Thank you so much for your reply ,Lucas. It's a bulk system. So the value of COMVEL_TOL should be set to 0 ?<br><br><div class="gmail_quote"><div dir="auto" class="gmail_attr">在2022年1月8日星期六 UTC+8 01:54:31<Lucas Lodeiro> 写道：<br/></div><blockquote class="gmail_quote" style="margin: 0 0 0 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"><div dir="ltr">Hi,<div><br></div><div>The non zero value at zero frequency is typical when you have a system/molecule with translational and rotational movement.</div><div>It is not clear if you are simulating a single molecule (without PBC) or a bulk system (with PBC). For the former case, you could control both with COMVEL_TOL, ANGVEL_TOL and ANGVEL_ZERO keywords. For the second, the angular movement cannot be controlled and just the translation of COM contributes to the zero frequency value. Also, the "natural" band width of the FFT could affect it when a signal is near zero frequency and its tail reaches the zero frequency.</div><div><br></div><div>About the MD... a timestep of 10 fs is a very huge one... if you have hydrogens, 0.5 fs is the best, and maybe 1.0 fs could work. Also if you are working with a bulk system, 14 ps of AIMD probably is not sufficient to obtain an equilibrated system in term of structure and in terms of thermal energy.</div><div><br></div><div>Regards - Lucas Lodeiro</div></div><br><div class="gmail_quote"></div><div class="gmail_quote"><div dir="ltr" class="gmail_attr">El vie, 7 ene 2022 a las 0:58, Kai (<<a href data-email-masked rel="nofollow">liangzi...@gmail.com</a>>) escribió:<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>
Hello everyone, <br></div><div>I am trying to
<span style="font-weight:normal;font-style:normal;white-space:normal">calculate the vibrational spectrum of an <span style="font-weight:normal;font-style:normal;white-space:normal">inorganic</span>
cluster using TRAVIS. It's simulated for 14 ps with a CSVR timeconstant of 1 ps and 10 fs timestep. I think I get the great shape of the
<span style="font-weight:normal;font-style:normal;white-space:normal">vibrational</span> curve. <b>But it shows a non zero value at 0 cm-1.</b>This should be unreasonable.
<span style="font-style:normal;white-space:normal">What should I do</span>?</span></div><div><span style="font-weight:normal;font-style:normal;white-space:normal"> I guess I should remove the 6 macroscopic degrees of freedom (3x translation, 3x rotation), but how?</span></div><div><span style="font-weight:normal;font-style:normal;white-space:normal"><br></span></div><div><span style="font-weight:normal;font-style:normal;white-space:normal">
Please help me.</span></div><div><span style="font-weight:normal;font-style:normal;white-space:normal">Thanks all.<img alt="power spectrum.png" width="533px" height="408px" src="https://groups.google.com/group/cp2k/attach/c5dd381cf48d2/power%20spectrum.png?part=0.1&view=1"><br>
</span>
</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 href data-email-masked rel="nofollow">cp2k+uns...@googlegroups.com</a>.<br>
To view this discussion on the web visit <a href="https://groups.google.com/d/msgid/cp2k/5737dad8-10cc-496f-b6b8-587067ba7b0cn%40googlegroups.com?utm_medium=email&utm_source=footer" target="_blank" rel="nofollow" data-saferedirecturl="https://www.google.com/url?hl=zh-CN&q=https://groups.google.com/d/msgid/cp2k/5737dad8-10cc-496f-b6b8-587067ba7b0cn%2540googlegroups.com?utm_medium%3Demail%26utm_source%3Dfooter&source=gmail&ust=1641699297805000&usg=AFQjCNGxni37ULPjR2jKELrTgGIMxgUFxA">https://groups.google.com/d/msgid/cp2k/5737dad8-10cc-496f-b6b8-587067ba7b0cn%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: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/55edd57a-6ed2-4621-a086-a2054d60ee34n%40googlegroups.com?utm_medium=email&utm_source=footer">https://groups.google.com/d/msgid/cp2k/55edd57a-6ed2-4621-a086-a2054d60ee34n%40googlegroups.com</a>.<br />