[Pw_forum] nscf calculation failure~

[lan haiping]

Thank you, Axel.

I just came to this error when i tried to study bandstructure of anatase
tio2 , with pbe-sp-van_ak.UPF from pwscf.org .
  Would you please tell me more details to fix this problem ? I would like
to try .

Regards,
hai-ping





On 11/14/06, Axel Kohlmeyer <akohlmey at cmm.chem.upenn.edu> wrote:
>
> On Sat, 11 Nov 2006, lan haiping wrote:
>
>
> HP> I browsed the mail list, it seems this error is related to ultrasoft
> HP> pseudopotential's bad behavior, as pointing out by paolo "S is the
> HP> overlap matrix in the Ultrasoft pseudopotential formalism. It has to
> HP> be positive definite. Likely one (or more than one) of the
> HP> pseudopotentials is bad "
>
> nevertheless, it may simply be that the pseudopotial is only
> 'marginally bad' or that different algorithms are less sensitive
> to the problematic pseudopotential(s). i know from personal experience,
> that a few of the pseudopotential generated from parameter files shipped
> with the vanderbilt atomic code have problems when re-creating them with
> the current version of the code, most likely due to changes in the
> fitting algorithm after the pseudopotential parameters were added.
>
> this seems to mainly affect rather heavy elements and pseudopotentials
> that were created as part of the dacapo project (or recreated with a
> different functional but using the same parameters). those potentials
> were conceived with an older version of the atomic code (7.0.0, see the
> dacapo homepage), where those problems may not have appeard. the
> potentials still test ok with the internal tests, so one really has to
> look through the (not exactly user friendly) log files. :-(
>
> one can usually correct for the problems (there are reports of
> 'negative densities' in the pseudopotential generation log) by
> adding a few additional constraints to the pseudopotential fits,
> but of course after that you need to re-verify the pseudopotential.
> it still is more convenient that having to build a pseudopotential
> completely from scratch...
>
> BTW. if somebody is interested in looking into this in more detail,
> for example by checking and (if needed) improving the pseudopotential
> files on www.pwscf.org, i should have a few example inputs with
> constraints (the explanation in the docs can be confusing) and can
> give a few (empirical!) hints on where to add those constraints.
>
> HP> But no CRASH is occured in 'scf'  or 'relax' calculation, it's too
> strange
> HP> to belevie the problem of pseudopotential,
>
> please check for the indicators listed above, or let us know
> what pseudopotential files you are using. if you can prove that
> the pseudopotentials you use do not suffer from the problem i
> mentioned, it would be a much higher incentive to fix the code.
>
> thanks and best regards,
>    axel.
>
> HP> I also try to use  'cg' method for diagonalization instead of  'david
> '
> HP> method, and no such CRASH would be occured.
> HP>
> HP> Regards,
> HP> hai-ping
> HP>
>
> --
> =======================================================================
> 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.
>
>
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