<div dir="ltr" style="color: rgb(34, 34, 34); font-family: Arial, Helvetica, sans-serif; font-size: small;">Thank you, Ramanish, for looking into this.</div><div style="color: rgb(34, 34, 34); font-family: Arial, Helvetica, sans-serif; font-size: small;">I tried many options with DFT, but nothing worked for me.</div><div style="color: rgb(34, 34, 34); font-family: Arial, Helvetica, sans-serif; font-size: small;">However, when I do use the biasing potential as in the provided example (<a href="https://www.cp2k.org/howto:gemc" target="_blank" style="color: rgb(17, 85, 204);">https://www.cp2k.org/howto:gemc</a>), then everything seems to be working fine. </div><div style="color: rgb(34, 34, 34); font-family: Arial, Helvetica, sans-serif; font-size: small;">A complete input file with a biasing potential is attached.</div><div style="color: rgb(34, 34, 34); font-family: Arial, Helvetica, sans-serif; font-size: small;">I hope this could help to track down the problem.</div><div style="color: rgb(34, 34, 34); font-family: Arial, Helvetica, sans-serif; font-size: small;"><br /></div><div style="color: rgb(34, 34, 34); font-family: Arial, Helvetica, sans-serif; font-size: small;">Thank you,</div><div style="color: rgb(34, 34, 34); font-family: Arial, Helvetica, sans-serif; font-size: small;">Slava</div><br /><div class="gmail_quote"><div dir="auto" class="gmail_attr">On Wednesday, August 2, 2023 at 3:30:47 PM UTC-4 sing...@umn.edu 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;"><div>Hi Slava, <br></div><div>I ran your files with the BLYP functional and PBE functional. You prediction was correct, I did see the density of the two phases becoming the same (see attached files). Dashed line denotes the density of box1 and the solid line denotes the density of box2.<br></div><div><br></div><div><img alt="Capture.PNG" width="407px" height="404.268px" src="https://groups.google.com/group/cp2k/attach/117a26f4fda6e/Capture.PNG?part=0.2&view=1"></div><div><br></div><div><img alt="Capture.PNG" width="420px" height="416px" src="https://groups.google.com/group/cp2k/attach/117a26f4fda6e/Capture.PNG?part=0.1&view=1"></div><div><br></div><div><br></div><div>Previously I was suspecting the the critical temperature of BLYP-water is lower than 650 K and that's why we see same density for the two boxes at 473 K, however, to my surprise, we observe the same result for PBE-water, which is supposed to have a Tc much higher than 650 K.
I will need to do some more tests to check this particular behavior. I
will run the VLE simulation with some other combinations of
basis_set/cutoff/functional.
</div><div><br></div><div>Best,</div><div>Ramanish<br></div><div><br></div><div><br></div><br><div class="gmail_quote"><div dir="auto" class="gmail_attr">On Monday, July 31, 2023 at 5:10:24 PM UTC-5 <a href data-email-masked rel="nofollow">sing...@umn.edu</a> 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"><div>Thanks for providing your files Slava. I will run for this case.</div><div><br></div><div>I am not sure if FIST can handle polarizable FF. I guess you can still estimate and come up with a non-
polarizable FF to be used in FIST (pre-sampling).</div><div>I will let you know what I get from running your water files.<br></div><br><div class="gmail_quote"><div dir="auto" class="gmail_attr">On Saturday, July 29, 2023 at 1:02:50 PM UTC-5 Vyacheslav Bryantsev 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 Ramanish,<div><br></div><div>Please find a complete input file attached to this email.</div><div>It does take some time to see the problem. After a few hours run on 3 intel nodes (36 cores) 12 water molecules moved from one box (liquid) to the other (gas).</div><div>This would continue until about an equal density in each box. </div><div><br></div><div>I get your point about having a decent force field for doing pre-sampling. </div><div>Would it be possible to use a polarizable force filed (PIM model) in the FIST module of CP2K? This is for modeling liquid AlCl3 consisting of pure Al2Cl6 dimers. The PIM force field is available for Al2Cl6.<br><br></div><div>Thank you,</div><div>Slava</div><div class="gmail_quote"><div dir="auto" class="gmail_attr">On Friday, July 28, 2023 at 10:55:32 PM UTC-4 <a rel="nofollow">sing...@umn.edu</a> 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"><div>Moreover, I would like to add that people experienced in FPMC using CP2K have told me that it does not matter much if you do not have a very good force field for your molecules. The biasing potential (ff) is more or less used to avoid overlaps during pre-sampling. You could estimate the epsilon, sigma, and charges using established FFs and the bond and angle constants can be estimated by fitting a parabolic function to the bond length and angle energy scan (you could do that in Gaussian). <br></div><div><br></div><div>But, as I do not know about your system, I do not know if it would still be applicable for the molecules you want to simulate.</div><div><br></div><div>Best,</div><div>Ramanish<br></div><br><div class="gmail_quote"><div dir="auto" class="gmail_attr">On Friday, July 28, 2023 at 9:49:56 PM UTC-5 <a rel="nofollow">sing...@umn.edu</a> 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"><div>Hi Slava, <br></div><div><br></div><div>Thanks for explaining the issue. I think I can try to run for this case and see if I face the same issue. Can you please tell me after how many steps you see the densities of the two boxes becoming nearly equal?</div><div><br></div><div>Best,</div><div>Ramanish<br></div><br><div class="gmail_quote"><div dir="auto" class="gmail_attr">On Friday, July 28, 2023 at 7:37:39 PM UTC-5 Vyacheslav Bryantsev 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 Ramanish,<div><br></div><div>Thank you for your comments and a suggestion. </div><div>I am looking for a way to run GEMC simulations in the case when we do not have a good force field.</div><div>After I turned off the LBIAS and made the DFT method exactly the same in two boxes, I still experience the same problem of getting water distributed about equally between the two phases. </div><div>The two boxes input files along with the output <i>mc_molecules</i> file showing a drift of water molecules from one box to the other are attached. </div><div>Again, if the force field is used in the second box, as in the provided example, <a href="https://www.cp2k.org/howto:gemc" rel="nofollow" style="color:rgb(26,115,232)" target="_blank" data-saferedirecturl="https://www.google.com/url?hl=en&q=https://www.cp2k.org/howto:gemc&source=gmail&ust=1691114994325000&usg=AOvVaw0aAE3kRBppQH-cvOStfcx_">https://www.cp2k.org/howto:gemc</a>, there is no issue. </div><div><br></div><div>Therefore, the problem of doing all the MC moves with DFT still persists. </div><div><br></div><div>Thank you,</div><div>Slava</div><div><br></div><div><br><br></div><div class="gmail_quote"><div dir="auto" class="gmail_attr">On Friday, July 28, 2023 at 1:36:05 PM UTC-4 <a rel="nofollow">sing...@umn.edu</a> 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"><div>Hi
Vyacheslav,</div><div><br></div><div>Could you please elaborate why you want to use DFT as biasing potential instead of a force field (FF) (for e.g. TIP3P)?</div><div>My understanding of the biasing potential is that a FF can be used to conduct some computationally cheap steps between two expensive DFT energy evaluations. If LBIAS is on, there will be NMOVES number of steps conducted using the FF you define in the biasing potential. </div><div><br></div><div> <img alt="Capture.PNG" width="682px" height="149px" src="https://groups.google.com/group/cp2k/attach/97b12439f1186/Capture.PNG?part=0.1&view=1"><br></div><div>
At the end of FF pre-sampling NMOVES, there is a comparison between the change in DFT energy and FF energy b/w the initial and final stages to determine if the final state would be accepted or not. <br></div><div><br></div><div>So, if you want to use DFT as your potential for pre-sampling, then it doesn't make sense to have LBIAS on. You can set LBIAS to FALSE, and do all the MC moves based on the DFT potential you define in box1.inp and box2.inp.<br></div><div>Let me know if this makes sense.</div><div><br></div><div>Best,</div><div>Ramanish<br></div><div class="gmail_quote"><div dir="auto" class="gmail_attr">On Wednesday, May 31, 2023 at 6:54:19 AM UTC-5 Vyacheslav Bryantsev 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"><p>Dear CP2K Developers,</p>
<p>I am looking into using the Gibbs Ensemble Monte Carlo
(GEMC) methos in CP2K to compute the liquid-vapor phase diagram using a fully
DFT-based method.</p><p>However, I have problems stabilizing liquid and vapor phases when doing simulations fully ab intio, as described below.</p>
<p>By taking input files for water from</p>
<p><a href="https://www.cp2k.org/howto:gemc" rel="nofollow" target="_blank" data-saferedirecturl="https://www.google.com/url?hl=en&q=https://www.cp2k.org/howto:gemc&source=gmail&ust=1691114994325000&usg=AOvVaw0aAE3kRBppQH-cvOStfcx_">https://www.cp2k.org/howto:gemc</a>
</p>
<p>and minimally changing them, I was able to run the GEMC
model and get sensible results for water. This input utilizes the BLYP
functional and an empirical model for pre-sampling, employing the FIST methods
as specified in the bias_template.inp file. The input files and the output
mc_molecules file are attached. The latter file
shows how many molecules are present during the GEMC run in the liquid
phase (between 64 and 62 water molecules) and the gas phase (between 0 and 2
water molecules).</p>
<p>The problem starts where I substitute the empirical
potential for water with the actual BLYP method in the bias_template.inp file
(I renamed that file to be bias_template-DFT.inp). Please note that I keep all
other settings the same as before, but only substituting the empirical water
model with the DFT model. Now, the
results of simulations have no sense. The water molecules from the liquid box
move to another gas phase box until two phases have roughly the same number of
water molecules. The mc_molecules-DFT
shows this problem. Using fully DFT calculations is supposed to give very
similar or slightly improved results, but instead it produces very different
and unexpected results. It looks like that replacing the FIST model with the
DFT model causes some changes in the program that treats swapping molecules
between the two boxes differently (almost like allowing them to swap only one
way). </p>
<p>At this stage, it is crucial to consult CP2K developers to
identify the factors that contribute to a significant change in the software's
behavior when transitioning from the utilization of the empirical potential in
bias_template.inp to using DFT. </p>
<p><br></p>
<p>Thank you,</p>
<p>Slava </p>
<p>Vyacheslav Bryantsev</p>
<p>Chemical
Separations Group</p>
<p>Oak Ridge National Laboratory</p></blockquote></div></blockquote></div></blockquote></div></blockquote></div></blockquote></div></blockquote></div></blockquote></div></blockquote></div>
<p></p>
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