerjee,
       if you happen by any chance to have a look inside INPUT_PW where the
variable smearing is defined you'll find a couple of references.
       hope this help.
       stefano

rudra Banerjee wrote:

> hello friend
> can you name a good resource on knowing what smearing is?
>
> On 11/30/06, *Nicola Marzari* <marzari at mit.edu 
> <mailto: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
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>
> -- 
> rudra
> -------------------------
> have a good time!