<div dir="ltr">Dear Lin,<div><br></div><div><a href="https://manual.cp2k.org/trunk/CP2K_INPUT/MOTION/MD.html#TIMESTEP">https://manual.cp2k.org/trunk/CP2K_INPUT/MOTION/MD.html#TIMESTEP</a> Timestep section tells us:<br></div><div><br></div><div><table class="gmail-default" summary="keyword_description" style="table-layout:fixed;width:1287px;font-family:"Times New Roman""><tbody><tr><td class="gmail-r" style="width:958px">Default value: <code class="gmail-upper" style="text-transform:uppercase">5.00000000E-001</code></td></tr><tr><td class="gmail-l" style="width:319px"></td><td class="gmail-r" style="width:958px"><a href="https://manual.cp2k.org/trunk/units.html" style="text-decoration-line:none">Default unit:</a><code> [fs]<br><br></code></td></tr></tbody></table><table class="gmail-default" summary="keyword_description" style="table-layout:fixed;width:1287px;font-family:"Times New Roman""><tbody><tr><td class="gmail-l" style="width:319px">So timestep is in fs. As for suggested values, I don't know. I didn't manage. To get higher excitation energies you will need a smaller timestep, otherwise these are "invisible" in the signal.<br><br>Steps means how many timesteps are calculated (so 100 steps with stepsize 1 would be 100 fs), more timesteps means less uncertainty in your Fourier transform, giving more distinct peaks (I think).<br><br>To figure out what the right timestep and steps are, you can take a look at some literature and compare with experts that you get the same value. And then also play around with stepsize and steps to see if your spectrum changes a lot. The spectrum should be independent of stepsize if you are around the right region. <br><br>Mario</td><td class="gmail-r" style="width:958px"><code><br></code></td></tr></tbody></table></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sat, Jul 11, 2020 at 10:11 AM <a href="mailto:xio...@gmail.com">xio...@gmail.com</a> <<a href="mailto:xiongl...@gmail.com">xiongl...@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><br>Dear Mario,<div> </div><div><div>Thank you very much for your help. In fact, I have just started using cp2k software. I have a question before you reply to me, that is why there is no *dat file in my output files. But now I understand that I need to add the 'FILENAME output' keyword in the 'MOMENTS' subsection.</div><div><br></div><div>Still, I have one question to ask you: What does the value of 'STEPS' in the 'MD' section of rt-TDDFT specifically mean? The interpretation of the official website is ambiguous. To calculate the spectra of different systems, do you have any suggestions for setting the STPES and TIMESTEP keywords?</div></div><div><br></div><div>Best wishes,</div><div><br></div><div>Lin</div><div class="gmail_quote"><div dir="auto" class="gmail_attr">在2020年7月11日星期六 UTC+8 上午2:29:44<<a href="mailto:mar...@student.uva.nl" target="_blank">mar...@student.uva.nl</a>> 写道：<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div>Dear Lin,</div><div><br></div><div>I am not at all an expert on the issue, but I do have this example file online. Also once you obtain the dipole moment as a function of time, you can perform a Fourier transform of the data. I have attached a python script to transform the data. Make sure it works properly yourself and make sure you read about why this works :-). The output you want for the spectrum should be called something like ch2o_pbe_rtp-output-moments.dat. I tried this for quantum dots and it didn't work. Maybe different timestep and basis/ potential are needed. Also, I don't know if the script can handle these small numbers. </div><div><br></div><div>Good luck,</div><div><br></div><div>Mario</div><div><br></div><div><br></div></div><br><div class="gmail_quote"></div><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, Jul 10, 2020 at 4:03 PM lin xiong <<a rel="nofollow">xio...@gmail.com</a>> wrote:<br></div></div><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><blockquote style="margin:0px 0px 0px 40px;border:medium none;padding:0px"></blockquote>Hi all,<br> <br><blockquote style="margin:0px 0px 0px 40px;border:medium none;padding:0px"></blockquote> Recently I learned that cp2k code has two ways to calculate the absorption spectrum, namely real time propagation TDDFT and TDDFPT. I would like to ask some questions about using rt-TDDFT to calculate the spectra.<div><br><div> 1. First of all, I would like to ask if my input file is correct? If the input file is correct, then there are two additional questions: 2. In which file (as shown in the figure below) is the data used to draw the spectrum stored? 3. How to use these data to plot the spectrum? </div></div><div><br></div><p style="text-align:center;clear:both"><img src="https://groups.google.com/group/cp2k/attach/10bc5f7cc4f80/25.jpg?part=0.0.1&view=1" alt="25.jpg" style="margin-left: 1em; margin-right: 1em;" title="" width="320" height="113"></p><div><br></div></div> <p></p></blockquote></div><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"> -- <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 rel="nofollow">cp...@googlegroups.com</a>.<br> To view this discussion on the web visit <a href="https://groups.google.com/d/msgid/cp2k/75ac4790-b50d-4289-b5aa-a8385584f19ao%40googlegroups.com?utm_medium=email&utm_source=footer" rel="nofollow" target="_blank">https://groups.google.com/d/msgid/cp2k/75ac4790-b50d-4289-b5aa-a8385584f19ao%40googlegroups.com</a>.<br> </blockquote></div> </blockquote></div> <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:cp...@googlegroups.com" target="_blank">cp...@googlegroups.com</a>.<br> To view this discussion on the web visit <a href="https://groups.google.com/d/msgid/cp2k/316ea557-701d-4fc6-8034-4057599edea0n%40googlegroups.com?utm_medium=email&utm_source=footer" target="_blank">https://groups.google.com/d/msgid/cp2k/316ea557-701d-4fc6-8034-4057599edea0n%40googlegroups.com</a>.<br> </blockquote></div>