<div>Thank you, Axel.</div>
<div> </div>
<div>I just came to this error when i tried to study bandstructure of anatase tio2 , with pbe-sp-van_ak.UPF from <a href="http://pwscf.org">pwscf.org</a> . </div>
<div> Would you please tell me more details to fix this problem ? I would like to try .</div>
<div> </div>
<div>Regards,</div>
<div>hai-ping</div>
<p> </p>
<div><br><br> </div>
<div><span class="gmail_quote">On 11/14/06, <b class="gmail_sendername">Axel Kohlmeyer</b> <<a href="mailto:akohlmey@cmm.chem.upenn.edu">akohlmey@cmm.chem.upenn.edu</a>> wrote:</span>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">On Sat, 11 Nov 2006, lan haiping wrote:<br><br><br>HP> I browsed the mail list, it seems this error is related to ultrasoft
<br>HP> pseudopotential's bad behavior, as pointing out by paolo "S is the<br>HP> overlap matrix in the Ultrasoft pseudopotential formalism. It has to<br>HP> be positive definite. Likely one (or more than one) of the
<br>HP> pseudopotentials is bad "<br><br>nevertheless, it may simply be that the pseudopotial is only<br>'marginally bad' or that different algorithms are less sensitive<br>to the problematic pseudopotential(s). i know from personal experience,
<br>that a few of the pseudopotential generated from parameter files shipped<br>with the vanderbilt atomic code have problems when re-creating them with<br>the current version of the code, most likely due to changes in the
<br>fitting algorithm after the pseudopotential parameters were added.<br><br>this seems to mainly affect rather heavy elements and pseudopotentials<br>that were created as part of the dacapo project (or recreated with a<br>
different functional but using the same parameters). those potentials<br>were conceived with an older version of the atomic code (7.0.0, see the<br>dacapo homepage), where those problems may not have appeard. the<br>potentials still test ok with the internal tests, so one really has to
<br>look through the (not exactly user friendly) log files. :-(<br><br>one can usually correct for the problems (there are reports of<br>'negative densities' in the pseudopotential generation log) by<br>adding a few additional constraints to the pseudopotential fits,
<br>but of course after that you need to re-verify the pseudopotential.<br>it still is more convenient that having to build a pseudopotential<br>completely from scratch...<br><br>BTW. if somebody is interested in looking into this in more detail,
<br>for example by checking and (if needed) improving the pseudopotential<br>files on <a href="http://www.pwscf.org">www.pwscf.org</a>, i should have a few example inputs with<br>constraints (the explanation in the docs can be confusing) and can
<br>give a few (empirical!) hints on where to add those constraints.<br><br>HP> But no CRASH is occured in 'scf' or 'relax' calculation, it's too strange<br>HP> to belevie the problem of pseudopotential,<br><br>please check for the indicators listed above, or let us know
<br>what pseudopotential files you are using. if you can prove that<br>the pseudopotentials you use do not suffer from the problem i<br>mentioned, it would be a much higher incentive to fix the code.<br><br>thanks and best regards,
<br> axel.<br><br>HP> I also try to use 'cg' method for diagonalization instead of 'david '<br>HP> method, and no such CRASH would be occured.<br>HP><br>HP> Regards,<br>HP> hai-ping<br>HP><br><br>--<br>
=======================================================================<br>Axel Kohlmeyer <a href="mailto:akohlmey@cmm.chem.upenn.edu">akohlmey@cmm.chem.upenn.edu</a> <a href="http://www.cmm.upenn.edu">http://www.cmm.upenn.edu
</a><br> Center for Molecular Modeling -- University of Pennsylvania<br>Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323<br>tel: 1-215-898-1582, fax: 1-215-573-6233, office-tel: 1-215-898-5425
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