Hi Matt,<div><br /></div><div>Thanks for the informative answer! I'm a real novice in MD simulations so that obvious explanation didn't occur to me..</div><div><br /></div><div>Kind regards,</div><div>Léon<br /><br /></div><div class="gmail_quote"><div dir="auto" class="gmail_attr">On Tuesday 9 January 2024 at 12:12:39 UTC+1 Matt Watkins wrote:<br/></div><blockquote class="gmail_quote" style="margin: 0 0 0 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">Hi, yes, if you start from a more or less optimised structure you expect around half of the initial kinetic energy to be converted into other modes (potential energy has to rise from the minimum so kinetic energy will decrease).<div>To just get a ball park temperature you can use the temperature rescaling algorithm to just rescale the kinetic energy if it drops too low.<br><div>Matt<br><br></div></div><div class="gmail_quote"><div dir="auto" class="gmail_attr">On Tuesday 9 January 2024 at 10:59:24 UTC Léon Luntadila Lufungula wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Dear all,<div><br></div><div>I'm running some ab initio NVE calculations to determine accurate settings for EPS_SCF, EPS_DEFAULT, CUTOFF and TIMESTEP for my production runs. I think I have found good values for each as I see little to no drift in the energy after 16ps of simulating and the oscillations also seem reasonable (see below for details). However, I see that the average temperature during my simulation is around 157 K, while I set TEMPERATURE to 298.15 K. (see input and ener files in attachment)</div><div><img alt="T.png" width="535px" height="397px" src="https://groups.google.com/group/cp2k/attach/2d5308a840ea1/T.png?part=0.5&view=1"><br></div><div>I know that NVE does not keep the temperature constant, but is it normal that it is nearly half of the set temperature? Any comments on this would be greatly appreciated!</div><div><br></div><div>MD convergence details (comments on this part are always welcome):</div><div><font color="#808080"><span style="font-family:Consolas,"Courier New",monospace;white-space:pre">The extrapolated drift per ns is: </span><span style="font-family:Consolas,"Courier New",monospace;white-space:pre"> 0.0001415478264154313 a.u </span><span style="font-family:Consolas,"Courier New",monospace;white-space:pre"> 44.697268403725126 K </span><span style="font-family:Consolas,"Courier New",monospace;white-space:pre"> </span><span style="font-family:Consolas,"Courier New",monospace;white-space:pre">The oscillations (standard deviation) of the energy is: </span><span style="font-family:Consolas,"Courier New",monospace;white-space:pre"> 2.6854768188532883e-05 a.u. </span><span style="font-family:Consolas,"Courier New",monospace;white-space:pre"> </span><span style="font-family:Consolas,"Courier New",monospace;white-space:pre">The average kinetic energy is: </span><span style="font-family:Consolas,"Courier New",monospace;white-space:pre"> 0.06610813204255318 a.u. </span><span style="font-family:Consolas,"Courier New",monospace;white-space:pre"> </span><span style="font-family:Consolas,"Courier New",monospace;white-space:pre">The average CPU time is: </span><span style="font-family:Consolas,"Courier New",monospace;white-space:pre"> 8.164207377190335 </span><span style="font-family:Consolas,"Courier New",monospace;white-space:pre"> </span><span style="font-family:Consolas,"Courier New",monospace;white-space:pre">The drift per ps is 0.0002 % of the kinetic energy. </span><span style="font-family:Consolas,"Courier New",monospace;white-space:pre">The oscillations are 0.0406 % of the kinetic energy.</span></font><br></div><div><font color="#808080"><span style="font-family:Consolas,"Courier New",monospace;white-space:pre"><img alt="E.png" width="535px" height="383px" src="https://groups.google.com/group/cp2k/attach/2d5308a840ea1/E.png?part=0.3&view=1"><img alt="U_and_E.png" width="535px" height="400px" src="https://groups.google.com/group/cp2k/attach/2d5308a840ea1/U_and_E.png?part=0.1&view=1"><br></span></font></div><div><font color="#000000">The time until equilibration was chosen to be 5ps based on the figures above and all mentioned quantities above have been calculated from 5ps to the final step of the simulation (~16ps).</font></div><div><font color="#000000">Drift was calculated by taking the difference in the cumulative average of the constant of motion over the equilibrium period (5-16ps) and dividing by the timerange (~11ps) to get the drift per ps. This was then multiplied by 1000 to get the drift per ns.</font></div><div><font color="#000000">The oscillations were calculated by taking the standard deviation of the constant of motion over the equilibrium period.</font></div><div><font color="#000000">As instructed by the <a href="https://manual.cp2k.org/trunk/methods/sampling/molecular_dynamics.html" rel="nofollow" target="_blank" data-saferedirecturl="https://www.google.com/url?hl=en-GB&q=https://manual.cp2k.org/trunk/methods/sampling/molecular_dynamics.html&source=gmail&ust=1704886776468000&usg=AOvVaw3mKdyNxpfaKStC9vEpJ88n">manual</a> in the section of MD Convergence, the drift per ps and oscillations are calculated as percentages of the kinetic energy. As these values are well below 1% and the constant of motion seems to be quite stable in the pictures, I can conclude that the settings are appropriate to maintain stable dynamics. EPS_SCF 6 gave a significant drift, therefore EPS_SCF 7 was chosen. I'm also looking into lower values for EPS_DEFAULT to reduce the CPU time.</font></div><div><font color="#000000"><br></font></div><div><font color="#000000">If someone has comments or suggestions on my way of calculating and interpreting the drift and oscillations, I'd be happy to hear them!</font></div><div><font color="#000000"><br></font></div><div><font color="#000000">Best wishes for 2024!</font></div><div><font color="#000000"><br></font></div><div><font color="#000000">Kind regards,</font></div><div><font color="#000000">Léon</font></div><div><font color="#808080"><span style="font-family:Consolas,"Courier New",monospace;white-space:pre"><br></span></font></div></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/c9f077ab-1e8c-4292-b722-4c7939af0b03n%40googlegroups.com?utm_medium=email&utm_source=footer">https://groups.google.com/d/msgid/cp2k/c9f077ab-1e8c-4292-b722-4c7939af0b03n%40googlegroups.com</a>.<br />