<div dir="ltr"><div><div>Hi,<br></div>Thanks for the pieces of advice. One last question, the electronic temperature is set by default at 300 K, but no further information is given on how to adjust this parameter. One only can refer to the Fermi-Dirac distribution. Given that my 'nuclei' temperature is several thousand of Kelvin, should this electronic temperature be adjusted to a higher value?<br><br></div>Regards,<br></div><div class="gmail_extra"><br clear="all"><div><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr">- Fernan<br></div></div></div> <br><div class="gmail_quote">On Wed, Oct 25, 2017 at 7:40 AM, Marcella Iannuzzi <span dir="ltr"><<a href="mailto:marci...@gmail.com" target="_blank">marci...@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">Hi,<div><br></div><div>When the gap is so small, you need to add into the SCF unoccupied orbitals and to smear the occupation numbers.</div><div>The unphysical negative gap is an indication that the resulting electronic structure at that step is wrong. </div><div>This has obviously effects also on the forces and consequently on the trajectory. </div><div><br></div><div>Kind regards,</div><div>Marcella<span class=""><br><br>On Tuesday, October 24, 2017 at 7:49:38 PM UTC+2, Fernan Saiz wrote:</span><blockquote class="gmail_quote" style="margin:0;margin-left:0.8ex;border-left:1px #ccc solid;padding-left:1ex"><span class=""><div dir="ltr"><div><div>Hi,<br>Sorry for the confusion, I meant that after a few hundred MD steps, the SCF is not converging anymore.<br><br></div><div>At the 800th MD step, just 200 MD steps before the SCF does not converge, the band gap is 0.035644 eV at a pressure of 11.76 GPa. The pressure stays between around 5 and 15 GPa between the initial step and before the SCF starts not converging. At the 1000th MD step, when the SCF starts to not converging, the band gap is -0.026438 eV with a pressure that drops to -84.83 GPa. Please note that CP2k with PADE understimates the experimental band gap for the beta-SiC with a value of 0.991279 eV.<br><br></div></div>Thanks,<br></div></span><div><br clear="all"><div><div><div dir="ltr">- Fernan<br></div></div></div> <br><div class="gmail_quote"><span class="">On Tue, Oct 24, 2017 at 5:15 PM, <span dir="ltr"><<a rel="nofollow">hut...@chem.uzh.ch</a>></span> wrote:<br></span><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">Hi<br> <br> is that the band gap of your system at that pressure?<br> <br> Also, you say "the ab-initio molecular dynamics at NVE does not converge after several hundred steps"<br> Does that mean, after several hundred MD steps, the SCF is not converging anymore,<br> or the SCF did not converge within several hundred steps?<br> </span><span><span class=""><br> regards<br> <br> Juerg Hutter<br> ------------------------------<wbr>------------------------------<wbr>--<br> Juerg Hutter Phone : <a value="+41446354491">++41 44 635 4491</a><br> Institut für Chemie C FAX : <a value="+41446356838">++41 44 635 6838</a><br></span> Universität Zürich E-mail: <a rel="nofollow">hut...@chem.uzh.ch</a><span class=""><br> <a href="https://maps.google.com/?q=Winterthurerstrasse+190&entry=gmail&source=g">Winterthurerstrasse 190</a><br> CH-8057 Zürich, Switzerland<br> ------------------------------<wbr>------------------------------<wbr>---<br> <br></span> -----<a rel="nofollow">cp...@googlegroups.com</a> wrote: -----<br> </span>To: <a rel="nofollow">cp...@googlegroups.com</a><br> <span>From: Fernan Saiz<br> Sent by: <a rel="nofollow">cp...@googlegroups.com</a><br> </span><span class="">Date: 10/24/2017 05:14PM<br> Subject: Re: [CP2K:9582] convergence problems when melting SiC at high pressure<br> </span><div><div><span class=""><br> Hi,<br> The band gap of beta-SiC is 2.36 eV. What are parameters could be adjusted?<br> <br> Thanks,<br> <br> - Fernan<br> <br></span><span class=""> On Tue, Oct 24, 2017 at 8:46 AM, <<a rel="nofollow">hut...@chem.uzh.ch</a>> wrote:<br> Hi<br> <br> what do you expect for the band gap of this system?<br> For small band gap systems you might need to adjust<br> your simulation methods.<br> <br> regards<br> <br> Juerg Hutter<br> -----------------------------<wbr>------------------------------<wbr>---<br> Juerg Hutter Phone : <a value="+41446354491">++41 44 635 4491</a><br> Institut für Chemie C FAX : <a value="+41446356838">++41 44 635 6838</a><br></span> Universität Zürich E-mail: <a rel="nofollow">hut...@chem.uzh.ch</a><span class=""><br> <a href="https://maps.google.com/?q=Winterthurerstrasse+190&entry=gmail&source=g">Winterthurerstrasse 190</a><br> CH-8057 Zürich, Switzerland<br> -----------------------------<wbr>------------------------------<wbr>----<br> <br></span> -----<a rel="nofollow">cp...@googlegroups.com</a> wrote: -----<br> To: cp2k <<a rel="nofollow">cp...@googlegroups.com</a>><br> From: Fernan Saiz<br> Sent by: <a rel="nofollow">cp...@googlegroups.com</a><span class=""><br> Date: 10/22/2017 08:34PM<br> Subject: [CP2K:9574] convergence problems when melting SiC at high pressure<br> <br> Hello,<br> I am studying the melting of a 256-atom SiC system at high pressures using the Z-method. I face the problem that when the pressure is around 10 o 20 GPa (obtained by reducing 1% the simulation cell size), the ab-initio molecular dynamics at NVE does not converge after several hundred steps. I tried reducing the timestep to 0.05 fs with a cutoff of 800 Ry for an initial temperature of 9000 K, which after a few hundred steps goes down to to some 4000 K and the system starts to melt. However, this system does not converge even though I used the CG minimizer with a eps_max 1.0E-6 for the inner and outer loops, the preconditioner FULL_ALL with the PADE functional. Input script file is attached.<br> <br> I was wondering if I could receive any useful piece of advice.<br> <br> Best regards,<br> - Fernan Saiz<br> Department of chemistry<br> Imperial College London<br> <br> --<br> You received this message because you are subscribed to the Google Groups "cp2k" group.<br></span> To unsubscribe from this group and stop receiving emails from it, send an email to <a rel="nofollow">cp2k+...@googlegroups.com</a>.<br> To post to this group, send email to <a rel="nofollow">cp...@googlegroups.com</a>.<span class=""><br> Visit this group at <a href="https://groups.google.com/group/cp2k" rel="nofollow" target="_blank">https://groups.google.com/grou<wbr>p/cp2k</a>.<br> For more options, visit <a href="https://groups.google.com/d/optout" rel="nofollow" target="_blank">https://groups.google.com/d/op<wbr>tout</a>.<br> <br> <br> [attachment "sic.inp" removed by Jürg Hutter/at/UZH]<br> <br> <br> --<br> You received this message because you are subscribed to a topic in the Google Groups "cp2k" group.<br> To unsubscribe from this topic, visit <a href="https://groups.google.com/d/topic/cp2k/Zix1oKixhhA/unsubscribe" rel="nofollow" target="_blank">https://groups.google.com/d/to<wbr>pic/cp2k/Zix1oKixhhA/unsubscri<wbr>be</a>.<br></span> To unsubscribe from this group and all its topics, send an email to <a rel="nofollow">cp2k+...@googlegroups.com</a>.<br> To post to this group, send email to <a rel="nofollow">cp...@googlegroups.com</a>.<span class=""><br> Visit this group at <a href="https://groups.google.com/group/cp2k" rel="nofollow" target="_blank">https://groups.google.com/grou<wbr>p/cp2k</a>.<br> For more options, visit <a href="https://groups.google.com/d/optout" rel="nofollow" target="_blank">https://groups.google.com/d/op<wbr>tout</a>.<br> <br> <br> --<br> You received this message because you are subscribed to the Google Groups "cp2k" group.<br></span> To unsubscribe from this group and stop receiving emails from it, send an email to <a rel="nofollow">cp2k+...@googlegroups.com</a>.<br> To post to this group, send email to <a rel="nofollow">cp...@googlegroups.com</a>.<span class=""><br> Visit this group at <a href="https://groups.google.com/group/cp2k" rel="nofollow" target="_blank">https://groups.google.com/grou<wbr>p/cp2k</a>.<br> For more options, visit <a href="https://groups.google.com/d/optout" rel="nofollow" target="_blank">https://groups.google.com/d/op<wbr>tout</a>.<br> <br> <br> --<br> You received this message because you are subscribed to a topic in the Google Groups "cp2k" group.<br> To unsubscribe from this topic, visit <a href="https://groups.google.com/d/topic/cp2k/Zix1oKixhhA/unsubscribe" rel="nofollow" target="_blank">https://groups.google.com/d/to<wbr>pic/cp2k/Zix1oKixhhA/unsubscri<wbr>be</a>.<br></span> To unsubscribe from this group and all its topics, send an email to <a rel="nofollow">cp2k+...@googlegroups.com</a>.<br> To post to this group, send email to <a rel="nofollow">cp...@googlegroups.com</a>.<span class=""><br> Visit this group at <a href="https://groups.google.com/group/cp2k" rel="nofollow" target="_blank">https://groups.google.com/grou<wbr>p/cp2k</a>.<br> For more options, visit <a href="https://groups.google.com/d/optout" rel="nofollow" target="_blank">https://groups.google.com/d/op<wbr>tout</a>.<br> </span></div></div></blockquote></div><br></div> </blockquote></div></div><div class="HOEnZb"><div class="h5"> <p></p> -- <br> You received this message because you are subscribed to a topic in the Google Groups "cp2k" group.<br> To unsubscribe from this topic, visit <a href="https://groups.google.com/d/topic/cp2k/Zix1oKixhhA/unsubscribe" target="_blank">https://groups.google.com/d/<wbr>topic/cp2k/Zix1oKixhhA/<wbr>unsubscribe</a>.<br> To unsubscribe from this group and all its topics, send an email to <a href="mailto:cp2k+uns...@googlegroups.com" target="_blank">cp2k+unsubscribe@googlegroups.<wbr>com</a>.<br> To post to this group, send email to <a href="mailto:cp...@googlegroups.com" target="_blank">cp...@googlegroups.com</a>.<br> Visit this group at <a href="https://groups.google.com/group/cp2k" target="_blank">https://groups.google.com/<wbr>group/cp2k</a>.<br> For more options, visit <a href="https://groups.google.com/d/optout" target="_blank">https://groups.google.com/d/<wbr>optout</a>.<br> </div></div></blockquote></div><br></div>