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On 08/18/2010 12:54 AM, meysam pazoki wrote:
<blockquote
cite="mid:AANLkTimoaas2550ykKHQSgGKot3N-OEfLv019_=ArLbQ@mail.gmail.com"
type="cite"><br>
<br>
<div class="gmail_quote">---------- Forwarded message ----------<br>
From: <b class="gmail_sendername">meysam pazoki</b> <span dir="ltr"><<a
moz-do-not-send="true" href="mailto:meysam.pazoki@gmail.com">meysam.pazoki@gmail.com</a>></span><br>
Date: Tue, Jul 20, 2010 at 11:46 PM<br>
Subject: Graphene Structural Relaxation<br>
To: <a moz-do-not-send="true" href="mailto:pw_forum-request@pwscf.org">pw_forum-request@pwscf.org</a><br>
<br>
<br>
<div>Dear PWSCF users</div>
<div> </div>
<div>I have a problem in relaxation of grahene super cell with 24
atoms. In relaxation procedure ,graphene hooney-comb structure
completely destroys and atoms have no regular ordering after relaxation
procedure.I use pbe-rrkjus psudopotential,4 3 3 kpoint grid,30 rydberg
cutff energy,300 rydberg ecutrho.</div>
<div>I use both ion_damps & bfgs algorithms and get similar
results.</div>
<div>If i change the ecutrho to 100, atoms have an irregular
positions in 3 dimension,but when ecut rho set to 300 atoms have
irregular position in-plane.</div>
<div>furthermore if i set :<span lang="EN">trust_radius_ini=.1D0,trust_radius_max=.3D0,bfgs_ndim
= 3,</span></div>
<div><span lang="EN">I have the honeycomb structure but some of c
atoms exprience great forces like:</span></div>
<div><span lang="EN"><span lang="EN">
<p>atom 19 type 1 force = 11948.08469282 -219.69802882 0.00000000</p>
<p>atom 20 type 1 force = 11782.00343549 12.01959200 0.00000000</p>
<p>atom 21 type 1 force = 11748.09287051 115.25218004 0.00000000</p>
<p>atom 22 type 1 force = 11241.09464255 -222.56999757 0.00000000</p>
<p>atom 23 type 1 force = -0.50941109 0.26861287 0.00000000</p>
<p>atom 24 type 1 force = 11905.77649683 -91.34763119 0.00000000</p>
</span></span></div>
</div>
</blockquote>
<br>
These forces are simply crazy... I mean, if the units are those used by
PWscf (Ry/Bohr) the forces that you are reporting are huge! If you have
used the PP on the QE website, then the atomic positions and/or the
cell dimensions that you have supplied to PWscf must be far off the
equilibrium ones. Please provide an input file.<br>
<br>
GS<br>
<br>
<blockquote
cite="mid:AANLkTimoaas2550ykKHQSgGKot3N-OEfLv019_=ArLbQ@mail.gmail.com"
type="cite">
<div class="gmail_quote">
<div><span lang="EN"><span lang="EN">
<p>My question is what is wrong in my structure relaxation procedure
that result in such non-physical data.</p>
</span></span>It would appreciated if anyone can help me in this
problem</div>
<div> </div>
<div>Thanks in advance</div>
<div> </div>
<font color="#888888">
<div>meysam pazoki</div>
<div>Ph.D student of physics</div>
<div>Sharif university of technology</div>
</font></div>
<br>
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</blockquote>
<br>
<br>
<pre class="moz-signature" cols="72">--
Gabriele Sclauzero, EPFL SB ITP CSEA
PH H2 462, Station 3, CH-1015 Lausanne
</pre>
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