Dear cp2k community,<div><br></div><div>I'm confused about two EXTERNAL_POTENTIAL sections:</div><div><br></div><div><a href="https://manual.cp2k.org/cp2k-9_1-branch/CP2K_INPUT/FORCE_EVAL/EXTERNAL_POTENTIAL.html">https://manual.cp2k.org/cp2k-9_1-branch/CP2K_INPUT/FORCE_EVAL/EXTERNAL_POTENTIAL.html</a></div><div><br></div><div>and</div><div><br></div><div><a href="https://manual.cp2k.org/cp2k-9_1-branch/CP2K_INPUT/FORCE_EVAL/DFT/EXTERNAL_POTENTIAL.html">https://manual.cp2k.org/cp2k-9_1-branch/CP2K_INPUT/FORCE_EVAL/DFT/EXTERNAL_POTENTIAL.html</a></div><div><br></div><div>I notice differences between keywords and subsections and I want to simulate interaction of different solutes in the bulk water with the polarized graphene suface.</div><div><br></div><div>My section within the FORCE_EVAL:<br></div><div><br></div><div>  &EXTERNAL_POTENTIAL<br></div><div>    ATOMS_LIST 61..363                      # applied only on waters present in the system<br>    FUNCTION (A/B)*exp(-Z/Z0)         # potential that decays exponentially<br>    VALUES [eV] -3.0 [angstrom] 1.0 [angstrom] 6.0<br>    PARAMETERS A B Z0<br>  &END EXTERNAL_POTENTIAL<br></div><div><br></div><div>With this setup I noticed that the total energy is lower compared when no external potential is present and water molecules interact in the way I expected.</div><div><br></div><div>So, the questions are:<br>1) Is this the right way to simulate interaction with the electric field that originate from some surface, or should I employ EFIELD keywords or something similar?</div><div>2) Do I need to define EXTERNAL_POTENTIAL section within the DFT section as well, since I don't need some of the specific options there?<br></div><div>3) Could someone explain how PBC are entangled with the EXTERNAL_POTENTIAL?</div><div><br></div><div>Thanks,</div><div>Branislav</div><div><br></div>

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