Dear Stefano,<br>
i am using the following: <br>
&system: ibrav=0, nat= 98, ntyp=4, ecutwfc = 30.0,ecutrho =
180.0,occupations='smearing', smearing='methfessel-paxton',
degauss=0.003,nbnd=500,<br>
&electrons: conv_thr = 1.0e-5,mixing_beta = 0.1,<br>
K_points sampling: 4 4 4 0 0 0, <br>
the system is insulator and non-magnetic for sure. the number of bands
are little higher than what is actually required for an insulator. Tha
same k points sampling for smaller similar system gave results
which tallies well reported data. <br>
Shall i stop the calculation or let it run to completion? after
compleion, then i can take the new refined data as my input and reduced
conv_thr and re-run the calculation again. <br>
regards<br>
artee<br>
department of physics<br>
Bhavnagar university<br>
india<br>
<br><div><span class="gmail_quote">On 3/22/09, <b class="gmail_sendername">Stefano de Gironcoli</b> <<a href="mailto:degironc@sissa.it">degironc@sissa.it</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
dear artee sharma,<br> <br> conv_thr=1.0e-5 is a rather large value, acceptable if you just want<br> the energy but not if you want forces. 1.0e-6 is the default and for<br> relaxations one rather tends to reduce it...<br>
<br> Convergence for large systems (especially inhomogeneous metallic ones)<br> may be slow. mixing_mode='local-TF' usually helps in these cases. are<br> you using it ?<br> <br> Even when the first scf convergence is painfully slow the subsequent<br>
ones should be better as potential and wfcs are extapolated from<br> previous steps. check that you are indeed using these extrapolations<br> (should however be the default for relaxation, so probably you do).<br> <br> Sometime when a system does not want to converge it's trying to tell<br>
you something ... Is it a magnetic or metallic system ? are you using<br> smearing ? are you sure the number of bands and your k-point sampling<br> is accurate enough ?<br> <br> hope this helps,<br> stefano<br> <br> Stefano de Gironcoli - SISSA and DEMOCRITOS<br>
<br><br> Quoting artee sharma <<a href="mailto:mailtoartee@gmail.com">mailtoartee@gmail.com</a>>:<br> <br> > Dear Stefano.<br> > thanks for reply. my conv_thr in input file is 1.0e-5? i have a large<br> <br>
> system, takes too much time to convarage, so kept it low. Shall i decrease<br> > it by further one order?<br> > latest output is showing:<br>
> Total force =
0.023049 Total SCF correction
= 0.002483<br> > so i think my system has not converged yet, force is high.<br> <br>> regards<br> > artee sharma<br> > Department of physics<br> > Bhavnagar University<br> > India<br> ><br> ><br>
><br> ><br> > On Sat, Mar 21, 2009 at 11:46 AM, Stefano de Gironcoli<br> > <<a href="mailto:degironc@sissa.it">degironc@sissa.it</a>>wrote:<br> ><br> >> I think it might be better to stop it. According to the message the forces<br>
>> you are calculating may be not accurate and any further relaxation based on<br> >> them is not likely to improve your geometry.<br> >><br> >> However, are you sure your system is not yet relaxed enough ?<br>
>> What is your conv_thr and your force threshold ?<br> >><br> >> stefano de Gironcoli - SISSA & DEMOCRITOS<br> >><br> >> PS: don't forget to provide your affiliation<br> >><br>
>><br> >><br> >><br> >><br> >> Quoting artee sharma <<a href="mailto:mailtoartee@gmail.com">mailtoartee@gmail.com</a>>:<br> >> **<br> >><br> >><br> >> ----------------------------------------------------------------<br>
>> SISSA Webmail <a href="https://webmail.sissa.it/">https://webmail.sissa.it/</a><br> >> Powered by Horde <a href="http://www.horde.org/">http://www.horde.org/</a><br> >><br> >><br> >><br>
><br> <br> <br> <br> ----------------------------------------------------------------<br> SISSA Webmail <a href="https://webmail.sissa.it/">https://webmail.sissa.it/</a><br> Powered by Horde <a href="http://www.horde.org/">http://www.horde.org/</a><br>
<br> <br> _______________________________________________<br> Pw_forum mailing list<br> <a href="mailto:Pw_forum@pwscf.org">Pw_forum@pwscf.org</a><br> <a href="http://www.democritos.it/mailman/listinfo/pw_forum">http://www.democritos.it/mailman/listinfo/pw_forum</a><br>
</blockquote></div><br>