Paolo and Martin, Thanks a lot for the advice, I am now looking at the details of how to do it.
Martin, They are metal substrates. I will look at those papers in details. I was planning to use both Grimme corrections and a VdW functional to compare the results. Thanks again for the advice. Very helpful. Matthieu Martin Andersson <[email protected]> a écrit : > Hi Matthieu, > > 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 Langmuir 29, > 11062-11073,(2013)). The idea came from Ehrlich et al ChemPhysChem > 12, 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. > > For metals, I had good success in Andersson MP Journal of > Theoretical Chemistry 2013, 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. > > 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... > > Or you could of course also switch to a suitable vdw functional > if > you like instead. > > Cheers and good luck, > > ———————————————————————— > Martin P. Andersson > Associate Professor > Nano-Science Center, Department of Chemistry > University of Copenhagen, Denmark > > Tel: +45 3532 0280 > Mobile: +46 733 893091 > E-mail: [email protected] > ———————————————————————— > > > > > > > > > >> On 12 May 2016, at 20:22, Matthieu Fortin-Deschênes >> <[email protected]> wrote: >> >> Hi all, >> >> I'm trying to calculate some basic properties of graphene on various >> substrates using Grimme correction for VdW interactions. The Grimme >> corrections seem to deteriorate the results (lattice parameter and >> binding energy) of the graphene as well of the substrate compared to >> experimental results. >> >> I was wondering if it's possible to set C_ij=0 for i=j (no correction >> for C-C interactions, as well as substrate-substrate interaction), but >> non-zero C_ij for graphene-substrate interactions. As far as i know, >> C_i are defined for each element and C_ij is calculated from >> sqrt(C_i*C_j). I would like to set all C_ij by myself. >> >> Thank you >> >> Matthieu Fortin-Deschênes >> Polytechnique Montreal >> >> >> _______________________________________________ >> Pw_forum mailing list >> [email protected] >> http://pwscf.org/mailman/listinfo/pw_forum _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
