Dear Guido, Thanks for your consideration and very instructive comments.
Bests. ------------------------------------------- Yavar Taghipour PhD Student Physics Group, AEOI Tehran-Iran Email: ytaghipour at aeoi.org.ir Phone: +98 (0) 21 82064556 ----------------------------------------------------------- ----- Original Message ----- From: "Guido Fratesi" <frat...@mater.unimib.it> To: <pw_forum at pwscf.org> Sent: Thursday, April 19, 2012 2:55 PM Subject: Re: [Pw_forum] on the way of approximating a large slab > Dear Yavar, > > I hope a comment on your question (unfortunately not an answer) could be > helpful. > Notice that the properties of the adsorbed species may converge faster > than those of the clean surface alone. So, if you are interested in the > distance of the molecule from the surface, or the adsorption energy, > these may be described with a thin slab better than the interlayer > relaxation or the surface energy of the clean substrate (or even worse, > the surface electronic structure). You could practice by adsorbing a > smaller molecule or a fragment. I'd expect that much less than 14 layers > could be sufficient rather often. > > (then, I remember about an "Effective Screening Medium Method" > implemented in QE, there's also an example, but I don't know much about > it) > > HTH > Guido > > Il 04/19/2012 11:57 AM, Yavar Taghipour Azar ha scritto: >> Dear QE users >> >> I want to model adsorption of a large molecule on a relatively large >> slab. After test convergence on the number of layers for clean surface, >> I found 14 layers are needed, but for well-known technical reasons (time >> and memory limitation), I am thinking on how can one take into account >> the atoms of just some 3 topmost layers of the slab, and the effects of >> the remaining layers of the slab as an external potential. >> >> Is it a meaningful question and what about its feasibility in the >> context of QE? >> >> Thanks in advance. >> >> ------------------------------------------- >> Yavar Taghipour >> PhD Student >> Physics Group, AEOI >> Tehran-Iran >> Email: ytaghipour at aeoi.org.ir <mailto:ytaghipour at aeoi.org.ir> >> Phone: +98 (0) 21 82064556 >> ----------------------------------------------------------- >> >> >> _______________________________________________ >> Pw_forum mailing list >> Pw_forum at pwscf.org >> http://www.democritos.it/mailman/listinfo/pw_forum > > -- > Guido Fratesi > > Dipartimento di Scienza dei Materiali > Universita` degli Studi di Milano-Bicocca > via Cozzi 53, 20125 Milano, Italy > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > >