<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Hi Matthieu,<div class=""><br class=""></div><div style="text-indent: -36px;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>I was curious as to which substrates you are putting graphene on. Because if you are looking at either ionic solids or metals, the Grimme corrections are going to be a bit too strong, but it can be fixed. We have had success for calculating adsorption energies on minerals by reducing the C6 parameter for the cations in the substrate by about an order of magnitude (we decreased the parameter by 33 for Ca in calcite in (Okhrimenko et al <i style="text-indent: -36px;" class="">Langmuir</i><span style="text-indent: -36px;" class=""> </span><b style="text-indent: -36px;" class="">29</b><span style="text-indent: -36px;" class="">, 11062-11073,(2013)). The idea came from Ehrlich et al </span><i style="text-indent: -36px;" class="">ChemPhysChem</i><span style="text-indent: -36px;" class=""> </span><b style="text-indent: -36px;" class="">12</b><span style="text-indent: -36px;" class="">, 3414-3420,(2011). For cations in ionic solids (e.g. oxides, minerals), the polarisability is significantly smaller because of the smaller electron cloud of a cation compared to the corresponding neutral atom.</span></div><div style="text-indent: -36px;" class=""><span style="text-indent: -36px;" class=""><br class=""></span></div><div style="text-indent: -36px;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>For metals, I had good success in Andersson MP <i class="">Journal of Theoretical Chemistry</i> <b class="">2013</b>, Article ID 327839,(2013), where I modified Grimme corrections to make it work better for metals by using a shorter cutoff to simulate screening by the conduction electrons and switching the C6 parameters for the metal to the parameter of the noble gas in the row above.</div><div style="text-indent: -36px;" class=""><br class=""></div><div style="text-indent: -36px;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>In either of the two cases, you only need to modify the mm_dispersion.f90 file and recompile. I have a couple of different mm_dispersion.f90 files lying around if you need one...</div><div style="text-indent: -36px;" class=""><br class=""></div><div style="text-indent: -36px;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>Or you could of course also switch to a suitable vdw functional if you like instead.</div><div style="text-indent: -36px;" class=""><br class=""></div><div style="text-indent: -36px;" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>Cheers and good luck,</div><div class=""><div style="text-indent: -36px;" class=""><br class=""></div><div class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class="">————————————————————————</div><div class="">Martin P. Andersson</div><div class="">Associate Professor</div><div class="">Nano-Science Center, Department of Chemistry</div><div class="">University of Copenhagen, Denmark</div><div class=""><br class=""></div><div class="">Tel: +45 3532 0280</div><div class="">Mobile: +46 733 893091</div><div class="">E-mail: <a href="mailto:ma@nano.ku.dk" class="">ma@nano.ku.dk</a></div><div class="">————————————————————————</div></div><br class="Apple-interchange-newline"></div><br class="Apple-interchange-newline"></div><br class="Apple-interchange-newline"></div><br class="Apple-interchange-newline"></div></div></div></div></div></div><div class=""><div style="color: rgb(0, 0, 0); letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div style="color: rgb(0, 0, 0); letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class="Apple-interchange-newline"></div><br class="Apple-interchange-newline"></div><br class="Apple-interchange-newline"><br class="Apple-interchange-newline">
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<br class=""><div><blockquote type="cite" class=""><div class="">On 12 May 2016, at 20:22, Matthieu Fortin-Deschênes <<a href="mailto:matthieu.fortin-deschenes@polymtl.ca" class="">matthieu.fortin-deschenes@polymtl.ca</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="">Hi all,<br class=""><br class="">I'm trying to calculate some basic properties of graphene on various <br class="">substrates using Grimme correction for VdW interactions. The Grimme <br class="">corrections seem to deteriorate the results (lattice parameter and <br class="">binding energy) of the graphene as well of the substrate compared to <br class="">experimental results.<br class=""><br class="">I was wondering if it's possible to set C_ij=0 for i=j (no correction <br class="">for C-C interactions, as well as substrate-substrate interaction), but <br class="">non-zero C_ij for graphene-substrate interactions. As far as i know, <br class="">C_i are defined for each element and C_ij is calculated from <br class="">sqrt(C_i*C_j). I would like to set all C_ij by myself.<br class=""><br class="">Thank you<br class=""><br class="">Matthieu Fortin-Deschênes<br class="">Polytechnique Montreal<br class=""><br class=""><br class="">_______________________________________________<br class="">Pw_forum mailing list<br class=""><a href="mailto:Pw_forum@pwscf.org" class="">Pw_forum@pwscf.org</a><br class="">http://pwscf.org/mailman/listinfo/pw_forum</div></div></blockquote></div><br class=""></body></html>