<html xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"> <head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <meta name="Generator" content="Microsoft Word 15 (filtered medium)"> <style></style> </head> <body lang="en-CH" link="blue" vlink="purple" style="word-wrap:break-word"> <div class="WordSection1"> <p class="MsoNormal"><span lang="DE-CH" style="font-size:11.0pt;mso-fareast-language:EN-US">Dear Léon<o:p></o:p></span></p> <p class="MsoNormal"><span lang="DE-CH" style="font-size:11.0pt;mso-fareast-language:EN-US"><o:p> </o:p></span></p> <p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;mso-fareast-language:EN-US">The timings appear reasonable to me. The run time for a small unit cell with just 12 atoms using a moderate number of k points can be much faster than a Gamma point calculation for a system with 600 atoms. The timings might get a bit closer when a wavefunction restart file is available.<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;mso-fareast-language:EN-US"><o:p> </o:p></span></p> <p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;mso-fareast-language:EN-US">Best<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;mso-fareast-language:EN-US"><o:p> </o:p></span></p> <p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;mso-fareast-language:EN-US">Matthias<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;mso-fareast-language:EN-US"><o:p> </o:p></span></p> <div id="mail-editor-reference-message-container"> <div> <div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm"> <p class="MsoNormal" style="mso-margin-top-alt:0cm;margin-right:0cm;margin-bottom:12.0pt;margin-left:36.0pt"> <b><span style="font-size:12.0pt;color:black">From: </span></b><span style="font-size:12.0pt;color:black">cp2k@googlegroups.com <cp2k@googlegroups.com> on behalf of Léon Luntadila Lufungula <Leon.luntadilalufungula@uantwerpen.be><br> <b>Date: </b>Tuesday, 20 June 2023 at 15:09<br> <b>To: </b>cp2k <cp2k@googlegroups.com><br> <b>Subject: </b>[CP2K:18941] Re: k-points vs. supercell approach<o:p></o:p></span></p> </div> <p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt">Dear all,<o:p></o:p></span></p> <div> <p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt"><o:p> </o:p></span></p> </div> <div> <p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt">I am currently continuing with k-point sampling as this method is much faster than the supercell calculations. However, I still don't quite understand why/how this is the case... On most of the posts I read on this forum, people state that the supercell approach should preferably be used as this is the standard in CP2K, so I don't understand why there is such a large difference in favor of k-point sampling in my case. Could anyone confirm/deny that this could be normal behaviour? I still would prefer to use the supercell approach as it has more functionalities, but I can't consider it a valid option if the computational cost is so much larger than the k-points approach...<o:p></o:p></span></p> </div> <div> <p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt"><o:p> </o:p></span></p> </div> <div> <p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt">Kind regards,<o:p></o:p></span></p> </div> <div> <p class="MsoNormal" style="mso-margin-top-alt:0cm;margin-right:0cm;margin-bottom:12.0pt;margin-left:36.0pt"> <span style="font-size:11.0pt">Léon<o:p></o:p></span></p> </div> <div> <div> <p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt">On Monday, 19 June 2023 at 14:18:48 UTC+2 Léon Luntadila Lufungula wrote:<o:p></o:p></span></p> </div> <blockquote style="border:none;border-left:solid #CCCCCC 1.0pt;padding:0cm 0cm 0cm 6.0pt;margin-left:4.8pt;margin-right:0cm"> <p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt">Dear CP2K community,<o:p></o:p></span></p> <div> <p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt"><o:p> </o:p></span></p> </div> <div> <p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt">I'm quite new to CP2K and I am trying to build my input files step-by-step to eventually do calculations on modified surfaces. Currently I'm still doing single point calculations on my bulk structure (anatase TiO2) to optimize the calculation parameters. I have already converged the values of the CUTOFF and REL_CUTOFF parameters and was now looking at comparing k-point sampling to gamma point calculations within the supercell approach. <o:p></o:p></span></p> </div> <div> <p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt"><o:p> </o:p></span></p> </div> <div> <p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt">I was initially thinking about using the supercell approach as some things are not yet implemented for k-points, such as the OT method for example, but I noticed that supercell calculations are considerably slower than k-point calculations. I have attached the input and output files for both approaches for the largest cell/k-mesh I have used, which is 5x5x2. The k-point calculation only took 14.342s, whereas the supercell calculation took a whopping 649.442s...<o:p></o:p></span></p> </div> <div> <p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt"><o:p> </o:p></span></p> </div> <div> <p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt">So my question is if I should just continue with k-points sampling or if there is something wrong with my inputs which results in the large difference in calculation time? The k-point calculation also throws a warning "*** WARNING in cryssym.F:165 :: Symmetry library SPGLIB not available ***", but I also don't know if this may be the reason for the discrepency or if I may ignore this warning.<o:p></o:p></span></p> </div> <div> <p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt"><o:p> </o:p></span></p> </div> <div> <p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt">Any help would be greatly appreciated!<o:p></o:p></span></p> </div> <div> <p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt"><o:p> </o:p></span></p> </div> <div> <p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt">Kind regards,<o:p></o:p></span></p> </div> <div> <p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt">Léon<o:p></o:p></span></p> </div> </blockquote> </div> <p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt">-- <br> You received this message because you are subscribed to the Google Groups "cp2k" group.<br> To unsubscribe from this group and stop receiving emails from it, send an email to <a href="mailto:cp2k+unsubscribe@googlegroups.com">cp2k+unsubscribe@googlegroups.com</a>.<br> To view this discussion on the web visit <a href="https://groups.google.com/d/msgid/cp2k/3e2ebd58-9a77-45b2-8d4a-204fd049bae3n%40googlegroups.com?utm_medium=email&utm_source=footer"> https://groups.google.com/d/msgid/cp2k/3e2ebd58-9a77-45b2-8d4a-204fd049bae3n%40googlegroups.com</a>.<o:p></o:p></span></p> </div> </div> </div> </body> </html> <p></p> -- <br /> You received this message because you are subscribed to the Google Groups "cp2k" group.<br /> To unsubscribe from this group and stop receiving emails from it, send an email to <a href="mailto:cp2k+unsubscribe@googlegroups.com">cp2k+unsubscribe@googlegroups.com</a>.<br /> To view this discussion on the web visit <a href="https://groups.google.com/d/msgid/cp2k/ZRAP278MB082769A4309F4FABFB382D3EF45CA%40ZRAP278MB0827.CHEP278.PROD.OUTLOOK.COM?utm_medium=email&utm_source=footer">https://groups.google.com/d/msgid/cp2k/ZRAP278MB082769A4309F4FABFB382D3EF45CA%40ZRAP278MB0827.CHEP278.PROD.OUTLOOK.COM</a>.<br />