Thanks for the reply Matthias. I've had moderate success following what you suggested.<div><br></div><div>One issue that still persists, however, is that for some calculations I can only get convergence by using PLUS_U_METHOD LOWDIN. For example, MnO with Ueff=1.75eV, diagonalization and small smearing (T=100). I've tried using diagonalization and OT with MULLIKEN to get convergence, but sometimes LOWDIN seems to be the only way. Unfortunately, Lowdin does not support forces, so relaxations are out of the question. </div><div><br></div><div>Do you have a suggestion for how to work around this?<br><div><br></div><div>-Nick<br><br></div></div><div class="gmail_quote"><div dir="auto" class="gmail_attr">On Friday, April 16, 2021 at 11:00:09 PM UTC-7 Matthias Krack 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 lang="EN-US" link="blue" vlink="purple"> <div> <p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d">Hello Nick<u></u><u></u></span></p> <p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d"><u></u> <u></u></span></p> <p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d">I do not recommend the use of the PLUS_U_METHOD MULLIKEN_CHARGES. Just use the PLUS_U_METHOD MULLIKEN. The Mulliken population analysis can give unphysical orbital occupations, i.e. values greater than one (UKS case) or two (RKS case). Often the maximum occupation is only slightly exceeded and the warning can be ignored safely. You can print the orbital occupations for the orbitals affected by the +U correction with this <a href="https://manual.cp2k.org/cp2k-8_1-branch/CP2K_INPUT/FORCE_EVAL/DFT/PRINT/PLUS_U.html" target="_blank" rel="nofollow" data-saferedirecturl="https://www.google.com/url?hl=en&q=https://manual.cp2k.org/cp2k-8_1-branch/CP2K_INPUT/FORCE_EVAL/DFT/PRINT/PLUS_U.html&source=gmail&ust=1619111544291000&usg=AFQjCNFhqsU73kKezicmWKi4wkPIA_00Ag"> print key</a> at the PRINT_LEVEL medium to check the actual occupation. Note, that the U values found appropriate with PW codes in the literature are not necessarily optimal for CP2K, too. CP2K often gives a similar effect, e.g. impact on the band gap, for smaller U values.<u></u><u></u></span></p> <p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d"><u></u> <u></u></span></p> <p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d">HTH<u></u><u></u></span></p> <p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d"><u></u> <u></u></span></p> <p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d">Matthias<u></u><u></u></span></p> <p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d"><u></u> <u></u></span></p> <div style="border:none;border-left:solid blue 1.5pt;padding:0cm 0cm 0cm 4.0pt"></div></div></div><div lang="EN-US" link="blue" vlink="purple"><div><div style="border:none;border-left:solid blue 1.5pt;padding:0cm 0cm 0cm 4.0pt"> <div> <div style="border:none;border-top:solid #e1e1e1 1.0pt;padding:3.0pt 0cm 0cm 0cm"> <p class="MsoNormal"><b><span lang="DE" style="font-size:11.0pt;font-family:"Calibri",sans-serif">Von:</span></b><span lang="DE" style="font-size:11.0pt;font-family:"Calibri",sans-serif"> <a href data-email-masked rel="nofollow">c...@googlegroups.com</a> <<a href data-email-masked rel="nofollow">c...@googlegroups.com</a>> <b>Im Auftrag von </b>Nicholas Winner<br> <b>Gesendet:</b> Freitag, 16. April 2021 22:57<br> <b>An:</b> cp2k <<a href data-email-masked rel="nofollow">c...@googlegroups.com</a>><br> <b>Betreff:</b> [CP2K:15147] DFT+U unphysical warning<u></u><u></u></span></p> </div> </div> <p class="MsoNormal"><u></u> <u></u></p> <p>Hello all, I am running some DFT+U calculations on Mn-O systems. While I have found a cp2k effective U value in the literature of ~1.3 eV for Mn. I notice that when tuning the value myself, I begin seeing the following warning once the U value reaches 0.5eV.<u></u><u></u></p> <p>*** WARNING in dft_plus_u.F:2006 :: DFT+U energy contibution is negative ***<u></u><u></u></p> <p> *** possibly due to unphysical Mulliken charges! <u></u><u></u></p> <p>Now this is only a warning, not an indication that the calculation is *necessarily* wrong, but it is troubling at least. Especially when my U value is nowhere near the size of lit value. I am using PLUS_U_METHOD MULLIKEN_CHARGES in order to have a marginally more robust solution. Does anyone have experience with how seriously to take this warning? I don't have a frame of reference to know if I should ignore it.<u></u><u></u></p> <p><u></u> <u></u></p> <p>-Nick<u></u><u></u></p> </div></div></div><div lang="EN-US" link="blue" vlink="purple"><div><div style="border:none;border-left:solid blue 1.5pt;padding:0cm 0cm 0cm 4.0pt"><p class="MsoNormal">-- <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">cp...@googlegroups.com</a>.<br> To view this discussion on the web visit <a href="https://groups.google.com/d/msgid/cp2k/f41c9258-21be-4389-a69f-55aab2a808d4n%40googlegroups.com?utm_medium=email&utm_source=footer" target="_blank" rel="nofollow" data-saferedirecturl="https://www.google.com/url?hl=en&q=https://groups.google.com/d/msgid/cp2k/f41c9258-21be-4389-a69f-55aab2a808d4n%2540googlegroups.com?utm_medium%3Demail%26utm_source%3Dfooter&source=gmail&ust=1619111544291000&usg=AFQjCNFT-v_GwBl1c8CCMzHAGtiYa6iS8g"> https://groups.google.com/d/msgid/cp2k/f41c9258-21be-4389-a69f-55aab2a808d4n%40googlegroups.com</a>.<u></u><u></u></p> </div> </div> </div> </blockquote></div>