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<p>$ grep -n '<span dir="ltr">bfgs converged in' */*.f90 */*/*.f90</span></p>
<p>Modules/bfgs_module.f90:912: & FMT = '(/,5X,"bfgs converged in ",I3," scf cycles and ", &</p>
<p><br>
</p>
<p>Around line 912 of Modules/bfgs_module.f90, you find<br>
</p>
<p> IF ( conv_bfgs ) THEN<br>
!<br>
WRITE( UNIT = stdout, &<br>
& FMT = '(/,5X,"bfgs converged in ",I3," scf cycles and ", &<br>
& I3," bfgs steps")' ) scf_iter, bfgs_iter</p>
<p><br>
</p>
<p>You search for "conv_bfgs" and you find</p>
<p> !<br>
! ... convergence is checked here<br>
!<br>
energy_error = ABS( energy_p - energy )<br>
grad_error = MAXVAL( ABS( MATMUL( TRANSPOSE(hinv_block), grad(1:n-9)) ) )<br>
conv_bfgs = energy_error < energy_thr<br>
conv_bfgs = conv_bfgs .AND. ( grad_error < grad_thr )</p>
<p><br>
</p>
<p>"grad_error" is the largest component of the gradient (i.e. forces; the last 9 values are stresses). You should figure out the relation between forces as printed in the output and "grad_error", via variables "grad" (presumably the forces) and "hinv_block"
(a transformation matrix from cartesian to crystal coordinates, I guess).</p>
<p><br>
</p>
<p>Anyway: 10^{-9} is an exceedingly small threshold for forces.<br>
</p>
<p><br>
</p>
<p>Paolo<br>
</p>
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<div id="divRplyFwdMsg" dir="ltr"><font style="font-size:11pt" color="#000000" face="Calibri, sans-serif"><b>From:</b> pw_forum-bounces@pwscf.org <pw_forum-bounces@pwscf.org> on behalf of Tianli Feng <tianli.feng2011@gmail.com><br>
<b>Sent:</b> Monday, April 13, 2015 18:19<br>
<b>To:</b> PWSCF Forum<br>
<b>Subject:</b> Re: [Pw_forum] force convergence in vc-relax</font>
<div> </div>
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<div dir="ltr">Hi Florian, I have not got the issue resolved yet.
<div><br>
</div>
<div>Hi Paolo, How can we find the explanation in that code? Many thanks.</div>
<div class="gmail_extra"><br clear="all">
<div>
<div class="gmail_signature">
<div dir="ltr">Best wishes,
<div>Tianli</div>
<div>------------</div>
<div>Tianli Feng</div>
<div>Mechanical Engineering, Purdue University</div>
<div>---The truth is not what you see, but what it is.</div>
</div>
</div>
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<br>
<div class="gmail_quote">On Mon, Apr 13, 2015 at 4:10 AM, Paolo Giannozzi <span dir="ltr">
<<a href="mailto:paolo.giannozzi@uniud.it" target="_blank">paolo.giannozzi@uniud.it</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex; border-left:1px #ccc solid; padding-left:1ex">
<span class="">On Mon, 2015-04-13 at 00:16 -0700, Florian Altvater wrote:<br>
<br>
> did this issue ever get resolved/answered? I would also be very<br>
> interested in a solution/explanation of the behavior.<br>
<br>
</span>The explanation is available in the part of code that perform the<br>
convergence check on forces<br>
<br>
P.<br>
<div class="HOEnZb">
<div class="h5">> I also get relaxations where individual forces are higher than the<br>
> threshold, without the line stating that "SCF correction compared to<br>
> forces is large", in case that would be a reason here. Also happens in<br>
> regular "relax" calculations.<br>
><br>
> Thanks so much,<br>
> Florian<br>
><br>
> --<br>
> Florian Brown-Altvater<br>
> PhD Candidate<br>
> Neaton group<br>
> UC Berkeley/LBNL<br>
><br>
> Am 08.04.2015 um 12:07 schrieb Tianli Feng:<br>
><br>
> > Dear All,<br>
> ><br>
> ><br>
> > I would really appreciate if anyone can help to explain a output in<br>
> > relaxing a structure. I used vc-relax to relax a lattice<br>
> > with forc_conv_thr set as 1.0D-9. After 44 steps, the results<br>
> > converge as following:<br>
> ><br>
> ><br>
> > Forces acting on atoms (Ry/au):<br>
> ><br>
> ><br>
> > atom 1 type 1 force = 0.00000638 0.00000000<br>
> > 0.00000092<br>
> > atom 2 type 1 force = 0.00000602 0.00000000<br>
> > 0.00000671<br>
> > atom 3 type 1 force = -0.00000074 0.00000000<br>
> > 0.00000243<br>
> > atom 4 type 1 force = 0.00000358 0.00000000<br>
> > -0.00000082<br>
> > atom 5 type 2 force = -0.00000821 0.00000000<br>
> > -0.00000732<br>
> > atom 6 type 2 force = -0.00000635 0.00000000<br>
> > -0.00000202<br>
> > atom 7 type 2 force = 0.00000337 0.00000000<br>
> > -0.00000058<br>
> > atom 8 type 2 force = -0.00000406 0.00000000<br>
> > 0.00000068<br>
> ><br>
> ><br>
> > Total force = 0.000018 Total SCF correction =<br>
> > 0.000002<br>
> > SCF correction compared to forces is large: reduce conv_thr to<br>
> > get better values<br>
> ><br>
> ><br>
> > bfgs converged in 44 scf cycles and 43 bfgs steps<br>
> > (criteria: energy < 1.0E-04, force < 1.0E-09, cell <<br>
> > 5.0E-01)<br>
> ><br>
> ><br>
> > The last line says the relaxation converges with force <1.0E-9, but<br>
> > I saw the forces acting on each atom are not smaller than 1e-9. Does<br>
> > anyone has experience on relaxing a lattice and know what is<br>
> > happening? Many thanks!!<br>
> ><br>
> ><br>
> > Sincerely,<br>
> > Best wishes,<br>
> > Tianli<br>
> > ------------<br>
> > Tianli Feng<br>
> > Mechanical Engineering, Purdue University<br>
> > ---The truth is not what you see, but what it is.<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://pwscf.org/mailman/listinfo/pw_forum" target="_blank">http://pwscf.org/mailman/listinfo/pw_forum</a><br>
><br>
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<span class="HOEnZb"><font color="#888888">--<br>
Paolo Giannozzi, Dept. Chemistry&Physics&Environment,<br>
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy<br>
Phone <a href="tel:%2B39-0432-558216" value="+390432558216">+39-0432-558216</a>, fax
<a href="tel:%2B39-0432-558222" value="+390432558222">+39-0432-558222</a><br>
</font></span>
<div class="HOEnZb">
<div class="h5"><br>
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