<div>Dear Fatma</div>
<div>I think the best option for you is the vc (volume-cell) relaxation. In this kind of calculations all lattice parameters and atomic positions are relaxed simultaneously. Please see the INPUT_PW file for adjusting the required input parameters.</div>
<div>another option is to relax lattice parameters one by one. In each step you should vary one lattice parameter and fix others. After finding the optimized value of this lattice parameter, it should be fixed and another lattice parameter should be optimized. The following sequence of relaxation may be useful:</div>
<div> </div>
<div>1. betha (a, b/a, and c/a are fixed to experimental or any other reported value)</div>
<div>2. Volume (betha, b/a, and c/a should be fixed)</div>
<div>3. b/a (betha, Volume, and c/a are fixed)</div>
<div>4. c/a (bethe, Volume, and b/a are fixed)</div>
<div> </div>
<div>it is better to repeat the above sequence more than one time.</div>
<div> </div>
<div>It should be noted that vc relaxation seems to be more appropriate for you.</div>
<div> </div>
<div>Javad</div>
<div><br><br> </div>
<div class="gmail_quote">On Mon, Jul 7, 2008 at 10:52 PM, Fatma Litimein <<a href="mailto:flitimein@yahoo.fr">flitimein@yahoo.fr</a>> wrote:<br>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">
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<div></div>
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<font size="3"><font face="Times New Roman"><i>Dear PWscf users, </i></font></font></form>
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<div style="MARGIN: 5pt 0cm; DIRECTION: ltr; TEXT-ALIGN: left"><font size="3"><font face="Times New Roman"><i>I have a question about optimization of an monoclinic<span> </span>structure, so to do that have I to optimize c/a, V, b/a, V, ...., beta,<span> V</span>, in SCF manner until convergence of the structure or can I<span> </span>perform just one c/a, b/a, V optimization ? How can I to optimize i.e. beta angel? Any comments are welcome. </i></font></font></div>
<div style="MARGIN: 5pt 0cm; DIRECTION: ltr; TEXT-ALIGN: left"><font size="3"><font face="Times New Roman"><i><span lang="FR">Thank you in advance </span></i></font></font><span lang="FR"></span></div><br><br></div></div>
<br><br>=======================================================<br>Fatma Litimein <br>Computational Materials Science Laboratory,<br>Physics Department, University of Sidi Bel Abbes<br>Sidi Bel Abbes, 22000 - Algeria<br>Tel:+213 48-54-95-46 Fax:+213 48-54-19-28 <a href="mailto:flitimein@yahoo.fr" target="_blank">flitimein@yahoo.fr</a><br>
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<br></blockquote></div><br><br clear="all"><br>-- <br>======================================<br>Seyed Javad Hashemifar, Ph.D.<br>current address:<br>Physics Department, University of Duisburg-Essen, <br>47057 Duisburg, Germany<br>
Tel:+49 203 379 4743 Fax:+49 203 379 4741<br>permanent address:<br>Physics Department, Isfahan University of Technology<br>84154 Isfahan, Iran<br>Tel: +98 311 391 2375 Fax:+98 311 3912376<br>---------------------------------------------------------------------------