<div>Dear Mr. Hutter,<br></div><div><br></div><div>thank you for your reply!</div><div><br></div><div>@Literature</div><div>I am reading now 2 papers:</div><div>* Nicola A. Spaldin DOI: 10.1016/j.jssc.2012.05.010 -- more about the problem of calculation dipole moment (polarization)<br></div><div>* Konstantin N. Kudin, Roberto Car, and Raffaele Resta DOI: 10.1063/1.2743018 <br></div><div><br></div><div>Can you, please, suggest more relevant literature?<br></div><div><br></div><div>@Reference point</div><div>Are you talking about this: https://manual.cp2k.org/cp2k-8_1-branch/CP2K_INPUT/FORCE_EVAL/DFT/PRINT/MOMENTS.html#REFERENCE_POINT ?</div><div><br></div><div>I see there 4 points which could be a good options, however, all of them has good default values:</div><div><br></div><div>* REFERENCE <span><span><span><span>
Default value:
<span>ZERO</span></span></span></span></span><span><span><span><span></span><span><span></span></span></span></span></span><br>* REFERENCE_2 <span><span><span><span>
Default value:
<span>ZERO</span></span></span></span></span><br>* REFERENCE_POINT Default values:
<span>0.00000000E+000 0.00000000E+000 0.00000000E+000</span><span><span><span><span><span></span></span></span></span></span><br>* REFERENCE_POINT_2 <span><span><span><span>Default values:
<span>0.00000000E+000 0.00000000E+000 0.00000000E+000</span><span></span></span></span></span></span></div><div><br></div><div>I am not sure that some others values can bring some benefits for the simple cubic system with 64 molecules (sparely distributed).<br></div><div><br></div><div><br></div><div>With best regards,</div><div>Alexander Kazakov<br></div><br><div class="gmail_quote"><div dir="auto" class="gmail_attr">понедельник, 28 июня 2021 г. в 10:32:08 UTC+2, jgh: <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
<br>
<br>dipole moments in periodic systems are only defined modulo 2Pi/L
<br>(for simple cubic systems). The value is calculated through a
<br>complex Logarithm that can lead to results on different branches
<br>with offsets. Have a look at the literature for more complete
<br>discussions and more general formulas.
<br>The choice of reference point can lead to a reduced number of
<br>"jumps" and easier post-processing.
<br>
<br>regards
<br>
<br>Juerg Hutter
<br>--------------------------------------------------------------
<br>Juerg Hutter Phone : <a href="tel:+41%2044%20635%2044%2091" value="+41446354491" target="_blank" rel="nofollow">++41 44 635 4491</a>
<br>Institut für Chemie C FAX : <a href="tel:+41%2044%20635%2068%2038" value="+41446356838" target="_blank" rel="nofollow">++41 44 635 6838</a>
<br>Universität Zürich E-mail: <a href data-email-masked rel="nofollow">h...@chem.uzh.ch</a>
<br>Winterthurerstrasse 190
<br>CH-8057 Zürich, Switzerland
<br>---------------------------------------------------------------
<br>
<br>-----<a href data-email-masked rel="nofollow">c...@googlegroups.com</a> wrote: -----
<br>To: "cp2k" <<a href data-email-masked rel="nofollow">c...@googlegroups.com</a>>
<br>From: "Alexander Kazakov"
<br>Sent by: <a href data-email-masked rel="nofollow">c...@googlegroups.com</a>
<br>Date: 06/25/2021 03:58PM
<br>Subject: [CP2K:15636] Re: Dipole Moment. Help wanted.
<br>
<br>Yeap. Topology is here.
<br>
<br>
<br>Best regards,
<br>Alexander Kazakov
<br>
<br>пятница, 25 июня 2021 г. в 15:55:24 UTC+2, Alexander Kazakov:
<br>Dear CP2K community,
<br>
<br>I am simulating 64 molecules of water using DFT in NVT ensemble using PBC. I interested in dipole moment values as a trajectory with MD step.
<br>
<br>Here is what I have so far:
<br>
<br>
<br>You can see 4 curves: 3 of them are components (x,y,z) and the last one is the length of the vector. All of them are functions of the MD step.
<br>
<br>Let's focus on curves that correspond to x and z components. You can see that there is a kind of "jump" at certain ranges. These "jump" actually resemble a crossing kind of boundary condition. You can see how well it is fit the blue curve on the top to the bottom (the same is applied for the purple curve).
<br>Personally, I think it is indeed a kind of boundary condition, however, I have no idea what 30 means.
<br>
<br>Then I found these certain steps where it happens:
<br>
<br>MD STEP
<br>26
<br> X= -19.18787840 Y= 5.85693184 Z= 29.55510907 Total= 35.72090144
<br>27
<br> X= -19.18076162 Y= 5.52351367 Z= -29.53176935 Total= 35.64458192
<br>
<br>So the z component apparently changed the sign. So I thought that something horrible happened in the system. I plotted position atom change as a function of atom ID:
<br>(if the picture has very poor quality, please find enclosed pdf version)
<br>
<br>
<br>Alright, there is an interesting plot here. We see the different amplitude of change through the atom IDs. So first 2/3 of the curve correspond to hydrogen atoms displacement, whereas the last part corresponds to oxygen atoms.
<br>
<br>So back to questions. Could you tell me, why some components of the dipole moment "jump" changing the sigh? Is it possible to force dipole moment to stay on one side of the "boundary"? There are no doubts that hydrogen atoms should move "actively" than oxygen atoms, but I don't understand what has changed dramatically in the system. Lastly, if you can give me a hint for number 30 in the boundary (see figure), I would be thankful!
<br>
<br>As because I check CP2K 6.1, 7.1, 8.1, and 8.2 and I got the same behaviour with jumps I assume that I did something wrong or misunderstand something.
<br>Please find enclosed FORCE_EVAL section of my script.
<br>
<br>Additionally I am sending topology of the system.
<br>
<br>If additionaly information is required, please let me know.
<br>
<br>Best regards,
<br>Alexander Kazakov
<br>
<br>
<br>
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<br>
<br>[attachment "W64.xyz" removed by Jürg Hutter/at/UZH]
<br></blockquote></div>