So, I think in this case you should also relax the z-axis: The system tends to fill the vacuum by moving atoms since it cannot adapt the cell parameter.
Pascal Le 16 nov. 2015 à 21:49, Jaret Qi <[email protected]> a écrit : > To make it clear, I am not adding vacuum to isolate my system like in > graphene where we make the z-axis large enough to make it graphene not > graphite. My system is a (001) interface between semi-metallic and > semiconductor, so i am trying to minimize the interaction along the interface > which is along the z-axis and study some properties and match it with > experimental results. I need a reasonable vacuum so I began with 4A. > > > > > > On Monday, November 16, 2015 1:31 PM, Nicola Marzari <[email protected]> > wrote: > > > On 16/11/2015 21:17, Jaret Qi wrote: > > but that will cost time! > > you are right! just keep the 4 angstroms, no one will notice. > > (actually, skip the calculations altogether, and make up some > plausible numbers in your paper - that will be even faster). > > nicola > > > > > > > > > On Monday, November 16, 2015 9:26 AM, Pascal Boulet > > <[email protected]> wrote: > > > > > > Hello, > > > > 4 angstroms wide seems to be very small for the vacuum. As a rule of > > thumb you should use at least 2.5 times the thickness of your slab. This > > is what we observed in the calculations of semiconductor slabs. This has > > to be tested. > > > > Pascal > > > > Le 16 nov. 2015 à 16:40, Jaret Qi <[email protected] > > <mailto:[email protected]>> a écrit : > > > >> Hello all, > >> I am trying to minimize the interaction between my system and its > >> periodic images. To do so, I introduced a layer of vacuum along the > >> z-axis by increasing the lattice vector along the z-axis by 4A. At the > >> same time, I fixed it by using this parameter: cell_dofree='2Dxy', > >> But I have noticed atoms that are close to the vacuum move along the > >> z-axis and vacuum is decreasing, is this wrong or I should use > >> different cell_dofree? > >> note:relaxation still ongoing, not relaxed yet. > >> > >> > >> JARET, > >> ASU > >> _______________________________________________ > >> Pw_forum mailing list > >> [email protected] <mailto:[email protected]> > >> http://pwscf.org/mailman/listinfo/pw_forum > > > > -- > > Pascal Boulet /- MCF HDR, Resp. L1 MPCI - DEPARTEMENT CHIMIE/ > > Aix-Marseille Université - ST JEROME - Avenue Escadrille Normandie > > Niemen - 13013 Marseille > > Tél: +33(0)4 13 55 18 10 - Fax : +33(0)4 13 55 18 50 > > Site : http://allos.up.univ-mrs.fr/pascal - Email : > > [email protected] <mailto:[email protected]> > > /Afin de respecter l'environnement, merci de n'imprimer cet email que si > > nécessaire./ > > > > > > > > > > > > > _______________________________________________ > > Pw_forum mailing list > > [email protected] > > http://pwscf.org/mailman/listinfo/pw_forum > > > > > -- > ---------------------------------------------------------------------- > Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL > Director, National Centre for Competence in Research NCCR MARVEL, EPFL > http://theossrv1.epfl.ch/Main/Contact http://nccr-marvel.ch/en/project > > > -- Pascal Boulet - MCF HDR, Resp. L1 MPCI - DEPARTEMENT CHIMIE Aix-Marseille Université - ST JEROME - Avenue Escadrille Normandie Niemen - 13013 Marseille Tél: +33(0)4 13 55 18 10 - Fax : +33(0)4 13 55 18 50 Site : http://allos.up.univ-mrs.fr/pascal - Email : [email protected] Afin de respecter l'environnement, merci de n'imprimer cet email que si nécessaire.
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