> On 17 May 2016, at 19:28, rojib raj <[email protected]> wrote: > > dear altruists, > while finding band structure for bilayer graphene, I used "ibrav=4" > now can somebody tell me why we use the value of ibrav =4 ??? > I think this value indicates 3D structure of graphene which is actually > graphite not graphene.....it would be helpful if somebody could explain > this... > > thanks in advance....... > > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum
Dear someone, 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 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 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 interact. That is usually referred to as supercell. I think you can find, even in the quantum-espresso web site, tutorials and presentations that explain, among the others, the concept of supercell. Users are, usually, kindly requested to sign their posts on this forum, including affiliation. Giovanni -- Giovanni Cantele, PhD CNR-SPIN c/o Dipartimento di Fisica Universita' di Napoli "Federico II" Complesso Universitario M. S. Angelo - Ed. 6 Via Cintia, I-80126, Napoli, Italy e-mail: [email protected] Phone: +39 081 676910 Skype contact: giocan74 ResearcherID: http://www.researcherid.com/rid/A-1951-2009 Web page: http://people.na.infn.it/~cantele
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