<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div>I have run into convergence issues (fluctuations about a minimum) with larger cells and too tight of a force and energy tolerance (yours are quite tight).</div><div><br></div><div>You may want to back off the tolerances a bit, then restart it with tighter tolerances, incrementing until you get the desired accuracy. That or only set 1 of the tolerances tight. Since both criteria need to be met, you may be over-constraining the system and so you get fluctuations. One approach may be to back off the energy tolerance, so that the forces are tightly converged (which often occurs after the energy has converged well)</div><div><br></div><div>Or I could be completely wrong.</div><div><br></div><div>Dave</div><br><div><div>On Jan 24, 2009, at 4:48 AM, hania djani-ait aissa wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0; "><div class="hmmessage" style="font-size: 10pt; font-family: Verdana; ">Dear all,<br>i am doing calculation on orthorombic system containing 36 atoms (Bi2WO6). My computer is a workstation HP xw6400 quad-core Xeon, 2GB. Vc-relax on this system spent more than 01 mounth and still not finish. the energy is converging but forces fluctuate. is there something wrong in my input in terms of umass or dt? or have i to capitulate to this very slow convergence?<br>here is the input file. Any suggestions will welcome.<span class="Apple-converted-space"> </span><br><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; "><span lang="EN-GB"><font color="#000000"><font face="Courier New">&control<br><span> <span class="Apple-converted-space"> </span></span>calculation<span> <span class="Apple-converted-space"> </span></span>= 'vc-relax'<br><span> <span class="Apple-converted-space"> </span></span>restart_mode = 'from_scratch'<br><span> <span class="Apple-converted-space"> </span></span>pseudo_dir<span> <span class="Apple-converted-space"> </span></span>= '/root/pwscf/pseudo/'<br><span> <span class="Apple-converted-space"> </span></span>outdir<span> <span class="Apple-converted-space"> </span></span>= '/root/tmp/'<br><span> <span class="Apple-converted-space"> </span></span>tstress<span> <span class="Apple-converted-space"> </span></span>= .TRUE.<br><span> <span class="Apple-converted-space"> </span></span>tprnfor<span> <span class="Apple-converted-space"> </span></span>= .TRUE.<br><span> <span class="Apple-converted-space"> </span></span>nstep<span> <span class="Apple-converted-space"> </span></span>= 55<br><span> <span class="Apple-converted-space"> </span></span>etot_conv_thr= 1e-5,<br><span> <span class="Apple-converted-space"> </span></span>forc_conv_thr= 1e-4,<br><span> <span class="Apple-converted-space"> </span></span>dt<span> <span class="Apple-converted-space"> </span></span>= 30,<br><span> </span>/<br><span> </span>&system<br><span> <span class="Apple-converted-space"> </span></span>ibrav=8<br><span> <span class="Apple-converted-space"> </span></span>celldm(1)=10.37,<span class="Apple-converted-space"> </span><br><span> <span class="Apple-converted-space"> </span></span>celldm(2)=0.996,<span class="Apple-converted-space"> </span><br><span> <span class="Apple-converted-space"> </span></span>celldm(3)=3.00,<span class="Apple-converted-space"> </span><br><span> <span class="Apple-converted-space"> </span></span>nat=36<br><span> <span class="Apple-converted-space"> </span></span>ntyp=3<br><span> <span class="Apple-converted-space"> </span></span>ecutwfc=35.0<br><span> <span class="Apple-converted-space"> </span></span>ecutrho=200.0,<br><span> <span class="Apple-converted-space"> </span></span><br><span> </span>/<br><span> </span>&electrons<br><span> <span class="Apple-converted-space"> </span></span></font></font></span><span lang="DE"><font color="#000000"><font face="Courier New">conv_thr = 1e-8,<br><span> <span class="Apple-converted-space"> </span></span>mixing_beta=0.7,<br><span> </span></font></font></span><font color="#000000"><font face="Courier New"><span lang="EN-GB">/<br><span> </span>&ions<br><span> </span>/<br>&cell<br><span> <span class="Apple-converted-space"> </span></span>cell_dynamics = 'damp-w',<br><span> <span class="Apple-converted-space"> </span></span>press<span> <span class="Apple-converted-space"> </span></span>= 0.00,<br><span> <span class="Apple-converted-space"> </span></span>wmass<span> <span class="Apple-converted-space"> </span></span>= 0.004,<br>/<span> <span class="Apple-converted-space"> </span></span><br>ATOMIC_SPECIES<br><span> <span class="Apple-converted-space"> </span></span><br><span> <span class="Apple-converted-space"> </span></span>W<span> <span class="Apple-converted-space"> </span></span>183.84<span> <span class="Apple-converted-space"> </span></span>W.pz-bhs.UPF<br><span> <span class="Apple-converted-space"> </span></span>Bi<span> <span class="Apple-converted-space"> </span></span>208.98<span> <span class="Apple-converted-space"> </span></span>083-Bi-ca-d-vgrp_ji.uspp.UPF<br><span> <span class="Apple-converted-space"> </span></span>O<span> <span class="Apple-converted-space"> </span></span>15.9994<span> <span class="Apple-converted-space"> </span></span>O.pz-van_ak.UPF<br><span> </span><br>ATOMIC_POSITIONS alat<br>W<span> <span class="Apple-converted-space"> </span></span><span> </span>0.000000000<span> <span class="Apple-converted-space"> </span></span>0.005016973<span> <span class="Apple-converted-space"> </span></span>0.747761262<span> <span class="Apple-converted-space"> </span></span>0 1 1<br>W<span> <span class="Apple-converted-space"> </span></span>0.500000000<span> <span class="Apple-converted-space"> </span></span>0.990983027<span> <span class="Apple-converted-space"> </span></span>2.252238738<span> <span class="Apple-converted-space"> </span></span>0 1 1<br></span>W<span> <span class="Apple-converted-space"> </span></span>0.500000000<span> <span class="Apple-converted-space"> </span></span>0.492983027<span> <span class="Apple-converted-space"> </span></span>0.747761262<span> <span class="Apple-converted-space"> </span></span>0 1 1<br>W<span> <span class="Apple-converted-space"> </span></span>0.000000000<span> <span class="Apple-converted-space"> </span></span>0.503016973<span> <span class="Apple-converted-space"> </span></span>2.252238738<span> <span class="Apple-converted-space"> </span></span>0 1 1<br>Bi<span> <span class="Apple-converted-space"> </span></span>0.964931181<span> <span class="Apple-converted-space"> </span></span>0.523336245<span> <span class="Apple-converted-space"> </span></span>1.268793038<br>Bi<span> <span class="Apple-converted-space"> </span></span>0.464931181<span> <span class="Apple-converted-space"> </span></span>0.472663755<span> <span class="Apple-converted-space"> </span></span>1.731206962<br>Bi<span> <span class="Apple-converted-space"> </span></span>0.464931181<span> <span class="Apple-converted-space"> </span></span>0.970663755<span> <span class="Apple-converted-space"> </span></span>1.268793038<br>Bi<span> <span class="Apple-converted-space"> </span></span>0.964931181<span> <span class="Apple-converted-space"> </span></span>0.025336245<span> <span class="Apple-converted-space"> </span></span>1.731206962<br>Bi<span> <span class="Apple-converted-space"> </span></span>0.981726782<span> <span class="Apple-converted-space"> </span></span>0.473760364<span> <span class="Apple-converted-space"> </span></span>0.230569958<br>Bi<span> <span class="Apple-converted-space"> </span></span>0.481726782<span> <span class="Apple-converted-space"> </span></span>0.522239636<span> <span class="Apple-converted-space"> </span></span>2.769430042<br>Bi<span> <span class="Apple-converted-space"> </span></span>0.481726782<span> <span class="Apple-converted-space"> </span></span>0.024239636<span> <span class="Apple-converted-space"> </span></span>0.230569958<br>Bi<span> <span class="Apple-converted-space"> </span></span>0.981726782<span> <span class="Apple-converted-space"> </span></span>0.971760364<span> <span class="Apple-converted-space"> </span></span>2.769430042<br>O<span> <span class="Apple-converted-space"> </span></span>0.100459245<span> <span class="Apple-converted-space"> </span></span>0.081203101<span> <span class="Apple-converted-space"> </span></span>0.435231801<br>O<span> <span class="Apple-converted-space"> </span></span>0.600459245<span> <span class="Apple-converted-space"> </span></span>0.914796899<span> <span class="Apple-converted-space"> </span></span>2.564768199<br></font></font><font color="#000000"><font face="Courier New"><span lang="EN-GB">O<span> <span class="Apple-converted-space"> </span></span>0.600459245<span> <span class="Apple-converted-space"> </span></span>0.416796899<span> <span class="Apple-converted-space"> </span></span>0.435231801<br>O<span> <span class="Apple-converted-space"> </span></span>0.100459245<span> <span class="Apple-converted-space"> </span></span>0.579203101<span> <span class="Apple-converted-space"> </span></span>2.564768199<br>O<span> <span class="Apple-converted-space"> </span></span>0.264260826<span> <span class="Apple-converted-space"> </span></span>0.262143525<span> <span class="Apple-converted-space"> </span></span>3.000064967<br>O<span> <span class="Apple-converted-space"> </span></span>0.764260826<span> <span class="Apple-converted-space"> </span></span>0.733856475<span> <span class="Apple-converted-space"> </span></span>-0.000064967<br>O<span> <span class="Apple-converted-space"> </span></span>0.764260826<span> <span class="Apple-converted-space"> </span></span>0.235856475<span> <span class="Apple-converted-space"> </span></span>3.000064967<br>O<span> <span class="Apple-converted-space"> </span></span>0.264260826<span> <span class="Apple-converted-space"> </span></span>0.760143525<span> <span class="Apple-converted-space"> </span></span>-0.000064967<br>O<span> <span class="Apple-converted-space"> </span></span>0.247153777<span> <span class="Apple-converted-space"> </span></span>0.235070329<span> <span class="Apple-converted-space"> </span></span>1.501190932<br>O<span> <span class="Apple-converted-space"> </span></span>0.747153777<span> <span class="Apple-converted-space"> </span></span>0.760929671<span> <span class="Apple-converted-space"> </span></span>1.498809068<br>O<span> <span class="Apple-converted-space"> </span></span>0.747153777<span> <span class="Apple-converted-space"> </span></span>0.262929671<span> <span class="Apple-converted-space"> </span></span>1.501190932<br>O<span> <span class="Apple-converted-space"> </span></span>0.247153777<span> <span class="Apple-converted-space"> </span></span>0.733070329<span> <span class="Apple-converted-space"> </span></span>1.498809068<br>O<span> <span class="Apple-converted-space"> </span></span>0.283152650<span> <span class="Apple-converted-space"> </span></span>0.701520345<span> <span class="Apple-converted-space"> </span></span>0.680189839<br>O<span> <span class="Apple-converted-space"> </span></span>0.783152650<span> <span class="Apple-converted-space"> </span></span>0.294479655<span> <span class="Apple-converted-space"> </span></span>2.319810161<br>O<span> <span class="Apple-converted-space"> </span></span>0.783152650<span> <span class="Apple-converted-space"> </span></span>0.792479655<span> <span class="Apple-converted-space"> </span></span>0.680189839<br>O<span> <span class="Apple-converted-space"> </span></span>0.283152650<span> <span class="Apple-converted-space"> </span></span>0.203520345<span> <span class="Apple-converted-space"> </span></span>2.319810161<br>O<span> <span class="Apple-converted-space"> </span></span>0.335776234<span> <span class="Apple-converted-space"> </span></span>0.239505837<span> <span class="Apple-converted-space"> </span></span>0.816308565<br>O<span> <span class="Apple-converted-space"> </span></span>0.835776234<span> <span class="Apple-converted-space"> </span></span>0.756494163<span> <span class="Apple-converted-space"> </span></span>2.183691435<br>O<span> <span class="Apple-converted-space"> </span></span>0.835776234<span> <span class="Apple-converted-space"> </span></span>0.258494163<span> <span class="Apple-converted-space"> </span></span>0.816308565<br>O<span> <span class="Apple-converted-space"> </span></span>0.335776234<span> <span class="Apple-converted-space"> </span></span>0.737505837<span> <span class="Apple-converted-space"> </span></span>2.183691435<br>O<span> <span class="Apple-converted-space"> </span></span>0.586065178<span> <span class="Apple-converted-space"> </span></span>0.587540848<span> <span class="Apple-converted-space"> </span></span>1.058853940<br>O<span> <span class="Apple-converted-space"> </span></span>0.086065178<span> <span class="Apple-converted-space"> </span></span>0.408459152<span> <span class="Apple-converted-space"> </span></span>1.941146060<br></span>O<span> <span class="Apple-converted-space"> </span></span>0.086065178<span> <span class="Apple-converted-space"> </span></span>0.906459152<span> <span class="Apple-converted-space"> </span></span>1.058853940<br>O<span> <span class="Apple-converted-space"> </span></span>0.586065178<span> <span class="Apple-converted-space"> </span></span>0.089540848<span> <span class="Apple-converted-space"> </span></span>1.941146060<br><br><br><span> </span>K_POINTS {automatic}<br><span> <span class="Apple-converted-space"> </span></span>5 5 5 1 1 1<br><o:p> </o:p></font></font></div>thanks a lot<br> <br>Hania Djani-ait aissa<br>PHD student<br>Algeria<br> <font face="Arial" size="1"><br><p align="left" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; "> </p></font><rte_text></rte_text><br><hr>Téléchargez le nouveau Windows Live Messenger !<span class="Apple-converted-space"> </span><a href="http://get.live.com/messenger/overview" target="_new">Téléchargez Messenger, c'est gratuit !</a><span class="Apple-converted-space"> </span>_______________________________________________<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></div></span></blockquote></div><br><div apple-content-edited="true"> <span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Helvetica" size="3" style="font: normal normal normal 12px/normal Helvetica; font-size: 12px; ">David E. Farrell</font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; ">Post-Doctoral Fellow</span></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; ">Department of Materials Science and Engineering</span></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Helvetica" size="3" style="font: normal normal normal 12px/normal Helvetica; font-size: 12px; ">Northwestern University</font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Helvetica" size="3" style="font: normal normal normal 12px/normal Helvetica; font-size: 12px; ">email: <a href="mailto:d-farrell2@northwestern.edu">d-farrell2@northwestern.edu</a></font></div></div></div></span> </div><br></body></html>