<div dir="ltr">The Wannier center does not mean the electron is there, because electron is only known by a probability and electrons are indistinguishable. <div>You can think the dipole moment operator is Wannier center multiplying the electron charge. </div><div><br></div><div>For non-periodic electrons, there should be methods just like Wannier functions for periodic electrons. </div><div><br></div><div>FY</div></div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">On Sun, Jan 19, 2025 at 4:24 PM Fangyong Yan <<a href="mailto:fangyongyan2023@gmail.com">fangyongyan2023@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"><div dir="ltr">Dear Hana, <div><br></div><div>Wannier function is only for periodic systems. (see for example, our paper: Infrared Spectroscopy of Li+ Solvation in EmimBF4 and in Propylene Carbonate: Ab Initio Molecular Dynamics and Experiment, JPCB, 2022)</div><div>The wannier center is treated as the expectation value of the position of individual
electrons. That is why we can obtain molecules, or cation with +1 charge, and anion with -1 charge. Because </div><div>all the charges (electrons, nuclei), are integer.</div><div>Wannier function is one way to partition the electron density, there are other methods to partition the charge density. </div><div><br></div><div>For a molecule, the dipole moment is invariant to your chosen origin. For a cation or anion, dipole is dependent on your origin, but the change of dipole is not, and IR intensity is related to the change of dipole. </div><div><br></div><div>Good luck!!</div><div><br></div><div>Fangyong</div><div></div><div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sat, Jan 18, 2025 at 12:40 PM Hana <<a href="mailto:holiaei2@illinois.edu" target="_blank">holiaei2@illinois.edu</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">Hello,<div><br></div><div>I am trying to calculate the dipole moment of my non-periodic system. The system has more than one molecule, and I am interested in calculating both molecular and total dipole moment. Currently, I use two sections (section1: FORCE_EVAL/DFT/LOCALIZE, section 2: FORCE_EVAL/DFT/PRINT/MOMENTS) in my input, as elaborated at the end of this message. Section 2 outputs a total dipole moment of 18.9465 Debye. From section 1 and using the Wannier centers, I get a total dipole moment of 18.9876 Debye. Here is my first question: Is this discrepancy normal? According to CP2K documentation, the first value (from section 2) is based on "simple operator". However, I am not sure what that is, and whether it justifies the discrepancy?</div><div><br></div><div>Also, I have another question. In section 1, I have the TOTAL_DIPOLE and MOLECULAR_DIPOLES subsections as well. The dipole values that I get from these two are completely (orders of magnitude) different from the values mentioned in the previous paragraph (~19 Debye), although I set all the reference points to zero. Moreover, for the molecular dipole, the output file shows zero for most of the atoms, and non-zero values for the rest of them. Therefore, I cannot find the "molecule" concept there. Here is my second question: Am I missing anything when using these two subsections (TOTAL_DIPOLE and MOLECULAR_DIPOLES)?</div><div><br></div><div>Thanks in advance for your help, and sorry for the long message!</div><div><br></div><div><b>section 1:</b></div><div> &LOCALIZE<br> MAX_ITER 1000<br> METHOD JACOBI<br> EPS_LOCALIZATION 1.0E-6<br> &PRINT<br> &WANNIER_CENTERS<br> IONS+CENTERS .TRUE.<br> &END<br> &TOTAL_DIPOLE<br> PERIODIC F<br> REFERENCE ZERO<br> FILENAME total<br> &END<br> &MOLECULAR_DIPOLES<br> PERIODIC F<br> REFERENCE ZERO<br> FILENAME molecular<br> &END<br> &END<br> &END<br></div><div><br></div><div><b>section 2:</b></div><div> &PRINT<br> &MOMENTS</div><div> PERIODIC F<br> REFERENCE ZERO<br> FILENAME dipole<br> &END<br> &END<br></div>
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