<div dir="ltr">Dear <span class="" style="border-collapse:collapse;font-family:arial,sans-serif;font-size:18px">B.Satyanarayana,</span><div><span class="" style="border-collapse:collapse;font-family:arial,sans-serif;font-size:18px"><br>
</span></div><div><span class="" style="border-collapse:collapse;font-family:arial,sans-serif;font-size:18px"> My personal opinions:</span></div><div><font class="Apple-style-span" face="arial, sans-serif"><span class="Apple-style-span" style="border-collapse:collapse"><br>
</span></font></div><div><font class="Apple-style-span" face="arial, sans-serif"><span class="Apple-style-span" style="border-collapse:collapse">1) What is determined as "converged" depends on the quantity observed and accuracy wanted (thus on the person making the choice). For example the pressure tensor, being a second derivative of the energy, converges much slower than the forces (first-order derivative) that in turn converges much slower than the energy (zero-order quantity)</span></font></div>
<div><font class="Apple-style-span" face="arial, sans-serif"><span class="Apple-style-span" style="border-collapse:collapse"><br></span></font></div><div><font class="Apple-style-span" face="arial, sans-serif"><span class="Apple-style-span" style="border-collapse:collapse">2) In my opinion there are several simulations in the literature that are not converged (and this does not apply to CP2K only). I don't make any statement about the convergence in the article that you cited, just that it is better to test oneself: After that one also understands the convergence, the system, the method etc better</span></font></div>
<div><font class="Apple-style-span" face="arial, sans-serif"><span class="Apple-style-span" style="border-collapse:collapse"><br></span></font></div><div><font class="Apple-style-span" face="arial, sans-serif"><span class="Apple-style-span" style="border-collapse:collapse">3) The energy on the line 'FORCE_EVAL' is the potential energy, not the quantity that should be conserved. This shows that the energy does not explode, not more (and the sample is very short, plus probably taken at the beginning of the simulation when the things still vary more, due to the rough equilibration needed</span></font></div>
<div><font class="Apple-style-span" face="arial, sans-serif"><span class="Apple-style-span" style="border-collapse:collapse"><br></span></font></div><div><font class="Apple-style-span" face="arial, sans-serif"><span class="Apple-style-span" style="border-collapse:collapse">4) You see that the value of the determinant of the stress tensor diverges _very_ fast, so there is certainly at least one problem. I was hinted that the time constant that you have taken for the barostat is excessively small: This would basically try to make the cell respond to the fastest oscillations in your system (I hope that there _is_ something oscillating at 4000 cm^-1, it would be necessary for the thermostat chain you have). I don't know if this is the only reason, but I would switch the time constant to something larger, for example of the order picoseconds</span></font></div>
<div><font class="Apple-style-span" face="arial, sans-serif"><span class="Apple-style-span" style="border-collapse:collapse"><br></span></font></div><div><font class="Apple-style-span" face="arial, sans-serif"><span class="Apple-style-span" style="border-collapse:collapse">5) The convergence in the electronic structure indeed looks smooth on the linear scale, but here one usually uses logarithmic scale in order to see how the energy converges closer to the self-consistency. Another useful check is to calculate the eigenvalues and see that the HOMO-LUMO gap (in molecules) or between the valence and conducation band is more or less that you expected</span></font></div>
<div><font class="Apple-style-span" face="arial, sans-serif"><span class="Apple-style-span" style="border-collapse:collapse"><br></span></font></div><div><font class="Apple-style-span" face="arial, sans-serif"><span class="Apple-style-span" style="border-collapse:collapse"> This after a quick glimpse on your report, maybe I missed again something relevant though.</span></font></div>
<div><font class="Apple-style-span" face="arial, sans-serif"><span class="Apple-style-span" style="border-collapse:collapse"><br></span></font></div><div><font class="Apple-style-span" face="arial, sans-serif"><span class="Apple-style-span" style="border-collapse:collapse"> Good Luck, :)</span></font></div>
<div><font class="Apple-style-span" face="arial, sans-serif"><span class="Apple-style-span" style="border-collapse:collapse"><br></span></font></div><div><font class="Apple-style-span" face="arial, sans-serif"><span class="Apple-style-span" style="border-collapse:collapse"> apsi</span></font></div>
<div><font class="Apple-style-span" face="arial, sans-serif"><span class="Apple-style-span" style="border-collapse:collapse"><br></span></font></div><div class="gmail_extra"><br><br><div class="gmail_quote">2013/9/20 Bonakala Satyanarayana <span dir="ltr"><<a href="mailto:satyanaray...@gmail.com" target="_blank">satyanaray...@gmail.com</a>></span><br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Dear Seitsonen,<div> Thank you for your reply. </div><div>1) I performed NVT simulation with same input, what I have enclosed. It ran well. These are the converged energy values: </div>
<div><div>
ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.): -7812.764025944994501</div><div> ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.): -7812.749474147461115</div><div> ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.): -7812.722559495744463</div>
<div> ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.): -7812.689485930668525</div><div> ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.): -7812.657322690376532</div><div> ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.): -7812.631945457889742</div>
<div> ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.): -7812.616274832782437</div><div> ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.): -7812.609299468986137</div></div><div>2) I have taken cut-off as per literature (<span style="line-height:1.4em;font-size:1.15em;font-family:'Trebuchet MS',Arial,Helvetica,sans-serif">Elucidating the Breathing of the Metal–Organic Framework MIL-53(Sc) with ab Initio Molecular Dynamics Simulations and in Situ X-ray Powder Diffraction Experiments, Duren et al., JACS). Here, they have tested for MIL MOFs and reported optimum cut-off is 350 Ry. </span></div>
<div><span style="line-height:1.4em;font-size:1.15em;font-family:'Trebuchet MS',Arial,Helvetica,sans-serif"><br></span></div><div>Dear Hutter,</div><div><br></div><div>1) Yes, my system is stable in NVT simulation</div>
<div><br></div><div>2) Det( stress tensor) values are </div><div> Det(stress tensor) : -7.84528984E-04</div><div> Det(stress tensor) : -1.66559235E-02</div><div> Det(stress tensor) : -1.44160312E+00</div>
<div> Det(stress tensor) : 2.03287049E+02</div><div> Det(stress tensor) : -4.82023324E+03</div><div> Det(stress tensor) : 4.36251297E+07</div><div> BAROSTAT temperature is increasing:<br></div><div>
BAROSTAT TEMP[K] = 0.250067070500E+03</div><div> BAROSTAT TEMP[K] = 0.407906043312E+05</div><div> BAROSTAT TEMP[K] = 0.373591928441E+06</div><div> BAROSTAT TEMP[K] = 0.458891514234E+08</div>
<div><br></div><div>3) SCF convergence is smooth. I enclosed the convergence vs steps <span style="font-size:12.800000190734863px;color:rgb(51,51,51);font-family:'Trebuchet MS',Arial,Helvetica,sans-serif;font-weight:bold;line-height:16.637500762939453px"> </span></div>
<div><span style="font-size:12.800000190734863px;color:rgb(51,51,51);font-family:'Trebuchet MS',Arial,Helvetica,sans-serif;font-weight:bold;line-height:16.637500762939453px"><br></span></div></div><div class="gmail_extra">
<br clear="all"><div><div dir="ltr">Thank you<br><br>B.Satyanarayana, Ph. D<br>Molecular modeling lab<div>JNCASR<br>Bangalore</div></div></div>
<br><br><div class="gmail_quote">On Thu, Sep 19, 2013 at 2:34 PM, Ari Paavo Seitsonen <span dir="ltr"><<a href="mailto:ari.p.s...@gmail.com" target="_blank">ari.p.s...@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 dir="ltr"><div>Dear Satyanarayana B,<br></div><div><br></div><div> Indeed the energy does not "drift", it explodes. What did happen in an NVT simulation with otherwise the same input, did the simulation work fine?</div>
<div><br></div><div> To me the cut-off energy of 350 Ry looks low, even with the PBE functional (smoother than BLYP); did you test that it is sufficient?</div><div><br></div><div> Greetings from Zurich,</div><div><br>
</div><div> apsi</div><div><br></div><div>PS Does some one know, are the methods in &XC_GRID ... &END XC_GRID consistent with an NPT simulation?</div><div class="gmail_extra"><div><div><br><br><div class="gmail_quote">
2013/9/19 Matt W <span dir="ltr"><<a href="mailto:MattWa...@gmail.com" target="_blank">MattWa...@gmail.com</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr"><div>Hi,<br></div><div><br></div><div>well your system is clearly exploding. Your cell_ref parameters look inconsistent with your actual cell - maybe the stress tensor is very bad!</div><div><div>
<br></div><div> &SUBSYS</div><blockquote class="gmail_quote" style="margin:0;margin-left:0.8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div><div> &CELL</div><div> ABC 21.8620 16.2099 43.6020</div>
<div> ALPHA_BETA_GAMMA 90.0 92.7540 90.0</div><div> &CELL_REF</div><div> ABC 22.8620 17.2099 44.6020</div><div> ALPHA_BETA_GAMMA 90.0 126.0 90.0</div><div> &END CELL_REF</div><div> </div>
<div> &END CELL</div><div><br></div></div></div></blockquote></div></div><div><div>
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