<div dir="ltr">Hello Matt,<br><br>Thanks for the prompt answer! Can you direct me to any publication where they have done such tests?<br><br>Regards,<br>Rahul<br><br>On Thursday, January 4, 2018 at 7:19:02 PM UTC+5:30, Matt W wrote:<blockquote class="gmail_quote" style="margin: 0;margin-left: 0.8ex;border-left: 1px #ccc solid;padding-left: 1ex;"><div dir="ltr"><div>Probably it has just been done by checking that the results don't change 'too much' in many cases.<br></div><div><br></div><div>You could run an isolated molecule/cluster and use the <a href="https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/DFT/POISSON/MULTIPOLE.html" target="_blank" rel="nofollow" onmousedown="this.href='https://www.google.com/url?q\x3dhttps%3A%2F%2Fmanual.cp2k.org%2Ftrunk%2FCP2K_INPUT%2FFORCE_EVAL%2FDFT%2FPOISSON%2FMULTIPOLE.html\x26sa\x3dD\x26sntz\x3d1\x26usg\x3dAFQjCNEidoOIDoWhskMPSW1qRaIVAHYsAA';return true;" onclick="this.href='https://www.google.com/url?q\x3dhttps%3A%2F%2Fmanual.cp2k.org%2Ftrunk%2FCP2K_INPUT%2FFORCE_EVAL%2FDFT%2FPOISSON%2FMULTIPOLE.html\x26sa\x3dD\x26sntz\x3d1\x26usg\x3dAFQjCNEidoOIDoWhskMPSW1qRaIVAHYsAA';return true;">MULTIPOLE</a> poisson solver (which is what you get when you use QMMM) and see how that compares to say the <a href="https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/DFT/POISSON/WAVELET.html" target="_blank" rel="nofollow" onmousedown="this.href='https://www.google.com/url?q\x3dhttps%3A%2F%2Fmanual.cp2k.org%2Ftrunk%2FCP2K_INPUT%2FFORCE_EVAL%2FDFT%2FPOISSON%2FWAVELET.html\x26sa\x3dD\x26sntz\x3d1\x26usg\x3dAFQjCNGLqFeqtQAUakQExGe3rn1uqoYPOA';return true;" onclick="this.href='https://www.google.com/url?q\x3dhttps%3A%2F%2Fmanual.cp2k.org%2Ftrunk%2FCP2K_INPUT%2FFORCE_EVAL%2FDFT%2FPOISSON%2FWAVELET.html\x26sa\x3dD\x26sntz\x3d1\x26usg\x3dAFQjCNGLqFeqtQAUakQExGe3rn1uqoYPOA';return true;">WAVELET</a> one, and what cell dimensions are needed.</div><div><br></div><div>Happy new year, too.<br></div><div><br></div><div>Matt<br><br>On Thursday, January 4, 2018 at 6:50:20 AM UTC, Rahul Hardikar wrote:<blockquote class="gmail_quote" style="margin:0;margin-left:0.8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Thanks for the reply Jiang,<br><br>Maybe I should rephrase my question. I understand that GEEP algorithm implementation takes care of the QMMM electrostatic coupling, however that does not give an<br>idea of the box size for QM/MM region. What I am specifically referring to is the following section in QMMM:<br><br>            <big><a href="https://manual.cp2k.org/cp2k-2_6-branch/CP2K_INPUT.html" rel="nofollow" target="_blank" onmousedown="this.href='https://www.google.com/url?q\x3dhttps%3A%2F%2Fmanual.cp2k.org%2Fcp2k-2_6-branch%2FCP2K_INPUT.html\x26sa\x3dD\x26sntz\x3d1\x26usg\x3dAFQjCNFQKl0t_EL7kaZdK_hCYF8cH3lpWQ';return true;" onclick="this.href='https://www.google.com/url?q\x3dhttps%3A%2F%2Fmanual.cp2k.org%2Fcp2k-2_6-branch%2FCP2K_INPUT.html\x26sa\x3dD\x26sntz\x3d1\x26usg\x3dAFQjCNFQKl0t_EL7kaZdK_hCYF8cH3lpWQ';return true;">CP2K_INPUT</a> /
               <a href="https://manual.cp2k.org/cp2k-2_6-branch/CP2K_INPUT/FORCE_EVAL.html" rel="nofollow" target="_blank" onmousedown="this.href='https://www.google.com/url?q\x3dhttps%3A%2F%2Fmanual.cp2k.org%2Fcp2k-2_6-branch%2FCP2K_INPUT%2FFORCE_EVAL.html\x26sa\x3dD\x26sntz\x3d1\x26usg\x3dAFQjCNH6bdL-Z7dVvMAdG5qOtZ_x9Ckyxw';return true;" onclick="this.href='https://www.google.com/url?q\x3dhttps%3A%2F%2Fmanual.cp2k.org%2Fcp2k-2_6-branch%2FCP2K_INPUT%2FFORCE_EVAL.html\x26sa\x3dD\x26sntz\x3d1\x26usg\x3dAFQjCNH6bdL-Z7dVvMAdG5qOtZ_x9Ckyxw';return true;">FORCE_EVAL</a> /
               <a href="https://manual.cp2k.org/cp2k-2_6-branch/CP2K_INPUT/FORCE_EVAL/QMMM.html" rel="nofollow" target="_blank" onmousedown="this.href='https://www.google.com/url?q\x3dhttps%3A%2F%2Fmanual.cp2k.org%2Fcp2k-2_6-branch%2FCP2K_INPUT%2FFORCE_EVAL%2FQMMM.html\x26sa\x3dD\x26sntz\x3d1\x26usg\x3dAFQjCNF7s9T8CHqvAIDClarKCI7MaWYwdg';return true;" onclick="this.href='https://www.google.com/url?q\x3dhttps%3A%2F%2Fmanual.cp2k.org%2Fcp2k-2_6-branch%2FCP2K_INPUT%2FFORCE_EVAL%2FQMMM.html\x26sa\x3dD\x26sntz\x3d1\x26usg\x3dAFQjCNF7s9T8CHqvAIDClarKCI7MaWYwdg';return true;">QMMM</a> /
               <a href="https://manual.cp2k.org/cp2k-2_6-branch/CP2K_INPUT/FORCE_EVAL/QMMM/CELL.html" rel="nofollow" target="_blank" onmousedown="this.href='https://www.google.com/url?q\x3dhttps%3A%2F%2Fmanual.cp2k.org%2Fcp2k-2_6-branch%2FCP2K_INPUT%2FFORCE_EVAL%2FQMMM%2FCELL.html\x26sa\x3dD\x26sntz\x3d1\x26usg\x3dAFQjCNHWY7ja_EMRvj4MtajexR46YOqlNg';return true;" onclick="this.href='https://www.google.com/url?q\x3dhttps%3A%2F%2Fmanual.cp2k.org%2Fcp2k-2_6-branch%2FCP2K_INPUT%2FFORCE_EVAL%2FQMMM%2FCELL.html\x26sa\x3dD\x26sntz\x3d1\x26usg\x3dAFQjCNHWY7ja_EMRvj4MtajexR46YOqlNg';return true;">CELL</a><br><br></big>where the box size of the QM/MM region can be specified with possibly smaller dimensions than the entire cell. So do you or other users know a method to estimate the minimum <br>dimensions of the QM/MM cell by looking at convergence with respect to some observable quantity in QMMM. Any help in this direction will be helpful!<br><br>Best Regrads and belated New Year wishes to cp2k users!<br><br>Rahul<br><br> <br>On Thursday, December 21, 2017 at 4:43:20 PM UTC+5:30, Tianshu Jiang in Beijing wrote:<blockquote class="gmail_quote" style="margin:0;margin-left:0.8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">hello <span style="white-space:nowrap">Hardikar,</span><div><span style="white-space:nowrap"><br></span></div><div><span style="white-space:nowrap">The dimension of QM box depends on your system, or the quantity where you are interested. </span></div><div><span style="white-space:nowrap">You can refer the paper "</span><span style="font-family:Helvetica;font-size:13pt;font-weight:700">An Efficient Real Space Multigrid QM/MM Electrostatic
Coupling</span><span style="white-space:nowrap">" written by Teodoro Laino for details.</span></div><div><span style="white-space:nowrap">The realization of QMMM in CP2K is based on this paper.</span></div><div><span style="white-space:nowrap"><br></span></div><div><span style="white-space:nowrap">Best wishes !</span></div><div><div><br>在 2017年12月20日星期三 UTC+8下午6:06:37，Rahul Hardikar写道：<blockquote class="gmail_quote" style="margin:0;margin-left:0.8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Dear CP2K Users/Experts,<div><br></div><div>Currently, in my QMMM setup I am maintaining box lengths same as the overall systems' box lengths. I am aware that one can reduce the box size for the QMMM</div><div>box thereby reducing the cost of QM calculations. However what is not clear to me is the role of electrostatics when QMMM box lengths are less the the overall lengths. So my question is (a) how one can estimate the QMMM box lengths and maintain the electrostatic interaction between QM and MM part consistent? and (b) how can I estimate the amount of vacuum to use to avoid any interaction between periodic images? I am using cubecruncher to crunch out plane averaged electrostatic potential and hartree energy from the corresponding cube files.  </div><div><br></div><div>Any suggestions and/or comments will be appreciated.</div><div><br></div><div>Best Regards,</div><div>Rahul Hardikar</div></div></blockquote></div></div></div></blockquote></div></blockquote></div></div></blockquote></div>