<html><head><meta http-equiv="content-type" content="text/html; charset=us-ascii"></head><body style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;"><div>Dear Rubee,</div><div><br></div><div>yes, CP2K can in principle be used for geometry optimization of a</div><div>rare-earth-containing molecule on a surface, including spin-polarized DFT+U.</div><div>A system containing 500 to 1500 atoms can be feasible with the GPW method,</div><div>a semilocal functional, suitable pseudopotentials, and sufficient parallel</div><div>computing resources.</div><div><br></div><div>However, the presence of a rare-earth element makes the electronic-structure</div><div>setup more important than the geometry optimizer itself.</div><div><br></div><div>For every element you need a mutually compatible basis set and</div><div>pseudopotential. In particular, verify which rare-earth electrons are included</div><div>in the valence of the selected pseudopotential and whether this is appropriate</div><div>for the oxidation state, bonding, and magnetic properties of interest. Do not</div><div>select a potential only because its element symbol is available.</div><div><br></div><div>DFT+U is activated in the KIND section. For a localized f shell the angular</div><div>momentum is L=3, for example:</div><div><br></div><div> &KIND Ln</div><div> ELEMENT Ln</div><div> BASIS_SET ...</div><div> POTENTIAL ...</div><div> &DFT_PLUS_U</div><div> L 3</div><div> U_MINUS_J [eV] ...</div><div> &END DFT_PLUS_U</div><div> &END KIND</div><div><br></div><div>Here `Ln`, the basis, the potential, and especially U_MINUS_J must be replaced</div><div>by values appropriate to the actual element and method. The U value is not a</div><div>universal atomic constant. It depends on the pseudopotential, basis,</div><div>functional, oxidation state, and target property, and should be justified or</div><div>computed for the intended system.</div><div><br></div><div>The calculation should normally be spin polarized. You should test the</div><div>multiplicity, initial atomic magnetizations, and possibly different initial</div><div>occupations of the localized shell. Rare-earth DFT+U calculations can converge</div><div>to different metastable occupation patterns, so SCF convergence alone does</div><div>not demonstrate that the physically relevant electronic state has been</div><div>obtained.</div><div><br></div><div>If spin-orbit coupling is important for the selected element or observable,</div><div>DFT+U by itself does not replace it. The Hamiltonian used for the structural</div><div>and STM calculations should be chosen consistently with the required physical</div><div>accuracy.</div><div><br></div><div>For a system of this size, I recommend first validating the setup on a smaller</div><div>model:</div><div><br></div><div>1. converge the basis sets, cutoffs, and pseudopotential;</div><div>2. compare relevant spin and DFT+U occupation states;</div><div>3. determine an appropriate U value;</div><div>4. check the slab thickness, vacuum, and lateral cell;</div><div>5. test whether Gamma-point sampling is sufficient;</div><div>6. only then scale to the complete 500-1500 atom system.</div><div><br></div><div>The subsequent STM calculation is also possible in principle, but CP2K's</div><div>current STM print section has important limitations. It uses a</div><div>Tersoff-Hamann-type post-processing of the Kohn-Sham states, is currently</div><div>implemented only for Gamma-point calculations, and sums the alpha- and</div><div>beta-spin contributions into one cube. Positive-bias images additionally</div><div>require enough unoccupied states through NLUMO.</div><div><br></div><div>A large real-space surface supercell may justify Gamma-point sampling, but</div><div>this must be checked against a smaller k-point-converged model. If explicit</div><div>k-point sampling is required for the electronic structure, CP2K's current STM</div><div>printer cannot directly generate the corresponding STM cubes.</div><div><br></div><div>Therefore, CP2K is a suitable candidate, but the answer depends on the actual</div><div>rare-earth element, pseudopotential, oxidation and spin state, functional,</div><div>U value, surface, and available hardware. Providing these details would make</div><div>it possible to recommend a more specific setup.</div><div><br></div><div>Best regards,</div><div>Thomas</div><div><br><blockquote type="cite"><div>Am 06.08.2026 um 16:34 schrieb Rubee Soni <rubee1702@gmail.com>:</div><br class="Apple-interchange-newline"><div><p>Dear All,</p><p>Can we use CP2K for the geometry optimization of a system containing a rare-earth atom? I would like to optimize the geometry of a molecule containing one rare-earth element adsorbed on a surface. The calculations would need to include DFT+U to properly describe the highly localized electrons of the rare-earth atom.</p><p>The systems I am interested in range from approximately 500 to 1500 atoms. In addition to geometry optimization, I am also planning to perform STM simulations of these systems. Would CP2K be suitable for carrying out both the geometry optimization and subsequent STM simulations for systems of this size?</p><p>Thank you.<br><br>Best,</p><p>Rubee</p><div><br class="webkit-block-placeholder"></div> -- <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 visit <a href="https://groups.google.com/d/msgid/cp2k/2971e381-caca-4a2f-8c06-1b42d6768972n%40googlegroups.com?utm_medium=email&utm_source=footer">https://groups.google.com/d/msgid/cp2k/2971e381-caca-4a2f-8c06-1b42d6768972n%40googlegroups.com</a>.<br> </div></blockquote></div><br></body></html> <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 visit <a href="https://groups.google.com/d/msgid/cp2k/924764C5-218F-42A7-9AF3-00409095B5D2%40gmail.com?utm_medium=email&utm_source=footer">https://groups.google.com/d/msgid/cp2k/924764C5-218F-42A7-9AF3-00409095B5D2%40gmail.com</a>.<br />