<html><head><meta http-equiv="Content-Type" content="text/html charset=iso-8859-1"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;">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.<div><br><div>Pascal</div><div><br><div><div>Le 16 nov. 2015 à 21:49, Jaret Qi <<a href="mailto:jaretqi@yahoo.com">jaretqi@yahoo.com</a>> a écrit :</div><br class="Apple-interchange-newline"><blockquote type="cite"><div style="background-color: rgb(255, 255, 255); font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 16px;"><div id="yui_3_16_0_1_1447699371956_11156">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.</div><div id="yui_3_16_0_1_1447699371956_11157"><br></div><div id="yui_3_16_0_1_1447699371956_11158"> <br></div><br><div class="qtdSeparateBR"><br><br></div><div style="display: block;" class="yahoo_quoted"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <div dir="ltr"> <font face="Arial" size="2"> On Monday, November 16, 2015 1:31 PM, Nicola Marzari <<a href="mailto:nicola.marzari@epfl.ch">nicola.marzari@epfl.ch</a>> wrote:<br> </font> </div> <br><br> <div class="y_msg_container">On 16/11/2015 21:17, Jaret Qi wrote:<br clear="none">> but that will cost time!<br clear="none"><br clear="none">you are right! just keep the 4 angstroms, no one will notice.<br clear="none"><br clear="none">(actually, skip the calculations altogether, and make up some<br clear="none">plausible numbers in your paper - that will be even faster).<br clear="none"><br clear="none"> nicola<br clear="none"><br clear="none">><br clear="none">><br clear="none">><br clear="none">> On Monday, November 16, 2015 9:26 AM, Pascal Boulet<br clear="none">> <<a shape="rect" ymailto="mailto:pascal.boulet@univ-amu.fr" href="mailto:pascal.boulet@univ-amu.fr">pascal.boulet@univ-amu.fr</a>> wrote:<br clear="none">><br clear="none">><br clear="none">> Hello,<br clear="none">><br clear="none">> 4 angstroms wide seems to be very small for the vacuum. As a rule of<br clear="none">> thumb you should use at least 2.5 times the thickness of your slab. This<br clear="none">> is what we observed in the calculations of semiconductor slabs. This has<br clear="none">> to be tested.<br clear="none">><br clear="none">> Pascal<br clear="none">><br clear="none">> Le 16 nov. 2015 à 16:40, Jaret Qi <<a shape="rect" ymailto="mailto:jaretqi@yahoo.com" href="mailto:jaretqi@yahoo.com">jaretqi@yahoo.com</a><br clear="none">> <mailto:<a shape="rect" ymailto="mailto:jaretqi@yahoo.com" href="mailto:jaretqi@yahoo.com">jaretqi@yahoo.com</a>>> a écrit :<br clear="none">><br clear="none">>> Hello all,<br clear="none">>> I am trying to minimize the interaction between my system and its<br clear="none">>> periodic images. To do so, I introduced a layer of vacuum along the<br clear="none">>> z-axis by increasing the lattice vector along the z-axis by 4A. At the<br clear="none">>> same time, I fixed it by using this parameter: cell_dofree='2Dxy',<br clear="none">>> But I have noticed atoms that are close to the vacuum move along the<br clear="none">>> z-axis and vacuum is decreasing, is this wrong or I should use<br clear="none">>> different cell_dofree?<br clear="none">>> note:relaxation still ongoing, not relaxed yet.<br clear="none">>><br clear="none">>><br clear="none">>> JARET,<br clear="none">>> ASU<br clear="none">>> _______________________________________________<br clear="none">>> Pw_forum mailing list<br clear="none">>> <a shape="rect" ymailto="mailto:Pw_forum@pwscf.org" href="mailto:Pw_forum@pwscf.org">Pw_forum@pwscf.org</a> <mailto:<a shape="rect" ymailto="mailto:Pw_forum@pwscf.org" href="mailto:Pw_forum@pwscf.org">Pw_forum@pwscf.org</a>><br clear="none">>> <a shape="rect" href="http://pwscf.org/mailman/listinfo/pw_forum" target="_blank">http://pwscf.org/mailman/listinfo/pw_forum</a><br clear="none">><br clear="none">> --<br clear="none">> Pascal Boulet /- MCF HDR, Resp. L1 MPCI - DEPARTEMENT CHIMIE/<br clear="none">> Aix-Marseille Université - ST JEROME - Avenue Escadrille Normandie<br clear="none">> Niemen - 13013 Marseille<br clear="none">> Tél: +33(0)4 13 55 18 10 - Fax : +33(0)4 13 55 18 50<br clear="none">> Site : <a shape="rect" href="http://allos.up.univ-mrs.fr/pascal" target="_blank">http://allos.up.univ-mrs.fr/pascal </a>- Email :<br clear="none">> <a shape="rect" ymailto="mailto:pascal.boulet@univ-amu.fr" href="mailto:pascal.boulet@univ-amu.fr">pascal.boulet@univ-amu.fr</a> <mailto:<a shape="rect" ymailto="mailto:pascal.boulet@univ-amu.fr" href="mailto:pascal.boulet@univ-amu.fr">pascal.boulet@univ-amu.fr</a>><br clear="none">> /Afin de respecter l'environnement, merci de n'imprimer cet email que si<br clear="none">> nécessaire./<div class="yqt2621883996" id="yqtfd08559"><br clear="none">><br clear="none">><br clear="none">><br clear="none">><br clear="none">><br clear="none">> _______________________________________________<br clear="none">> Pw_forum mailing list<br clear="none">> <a shape="rect" ymailto="mailto:Pw_forum@pwscf.org" href="mailto:Pw_forum@pwscf.org">Pw_forum@pwscf.org</a><br clear="none">> <a shape="rect" href="http://pwscf.org/mailman/listinfo/pw_forum" target="_blank">http://pwscf.org/mailman/listinfo/pw_forum</a></div><br clear="none">><br clear="none"><br clear="none">-- <br clear="none">----------------------------------------------------------------------<br clear="none">Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL<br clear="none">Director, National Centre for Competence in Research NCCR MARVEL, EPFL<br clear="none"><a shape="rect" href="http://theossrv1.epfl.ch/Main/Contact" target="_blank">http://theossrv1.epfl.ch/Main/Contact </a><a shape="rect" href="http://nccr-marvel.ch/en/project" target="_blank">http://nccr-marvel.ch/en/project</a><div class="yqt2621883996" id="yqtfd09972"><br clear="none"></div><br><br></div> </div> </div> </div></div></blockquote></div><br><div>
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