<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""><div><blockquote type="cite" class=""><div class="">On 17 May 2016, at 19:28, rojib raj <<a href="mailto:rojibeee@gmail.com" class="">rojibeee@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><p dir="ltr" class="">dear altruists,<br class="">
while finding band structure for bilayer graphene, I used "ibrav=4"<br class="">
now can somebody tell me why we use the value of ibrav =4 ???<br class="">
I think this value indicates 3D structure of graphene which is actually graphite not graphene.....it would be helpful if somebody could explain this...</p><p dir="ltr" class="">thanks in advance....... </p>
_______________________________________________<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></blockquote><br class=""></div><div>Dear someone,</div><div><br class=""></div><div>ibrav=4 corresponds to an hexagonal lattice. You use it to describe the graphite structure. However, if you want to study n-layer graphene, being Quantum-ESPRESSO</div><div>based on plane waves, you must define a lattice even if the system is not periodic in all three dimensions. That means that, in the case of graphene, you define an hexagonal</div><div>lattice with the graphene lattice constant in the x-y plane and with a c axis such that two periodic replicas of the graphene sheet a sufficiently far from each other that they do not</div><div>interact. That is usually referred to as supercell.</div><div><br class=""></div><div>I think you can find, even in the quantum-espresso web site, tutorials and presentations that explain, among the others, the concept of supercell.</div><div><br class=""></div><div>Users are, usually, kindly requested to sign their posts on this forum, including affiliation.</div><div><br class=""></div><div>Giovanni</div><br class=""><div class="">
-- <br class=""><br class="">Giovanni Cantele, PhD<br class="">CNR-SPIN<br class="">c/o Dipartimento di Fisica<br class="">Universita' di Napoli "Federico II"<br class="">Complesso Universitario M. S. Angelo - Ed. 6<br class="">Via Cintia, I-80126, Napoli, Italy<br class="">e-mail: <a href="mailto:giovanni.cantele@spin.cnr.it" class="">giovanni.cantele@spin.cnr.it</a><br class="">Phone: +39 081 676910<br class="">Skype contact: giocan74<br class=""><br class="">ResearcherID: <a href="http://www.researcherid.com/rid/A-1951-2009" class="">http://www.researcherid.com/rid/A-1951-2009</a><br class="">Web page: <a href="http://people.na.infn.it/~cantele" class="">http://people.na.infn.it/~cantele</a><br class="">
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