[Pw_forum] bilayer graphene band structure
giovanni.cantele at spin.cnr.it
Wed May 18 10:23:02 CEST 2016
> On 17 May 2016, at 19:28, rojib raj <rojibeee at gmail.com> 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.......
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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.
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Giovanni Cantele, PhD
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: giovanni.cantele at spin.cnr.it
Phone: +39 081 676910
Skype contact: giocan74
Web page: http://people.na.infn.it/~cantele
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