Dear Max,<div><br></div><div>I think that this rule is a myth, for the simple reason that more ecutwfc=more plane waves = more energy, In addition to that , the more system is big the bigger is the energy (and the energy jumps vs ecutwfc).</div><div>I suggest you to rerun the calculations with tstress = .true. & tprnfor = .true. , then you look after on the impact of ecutwfc upon force and stress tensor.</div><div><br></div><div>By plotting your data, I suggest that ecutwfc threshold is laying between 50 to 150 Ry.</div><div><br>On Fri, Jul 10, 2015 at 1:02 AM, max <aquiles011@gmail.com> wrote:<br>
<blockquote type="cite"><div dir="ltr">Dear Youssef and Giovanni,<br><br><span lang="en"><span>Thank you very much, I have doubt about convergence energy</span></span>.<br><br>I run scf calculations for ecutwfc from 10 to 250 Ry using ecutrho=4*ecutwfc and I get the values bellow ecutwfc vs etotal (values in Ry). I read that the convergence will be achieved when the difference
between two adjacent scf calculation is smaller than 0.1 meV [1] or 1 mRy [2], but this is for unit cell or for atoms (divide the energy difference between the number of atoms in unit cell)?<br><br>Other question, is normal that the convergence value for ecutwfc be more than 200 Ry?<br> <br>ecutwfc etotal<br>10 -941.67085713<br>15 -1005.07732548<br>20 -1038.00240543<br>25 -1058.8736733<br>30 -1073.25016374<br>35 -1082.62081233<br>40 -1089.10688841<br>45 -1093.8583202<br>50 -1097.63582121<br>55 -1100.63775846<br>60 -1103.0243432<br>65 -1105.15423136<br>70 -1107.08545327<br>75 -1108.79020201<br>80 -1110.27166937<br>85 -1111.59023819<br>90 -1112.768963<br>100 -1114.66472444<br>110 -1116.05760199<br>120 -1117.06611139<br>130 -1117.76952606<br>140 -1118.25442342<br>150 -1118.58413784<br>160 -1118.80480982<br>170 -1118.95194442<br>180 -1119.0489105<br>190 -1119.11208313<br>200 -1119.15329918<br>210 -1119.17990393<br>220 -1119.19703143<br>230 -1119.20790385<br>240 -1119.21481705<br>250 -1119.21915626<br><br>[1] <a href="https://www.mail-archive.com/pw_forum%40pwscf.org/msg11093.html" target="_blank">https://www.mail-archive.com/pw_forum%40pwscf.org/msg11093.html</a><br>[2] <a href="http://qe-forge.org/pipermail/pw_forum/2013-February/101122.html">http://qe-forge.org/pipermail/pw_forum/2013-February/101122.html</a><br></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Jul 7, 2015 at 7:35 PM, Youssef <span dir="ltr"><<a href="mailto:aharbil@gmail.com" target="_blank">aharbil@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div>Dear Max,</div><div><br></div><div>You can use the following 14 atoms coordinates for spinel AB2O4 (fd-3m origin choice 2), replace "x" with oxygen parameter from 32e wykoff site (0.2627 for your case)</div><div><br></div><div>A 0.125 0.125 0.125</div><div>A 0.875 0.375 0.375</div><div>B 0.5 0.5 0.5</div><div>B 0.25 0.75 0</div><div>B 0.75 0 0.25</div><div>B 0 0.25 0.75</div><div>O (x) (x) (x)</div><div>O (1.25-x) (x+0.5) (1.75-x)</div><div>O (x+0.75) (x+0.25) (1.5-x)</div><div>O (x+0.25) (1.5-x) (1.75+x)</div><div>O (1.75-x) (1.25-x) (x+0.5)</div><div>O (x+0.5) (1.75-x) (1.25-x)</div><div>O (1-x) (1-x) (1-x)</div><div>O (1.5-x) (x+0.75) (x+0.25)</div><div><br></div><div><br></div><div>to be used with ibarv = 2 and ATOMIC_POSITIONS alat (not crystal) , I didn't test it in QE, please confirm if it works!</div><div><br></div><div>Youssef Aharbil,</div><div>Laboratory of Physics and Chemistry of Materials</div><div>Faculty of sciences Ben msik, Casablanca</div><div>Morocco</div></blockquote></div><br><br clear="all"><br>-- <br><div class="gmail_signature"><div dir="ltr"><div>El éxito solo es para los que se arriesgan por sus objetivos.<br><br> Máximo Ramírez Mateo<br></div> Desarrollador de Software<br></div></div>
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