Dear Thomas,<div><br></div><div>Thanks for your response!</div><div><br></div><div>My reasoning for a cutoff much lower than the half box size arises from these two papers:</div><div><br></div><div>Yonetani, JCP, 2006: https://doi.org/10.1063/1.2198208</div><div>Spoel, Marren, JCTC, 2006: https://doi.org/10.1021/ct0502256</div><div><br></div><div>where it is suggested that the larger cutoff does not implies accuracy and can create "artifacts" in bulk water simulations, particularly if the force field was not parameterized for the larger ranges. I don't have experience in simulating larger bulk water box (such as the one I mentioned before), but does this reasoning makes sense or is there alternative explanation for this? Do you have any particular recommendations in such scenarios? Not specifically for QM/MM, but for FIST calculations as well.</div><div><br></div><div>Best Regards,</div><div>Mayank Dodia</div><div><br><br></div><div class="gmail_quote"><div dir="auto" class="gmail_attr">On Thursday, July 23, 2020 at 9:39:11 PM UTC+2 tkuehne 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 style="word-wrap:break-word;line-break:after-white-space">Dear Mayank, <div><br></div><div>the keyword EWALD_PRECISION in the same section already controls the real-space cutoff, </div><div>i.e. RCUT is only necessary to explicitly override the override the value and as such only useful </div><div>when you know what you are doing. </div><div><br></div><div>Best, </div><div>Thomas<br><div><br><blockquote type="cite"></blockquote></div></div></div><div style="word-wrap:break-word;line-break:after-white-space"><div><div><blockquote type="cite"><div>Am 22.07.2020 um 12:41 schrieb mayank...@<a href="http://gmail.com" target="_blank" rel="nofollow" data-saferedirecturl="https://www.google.com/url?hl=en&q=http://gmail.com&source=gmail&ust=1595630143125000&usg=AFQjCNHBnkPHIVKRkfzmLZNjDFnAhKV1Yw">gmail.com</a> <<a href data-email-masked rel="nofollow">may...@gmail.com</a>>:</div><br></blockquote></div></div></div><div style="word-wrap:break-word;line-break:after-white-space"><div><div><blockquote type="cite"><div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><div><div dir="ltr">Hi,<div><br></div><div>Sorry for reposting, but is there someone who can elaborate on the RCUT parameter in the QM/MM Multipole section?</div><div><br></div><div><a href="https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/QMMM/PERIODIC/MULTIPOLE.html" target="_blank" rel="nofollow" data-saferedirecturl="https://www.google.com/url?hl=en&q=https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/QMMM/PERIODIC/MULTIPOLE.html&source=gmail&ust=1595630143125000&usg=AFQjCNE1a_jJwwDJXTnh9rdEqnQRhTVDYA">https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/QMMM/PERIODIC/MULTIPOLE.html</a> <br></div></div></div><div><div></div></div></div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><div><div><div><br></div></div></div></div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none">Best Regards,</div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none">Mayank Dodia</div><div class="gmail_quote" style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><div dir="auto" class="gmail_attr">On Thursday, July 16, 2020 at 1:35:05 PM UTC+2 mayank...@<a href="http://gmail.com/" target="_blank" rel="nofollow" data-saferedirecturl="https://www.google.com/url?hl=en&q=http://gmail.com/&source=gmail&ust=1595630143125000&usg=AFQjCNF9WYw1DDsID9Z82vcX5Lc7mcHjSg">gmail.com</a><span> </span>wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex">Hi,<div><br></div><div>Are there any guidelines to set the RCUT parameter in the QM/MM Multipole section?</div><div><br></div><div><a href="https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/QMMM/PERIODIC/MULTIPOLE.html" rel="nofollow" target="_blank" data-saferedirecturl="https://www.google.com/url?hl=en&q=https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/QMMM/PERIODIC/MULTIPOLE.html&source=gmail&ust=1595630143125000&usg=AFQjCNE1a_jJwwDJXTnh9rdEqnQRhTVDYA">https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/QMMM/PERIODIC/MULTIPOLE.html</a> <br></div><div><br></div><div>Is the RCUT parameter here is equivalent to the FIST EWALD RCUT? In my case I have a larger MM box of 50*40*40 angstroms^3 and a smaller centered QM box of 40*30*30 angstroms^3, so in this case, the Multipole RCUT should be set to 19 angstroms (<R_min/2) or it is okay to set RCUT as same as FIST EWALD RCUT (~9-12 angstroms.)?</div><div><br></div><div>Best Regards,</div><div>Mayank Dodia</div></blockquote></div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><br></div></div></blockquote></div></div></div><div style="word-wrap:break-word;line-break:after-white-space"><div><div><blockquote type="cite"><div><span 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